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  • subprocess模块 sys模块

    常用模块学习—subprocess模块详解

    要通过Python去执行一条系统命令或脚本,系统的shell命令是独立于你的python进程之外的,每执行一条命令,就是发起一个新进程,通过python调用系统命令或脚本的模块在python2有os.system。

    >>> os.system('uname -a')
    Darwin Alexs-MacBook-Pro.local 15.6.0 Darwin Kernel Version 15.6.0: Sun Jun  4 21:43:07 PDT 2017; root:xnu-3248.70.3~1/RELEASE_X86_64 x86_64
    0

    0是指执行状态,代表执行成功

    这条命令的实现原理是什么呢?(视频中讲,解释进程间通信的问题...)

    除了os.system可以调用系统命令,,commands,popen2等也可以,比较乱,于是官方推出了subprocess,目地是提供统一的模块来实现对系统命令或脚本的调用。

    子流程模块允许您生成新的进程,连接到它们的输入/输出/错误管道,并获得它们的返回码。这个模块打算替换几个较老的模块和功能:os.system    os.spawn *

    调用子流程的推荐方法是使用run()函数来处理它所能处理的所有用例。对于更高级的用例,底层的Popen接口可以直接使用。

    run()函数在python3.5中添加;如果您需要保持与旧版本的兼容性,请参阅较旧的高级API部分。

    • 三种执行命令的方法

      • subprocess.run(*popenargs, input=None, timeout=None, check=False, **kwargs)          #官方推荐

      • subprocess.call(*popenargs, timeout=None, **kwargs)                 #跟上面实现的内容差不多,另一种写法

      • subprocess.Popen()             #上面各种方法的底层封装

    • run()方法

    用参数运行命令并返回一个完整的流程实例。返回的实例将具有属性args、returncode、stdout和stderr。

    默认情况下,stdout和stderr没有被捕获,这些属性将是None。通过stdout=管道和/或stderr=管道来捕获它们。

    如果检查是正确的,并且出口代码是非零的,那么它就会产生一个称为processerror。

    processerror对象将在returncode属性中拥有退货代码,如果捕捉到这些流,则输出&stderr属性。

    如果超时,并且进程花费的时间太长,将会抛出一个超时过期的异常。其他的参数与Popen构造函数是一样的。

    标准写法:

    subprocess.run(['df','-h'],stderr=subprocess.PIPE,stdout=subprocess.PIPE,check=True)

    涉及到管道|的命令需要这样写:

    subprocess.run('df -h|grep disk1',shell=True) #shell=True的意思是这条命令直接交给系统去执行,不需要python负责解析  

    subprocess.run()方法:

    [root@wuqianqian-learn ~]# python3
    >>> import subprocess
    >>> subprocess.run(['df','-h'])
    Filesystem      Size  Used Avail Use% Mounted on
    /dev/vda1        40G  2.1G   36G   6% /
    devtmpfs        911M     0  911M   0% /dev
    tmpfs           920M     0  920M   0% /dev/shm
    tmpfs           920M  340K  920M   1% /run
    tmpfs           920M     0  920M   0% /sys/fs/cgroup
    tmpfs           184M     0  184M   0% /run/user/0
    CompletedProcess(args=['df', '-h'], returncode=0)
    
    >>> a = subprocess.run(['df','-h'])
    Filesystem      Size  Used Avail Use% Mounted on
    /dev/vda1        40G  2.1G   36G   6% /
    devtmpfs        911M     0  911M   0% /dev
    tmpfs           920M     0  920M   0% /dev/shm
    tmpfs           920M  340K  920M   1% /run
    tmpfs           920M     0  920M   0% /sys/fs/cgroup
    tmpfs           184M     0  184M   0% /run/user/0
    
    >>> a
    CompletedProcess(args=['df', '-h'], returncode=0)
    >>> a.stdout.read()
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    AttributeError: 'NoneType' object has no attribute 'read'
    
    >>> a.returncode
    
    >>> a.args
    ['df', '-h']
    
    >>> a.check_returncode()
    
