1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
//! A module for working with processes.
//!
//! This module is mostly concerned with spawning and interacting with child
//! processes, but it also provides [`abort`] and [`exit`] for terminating the
//! current process.
//!
//! # Spawning a process
//!
//! The [`Command`] struct is used to configure and spawn processes:
//!
//! ```no_run
//! use std::process::Command;
//!
//! let output = Command::new("echo")
//!     .arg("Hello world")
//!     .output()
//!     .expect("Failed to execute command");
//!
//! assert_eq!(b"Hello world\n", output.stdout.as_slice());
//! ```
//!
//! Several methods on [`Command`], such as [`spawn`] or [`output`], can be used
//! to spawn a process. In particular, [`output`] spawns the child process and
//! waits until the process terminates, while [`spawn`] will return a [`Child`]
//! that represents the spawned child process.
//!
//! # Handling I/O
//!
//! The [`stdout`], [`stdin`], and [`stderr`] of a child process can be
//! configured by passing an [`Stdio`] to the corresponding method on
//! [`Command`]. Once spawned, they can be accessed from the [`Child`]. For
//! example, piping output from one command into another command can be done
//! like so:
//!
//! ```no_run
//! use std::process::{Command, Stdio};
//!
//! // stdout must be configured with `Stdio::piped` in order to use
//! // `echo_child.stdout`
//! let echo_child = Command::new("echo")
//!     .arg("Oh no, a tpyo!")
//!     .stdout(Stdio::piped())
//!     .spawn()
//!     .expect("Failed to start echo process");
//!
//! // Note that `echo_child` is moved here, but we won't be needing
//! // `echo_child` anymore
//! let echo_out = echo_child.stdout.expect("Failed to open echo stdout");
//!
//! let mut sed_child = Command::new("sed")
//!     .arg("s/tpyo/typo/")
//!     .stdin(Stdio::from(echo_out))
//!     .stdout(Stdio::piped())
//!     .spawn()
//!     .expect("Failed to start sed process");
//!
//! let output = sed_child.wait_with_output().expect("Failed to wait on sed");
//! assert_eq!(b"Oh no, a typo!\n", output.stdout.as_slice());
//! ```
//!
//! Note that [`ChildStderr`] and [`ChildStdout`] implement [`Read`] and
//! [`ChildStdin`] implements [`Write`]:
//!
//! ```no_run
//! use std::process::{Command, Stdio};
//! use std::io::Write;
//!
//! let mut child = Command::new("/bin/cat")
//!     .stdin(Stdio::piped())
//!     .stdout(Stdio::piped())
//!     .spawn()
//!     .expect("failed to execute child");
//!
//! // If the child process fills its stdout buffer, it may end up
//! // waiting until the parent reads the stdout, and not be able to
//! // read stdin in the meantime, causing a deadlock.
//! // Writing from another thread ensures that stdout is being read
//! // at the same time, avoiding the problem.
//! let mut stdin = child.stdin.take().expect("failed to get stdin");
//! std::thread::spawn(move || {
//!     stdin.write_all(b"test").expect("failed to write to stdin");
//! });
//!
//! let output = child
//!     .wait_with_output()
//!     .expect("failed to wait on child");
//!
//! assert_eq!(b"test", output.stdout.as_slice());
//! ```
//!
//! # Windows argument splitting
//!
//! On Unix systems arguments are passed to a new process as an array of strings,
//! but on Windows arguments are passed as a single commandline string and it is
//! up to the child process to parse it into an array. Therefore the parent and
//! child processes must agree on how the commandline string is encoded.
//!
//! Most programs use the standard C run-time `argv`, which in practice results
//! in consistent argument handling. However, some programs have their own way of
//! parsing the commandline string. In these cases using [`arg`] or [`args`] may
//! result in the child process seeing a different array of arguments than the
//! parent process intended.
//!
//! Two ways of mitigating this are:
//!
//! * Validate untrusted input so that only a safe subset is allowed.
//! * Use [`raw_arg`] to build a custom commandline. This bypasses the escaping
//!   rules used by [`arg`] so should be used with due caution.
//!
//! `cmd.exe` and `.bat` files use non-standard argument parsing and are especially
//! vulnerable to malicious input as they may be used to run arbitrary shell
//! commands. Untrusted arguments should be restricted as much as possible.
//! For examples on handling this see [`raw_arg`].
//!
//! ### Batch file special handling
//!
//! On Windows, `Command` uses the Windows API function [`CreateProcessW`] to
//! spawn new processes. An undocumented feature of this function is that
//! when given a `.bat` file as the application to run, it will automatically
//! convert that into running `cmd.exe /c` with the batch file as the next argument.
//!
//! For historical reasons Rust currently preserves this behaviour when using
//! [`Command::new`], and escapes the arguments according to `cmd.exe` rules.
//! Due to the complexity of `cmd.exe` argument handling, it might not be
//! possible to safely escape some special characters, and using them will result
//! in an error being returned at process spawn. The set of unescapeable
//! special characters might change between releases.
//!
//! Also note that running batch scripts in this way may be removed in the
//! future and so should not be relied upon.
//!
//! [`spawn`]: Command::spawn
//! [`output`]: Command::output
//!
//! [`stdout`]: Command::stdout
//! [`stdin`]: Command::stdin
//! [`stderr`]: Command::stderr
//!
//! [`Write`]: io::Write
//! [`Read`]: io::Read
//!
//! [`arg`]: Command::arg
//! [`args`]: Command::args
//! [`raw_arg`]: crate::os::windows::process::CommandExt::raw_arg
//!
//! [`CreateProcessW`]: https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-createprocessw

#![stable(feature = "process", since = "1.0.0")]
#![deny(unsafe_op_in_unsafe_fn)]

#[cfg(all(test, not(any(target_os = "emscripten", target_env = "sgx", target_os = "xous"))))]
mod tests;

use crate::convert::Infallible;
use crate::ffi::OsStr;
use crate::io::prelude::*;
use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
use crate::num::NonZero;
use crate::path::Path;
use crate::sys::pipe::{read2, AnonPipe};
use crate::sys::process as imp;
#[stable(feature = "command_access", since = "1.57.0")]
pub use crate::sys_common::process::CommandEnvs;
use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};
use crate::{fmt, fs, str};

/// Representation of a running or exited child process.
///
/// This structure is used to represent and manage child processes. A child
/// process is created via the [`Command`] struct, which configures the
/// spawning process and can itself be constructed using a builder-style
/// interface.
///
/// There is no implementation of [`Drop`] for child processes,
/// so if you do not ensure the `Child` has exited then it will continue to
/// run, even after the `Child` handle to the child process has gone out of
/// scope.
///
/// Calling [`wait`] (or other functions that wrap around it) will make
/// the parent process wait until the child has actually exited before
/// continuing.
///
/// # Warning
///
/// On some systems, calling [`wait`] or similar is necessary for the OS to
/// release resources. A process that terminated but has not been waited on is
/// still around as a "zombie". Leaving too many zombies around may exhaust
/// global resources (for example process IDs).
///
/// The standard library does *not* automatically wait on child processes (not
/// even if the `Child` is dropped), it is up to the application developer to do
/// so. As a consequence, dropping `Child` handles without waiting on them first
/// is not recommended in long-running applications.
///
/// # Examples
///
/// ```should_panic
/// use std::process::Command;
///
/// let mut child = Command::new("/bin/cat")
///     .arg("file.txt")
///     .spawn()
///     .expect("failed to execute child");
///
/// let ecode = child.wait().expect("failed to wait on child");
///
/// assert!(ecode.success());
/// ```
///
/// [`wait`]: Child::wait
#[stable(feature = "process", since = "1.0.0")]
pub struct Child {
    pub(crate) handle: imp::Process,

    /// The handle for writing to the child's standard input (stdin), if it
    /// has been captured. You might find it helpful to do
    ///
    /// ```ignore (incomplete)
    /// let stdin = child.stdin.take().unwrap();
    /// ```
    ///
    /// to avoid partially moving the `child` and thus blocking yourself from calling
    /// functions on `child` while using `stdin`.
    #[stable(feature = "process", since = "1.0.0")]
    pub stdin: Option<ChildStdin>,

    /// The handle for reading from the child's standard output (stdout), if it
    /// has been captured. You might find it helpful to do
    ///
    /// ```ignore (incomplete)
    /// let stdout = child.stdout.take().unwrap();
    /// ```
    ///
    /// to avoid partially moving the `child` and thus blocking yourself from calling
    /// functions on `child` while using `stdout`.
    #[stable(feature = "process", since = "1.0.0")]
    pub stdout: Option<ChildStdout>,

    /// The handle for reading from the child's standard error (stderr), if it
    /// has been captured. You might find it helpful to do
    ///
    /// ```ignore (incomplete)
    /// let stderr = child.stderr.take().unwrap();
    /// ```
    ///
    /// to avoid partially moving the `child` and thus blocking yourself from calling
    /// functions on `child` while using `stderr`.
    #[stable(feature = "process", since = "1.0.0")]
    pub stderr: Option<ChildStderr>,
}

/// Allows extension traits within `std`.
#[unstable(feature = "sealed", issue = "none")]
impl crate::sealed::Sealed for Child {}

impl AsInner<imp::Process> for Child {
    #[inline]
    fn as_inner(&self) -> &imp::Process {
        &self.handle
    }
}

impl FromInner<(imp::Process, imp::StdioPipes)> for Child {
    fn from_inner((handle, io): (imp::Process, imp::StdioPipes)) -> Child {
        Child {
            handle,
            stdin: io.stdin.map(ChildStdin::from_inner),
            stdout: io.stdout.map(ChildStdout::from_inner),
            stderr: io.stderr.map(ChildStderr::from_inner),
        }
    }
}

impl IntoInner<imp::Process> for Child {
    fn into_inner(self) -> imp::Process {
        self.handle
    }
}

#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for Child {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Child")
            .field("stdin", &self.stdin)
            .field("stdout", &self.stdout)
            .field("stderr", &self.stderr)
            .finish_non_exhaustive()
    }
}

/// A handle to a child process's standard input (stdin).
///
/// This struct is used in the [`stdin`] field on [`Child`].
///
/// When an instance of `ChildStdin` is [dropped], the `ChildStdin`'s underlying
/// file handle will be closed. If the child process was blocked on input prior
/// to being dropped, it will become unblocked after dropping.
///
/// [`stdin`]: Child::stdin
/// [dropped]: Drop
#[stable(feature = "process", since = "1.0.0")]
pub struct ChildStdin {
    inner: AnonPipe,
}

// In addition to the `impl`s here, `ChildStdin` also has `impl`s for
// `AsFd`/`From<OwnedFd>`/`Into<OwnedFd>` and
// `AsRawFd`/`IntoRawFd`/`FromRawFd`, on Unix and WASI, and
// `AsHandle`/`From<OwnedHandle>`/`Into<OwnedHandle>` and
// `AsRawHandle`/`IntoRawHandle`/`FromRawHandle` on Windows.

