1.os.system
使用os.system(cmd)即可在python中使用linux命令
os.system(cmd)的返回值。如果執行成功，那麼會返回0，表示命令執行成功。否則，則是執行錯誤。
使用os.system返回值是腳本的退出狀態碼，該方法在調用完shell腳本後，返回一個16位的二進制數，低位爲殺死所調用腳本的信號號碼，高位爲腳本的退出狀態碼（查看文章尾部擴展資料[1]），即腳本中“exit 1”的代碼執行後，os.system函數返回值的高位數則是1，如果低位數是0的情況下，則函數的返回值是0×0100,換算爲10進製得到256。
關於os.system中連續執行多條語句的情況（想法是切換路徑並且執行python）：
- 父進程的環境變量(environment variables)會默認傳遞到子進程中(工作目錄PWD就是環境變量之一)
- 使用system函數，子進程無法影響父進程中的環境變量
根據這兩點，執行第一條os.system('cd /data/kk/')引發的工作目錄變更作用範圍僅限於第一個被創建的子進程，故而當前的工作目錄沒有變更，到執行os.system('python test.py ')就會報錯。
2.os.popen()
通過 os.popen() 返回的是 file read 的對象，對其進行讀取 read() 的操作可以看到執行的輸出。
這種調用方式是通過管道的方式來實現（查看文章尾部擴展資料[2]），函數返回一個file-like的對象，裏面的內容是腳本輸出的內容（可簡單理解爲echo輸出的內容）。
output = os.popen('cat /proc/cpuinfo')
print output.read()
3.commands.getstatusoutput()
讀取程序執行的返回值和輸出
import commands
(status, output) = commands.getstatusoutput('cat /proc/cpuinfo')
print status, output
# (0, 'aaaaaaa')
4.示例
# -*- coding: UTF-8 -*-
import os
print 'test os.system...'
command = 'free -m 1> test.txt'
status = os.system(command)
if status != 0:
raise Exception('執行系統命令失敗, command=%s, status=%s' % (command, status))
print 'test os.popen...'
output = os.popen('cat /root/kangkai/test.txt')
print output.read()
print 'test commands...'
import commands
(status, output) = commands.getstatusoutput('ls /root/kangkai/')
print status, output
/*************************************************************************************************************/
擴展[1]：
linux命令執行後無論成功與否都有一個返回值：
如果爲 0，則表示命令執行成功，其它值則表示錯誤，具體的錯誤碼含義如下：
"OS error code 1: Operation not permitted"
"OS error code 2: No such file or directory"
"OS error code 3: No such process"
"OS error code 4: Interrupted system call"
"OS error code 5: Input/output error"
"OS error code 6: No such device or address"
"OS error code 7: Argument list too long"
"OS error code 8: Exec format error"
"OS error code 9: Bad file descriptor"
"OS error code 10: No child processes"
"OS error code 11: Resource temporarily unavailable"
"OS error code 12: Cannot allocate memory"
"OS error code 13: Permission denied"
"OS error code 14: Bad address"
"OS error code 15: Block device required"
"OS error code 16: Device or resource busy"
"OS error code 17: File exists"
"OS error code 18: Invalid cross-device link"
"OS error code 19: No such device"
"OS error code 20: Not a directory"
"OS error code 21: Is a directory"
"OS error code 22: Invalid argument"
"OS error code 23: Too many open files in system"
"OS error code 24: Too many open files"
"OS error code 25: Inappropriate ioctl for device"
"OS error code 26: Text file busy"
"OS error code 27: File too large"
"OS error code 28: No space left on device"
"OS error code 29: Illegal seek"
"OS error code 30: Read-only file system"
"OS error code 31: Too many links"
"OS error code 32: Broken pipe"
"OS error code 33: Numerical argument out of domain"
"OS error code 34: Numerical result out of range"
"OS error code 35: Resource deadlock avoided"
"OS error code 36: File name too long"
"OS error code 37: No locks available"
"OS error code 38: Function not implemented"
"OS error code 39: Directory not empty"
"OS error code 40: Too many levels of symbolic links"
"OS error code 42: No message of desired type"
"OS error code 43: Identifier removed"
"OS error code 44: Channel number out of range"
"OS error code 45: Level 2 not synchronized"
"OS error code 46: Level 3 halted"
"OS error code 47: Level 3 reset"
"OS error code 48: Link number out of range"
"OS error code 49: Protocol driver not attached"
"OS error code 50: No CSI structure available"
"OS error code 51: Level 2 halted"
"OS error code 52: Invalid exchange"
"OS error code 53: Invalid request descriptor"