    >>> a = subprocess.run(['df','-h'],stdout=subprocess.PIPE,stderr=subprocess.PIPE)
    
    >>> a.stdout
    b'Filesystem      Size  Used Avail Use% Mounted on
    /dev/vda1        40G  2.1G   36G   6% /
    devtmpfs        911M     0  911M   0% /dev
    tmpfs           920M     0  920M   0% /dev/shm
    tmpfs           920M  340K  920M   1% /run
    tmpfs           920M     0  920M   0% /sys/fs/cgroup
    tmpfs           184M     0  184M   0% /run/user/0
    '
    
    >>> a.stderr
    b''
    
    >>> a = subprocess.run(['df','-fdsfh'],stdout=subprocess.PIPE,stderr=subprocess.PIPE)
    
    >>> a.stdout
    b''
    >>> a.stderr
    b"df: invalid option -- 'f'
    Try 'df --help' for more information.
    "
    
    >>> a = subprocess.run(['df','-fdsfh'],stdout=subprocess.PIPE,stderr=subprocess.PIPE,check=True)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "/usr/lib64/python3.6/subprocess.py", line 418, in run
        output=stdout, stderr=stderr)
    subprocess.CalledProcessError: Command '['df', '-fdsfh']' returned non-zero exit status 1.
    
    >>> a = subprocess.run(['df','-fdsfh'],stdout=subprocess.PIPE,stderr=subprocess.PIPE,check=True)
    KeyboardInterrupt
    
    >>> exit()
    
    [root@wuqianqian-learn ~]# df 
    Filesystem     1K-blocks    Used Available Use% Mounted on
    /dev/vda1       41151808 2199444  36838932   6% /
    devtmpfs          932240       0    932240   0% /dev
    tmpfs             941748       0    941748   0% /dev/shm
    tmpfs             941748     340    941408   1% /run
    tmpfs             941748       0    941748   0% /sys/fs/cgroup
    tmpfs             188352       0    188352   0% /run/user/0
    
    [root@wuqianqian-learn ~]# df -h |grep vda1
    /dev/vda1        40G  2.1G   36G   6% /
    [root@wuqianqian-learn ~]# 
    [root@wuqianqian-learn ~]# 
    [root@wuqianqian-learn ~]# python3
    
    >>> a = subprocess.run(['df','-h','|','grep','vda1'],stdout=subprocess.PIPE,stderr=subprocess.PIPE,check=True)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    NameError: name 'subprocess' is not defined
    
    >>> import subprocess
    >>> a.stdout.read()     
    KeyboardInterrupt
    >>> a = subprocess.run(['df','-h','|','grep','vda1'],stdout=subprocess.PIPE,stderr=subprocess.PIPE,check=True)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "/usr/lib64/python3.6/subprocess.py", line 418, in run
        output=stdout, stderr=stderr)
    subprocess.CalledProcessError: Command '['df', '-h', '|', 'grep', 'vda1']' returned non-zero exit status 1.
    
    >>> a = subprocess.run(['df','-h','|','grep','vda1'],stdout=subprocess.PIPE,stderr=subprocess.PIPE)           
    >>> a.stderr
    b'df: xe2x80x98|xe2x80x99: No such file or directory
    df: xe2x80x98grepxe2x80x99: No such file or directory
    df: xe2x80x98vda1xe2x80x99: No such file or directory
    '
    >>> a = subprocess.run('df -h |grep vda1',stdout=subprocess.PIPE,stderr=subprocess.PIPE,shell=True)

    常用模块学习—subprocess模块详解2

    • subprocess.call()方法

    • #执行命令,返回命令执行状态 , 0 or 非0
      >>> retcode = subprocess.call(["ls", "-l"])
      
      #执行命令,如果命令结果为0,就正常返回,否则抛异常
      >>> subprocess.check_call(["ls", "-l"])
      
      #接收字符串格式命令,返回元组形式,第1个元素是执行状态,第2个是命令结果 
      >>> subprocess.getstatusoutput('ls /bin/ls')
      (0, '/bin/ls')
      