#[stable(feature = "process", since = "1.0.0")]
impl Write for ChildStdin {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        (&*self).write(buf)
    }

    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
        (&*self).write_vectored(bufs)
    }

    fn is_write_vectored(&self) -> bool {
        io::Write::is_write_vectored(&&*self)
    }

    #[inline]
    fn flush(&mut self) -> io::Result<()> {
        (&*self).flush()
    }
}

#[stable(feature = "write_mt", since = "1.48.0")]
impl Write for &ChildStdin {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.inner.write(buf)
    }

    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
        self.inner.write_vectored(bufs)
    }

    fn is_write_vectored(&self) -> bool {
        self.inner.is_write_vectored()
    }

    #[inline]
    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

impl AsInner<AnonPipe> for ChildStdin {
    #[inline]
    fn as_inner(&self) -> &AnonPipe {
        &self.inner
    }
}

impl IntoInner<AnonPipe> for ChildStdin {
    fn into_inner(self) -> AnonPipe {
        self.inner
    }
}

impl FromInner<AnonPipe> for ChildStdin {
    fn from_inner(pipe: AnonPipe) -> ChildStdin {
        ChildStdin { inner: pipe }
    }
}

#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for ChildStdin {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("ChildStdin").finish_non_exhaustive()
    }
}

/// A handle to a child process's standard output (stdout).
///
/// This struct is used in the [`stdout`] field on [`Child`].
///
/// When an instance of `ChildStdout` is [dropped], the `ChildStdout`'s
/// underlying file handle will be closed.
///
/// [`stdout`]: Child::stdout
/// [dropped]: Drop
#[stable(feature = "process", since = "1.0.0")]
pub struct ChildStdout {
    inner: AnonPipe,
}

// In addition to the `impl`s here, `ChildStdout` also has `impl`s for
// `AsFd`/`From<OwnedFd>`/`Into<OwnedFd>` and
// `AsRawFd`/`IntoRawFd`/`FromRawFd`, on Unix and WASI, and
// `AsHandle`/`From<OwnedHandle>`/`Into<OwnedHandle>` and
// `AsRawHandle`/`IntoRawHandle`/`FromRawHandle` on Windows.

#[stable(feature = "process", since = "1.0.0")]
impl Read for ChildStdout {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.inner.read(buf)
    }

    fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> io::Result<()> {
        self.inner.read_buf(buf)
    }

    fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
        self.inner.read_vectored(bufs)
    }

    #[inline]
    fn is_read_vectored(&self) -> bool {
        self.inner.is_read_vectored()
    }

    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
        self.inner.read_to_end(buf)
    }
}

impl AsInner<AnonPipe> for ChildStdout {
    #[inline]
    fn as_inner(&self) -> &AnonPipe {
        &self.inner
    }
}

impl IntoInner<AnonPipe> for ChildStdout {
    fn into_inner(self) -> AnonPipe {
        self.inner
    }
}

impl FromInner<AnonPipe> for ChildStdout {
    fn from_inner(pipe: AnonPipe) -> ChildStdout {
        ChildStdout { inner: pipe }
    }
}

#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for ChildStdout {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("ChildStdout").finish_non_exhaustive()
    }
}

/// A handle to a child process's stderr.
///
/// This struct is used in the [`stderr`] field on [`Child`].
///
/// When an instance of `ChildStderr` is [dropped], the `ChildStderr`'s
/// underlying file handle will be closed.
///
/// [`stderr`]: Child::stderr
/// [dropped]: Drop
#[stable(feature = "process", since = "1.0.0")]
pub struct ChildStderr {
    inner: AnonPipe,
}

// In addition to the `impl`s here, `ChildStderr` also has `impl`s for
// `AsFd`/`From<OwnedFd>`/`Into<OwnedFd>` and
// `AsRawFd`/`IntoRawFd`/`FromRawFd`, on Unix and WASI, and
// `AsHandle`/`From<OwnedHandle>`/`Into<OwnedHandle>` and
// `AsRawHandle`/`IntoRawHandle`/`FromRawHandle` on Windows.

#[stable(feature = "process", since = "1.0.0")]
impl Read for ChildStderr {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.inner.read(buf)
    }

    fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> io::Result<()> {
        self.inner.read_buf(buf)
    }

    fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
        self.inner.read_vectored(bufs)
    }

    #[inline]
    fn is_read_vectored(&self) -> bool {
        self.inner.is_read_vectored()
    }

    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
        self.inner.read_to_end(buf)
    }
}

impl AsInner<AnonPipe> for ChildStderr {
    #[inline]
    fn as_inner(&self) -> &AnonPipe {
        &self.inner
    }
}

impl IntoInner<AnonPipe> for ChildStderr {
    fn into_inner(self) -> AnonPipe {
        self.inner
    }
}

impl FromInner<AnonPipe> for ChildStderr {
    fn from_inner(pipe: AnonPipe) -> ChildStderr {
        ChildStderr { inner: pipe }
    }
}

#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for ChildStderr {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("ChildStderr").finish_non_exhaustive()
    }
}

/// A process builder, providing fine-grained control
/// over how a new process should be spawned.
///
/// A default configuration can be
/// generated using `Command::new(program)`, where `program` gives a path to the
/// program to be executed. Additional builder methods allow the configuration
/// to be changed (for example, by adding arguments) prior to spawning:
///
/// ```
/// use std::process::Command;
///
/// let output = if cfg!(target_os = "windows") {
///     Command::new("cmd")
///         .args(["/C", "echo hello"])
///         .output()
///         .expect("failed to execute process")
/// } else {
///     Command::new("sh")
///         .arg("-c")
///         .arg("echo hello")
///         .output()
///         .expect("failed to execute process")
/// };
///
/// let hello = output.stdout;
/// ```
///
/// `Command` can be reused to spawn multiple processes. The builder methods
/// change the command without needing to immediately spawn the process.
///
/// ```no_run
/// use std::process::Command;
///
/// let mut echo_hello = Command::new("sh");
/// echo_hello.arg("-c").arg("echo hello");
/// let hello_1 = echo_hello.output().expect("failed to execute process");
/// let hello_2 = echo_hello.output().expect("failed to execute process");
/// ```
///
/// Similarly, you can call builder methods after spawning a process and then
/// spawn a new process with the modified settings.
///
/// ```no_run
/// use std::process::Command;
///
/// let mut list_dir = Command::new("ls");
///
/// // Execute `ls` in the current directory of the program.
/// list_dir.status().expect("process failed to execute");
///
/// println!();
///
/// // Change `ls` to execute in the root directory.
/// list_dir.current_dir("/");
///
/// // And then execute `ls` again but in the root directory.
/// list_dir.status().expect("process failed to execute");
/// ```
#[stable(feature = "process", since = "1.0.0")]
#[cfg_attr(not(test), rustc_diagnostic_item = "Command")]
pub struct Command {
    inner: imp::Command,
}

/// Allows extension traits within `std`.
#[unstable(feature = "sealed", issue = "none")]
impl crate::sealed::Sealed for Command {}

impl Command {
    /// Constructs a new `Command` for launching the program at
    /// path `program`, with the following default configuration:
    ///
    /// * No arguments to the program
    /// * Inherit the current process's environment
    /// * Inherit the current process's working directory
    /// * Inherit stdin/stdout/stderr for [`spawn`] or [`status`], but create pipes for [`output`]
    ///
    /// [`spawn`]: Self::spawn
    /// [`status`]: Self::status
    /// [`output`]: Self::output
    ///
    /// Builder methods are provided to change these defaults and
    /// otherwise configure the process.
    ///
    /// If `program` is not an absolute path, the `PATH` will be searched in
    /// an OS-defined way.
    ///
    /// The search path to be used may be controlled by setting the
    /// `PATH` environment variable on the Command,
    /// but this has some implementation limitations on Windows
    /// (see issue #37519).
    ///
    /// # Platform-specific behavior
    ///
    /// Note on Windows: For executable files with the .exe extension,
    /// it can be omitted when specifying the program for this Command.
    /// However, if the file has a different extension,
    /// a filename including the extension needs to be provided,
    /// otherwise the file won't be found.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// Command::new("sh")
    ///     .spawn()
    ///     .expect("sh command failed to start");
    /// ```
    ///
    /// # Caveats
    ///
    /// [`Command::new`] is only intended to accept the path of the program. If you pass a program
    /// path along with arguments like `Command::new("ls -l").spawn()`, it will try to search for
    /// `ls -l` literally. The arguments need to be passed separately, such as via [`arg`] or
    /// [`args`].
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// Command::new("ls")
    ///     .arg("-l") // arg passed separately
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    ///
    /// [`arg`]: Self::arg
    /// [`args`]: Self::args
    #[stable(feature = "process", since = "1.0.0")]
    pub fn new<S: AsRef<OsStr>>(program: S) -> Command {
        Command { inner: imp::Command::new(program.as_ref()) }
    }

