先说总结

os.system：获取程序执行命令的返回值。
os.popen： 获取程序执行命令的输出结果。
commands：获取返回值和命令的输出结果。

1 os.system()

这个方法是直接调用标准C的system() 函数，仅仅在一个子终端运行系统命令，而不能获取命令执行后的返回信息，但是会在python终端中打印输出。

os.system(cmd)的返回值。os.system(cmd)的返回值只会有0(成功),1,2。
如果执行成功，那么会返回0，表示命令执行成功。否则，则是执行错误。

脚本退出码

参考：https://blog.csdn.net/qq_36380748/article/details/106787911
可以自己设定 sh 脚本，在脚本中插入返回码，这样就不会返回 0 了，而是返回码。

#!/bin/bash
 
echo "hello world!"
 
exit 1

我们使用os.system()执行脚本：

 
>>> import os
>>> cmd='./test.sh'
>>> mm=os.system(cmd)
hello world!
>>> print (mm)
256

可以看到shell脚本执行完成后，返回的值是256，但是跟我们实际想要的值不一样：

os.system的返回值并不是执行程序的返回结果。而是一个16位的数，它的高位才是返回码。也就是说os.system()返回256即 0×0100，返回码应该是其高位0×01即1。

使用os.system返回值是脚本的退出状态码，该方法在调用完shell脚本后，返回一个16位的二进制数，低位为杀死所调用脚本的信号号码，高位为脚本的退出状态码。

os.system()返回值为0 linux命令返回值也为0。一般来说，返回 0 表示运行成功。

os.system()返回值为256，十六位二进制数示为：00000001，00000000，高八位转成十进制为 1 对应 linux命令返回值 1。

os.system()返回值为512，十六位二进制数示为：00000010，00000000，高八位转成十进制为 2 对应 linux命令返回值 2。

2 os.popen()

os.popen()方法不仅执行命令而且返回执行后的信息对象(常用于需要获取执行命令后的返回信息)，是通过一个管道文件将结果返回。通过 os.popen() 返回的是 file read 的对象，对其进行读取 read() 的操作可以看到执行的输出。
os.popen(cmd)会把执行的cmd的输出作为值返回。

import os
result = os.popen('cat /etc/passwd')
print(result.read())

对比不同

def ping2(host, n):
    cmd = "ping {} {} {}".format(
        "-n" if sys.platform.lower() == "win32" else "-c",
        n,
        host,
    )
    return cmd, os.system(cmd)
    
def ping3(host, n):
    cmd = "ping {} {} {}".format(
        "-n" if sys.platform.lower() == "win32" else "-c",
        n,
        host,
    )
    return cmd, os.popen(cmd)

探究 ping3 输出的那个到底是啥：

3 commands 模块

import commands
status = commands.getstatus('cat /etc/passwd')
print(status)
output = commands.getoutput('cat /etc/passwd')
print(output)
(status, output) = commands.getstatusoutput('cat /etc/passwd')
print(status, output)

os.system() 返回结果大全

code 0 : succcessful
"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"

参考文献：
https://blog.csdn.net/qq_39426934/article/details/85559644?utm_medium=distribute.pc_relevant.none-task-blog-2_defaultbaidujs_baidulandingword~default-1-85559644-blog-106787911.pc_relevant_recovery_v2&spm=1001.2101.3001.4242.2&utm_relevant_index=4