      #接收字符串格式命令,并返回结果
      >>> subprocess.getoutput('ls /bin/ls')
      '/bin/ls'
      
      #执行命令,并返回结果,注意是返回结果,不是打印,下例结果返回给res
      >>> res=subprocess.check_output(['ls','-l'])
      >>> res
      b'total 0
      drwxr-xr-x 12 alex staff 408 Nov 2 11:05 OldBoyCRM
      '
      [root@wuqianqian-learn ~]# python3
      
      >>> import os
      >>> os.system('uname -a ')
      Linux wuqianqian-learn 2.6.32-696.el6.x86_64 #1 SMP Tue Mar 21 19:26:13 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
      >>> import subprocess              
      >>> subprocess.call(['ls','-lsh'])
      total 0
      >>> subprocess.check_call(['ls','-lsh'])
      total 0
      >>> subprocess.check_call(['ls','-lsh'])
      total 80K
      srwxr-xr-x 1 root root    0 May 30 10:25 Aegis-<Guid(5A2C30A2-A87D-490A-9281-6765EDAD7CBA)>
      4.0K drwx------ 3 root root 4.0K May 26 11:18 systemd-private-d3b6074cca274d6593128b80ade5cf96-ntpd.service-FZcU6R
      >>> subprocess.getoutput(['ls','-lsh']) 
      'Aegis-<Guid(5A2C30A2-A87D-490A-9281-6765EDAD7CBA)>
      systemd-private-d3b6074cca274d6593128b80ade5cf96-ntpd.service-FZcU6R'
      >>> subprocess.getoutput(['ls /bin/ls'])
      '/bin/ls'
      >>> res = subprocess.checkoutput(['ls','-l'])       
      Traceback (most recent call last):
        File "<stdin>", line 1, in <module>
      AttributeError: module 'subprocess' has no attribute 'checkoutput'
      >>> res = subprocess.check_output(['ls','-l'])
      >>> res
      b'total 4
      srwxr-xr-x 1 root root    0 May 30 10:25 Aegis-<Guid(5A2C30A2-A87D-490A-9281-6765EDAD7CBA)>
      drwx------ 3 root root 4096 May 26 11:18 systemd-private-d3b6074cca274d6593128b80ade5cf96-ntpd.service-FZcU6R
      '
      >>> help(subprocess.check_output)
      Help on function check_output in module subprocess:
      
      check_output(*popenargs, timeout=None, **kwargs)
          Run command with arguments and return its output.
          
          If the exit code was non-zero it raises a CalledProcessError.  The
          CalledProcessError object will have the return code in the returncode
          attribute and output in the output attribute.
          
          The arguments are the same as for the Popen constructor.  Example:
          
          >>> check_output(["ls", "-l", "/dev/null"])
          b'crw-rw-rw- 1 root root 1, 3 Oct 18  2007 /dev/null
      '
          
          The stdout argument is not allowed as it is used internally.
          To capture standard error in the result, use stderr=STDOUT.
          
          >>> check_output(["/bin/sh", "-c",
          ...               "ls -l non_existent_file ; exit 0"],
          ...              stderr=STDOUT)
          b'ls: non_existent_file: No such file or directory
      '
          
          There is an additional optional argument, "input", allowing you to
          pass a string to the subprocess's stdin.  If you use this argument
          you may not also use the Popen constructor's "stdin" argument, as
          it too will be used internally.  Example:
          
          >>> check_output(["sed", "-e", "s/foo/bar/"],
          ...              input=b"when in the course of fooman events
      ")
          b'when in the course of barman events
      '
          
          If universal_newlines=True is passed, the "input" argument must be a
          string and the return value will be a string rather than bytes.

      subprocess.Popen()方法常用参数

    • 常用参数

      • args:shell命令,可以是字符串或者序列类型(如:list,元组)

      • stdin, stdout, stderr:分别表示程序的标准输入、输出、错误句柄

      • preexec_fn:只在Unix平台下有效,用于指定一个可执行对象(callable object),它将在子进程运行之前被调用

      • shell:同上

      • cwd:用于设置子进程的当前目录

      • env:用于指定子进程的环境变量。如果env = None,子进程的环境变量将从父进程中继承。

    下面这2条语句执行会有什么区别?

    a=subprocess.run('sleep 10',shell=True,stdout=subprocess.PIPE)
    a=subprocess.Popen('sleep 10',shell=True,stdout=subprocess.PIPE)
    

    区别是Popen会在发起命令后立刻返回,而不等命令执行结果。这样的好处是什么呢?