    /// Adds an argument to pass to the program.
    ///
    /// Only one argument can be passed per use. So instead of:
    ///
    /// ```no_run
    /// # std::process::Command::new("sh")
    /// .arg("-C /path/to/repo")
    /// # ;
    /// ```
    ///
    /// usage would be:
    ///
    /// ```no_run
    /// # std::process::Command::new("sh")
    /// .arg("-C")
    /// .arg("/path/to/repo")
    /// # ;
    /// ```
    ///
    /// To pass multiple arguments see [`args`].
    ///
    /// [`args`]: Command::args
    ///
    /// Note that the argument is not passed through a shell, but given
    /// literally to the program. This means that shell syntax like quotes,
    /// escaped characters, word splitting, glob patterns, variable substitution,
    /// etc. have no effect.
    ///
    /// <div class="warning">
    ///
    /// On Windows, use caution with untrusted inputs. Most applications use the
    /// standard convention for decoding arguments passed to them. These are safe to
    /// use with `arg`. However, some applications such as `cmd.exe` and `.bat` files
    /// use a non-standard way of decoding arguments. They are therefore vulnerable
    /// to malicious input.
    ///
    /// In the case of `cmd.exe` this is especially important because a malicious
    /// argument can potentially run arbitrary shell commands.
    ///
    /// See [Windows argument splitting][windows-args] for more details
    /// or [`raw_arg`] for manually implementing non-standard argument encoding.
    ///
    /// [`raw_arg`]: crate::os::windows::process::CommandExt::raw_arg
    /// [windows-args]: crate::process#windows-argument-splitting
    ///
    /// </div>
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// Command::new("ls")
    ///     .arg("-l")
    ///     .arg("-a")
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn arg<S: AsRef<OsStr>>(&mut self, arg: S) -> &mut Command {
        self.inner.arg(arg.as_ref());
        self
    }

    /// Adds multiple arguments to pass to the program.
    ///
    /// To pass a single argument see [`arg`].
    ///
    /// [`arg`]: Command::arg
    ///
    /// Note that the arguments are not passed through a shell, but given
    /// literally to the program. This means that shell syntax like quotes,
    /// escaped characters, word splitting, glob patterns, variable substitution, etc.
    /// have no effect.
    ///
    /// <div class="warning">
    ///
    /// On Windows, use caution with untrusted inputs. Most applications use the
    /// standard convention for decoding arguments passed to them. These are safe to
    /// use with `arg`. However, some applications such as `cmd.exe` and `.bat` files
    /// use a non-standard way of decoding arguments. They are therefore vulnerable
    /// to malicious input.
    ///
    /// In the case of `cmd.exe` this is especially important because a malicious
    /// argument can potentially run arbitrary shell commands.
    ///
    /// See [Windows argument splitting][windows-args] for more details
    /// or [`raw_arg`] for manually implementing non-standard argument encoding.
    ///
    /// [`raw_arg`]: crate::os::windows::process::CommandExt::raw_arg
    /// [windows-args]: crate::process#windows-argument-splitting
    ///
    /// </div>
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// Command::new("ls")
    ///     .args(["-l", "-a"])
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn args<I, S>(&mut self, args: I) -> &mut Command
    where
        I: IntoIterator<Item = S>,
        S: AsRef<OsStr>,
    {
        for arg in args {
            self.arg(arg.as_ref());
        }
        self
    }

    /// Inserts or updates an explicit environment variable mapping.
    ///
    /// This method allows you to add an environment variable mapping to the spawned process or
    /// overwrite a previously set value. You can use [`Command::envs`] to set multiple environment
    /// variables simultaneously.
    ///
    /// Child processes will inherit environment variables from their parent process by default.
    /// Environment variables explicitly set using [`Command::env`] take precedence over inherited
    /// variables. You can disable environment variable inheritance entirely using
    /// [`Command::env_clear`] or for a single key using [`Command::env_remove`].
    ///
    /// Note that environment variable names are case-insensitive (but
    /// case-preserving) on Windows and case-sensitive on all other platforms.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// Command::new("ls")
    ///     .env("PATH", "/bin")
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn env<K, V>(&mut self, key: K, val: V) -> &mut Command
    where
        K: AsRef<OsStr>,
        V: AsRef<OsStr>,
    {
        self.inner.env_mut().set(key.as_ref(), val.as_ref());
        self
    }

    /// Inserts or updates multiple explicit environment variable mappings.
    ///
    /// This method allows you to add multiple environment variable mappings to the spawned process
    /// or overwrite previously set values. You can use [`Command::env`] to set a single environment
    /// variable.
    ///
    /// Child processes will inherit environment variables from their parent process by default.
    /// Environment variables explicitly set using [`Command::envs`] take precedence over inherited
    /// variables. You can disable environment variable inheritance entirely using
    /// [`Command::env_clear`] or for a single key using [`Command::env_remove`].
    ///
    /// Note that environment variable names are case-insensitive (but case-preserving) on Windows
    /// and case-sensitive on all other platforms.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::{Command, Stdio};
    /// use std::env;
    /// use std::collections::HashMap;
    ///
    /// let filtered_env : HashMap<String, String> =
    ///     env::vars().filter(|&(ref k, _)|
    ///         k == "TERM" || k == "TZ" || k == "LANG" || k == "PATH"
    ///     ).collect();
    ///
    /// Command::new("printenv")
    ///     .stdin(Stdio::null())
    ///     .stdout(Stdio::inherit())
    ///     .env_clear()
    ///     .envs(&filtered_env)
    ///     .spawn()
    ///     .expect("printenv failed to start");
    /// ```
    #[stable(feature = "command_envs", since = "1.19.0")]
    pub fn envs<I, K, V>(&mut self, vars: I) -> &mut Command
    where
        I: IntoIterator<Item = (K, V)>,
        K: AsRef<OsStr>,
        V: AsRef<OsStr>,
    {
        for (ref key, ref val) in vars {
            self.inner.env_mut().set(key.as_ref(), val.as_ref());
        }
        self
    }

    /// Removes an explicitly set environment variable and prevents inheriting it from a parent
    /// process.
    ///
    /// This method will remove the explicit value of an environment variable set via
    /// [`Command::env`] or [`Command::envs`]. In addition, it will prevent the spawned child
    /// process from inheriting that environment variable from its parent process.
    ///
    /// After calling [`Command::env_remove`], the value associated with its key from
    /// [`Command::get_envs`] will be [`None`].
    ///
    /// To clear all explicitly set environment variables and disable all environment variable
    /// inheritance, you can use [`Command::env_clear`].
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// Command::new("ls")
    ///     .env_remove("PATH")
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn env_remove<K: AsRef<OsStr>>(&mut self, key: K) -> &mut Command {
        self.inner.env_mut().remove(key.as_ref());
        self
    }

    /// Clears all explicitly set environment variables and prevents inheriting any parent process
    /// environment variables.
    ///
    /// This method will remove all explicitly added environment variables set via [`Command::env`]
    /// or [`Command::envs`]. In addition, it will prevent the spawned child process from inheriting
    /// any environment variable from its parent process.
    ///
    /// After calling [`Command::env_clear`], the iterator from [`Command::get_envs`] will be
    /// empty.
    ///
    /// You can use [`Command::env_remove`] to clear a single mapping.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// Command::new("ls")
    ///     .env_clear()
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn env_clear(&mut self) -> &mut Command {
        self.inner.env_mut().clear();
        self
    }

    /// Sets the working directory for the child process.
    ///
    /// # Platform-specific behavior
    ///
    /// If the program path is relative (e.g., `"./script.sh"`), it's ambiguous
    /// whether it should be interpreted relative to the parent's working
    /// directory or relative to `current_dir`. The behavior in this case is
    /// platform specific and unstable, and it's recommended to use
    /// [`canonicalize`] to get an absolute program path instead.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// Command::new("ls")
    ///     .current_dir("/bin")
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    ///
    /// [`canonicalize`]: crate::fs::canonicalize
    #[stable(feature = "process", since = "1.0.0")]
    pub fn current_dir<P: AsRef<Path>>(&mut self, dir: P) -> &mut Command {
        self.inner.cwd(dir.as_ref().as_ref());
        self
    }

    /// Configuration for the child process's standard input (stdin) handle.
    ///
    /// Defaults to [`inherit`] when used with [`spawn`] or [`status`], and
    /// defaults to [`piped`] when used with [`output`].
    ///
    /// [`inherit`]: Stdio::inherit
    /// [`piped`]: Stdio::piped
    /// [`spawn`]: Self::spawn
    /// [`status`]: Self::status
    /// [`output`]: Self::output
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::{Command, Stdio};
    ///
    /// Command::new("ls")
    ///     .stdin(Stdio::null())
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn stdin<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
        self.inner.stdin(cfg.into().0);
        self
    }

