具体内容如下：
1 os.system
例如 ipython中运行如下命令，返回运行状态status
os.system('cat /etc/passwdqc.conf')
min=disabled,24,11,8,7
max=40
passphrase=3
match=4
similar=deny
random=47
enforce=everyone
retry=3
Out[6]: 0
2 os.popen()
popen(command [, mode='r' [, bufsize]]) -> pipe
Open a pipe to/from a command returning a file object.
运行返回结果
In [20]: output = os.popen('cat /proc/cpuinfo')
In [21]: lineLen = []
In [22]: for line in output.readlines():
lineLen.append(len(line))
....:
In [23]: line
line lineLen
In [23]: lineLen
Out[23]:
[14,
25,
...
3 如何同时返回结果和运行状态，commands模块:
#String form: <module 'commands' from '/usr/lib64/python2.7/commands.pyc'>
File: /usr/lib64/python2.7/commands.py
Docstring:
Execute shell commands via os.popen() and return status, output.
Interface summary:
import commands
outtext = commands.getoutput(cmd)
(exitstatus, outtext) = commands.getstatusoutput(cmd)
outtext = commands.getstatus(file) # returns output of "ls -ld file"
A trailing newline is removed from the output string.
Encapsulates the basic operation:
pipe = os.popen('{ ' + cmd + '; } 2>&1', 'r')
text = pipe.read()
sts = pipe.close()
commands示例如下:
In [24]: (status, output) = commands.getstatusoutput('cat /proc/cpuinfo')
In [25]: status
Out[25]: 0
In [26]: len(output)
Out[26]: 3859
4 使用模块subprocess
ipython 中运行"?subprocess"可以发现subprocess是python用来替换os.popen()等管道操作命令的新模块
A more real-world example would look like this:
try:
retcode = call("mycmd" + " myarg", shell=True)
if retcode < 0:
print >>sys.stderr, "Child was terminated by signal", -retcode
else:
print >>sys.stderr, "Child returned", retcode
except OSError, e:
print >>sys.stderr, "Execution failed:", e
相对于上面几种方式，subprocess便于控制和监控进程运行结果,subprocess提供多种函数便于应对父进程对子进程不同要求:
4.1.1 subprocess.call()
父进程父进程等待子进程完成，返回exit code
4.1.2 subprocess.check_call()
父进程等待子进程完成,返回0，如果returncode不为0，则举出错误subprocess.CalledProcessError，该对象包含有returncode属性，可用try...except...来检查
4.1.3 subprocess.check_output()
父进程等待子进程完成
返回子进程向标准输出的输出结果
检查退出信息，如果returncode不为0，则举出错误subprocess.CalledProcessError，该对象包含有returncode属性和output属性，output属性为标准输出的输出结果，可用try...except...来检查
例如:
In [32]: out = subprocess.call("ls -l", shell=True)
total 42244
-rw-rw-r--. 1 *** *** 366 May 26 09:10 ChangeLog
4.2.1
上面三个函数都是源于Popen()函数的wapper(封装),如果需要更加个性化应用，那么就需要使用popen()函数
Popen对象创建后，主程序不会自动等待子进程完成。我们必须调用对象的wait()方法，父进程才会等待 (也就是阻塞block)
[wenwt@localhost syntax]$ rm subprocess.pyc [wenwt@localhost syntax]$ python process.py parent process [wenwt@localhost syntax]$ PING www.google.com (173.194.219.99) 56(84) bytes of data. ^C [wenwt@localhost syntax]$ --- www.google.com ping statistics --- 5 packets transmitted, 0 received, 100% packet loss, time 3999ms
加上wait方法:
[wenwt@localhost syntax]$ python process.py PING www.google.com (173.194.219.103) 56(84) bytes of data. --- www.google.com ping statistics --- 5 packets transmitted, 0 received, 100% packet loss, time 3999ms parent process
补充介绍：Python 执行终端命令的方法
import os
import subprocess
'''
os.system模块
os.system("ls -hl") 执行命令并返回状态码，当返回0表示成功；返回256表示失败，痛点是无法返回output
os.popen模块
os.popen("ls -hl") 执行命令，之后通过.read()方法获取output返回值
subprocess模块
subprocess.getstatusoutput("ls -hl") 执行命令，并返回状态status、输出output
subprocess.getoutput("ls -hl") 执行命令，只返回输出结果output
subprocess.call("ls -hl") 执行命令并返回状态码 和os.system("ls -hl")类似
'''
def test_system(cmd):
status = os.system(cmd) # 会自动输出output到控制台 但是无法接收，status为0表示成功、status为256表示失败
print(status)
def test_popen(cmd):
output = os.popen(cmd).read() # 只会获取到命令的output，如果是有output的错误命令 会输出output，否则输出空白
print(output)
def test_getoutput(cmd):
output = subprocess.getoutput(cmd) # 和os.popen(cmd)类似
print(output)
def test_getstatusoutput(cmd):
status, output = subprocess.getstatusoutput(cmd) # 执行命令，并返回状态status、输出output
print(status)
print(output)
def test_call(cmd):
status = subprocess.call(cmd) # 和os.system(cmd)类似
print(status)
if __name__ == '__main__':
# test_system('ls -lh') # test_system('test')
# test_popen('pwd') # test_popen('test')
# test_getoutput('pwd')
# test_getstatusoutput('pwd')
test_call('pwd')
以上内容就是本文的全部叙述，希望大家喜欢。