    如果你调用的命令或脚本 需要执行10分钟,你的主程序不需卡在这里等10分钟,可以继续往下走,干别的事情,每过一会,通过一个什么方法来检测一下命令是否执行完成就好了。

    Popen调用后会返回一个对象,可以通过这个对象拿到命令执行结果或状态等,该对象有以下方法

    poll()

    Check if child process has terminated. Returns returncode

    wait()

    Wait for child process to terminate. Returns returncode attribute.

    terminate()终止所启动的进程Terminate the process with SIGTERM

    kill() 杀死所启动的进程 Kill the process with SIGKILL

    communicate()与启动的进程交互,发送数据到stdin,并从stdout接收输出,然后等待任务结束

    a = subprocess.Popen('python3 guess_age.py',stdout=subprocess.PIPE,stderr=subprocess.PIPE,stdin=subprocess.PIPE,shell=True)
    
    >>> a.communicate(b'22')
    
    (b'your guess:try bigger
    ', b'')

    send_signal(signal.xxx)发送系统信号

    pid 拿到所启动进程的进程号

    [root@wuqianqian-learn ~]# python3
    
    >>> import os
    >>> os.system('uname -a ')
    Linux wuqianqian-learn 2.6.32-696.el6.x86_64 #1 SMP Tue Mar 21 19:26:13 UTC 2017 x86_64 x86_64 x86_6
    >>> import subprocess              
    >>> subprocess.call(['ls','-lsh'])
    total 0
    >>> subprocess.check_call(['ls','-lsh'])
    total 0
    >>> subprocess.check_call(['ls','-lsh'])
    total 4.0K
    srwxr-xr-x 1 root root    0 May 30 10:25 Aegis-<Guid(5A2C30A2-A87D-490A-9281-6765EDAD7CBA)>
    4.0K drwx------ 3 root root 4.0K May 26 11:18 systemd-private-d3b6074cca274d6593128b80ade5cf96-ntpd.service-FZcU6R
    >>> subprocess.getoutput(['ls','-lsh']) 
    'Aegis-<Guid(5A2C30A2-A87D-490A-9281-6765EDAD7CBA)>
    systemd-private-d3b6074cca274d6593128b80ade5cf96-ntpd.service-FZcU6R'
    >>> subprocess.getoutput(['ls /bin/ls'])
    '/bin/ls'
    >>> res = subprocess.checkoutput(['ls','-l'])       
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    AttributeError: module 'subprocess' has no attribute 'checkoutput'
    >>> res = subprocess.check_output(['ls','-l'])
    >>> res
    b'total 4
    srwxr-xr-x 1 root root    0 May 30 10:25 Aegis-<Guid(5A2C30A2-A87D-490A-9281-6765EDAD7CBA)>
    drwx------ 3 root root 4096 May 26 11:18 systemd-private-d3b6074cca274d6593128b80ade5cf96-ntpd.service-FZcU6R
    '
    >>> help(subprocess.check_output)
    Help on function check_output in module subprocess:
    
    check_output(*popenargs, timeout=None, **kwargs)
        Run command with arguments and return its output.
        
        If the exit code was non-zero it raises a CalledProcessError.  The
        CalledProcessError object will have the return code in the returncode
        attribute and output in the output attribute.
        
        The arguments are the same as for the Popen constructor.  Example:
        
        >>> check_output(["ls", "-l", "/dev/null"])
        b'crw-rw-rw- 1 root root 1, 3 Oct 18  2007 /dev/null
    '
        
        The stdout argument is not allowed as it is used internally.
        To capture standard error in the result, use stderr=STDOUT.
        