    /// Configuration for the child process's standard output (stdout) handle.
    ///
    /// Defaults to [`inherit`] when used with [`spawn`] or [`status`], and
    /// defaults to [`piped`] when used with [`output`].
    ///
    /// [`inherit`]: Stdio::inherit
    /// [`piped`]: Stdio::piped
    /// [`spawn`]: Self::spawn
    /// [`status`]: Self::status
    /// [`output`]: Self::output
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::{Command, Stdio};
    ///
    /// Command::new("ls")
    ///     .stdout(Stdio::null())
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn stdout<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
        self.inner.stdout(cfg.into().0);
        self
    }

    /// Configuration for the child process's standard error (stderr) handle.
    ///
    /// Defaults to [`inherit`] when used with [`spawn`] or [`status`], and
    /// defaults to [`piped`] when used with [`output`].
    ///
    /// [`inherit`]: Stdio::inherit
    /// [`piped`]: Stdio::piped
    /// [`spawn`]: Self::spawn
    /// [`status`]: Self::status
    /// [`output`]: Self::output
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::{Command, Stdio};
    ///
    /// Command::new("ls")
    ///     .stderr(Stdio::null())
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn stderr<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
        self.inner.stderr(cfg.into().0);
        self
    }

    /// Executes the command as a child process, returning a handle to it.
    ///
    /// By default, stdin, stdout and stderr are inherited from the parent.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// Command::new("ls")
    ///     .spawn()
    ///     .expect("ls command failed to start");
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn spawn(&mut self) -> io::Result<Child> {
        self.inner.spawn(imp::Stdio::Inherit, true).map(Child::from_inner)
    }

    /// Executes the command as a child process, waiting for it to finish and
    /// collecting all of its output.
    ///
    /// By default, stdout and stderr are captured (and used to provide the
    /// resulting output). Stdin is not inherited from the parent and any
    /// attempt by the child process to read from the stdin stream will result
    /// in the stream immediately closing.
    ///
    /// # Examples
    ///
    /// ```should_panic
    /// use std::process::Command;
    /// use std::io::{self, Write};
    /// let output = Command::new("/bin/cat")
    ///     .arg("file.txt")
    ///     .output()
    ///     .expect("failed to execute process");
    ///
    /// println!("status: {}", output.status);
    /// io::stdout().write_all(&output.stdout).unwrap();
    /// io::stderr().write_all(&output.stderr).unwrap();
    ///
    /// assert!(output.status.success());
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn output(&mut self) -> io::Result<Output> {
        let (status, stdout, stderr) = self.inner.output()?;
        Ok(Output { status: ExitStatus(status), stdout, stderr })
    }

    /// Executes a command as a child process, waiting for it to finish and
    /// collecting its status.
    ///
    /// By default, stdin, stdout and stderr are inherited from the parent.
    ///
    /// # Examples
    ///
    /// ```should_panic
    /// use std::process::Command;
    ///
    /// let status = Command::new("/bin/cat")
    ///     .arg("file.txt")
    ///     .status()
    ///     .expect("failed to execute process");
    ///
    /// println!("process finished with: {status}");
    ///
    /// assert!(status.success());
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn status(&mut self) -> io::Result<ExitStatus> {
        self.inner
            .spawn(imp::Stdio::Inherit, true)
            .map(Child::from_inner)
            .and_then(|mut p| p.wait())
    }

    /// Returns the path to the program that was given to [`Command::new`].
    ///
    /// # Examples
    ///
    /// ```
    /// use std::process::Command;
    ///
    /// let cmd = Command::new("echo");
    /// assert_eq!(cmd.get_program(), "echo");
    /// ```
    #[must_use]
    #[stable(feature = "command_access", since = "1.57.0")]
    pub fn get_program(&self) -> &OsStr {
        self.inner.get_program()
    }

    /// Returns an iterator of the arguments that will be passed to the program.
    ///
    /// This does not include the path to the program as the first argument;
    /// it only includes the arguments specified with [`Command::arg`] and
    /// [`Command::args`].
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ffi::OsStr;
    /// use std::process::Command;
    ///
    /// let mut cmd = Command::new("echo");
    /// cmd.arg("first").arg("second");
    /// let args: Vec<&OsStr> = cmd.get_args().collect();
    /// assert_eq!(args, &["first", "second"]);
    /// ```
    #[stable(feature = "command_access", since = "1.57.0")]
    pub fn get_args(&self) -> CommandArgs<'_> {
        CommandArgs { inner: self.inner.get_args() }
    }

    /// Returns an iterator of the environment variables explicitly set for the child process.
    ///
    /// Environment variables explicitly set using [`Command::env`], [`Command::envs`], and
    /// [`Command::env_remove`] can be retrieved with this method.
    ///
    /// Note that this output does not include environment variables inherited from the parent
    /// process.
    ///
    /// Each element is a tuple key/value pair `(&OsStr, Option<&OsStr>)`. A [`None`] value
    /// indicates its key was explicitly removed via [`Command::env_remove`]. The associated key for
    /// the [`None`] value will no longer inherit from its parent process.
    ///
    /// An empty iterator can indicate that no explicit mappings were added or that
    /// [`Command::env_clear`] was called. After calling [`Command::env_clear`], the child process
    /// will not inherit any environment variables from its parent process.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ffi::OsStr;
    /// use std::process::Command;
    ///
    /// let mut cmd = Command::new("ls");
    /// cmd.env("TERM", "dumb").env_remove("TZ");
    /// let envs: Vec<(&OsStr, Option<&OsStr>)> = cmd.get_envs().collect();
    /// assert_eq!(envs, &[
    ///     (OsStr::new("TERM"), Some(OsStr::new("dumb"))),
    ///     (OsStr::new("TZ"), None)
    /// ]);
    /// ```
    #[stable(feature = "command_access", since = "1.57.0")]
    pub fn get_envs(&self) -> CommandEnvs<'_> {
        self.inner.get_envs()
    }

    /// Returns the working directory for the child process.
    ///
    /// This returns [`None`] if the working directory will not be changed.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::path::Path;
    /// use std::process::Command;
    ///
    /// let mut cmd = Command::new("ls");
    /// assert_eq!(cmd.get_current_dir(), None);
    /// cmd.current_dir("/bin");
    /// assert_eq!(cmd.get_current_dir(), Some(Path::new("/bin")));
    /// ```
    #[must_use]
    #[stable(feature = "command_access", since = "1.57.0")]
    pub fn get_current_dir(&self) -> Option<&Path> {
        self.inner.get_current_dir()
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for Command {
    /// Format the program and arguments of a Command for display. Any
    /// non-utf8 data is lossily converted using the utf8 replacement
    /// character.
    ///
    /// The default format approximates a shell invocation of the program along with its
    /// arguments. It does not include most of the other command properties. The output is not guaranteed to work
    /// (e.g. due to lack of shell-escaping or differences in path resolution).
    /// On some platforms you can use [the alternate syntax] to show more fields.
    ///
    /// Note that the debug implementation is platform-specific.
    ///
    /// [the alternate syntax]: fmt#sign0
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.inner.fmt(f)
    }
}

impl AsInner<imp::Command> for Command {
    #[inline]
    fn as_inner(&self) -> &imp::Command {
        &self.inner
    }
}

impl AsInnerMut<imp::Command> for Command {
    #[inline]
    fn as_inner_mut(&mut self) -> &mut imp::Command {
        &mut self.inner
    }
}

/// An iterator over the command arguments.
///
/// This struct is created by [`Command::get_args`]. See its documentation for
/// more.
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "command_access", since = "1.57.0")]
#[derive(Debug)]
pub struct CommandArgs<'a> {
    inner: imp::CommandArgs<'a>,
}

#[stable(feature = "command_access", since = "1.57.0")]
impl<'a> Iterator for CommandArgs<'a> {
    type Item = &'a OsStr;
    fn next(&mut self) -> Option<&'a OsStr> {
        self.inner.next()
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.inner.size_hint()
    }
}

#[stable(feature = "command_access", since = "1.57.0")]
impl<'a> ExactSizeIterator for CommandArgs<'a> {
    fn len(&self) -> usize {
        self.inner.len()
    }
    fn is_empty(&self) -> bool {
        self.inner.is_empty()
    }
}

/// The output of a finished process.
///
/// This is returned in a Result by either the [`output`] method of a
/// [`Command`], or the [`wait_with_output`] method of a [`Child`]
/// process.
///
/// [`output`]: Command::output
/// [`wait_with_output`]: Child::wait_with_output
#[derive(PartialEq, Eq, Clone)]
#[stable(feature = "process", since = "1.0.0")]
pub struct Output {
    /// The status (exit code) of the process.
    #[stable(feature = "process", since = "1.0.0")]
    pub status: ExitStatus,
    /// The data that the process wrote to stdout.
    #[stable(feature = "process", since = "1.0.0")]
    pub stdout: Vec<u8>,
    /// The data that the process wrote to stderr.
    #[stable(feature = "process", since = "1.0.0")]
    pub stderr: Vec<u8>,
}

// If either stderr or stdout are valid utf8 strings it prints the valid
// strings, otherwise it prints the byte sequence instead
#[stable(feature = "process_output_debug", since = "1.7.0")]
impl fmt::Debug for Output {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        let stdout_utf8 = str::from_utf8(&self.stdout);
        let stdout_debug: &dyn fmt::Debug = match stdout_utf8 {
            Ok(ref str) => str,
            Err(_) => &self.stdout,
        };

        let stderr_utf8 = str::from_utf8(&self.stderr);
        let stderr_debug: &dyn fmt::Debug = match stderr_utf8 {
            Ok(ref str) => str,
            Err(_) => &self.stderr,
        };

        fmt.debug_struct("Output")
            .field("status", &self.status)
            .field("stdout", stdout_debug)
            .field("stderr", stderr_debug)
            .finish()
    }
}