"OS error code 54: Exchange full"
"OS error code 55: No anode"
"OS error code 56: Invalid request code"
"OS error code 57: Invalid slot"
"OS error code 59: Bad font file format"
"OS error code 60: Device not a stream"
"OS error code 61: No data available"
"OS error code 62: Timer expired"
"OS error code 63: Out of streams resources"
"OS error code 64: Machine is not on the network"
"OS error code 65: Package not installed"
"OS error code 66: Object is remote"
"OS error code 67: Link has been severed"
"OS error code 68: Advertise error"
"OS error code 69: Srmount error"
"OS error code 70: Communication error on send"
"OS error code 71: Protocol error"
"OS error code 72: Multihop attempted"
"OS error code 73: RFS specific error"
"OS error code 74: Bad message"
"OS error code 75: Value too large for defined data type"
"OS error code 76: Name not unique on network"
"OS error code 77: File descriptor in bad state"
"OS error code 78: Remote address changed"
"OS error code 79: Can not access a needed shared library"
"OS error code 80: Accessing a corrupted shared library"
"OS error code 81: .lib section in a.out corrupted"
"OS error code 82: Attempting to link in too many shared libraries"
"OS error code 83: Cannot exec a shared library directly"
"OS error code 84: Invalid or incomplete multibyte or wide character"
"OS error code 85: Interrupted system call should be restarted"
"OS error code 86: Streams pipe error"
"OS error code 87: Too many users"
"OS error code 88: Socket operation on non-socket"
"OS error code 89: Destination address required"
"OS error code 90: Message too long"
"OS error code 91: Protocol wrong type for socket"
"OS error code 92: Protocol not available"
"OS error code 93: Protocol not supported"
"OS error code 94: Socket type not supported"
"OS error code 95: Operation not supported"
"OS error code 96: Protocol family not supported"
"OS error code 97: Address family not supported by protocol"
"OS error code 98: Address already in use"
"OS error code 99: Cannot assign requested address"
"OS error code 100: Network is down"
"OS error code 101: Network is unreachable"
"OS error code 102: Network dropped connection on reset"
"OS error code 103: Software caused connection abort"
"OS error code 104: Connection reset by peer"
"OS error code 105: No buffer space available"
"OS error code 106: Transport endpoint is already connected"
"OS error code 107: Transport endpoint is not connected"
"OS error code 108: Cannot send after transport endpoint shutdown"
"OS error code 109: Too many references: cannot splice"
"OS error code 110: Connection timed out"
"OS error code 111: Connection refused"
"OS error code 112: Host is down"
"OS error code 113: No route to host"
"OS error code 114: Operation already in progress"
"OS error code 115: Operation now in progress"
"OS error code 116: Stale NFS file handle"
"OS error code 117: Structure needs cleaning"
"OS error code 118: Not a XENIX named type file"
"OS error code 119: No XENIX semaphores available"
"OS error code 120: Is a named type file"
"OS error code 121: Remote I/O error"
"OS error code 122: Disk quota exceeded"
"OS error code 123: No medium found"
"OS error code 124: Wrong medium type"
"OS error code 125: Operation canceled"
"OS error code 126: Required key not available"
"OS error code 127: Key has expired"
"OS error code 128: Key has been revoked"
"OS error code 129: Key was rejected by service"
"OS error code 130: Owner died"
"OS error code 131: State not recoverable"
擴展[2]：
popen()函數通過創建一個管道，調用fork()產生一個子進程，執行一個shell以運行命令來開啓一個進程。popen()的返回值是個標準I/O流，這個管道必須由pclose()函數關閉，而不是fclose()函數。
pclose()函數關閉標準I/O流，等待命令執行結束，然後返回shell的終止狀態。如果shell不能被執行，則pclose()返回的終止狀態與shell已執行exit一樣。