/// Describes what to do with a standard I/O stream for a child process when
/// passed to the [`stdin`], [`stdout`], and [`stderr`] methods of [`Command`].
///
/// [`stdin`]: Command::stdin
/// [`stdout`]: Command::stdout
/// [`stderr`]: Command::stderr
#[stable(feature = "process", since = "1.0.0")]
pub struct Stdio(imp::Stdio);

impl Stdio {
    /// A new pipe should be arranged to connect the parent and child processes.
    ///
    /// # Examples
    ///
    /// With stdout:
    ///
    /// ```no_run
    /// use std::process::{Command, Stdio};
    ///
    /// let output = Command::new("echo")
    ///     .arg("Hello, world!")
    ///     .stdout(Stdio::piped())
    ///     .output()
    ///     .expect("Failed to execute command");
    ///
    /// assert_eq!(String::from_utf8_lossy(&output.stdout), "Hello, world!\n");
    /// // Nothing echoed to console
    /// ```
    ///
    /// With stdin:
    ///
    /// ```no_run
    /// use std::io::Write;
    /// use std::process::{Command, Stdio};
    ///
    /// let mut child = Command::new("rev")
    ///     .stdin(Stdio::piped())
    ///     .stdout(Stdio::piped())
    ///     .spawn()
    ///     .expect("Failed to spawn child process");
    ///
    /// let mut stdin = child.stdin.take().expect("Failed to open stdin");
    /// std::thread::spawn(move || {
    ///     stdin.write_all("Hello, world!".as_bytes()).expect("Failed to write to stdin");
    /// });
    ///
    /// let output = child.wait_with_output().expect("Failed to read stdout");
    /// assert_eq!(String::from_utf8_lossy(&output.stdout), "!dlrow ,olleH");
    /// ```
    ///
    /// Writing more than a pipe buffer's worth of input to stdin without also reading
    /// stdout and stderr at the same time may cause a deadlock.
    /// This is an issue when running any program that doesn't guarantee that it reads
    /// its entire stdin before writing more than a pipe buffer's worth of output.
    /// The size of a pipe buffer varies on different targets.
    ///
    #[must_use]
    #[stable(feature = "process", since = "1.0.0")]
    pub fn piped() -> Stdio {
        Stdio(imp::Stdio::MakePipe)
    }

    /// The child inherits from the corresponding parent descriptor.
    ///
    /// # Examples
    ///
    /// With stdout:
    ///
    /// ```no_run
    /// use std::process::{Command, Stdio};
    ///
    /// let output = Command::new("echo")
    ///     .arg("Hello, world!")
    ///     .stdout(Stdio::inherit())
    ///     .output()
    ///     .expect("Failed to execute command");
    ///
    /// assert_eq!(String::from_utf8_lossy(&output.stdout), "");
    /// // "Hello, world!" echoed to console
    /// ```
    ///
    /// With stdin:
    ///
    /// ```no_run
    /// use std::process::{Command, Stdio};
    /// use std::io::{self, Write};
    ///
    /// let output = Command::new("rev")
    ///     .stdin(Stdio::inherit())
    ///     .stdout(Stdio::piped())
    ///     .output()
    ///     .expect("Failed to execute command");
    ///
    /// print!("You piped in the reverse of: ");
    /// io::stdout().write_all(&output.stdout).unwrap();
    /// ```
    #[must_use]
    #[stable(feature = "process", since = "1.0.0")]
    pub fn inherit() -> Stdio {
        Stdio(imp::Stdio::Inherit)
    }

    /// This stream will be ignored. This is the equivalent of attaching the
    /// stream to `/dev/null`.
    ///
    /// # Examples
    ///
    /// With stdout:
    ///
    /// ```no_run
    /// use std::process::{Command, Stdio};
    ///
    /// let output = Command::new("echo")
    ///     .arg("Hello, world!")
    ///     .stdout(Stdio::null())
    ///     .output()
    ///     .expect("Failed to execute command");
    ///
    /// assert_eq!(String::from_utf8_lossy(&output.stdout), "");
    /// // Nothing echoed to console
    /// ```
    ///
    /// With stdin:
    ///
    /// ```no_run
    /// use std::process::{Command, Stdio};
    ///
    /// let output = Command::new("rev")
    ///     .stdin(Stdio::null())
    ///     .stdout(Stdio::piped())
    ///     .output()
    ///     .expect("Failed to execute command");
    ///
    /// assert_eq!(String::from_utf8_lossy(&output.stdout), "");
    /// // Ignores any piped-in input
    /// ```
    #[must_use]
    #[stable(feature = "process", since = "1.0.0")]
    pub fn null() -> Stdio {
        Stdio(imp::Stdio::Null)
    }

    /// Returns `true` if this requires [`Command`] to create a new pipe.
    ///
    /// # Example
    ///
    /// ```
    /// #![feature(stdio_makes_pipe)]
    /// use std::process::Stdio;
    ///
    /// let io = Stdio::piped();
    /// assert_eq!(io.makes_pipe(), true);
    /// ```
    #[unstable(feature = "stdio_makes_pipe", issue = "98288")]
    pub fn makes_pipe(&self) -> bool {
        matches!(self.0, imp::Stdio::MakePipe)
    }
}

impl FromInner<imp::Stdio> for Stdio {
    fn from_inner(inner: imp::Stdio) -> Stdio {
        Stdio(inner)
    }
}

#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for Stdio {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Stdio").finish_non_exhaustive()
    }
}

#[stable(feature = "stdio_from", since = "1.20.0")]
impl From<ChildStdin> for Stdio {
    /// Converts a [`ChildStdin`] into a [`Stdio`].
    ///
    /// # Examples
    ///
    /// `ChildStdin` will be converted to `Stdio` using `Stdio::from` under the hood.
    ///
    /// ```rust,no_run
    /// use std::process::{Command, Stdio};
    ///
    /// let reverse = Command::new("rev")
    ///     .stdin(Stdio::piped())
    ///     .spawn()
    ///     .expect("failed reverse command");
    ///
    /// let _echo = Command::new("echo")
    ///     .arg("Hello, world!")
    ///     .stdout(reverse.stdin.unwrap()) // Converted into a Stdio here
    ///     .output()
    ///     .expect("failed echo command");
    ///
    /// // "!dlrow ,olleH" echoed to console
    /// ```
    fn from(child: ChildStdin) -> Stdio {
        Stdio::from_inner(child.into_inner().into())
    }
}

#[stable(feature = "stdio_from", since = "1.20.0")]
impl From<ChildStdout> for Stdio {
    /// Converts a [`ChildStdout`] into a [`Stdio`].
    ///
    /// # Examples
    ///
    /// `ChildStdout` will be converted to `Stdio` using `Stdio::from` under the hood.
    ///
    /// ```rust,no_run
    /// use std::process::{Command, Stdio};
    ///
    /// let hello = Command::new("echo")
    ///     .arg("Hello, world!")
    ///     .stdout(Stdio::piped())
    ///     .spawn()
    ///     .expect("failed echo command");
    ///
    /// let reverse = Command::new("rev")
    ///     .stdin(hello.stdout.unwrap())  // Converted into a Stdio here
    ///     .output()
    ///     .expect("failed reverse command");
    ///
    /// assert_eq!(reverse.stdout, b"!dlrow ,olleH\n");
    /// ```
    fn from(child: ChildStdout) -> Stdio {
        Stdio::from_inner(child.into_inner().into())
    }
}

#[stable(feature = "stdio_from", since = "1.20.0")]
impl From<ChildStderr> for Stdio {
    /// Converts a [`ChildStderr`] into a [`Stdio`].
    ///
    /// # Examples
    ///
    /// ```rust,no_run
    /// use std::process::{Command, Stdio};
    ///
    /// let reverse = Command::new("rev")
    ///     .arg("non_existing_file.txt")
    ///     .stderr(Stdio::piped())
    ///     .spawn()
    ///     .expect("failed reverse command");
    ///
    /// let cat = Command::new("cat")
    ///     .arg("-")
    ///     .stdin(reverse.stderr.unwrap()) // Converted into a Stdio here
    ///     .output()
    ///     .expect("failed echo command");
    ///
    /// assert_eq!(
    ///     String::from_utf8_lossy(&cat.stdout),
    ///     "rev: cannot open non_existing_file.txt: No such file or directory\n"
    /// );
    /// ```
    fn from(child: ChildStderr) -> Stdio {
        Stdio::from_inner(child.into_inner().into())
    }
}

#[stable(feature = "stdio_from", since = "1.20.0")]
impl From<fs::File> for Stdio {
    /// Converts a [`File`](fs::File) into a [`Stdio`].
    ///
    /// # Examples
    ///
    /// `File` will be converted to `Stdio` using `Stdio::from` under the hood.
    ///
    /// ```rust,no_run
    /// use std::fs::File;
    /// use std::process::Command;
    ///
    /// // With the `foo.txt` file containing "Hello, world!"
    /// let file = File::open("foo.txt").unwrap();
    ///
    /// let reverse = Command::new("rev")
    ///     .stdin(file)  // Implicit File conversion into a Stdio
    ///     .output()
    ///     .expect("failed reverse command");
    ///
    /// assert_eq!(reverse.stdout, b"!dlrow ,olleH");
    /// ```
    fn from(file: fs::File) -> Stdio {
        Stdio::from_inner(file.into_inner().into())
    }
}

#[stable(feature = "stdio_from_stdio", since = "1.74.0")]
impl From<io::Stdout> for Stdio {
    /// Redirect command stdout/stderr to our stdout
    ///
    /// # Examples
    ///
    /// ```rust
    /// #![feature(exit_status_error)]
    /// use std::io;
    /// use std::process::Command;
    ///
    /// # fn test() -> Result<(), Box<dyn std::error::Error>> {
    /// let output = Command::new("whoami")
    // "whoami" is a command which exists on both Unix and Windows,
    // and which succeeds, producing some stdout output but no stderr.
    ///     .stdout(io::stdout())
    ///     .output()?;
    /// output.status.exit_ok()?;
    /// assert!(output.stdout.is_empty());
    /// # Ok(())
    /// # }
    /// #
    /// # if cfg!(unix) {
    /// #     test().unwrap();
    /// # }
    /// ```
    fn from(inherit: io::Stdout) -> Stdio {
        Stdio::from_inner(inherit.into())
    }
}

#[stable(feature = "stdio_from_stdio", since = "1.74.0")]
impl From<io::Stderr> for Stdio {
    /// Redirect command stdout/stderr to our stderr
    ///
    /// # Examples
    ///
    /// ```rust
    /// #![feature(exit_status_error)]
    /// use std::io;
    /// use std::process::Command;
    ///
    /// # fn test() -> Result<(), Box<dyn std::error::Error>> {
    /// let output = Command::new("whoami")
    ///     .stdout(io::stderr())
    ///     .output()?;
    /// output.status.exit_ok()?;
    /// assert!(output.stdout.is_empty());
    /// # Ok(())
    /// # }
    /// #
    /// # if cfg!(unix) {
    /// #     test().unwrap();
    /// # }
    /// ```
    fn from(inherit: io::Stderr) -> Stdio {
        Stdio::from_inner(inherit.into())
    }
}

/// Describes the result of a process after it has terminated.
///
/// This `struct` is used to represent the exit status or other termination of a child process.
/// Child processes are created via the [`Command`] struct and their exit
/// status is exposed through the [`status`] method, or the [`wait`] method
/// of a [`Child`] process.
///
/// An `ExitStatus` represents every possible disposition of a process.  On Unix this
/// is the **wait status**.  It is *not* simply an *exit status* (a value passed to `exit`).
///
/// For proper error reporting of failed processes, print the value of `ExitStatus` or
/// `ExitStatusError` using their implementations of [`Display`](crate::fmt::Display).
///
/// # Differences from `ExitCode`
///
/// [`ExitCode`] is intended for terminating the currently running process, via
/// the `Termination` trait, in contrast to `ExitStatus`, which represents the
/// termination of a child process. These APIs are separate due to platform
/// compatibility differences and their expected usage; it is not generally
/// possible to exactly reproduce an `ExitStatus` from a child for the current
/// process after the fact.
///
/// [`status`]: Command::status
/// [`wait`]: Child::wait
//
// We speak slightly loosely (here and in various other places in the stdlib docs) about `exit`
// vs `_exit`.  Naming of Unix system calls is not standardised across Unices, so terminology is a
// matter of convention and tradition.  For clarity we usually speak of `exit`, even when we might
// mean an underlying system call such as `_exit`.
#[derive(PartialEq, Eq, Clone, Copy, Debug)]
#[stable(feature = "process", since = "1.0.0")]
pub struct ExitStatus(imp::ExitStatus);

/// The default value is one which indicates successful completion.
#[stable(feature = "process_exitstatus_default", since = "1.73.0")]
impl Default for ExitStatus {
    fn default() -> Self {
        // Ideally this would be done by ExitCode::default().into() but that is complicated.
        ExitStatus::from_inner(imp::ExitStatus::default())
    }
}

/// Allows extension traits within `std`.
#[unstable(feature = "sealed", issue = "none")]
impl crate::sealed::Sealed for ExitStatus {}

impl ExitStatus {
    /// Was termination successful?  Returns a `Result`.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(exit_status_error)]
    /// # if cfg!(unix) {
    /// use std::process::Command;
    ///
    /// let status = Command::new("ls")
    ///     .arg("/dev/nonexistent")
    ///     .status()
    ///     .expect("ls could not be executed");
    ///
    /// println!("ls: {status}");
    /// status.exit_ok().expect_err("/dev/nonexistent could be listed!");
    /// # } // cfg!(unix)
    /// ```
    #[unstable(feature = "exit_status_error", issue = "84908")]
    pub fn exit_ok(&self) -> Result<(), ExitStatusError> {
        self.0.exit_ok().map_err(ExitStatusError)
    }

    /// Was termination successful? Signal termination is not considered a
    /// success, and success is defined as a zero exit status.
    ///
    /// # Examples
    ///
    /// ```rust,no_run
    /// use std::process::Command;
    ///
    /// let status = Command::new("mkdir")
    ///     .arg("projects")
    ///     .status()
    ///     .expect("failed to execute mkdir");
    ///
    /// if status.success() {
    ///     println!("'projects/' directory created");
    /// } else {
    ///     println!("failed to create 'projects/' directory: {status}");
    /// }
    /// ```
    #[must_use]
    #[stable(feature = "process", since = "1.0.0")]
    pub fn success(&self) -> bool {
        self.0.exit_ok().is_ok()
    }

    /// Returns the exit code of the process, if any.
    ///
    /// In Unix terms the return value is the **exit status**: the value passed to `exit`, if the
    /// process finished by calling `exit`.  Note that on Unix the exit status is truncated to 8
    /// bits, and that values that didn't come from a program's call to `exit` may be invented by the
    /// runtime system (often, for example, 255, 254, 127 or 126).
    ///
    /// On Unix, this will return `None` if the process was terminated by a signal.
    /// [`ExitStatusExt`](crate::os::unix::process::ExitStatusExt) is an
    /// extension trait for extracting any such signal, and other details, from the `ExitStatus`.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// let status = Command::new("mkdir")
    ///     .arg("projects")
    ///     .status()
    ///     .expect("failed to execute mkdir");
    ///
    /// match status.code() {
    ///     Some(code) => println!("Exited with status code: {code}"),
    ///     None => println!("Process terminated by signal")
    /// }
    /// ```
    #[must_use]
    #[stable(feature = "process", since = "1.0.0")]
    pub fn code(&self) -> Option<i32> {
        self.0.code()
    }
}

impl AsInner<imp::ExitStatus> for ExitStatus {
    #[inline]
    fn as_inner(&self) -> &imp::ExitStatus {
        &self.0
    }
}

impl FromInner<imp::ExitStatus> for ExitStatus {
    fn from_inner(s: imp::ExitStatus) -> ExitStatus {
        ExitStatus(s)
    }
}

#[stable(feature = "process", since = "1.0.0")]
impl fmt::Display for ExitStatus {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)
    }
}

/// Allows extension traits within `std`.
#[unstable(feature = "sealed", issue = "none")]
impl crate::sealed::Sealed for ExitStatusError {}

/// Describes the result of a process after it has failed
///
/// Produced by the [`.exit_ok`](ExitStatus::exit_ok) method on [`ExitStatus`].
///
/// # Examples
///
/// ```
/// #![feature(exit_status_error)]
/// # if cfg!(unix) {
/// use std::process::{Command, ExitStatusError};
///
/// fn run(cmd: &str) -> Result<(),ExitStatusError> {
///     Command::new(cmd).status().unwrap().exit_ok()?;
///     Ok(())
/// }
///
/// run("true").unwrap();
/// run("false").unwrap_err();
/// # } // cfg!(unix)
/// ```
#[derive(PartialEq, Eq, Clone, Copy, Debug)]
#[unstable(feature = "exit_status_error", issue = "84908")]
// The definition of imp::ExitStatusError should ideally be such that
// Result<(), imp::ExitStatusError> has an identical representation to imp::ExitStatus.
pub struct ExitStatusError(imp::ExitStatusError);

#[unstable(feature = "exit_status_error", issue = "84908")]
impl ExitStatusError {
    /// Reports the exit code, if applicable, from an `ExitStatusError`.
    ///
    /// In Unix terms the return value is the **exit status**: the value passed to `exit`, if the
    /// process finished by calling `exit`.  Note that on Unix the exit status is truncated to 8
    /// bits, and that values that didn't come from a program's call to `exit` may be invented by the
    /// runtime system (often, for example, 255, 254, 127 or 126).
    ///
    /// On Unix, this will return `None` if the process was terminated by a signal.  If you want to
    /// handle such situations specially, consider using methods from
    /// [`ExitStatusExt`](crate::os::unix::process::ExitStatusExt).
    ///
    /// If the process finished by calling `exit` with a nonzero value, this will return
    /// that exit status.
    ///
    /// If the error was something else, it will return `None`.
    ///
    /// If the process exited successfully (ie, by calling `exit(0)`), there is no
    /// `ExitStatusError`.  So the return value from `ExitStatusError::code()` is always nonzero.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(exit_status_error)]
    /// # #[cfg(unix)] {
    /// use std::process::Command;
    ///
    /// let bad = Command::new("false").status().unwrap().exit_ok().unwrap_err();
    /// assert_eq!(bad.code(), Some(1));
    /// # } // #[cfg(unix)]
    /// ```
    #[must_use]
    pub fn code(&self) -> Option<i32> {
        self.code_nonzero().map(Into::into)
    }

    /// Reports the exit code, if applicable, from an `ExitStatusError`, as a [`NonZero`].
    ///
    /// This is exactly like [`code()`](Self::code), except that it returns a <code>[NonZero]<[i32]></code>.
    ///
    /// Plain `code`, returning a plain integer, is provided because it is often more convenient.
    /// The returned value from `code()` is indeed also nonzero; use `code_nonzero()` when you want
    /// a type-level guarantee of nonzeroness.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(exit_status_error)]
    ///
    /// # if cfg!(unix) {
    /// use std::num::NonZero;
    /// use std::process::Command;
    ///
    /// let bad = Command::new("false").status().unwrap().exit_ok().unwrap_err();
    /// assert_eq!(bad.code_nonzero().unwrap(), NonZero::new(1).unwrap());
    /// # } // cfg!(unix)
    /// ```
    #[must_use]
    pub fn code_nonzero(&self) -> Option<NonZero<i32>> {
        self.0.code()
    }

    /// Converts an `ExitStatusError` (back) to an `ExitStatus`.
    #[must_use]
    pub fn into_status(&self) -> ExitStatus {
        ExitStatus(self.0.into())
    }
}

#[unstable(feature = "exit_status_error", issue = "84908")]
impl From<ExitStatusError> for ExitStatus {
    fn from(error: ExitStatusError) -> Self {
        Self(error.0.into())
    }
}

#[unstable(feature = "exit_status_error", issue = "84908")]
impl fmt::Display for ExitStatusError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "process exited unsuccessfully: {}", self.into_status())
    }
}

#[unstable(feature = "exit_status_error", issue = "84908")]
impl crate::error::Error for ExitStatusError {}

/// This type represents the status code the current process can return
/// to its parent under normal termination.
///
/// `ExitCode` is intended to be consumed only by the standard library (via
/// [`Termination::report()`]), and intentionally does not provide accessors like
/// `PartialEq`, `Eq`, or `Hash`. Instead the standard library provides the
/// canonical `SUCCESS` and `FAILURE` exit codes as well as `From<u8> for
/// ExitCode` for constructing other arbitrary exit codes.
///
/// # Portability
///
/// Numeric values used in this type don't have portable meanings, and
/// different platforms may mask different amounts of them.
///
/// For the platform's canonical successful and unsuccessful codes, see
/// the [`SUCCESS`] and [`FAILURE`] associated items.
///
/// [`SUCCESS`]: ExitCode::SUCCESS
/// [`FAILURE`]: ExitCode::FAILURE
///
/// # Differences from `ExitStatus`
///
/// `ExitCode` is intended for terminating the currently running process, via
/// the `Termination` trait, in contrast to [`ExitStatus`], which represents the
/// termination of a child process. These APIs are separate due to platform
/// compatibility differences and their expected usage; it is not generally
/// possible to exactly reproduce an `ExitStatus` from a child for the current
/// process after the fact.
///
/// # Examples
///
/// `ExitCode` can be returned from the `main` function of a crate, as it implements
/// [`Termination`]:
///
/// ```
/// use std::process::ExitCode;
/// # fn check_foo() -> bool { true }
///
/// fn main() -> ExitCode {
///     if !check_foo() {
///         return ExitCode::from(42);
///     }
///
///     ExitCode::SUCCESS
/// }
/// ```
#[derive(Clone, Copy, Debug)]
#[stable(feature = "process_exitcode", since = "1.61.0")]
pub struct ExitCode(imp::ExitCode);

/// Allows extension traits within `std`.
#[unstable(feature = "sealed", issue = "none")]
impl crate::sealed::Sealed for ExitCode {}

#[stable(feature = "process_exitcode", since = "1.61.0")]
impl ExitCode {
    /// The canonical `ExitCode` for successful termination on this platform.
    ///
    /// Note that a `()`-returning `main` implicitly results in a successful
    /// termination, so there's no need to return this from `main` unless
    /// you're also returning other possible codes.
    #[stable(feature = "process_exitcode", since = "1.61.0")]
    pub const SUCCESS: ExitCode = ExitCode(imp::ExitCode::SUCCESS);

    /// The canonical `ExitCode` for unsuccessful termination on this platform.
    ///
    /// If you're only returning this and `SUCCESS` from `main`, consider
    /// instead returning `Err(_)` and `Ok(())` respectively, which will
    /// return the same codes (but will also `eprintln!` the error).
    #[stable(feature = "process_exitcode", since = "1.61.0")]
    pub const FAILURE: ExitCode = ExitCode(imp::ExitCode::FAILURE);

    /// Exit the current process with the given `ExitCode`.
    ///
    /// Note that this has the same caveats as [`process::exit()`][exit], namely that this function
    /// terminates the process immediately, so no destructors on the current stack or any other
    /// thread's stack will be run. If a clean shutdown is needed, it is recommended to simply
    /// return this ExitCode from the `main` function, as demonstrated in the [type
    /// documentation](#examples).
    ///
    /// # Differences from `process::exit()`
    ///
    /// `process::exit()` accepts any `i32` value as the exit code for the process; however, there
    /// are platforms that only use a subset of that value (see [`process::exit` platform-specific
    /// behavior][exit#platform-specific-behavior]). `ExitCode` exists because of this; only
    /// `ExitCode`s that are supported by a majority of our platforms can be created, so those
    /// problems don't exist (as much) with this method.
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(exitcode_exit_method)]
    /// # use std::process::ExitCode;
    /// # use std::fmt;
    /// # enum UhOhError { GenericProblem, Specific, WithCode { exit_code: ExitCode, _x: () } }
    /// # impl fmt::Display for UhOhError {
    /// #     fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result { unimplemented!() }
    /// # }
    /// // there's no way to gracefully recover from an UhOhError, so we just
    /// // print a message and exit
    /// fn handle_unrecoverable_error(err: UhOhError) -> ! {
    ///     eprintln!("UH OH! {err}");
    ///     let code = match err {
    ///         UhOhError::GenericProblem => ExitCode::FAILURE,
    ///         UhOhError::Specific => ExitCode::from(3),
    ///         UhOhError::WithCode { exit_code, .. } => exit_code,
    ///     };
    ///     code.exit_process()
    /// }
    /// ```
    #[unstable(feature = "exitcode_exit_method", issue = "97100")]
    pub fn exit_process(self) -> ! {
        exit(self.to_i32())
    }
}

impl ExitCode {
    // This is private/perma-unstable because ExitCode is opaque; we don't know that i32 will serve
    // all usecases, for example windows seems to use u32, unix uses the 8-15th bits of an i32, we
    // likely want to isolate users anything that could restrict the platform specific
    // representation of an ExitCode
    //
    // More info: https://internals.rust-lang.org/t/mini-pre-rfc-redesigning-process-exitstatus/5426
    /// Converts an `ExitCode` into an i32
    #[unstable(
        feature = "process_exitcode_internals",
        reason = "exposed only for libstd",
        issue = "none"
    )]
    #[inline]
    #[doc(hidden)]
    pub fn to_i32(self) -> i32 {
        self.0.as_i32()
    }
}

/// The default value is [`ExitCode::SUCCESS`]
#[stable(feature = "process_exitcode_default", since = "1.75.0")]
impl Default for ExitCode {
    fn default() -> Self {
        ExitCode::SUCCESS
    }
}

#[stable(feature = "process_exitcode", since = "1.61.0")]
impl From<u8> for ExitCode {
    /// Constructs an `ExitCode` from an arbitrary u8 value.
    fn from(code: u8) -> Self {
        ExitCode(imp::ExitCode::from(code))
    }
}

impl AsInner<imp::ExitCode> for ExitCode {
    #[inline]
    fn as_inner(&self) -> &imp::ExitCode {
        &self.0
    }
}

impl FromInner<imp::ExitCode> for ExitCode {
    fn from_inner(s: imp::ExitCode) -> ExitCode {
        ExitCode(s)
    }
}

impl Child {
    /// Forces the child process to exit. If the child has already exited, `Ok(())`
    /// is returned.
    ///
    /// The mapping to [`ErrorKind`]s is not part of the compatibility contract of the function.
    ///
    /// This is equivalent to sending a SIGKILL on Unix platforms.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// let mut command = Command::new("yes");
    /// if let Ok(mut child) = command.spawn() {
    ///     child.kill().expect("command couldn't be killed");
    /// } else {
    ///     println!("yes command didn't start");
    /// }
    /// ```
    ///
    /// [`ErrorKind`]: io::ErrorKind
    /// [`InvalidInput`]: io::ErrorKind::InvalidInput
    #[stable(feature = "process", since = "1.0.0")]
    pub fn kill(&mut self) -> io::Result<()> {
        self.handle.kill()
    }

    /// Returns the OS-assigned process identifier associated with this child.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// let mut command = Command::new("ls");
    /// if let Ok(child) = command.spawn() {
    ///     println!("Child's ID is {}", child.id());
    /// } else {
    ///     println!("ls command didn't start");
    /// }
    /// ```
    #[must_use]
    #[stable(feature = "process_id", since = "1.3.0")]
    pub fn id(&self) -> u32 {
        self.handle.id()
    }

    /// Waits for the child to exit completely, returning the status that it
    /// exited with. This function will continue to have the same return value
    /// after it has been called at least once.
    ///
    /// The stdin handle to the child process, if any, will be closed
    /// before waiting. This helps avoid deadlock: it ensures that the
    /// child does not block waiting for input from the parent, while
    /// the parent waits for the child to exit.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// let mut command = Command::new("ls");
    /// if let Ok(mut child) = command.spawn() {
    ///     child.wait().expect("command wasn't running");
    ///     println!("Child has finished its execution!");
    /// } else {
    ///     println!("ls command didn't start");
    /// }
    /// ```
    #[stable(feature = "process", since = "1.0.0")]
    pub fn wait(&mut self) -> io::Result<ExitStatus> {
        drop(self.stdin.take());
        self.handle.wait().map(ExitStatus)
    }

    /// Attempts to collect the exit status of the child if it has already
    /// exited.
    ///
    /// This function will not block the calling thread and will only
    /// check to see if the child process has exited or not. If the child has
    /// exited then on Unix the process ID is reaped. This function is
    /// guaranteed to repeatedly return a successful exit status so long as the
    /// child has already exited.
    ///
    /// If the child has exited, then `Ok(Some(status))` is returned. If the
    /// exit status is not available at this time then `Ok(None)` is returned.
    /// If an error occurs, then that error is returned.
    ///
    /// Note that unlike `wait`, this function will not attempt to drop stdin.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```no_run
    /// use std::process::Command;
    ///
    /// let mut child = Command::new("ls").spawn().unwrap();
    ///
    /// match child.try_wait() {
    ///     Ok(Some(status)) => println!("exited with: {status}"),
    ///     Ok(None) => {
    ///         println!("status not ready yet, let's really wait");
    ///         let res = child.wait();
    ///         println!("result: {res:?}");
    ///     }
    ///     Err(e) => println!("error attempting to wait: {e}"),
    /// }
    /// ```
    #[stable(feature = "process_try_wait", since = "1.18.0")]
    pub fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
        Ok(self.handle.try_wait()?.map(ExitStatus))
    }

    /// Simultaneously waits for the child to exit and collect all remaining
    /// output on the stdout/stderr handles, returning an `Output`
    /// instance.
    ///
    /// The stdin handle to the child process, if any, will be closed
    /// before waiting. This helps avoid deadlock: it ensures that the
    /// child does not block waiting for input from the parent, while
    /// the parent waits for the child to exit.
    ///
    /// By default, stdin, stdout and stderr are inherited from the parent.
    /// In order to capture the output into this `Result<Output>` it is
    /// necessary to create new pipes between parent and child. Use
    /// `stdout(Stdio::piped())` or `stderr(Stdio::piped())`, respectively.
    ///
    /// # Examples
    ///
    /// ```should_panic
    /// use std::process::{Command, Stdio};
    ///
    /// let child = Command::new("/bin/cat")
    ///     .arg("file.txt")
    ///     .stdout(Stdio::piped())
    ///     .spawn()
    ///     .expect("failed to execute child");
    ///
    /// let output = child
    ///     .wait_with_output()
    ///     .expect("failed to wait on child");
    ///
    /// assert!(output.status.success());
    /// ```
    ///
    #[stable(feature = "process", since = "1.0.0")]
    pub fn wait_with_output(mut self) -> io::Result<Output> {
        drop(self.stdin.take());

        let (mut stdout, mut stderr) = (Vec::new(), Vec::new());
        match (self.stdout.take(), self.stderr.take()) {
            (None, None) => {}
            (Some(mut out), None) => {
                let res = out.read_to_end(&mut stdout);
                res.unwrap();
            }
            (None, Some(mut err)) => {
                let res = err.read_to_end(&mut stderr);
                res.unwrap();
            }
            (Some(out), Some(err)) => {
                let res = read2(out.inner, &mut stdout, err.inner, &mut stderr);
                res.unwrap();
            }
        }

        let status = self.wait()?;
        Ok(Output { status, stdout, stderr })
    }
}

/// Terminates the current process with the specified exit code.
///
/// This function will never return and will immediately terminate the current
/// process. The exit code is passed through to the underlying OS and will be
/// available for consumption by another process.
///
/// Note that because this function never returns, and that it terminates the
/// process, no destructors on the current stack or any other thread's stack
/// will be run. If a clean shutdown is needed it is recommended to only call
/// this function at a known point where there are no more destructors left
/// to run; or, preferably, simply return a type implementing [`Termination`]
/// (such as [`ExitCode`] or `Result`) from the `main` function and avoid this
/// function altogether:
///
/// ```
/// # use std::io::Error as MyError;
/// fn main() -> Result<(), MyError> {
///     // ...
///     Ok(())
/// }
/// ```
///
/// In its current implementation, this function will execute exit handlers registered with `atexit`
/// as well as other platform-specific exit handlers (e.g. `fini` sections of ELF shared objects).
/// This means that Rust requires that all exit handlers are safe to execute at any time. In
/// particular, if an exit handler cleans up some state that might be concurrently accessed by other
/// threads, it is required that the exit handler performs suitable synchronization with those
/// threads. (The alternative to this requirement would be to not run exit handlers at all, which is
/// considered undesirable. Note that returning from `main` also calls `exit`, so making `exit` an
/// unsafe operation is not an option.)
///
/// ## Platform-specific behavior
///
/// **Unix**: On Unix-like platforms, it is unlikely that all 32 bits of `exit`
/// will be visible to a parent process inspecting the exit code. On most
/// Unix-like platforms, only the eight least-significant bits are considered.
///
/// For example, the exit code for this example will be `0` on Linux, but `256`
/// on Windows:
///
/// ```no_run
/// use std::process;
///
/// process::exit(0x0100);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[cfg_attr(not(test), rustc_diagnostic_item = "process_exit")]
pub fn exit(code: i32) -> ! {
    crate::rt::cleanup();
    crate::sys::os::exit(code)
}

/// Terminates the process in an abnormal fashion.
///
/// The function will never return and will immediately terminate the current
/// process in a platform specific "abnormal" manner.
///
/// Note that because this function never returns, and that it terminates the
/// process, no destructors on the current stack or any other thread's stack
/// will be run.
///
/// Rust IO buffers (eg, from `BufWriter`) will not be flushed.
/// Likewise, C stdio buffers will (on most platforms) not be flushed.
///
/// This is in contrast to the default behaviour of [`panic!`] which unwinds
/// the current thread's stack and calls all destructors.
/// When `panic="abort"` is set, either as an argument to `rustc` or in a
/// crate's Cargo.toml, [`panic!`] and `abort` are similar. However,
/// [`panic!`] will still call the [panic hook] while `abort` will not.
///
/// If a clean shutdown is needed it is recommended to only call
/// this function at a known point where there are no more destructors left
/// to run.
///
/// The process's termination will be similar to that from the C `abort()`
/// function.  On Unix, the process will terminate with signal `SIGABRT`, which
/// typically means that the shell prints "Aborted".
///
/// # Examples
///
/// ```no_run
/// use std::process;
///
/// fn main() {
///     println!("aborting");
///
///     process::abort();
///
///     // execution never gets here
/// }
/// ```
///
/// The `abort` function terminates the process, so the destructor will not
/// get run on the example below:
///
/// ```no_run
/// use std::process;
///
/// struct HasDrop;
///
/// impl Drop for HasDrop {
///     fn drop(&mut self) {
///         println!("This will never be printed!");
///     }
/// }
///
/// fn main() {
///     let _x = HasDrop;
///     process::abort();
///     // the destructor implemented for HasDrop will never get run
/// }
/// ```
///
/// [panic hook]: crate::panic::set_hook
#[stable(feature = "process_abort", since = "1.17.0")]
#[cold]
pub fn abort() -> ! {
    crate::sys::abort_internal();
}

/// Returns the OS-assigned process identifier associated with this process.
///
/// # Examples
///
/// Basic usage:
///
/// ```no_run
/// use std::process;
///
/// println!("My pid is {}", process::id());
/// ```
///
///
#[must_use]
#[stable(feature = "getpid", since = "1.26.0")]
pub fn id() -> u32 {
    crate::sys::os::getpid()
}

/// A trait for implementing arbitrary return types in the `main` function.
///
/// The C-main function only supports returning integers.
/// So, every type implementing the `Termination` trait has to be converted
/// to an integer.
///
/// The default implementations are returning `libc::EXIT_SUCCESS` to indicate
/// a successful execution. In case of a failure, `libc::EXIT_FAILURE` is returned.
///
/// Because different runtimes have different specifications on the return value
/// of the `main` function, this trait is likely to be available only on
/// standard library's runtime for convenience. Other runtimes are not required
/// to provide similar functionality.
#[cfg_attr(not(any(test, doctest)), lang = "termination")]
#[stable(feature = "termination_trait_lib", since = "1.61.0")]
#[rustc_on_unimplemented(on(
    cause = "MainFunctionType",
    message = "`main` has invalid return type `{Self}`",
    label = "`main` can only return types that implement `{Termination}`"
))]
pub trait Termination {
    /// Is called to get the representation of the value as status code.
    /// This status code is returned to the operating system.
    #[stable(feature = "termination_trait_lib", since = "1.61.0")]
    fn report(self) -> ExitCode;
}

#[stable(feature = "termination_trait_lib", since = "1.61.0")]
impl Termination for () {
    #[inline]
    fn report(self) -> ExitCode {
        ExitCode::SUCCESS
    }
}

#[stable(feature = "termination_trait_lib", since = "1.61.0")]
impl Termination for ! {
    fn report(self) -> ExitCode {
        self
    }
}

#[stable(feature = "termination_trait_lib", since = "1.61.0")]
impl Termination for Infallible {
    fn report(self) -> ExitCode {
        match self {}
    }
}

#[stable(feature = "termination_trait_lib", since = "1.61.0")]
impl Termination for ExitCode {
    #[inline]
    fn report(self) -> ExitCode {
        self
    }
}

#[stable(feature = "termination_trait_lib", since = "1.61.0")]
impl<T: Termination, E: fmt::Debug> Termination for Result<T, E> {
    fn report(self) -> ExitCode {
        match self {
            Ok(val) => val.report(),
            Err(err) => {
                io::attempt_print_to_stderr(format_args_nl!("Error: {err:?}"));
                ExitCode::FAILURE
            }
        }
    }
}