        >>> check_output(["/bin/sh", "-c",
        ...               "ls -l non_existent_file ; exit 0"],
        ...              stderr=STDOUT)
        b'ls: non_existent_file: No such file or directory
    '
        
        There is an additional optional argument, "input", allowing you to
        pass a string to the subprocess's stdin.  If you use this argument
        you may not also use the Popen constructor's "stdin" argument, as
        it too will be used internally.  Example:
        
        >>> check_output(["sed", "-e", "s/foo/bar/"],
        ...              input=b"when in the course of fooman events
    ")
        b'when in the course of barman events
    '
        
        If universal_newlines=True is passed, the "input" argument must be a
        string and the return value will be a string rather than bytes.
    
    >>> 
    >>> a = subprocess.run('sleep 10',shell=True,stdout=subprocess.PIPE)
    >>> subprocess.Popen()
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    TypeError: __init__() missing 1 required positional argument: 'args'
    >>> a = subprocess.Popen('sleep 10',shell=True,stdout=subprocess.PIPE)   
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a = subprocess.Popen('sleep 10',shell=True,stdout=subprocess.PIPE)
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> a.poll()
    >>> def sayhi():
    ... print('run...hahahah')
      File "<stdin>", line 2
        print('run...hahahah')
            ^
    IndentationError: expected an indented block
    >>> def sayhi():          
    ...     print('run...hahahah')
    ... a = subprocess.Popen('sleep 10',shell=True,stdout=subprocess.PIPE,preexec_fn=sayhi)
      File "<stdin>", line 3
        a = subprocess.Popen('sleep 10',shell=True,stdout=subprocess.PIPE,preexec_fn=sayhi)
        ^
    SyntaxError: invalid syntax
    >>> a = subprocess.Popen('sleep 10',shell=True,stdout=subprocess.PIPE,preexec_fn=sayhi)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    NameError: name 'sayhi' is not defined
    >>> def sayhi():              
    ...     print('run...hahahah')
    ... a = subprocess.Popen('sleep 10',shell=True,stdout=subprocess.PIPE,preexec_fn=sayhi)
      File "<stdin>", line 3
        a = subprocess.Popen('sleep 10',shell=True,stdout=subprocess.PIPE,preexec_fn=sayhi)
        ^
    SyntaxError: invalid syntax
    >>> import subprocess
    >>> def sayhi():              
    ...     print('run...hahahah')
    ... 
    >>> 
    >>> a = subprocess.Popen('sleep 10',shell=True,stdout=subprocess.PIPE,preexec_fn=sayhi)
    >>> a.stdout
    <_io.BufferedReader name=3>
    >>> a.stdout.read()
    b'run...hahahah
    '
    >>> a = subprocess.Popen('echo $PWD;sleep 4',shell=True,cwd="/tmp",stdout=subprocess.PIPE,preexec_fn=sayhi)  
    >>> a.stdout.read()
    b'run...hahahah
    /tmp
    '
    >>> a = subprocess.Popen('echo $PWD;sleep 4',shell=True,stdout=subprocess.PIPE,preexec_fn=sayhi)           
    >>> a.stdout.read()
    b'run...hahahah
    /root
    '
    >>> a = subprocess.Popen('echo $PWD;sleep 4',shell=True,stdout=subprocess.PIPE,preexec_fn=sayhi)
    >>> a.wait()
    >>> a = subprocess.Popen('echo $PWD;sleep 10',shell=True,stdout=subprocess.PIPE,preexec_fn=sayhi)
    >>> a.wait()
    >>> a = subprocess.Popen('sleep 100',shell=True,stdout=subprocess.PIPE)                          
    >>> a.pid
    >>> a.terminate()
    >>> a.pid
    >>> a.pid
    >>> a.pid
    >>> a.terminate()
    >>> a = subprocess.Popen('sleep 100',shell=True,stdout=subprocess.PIPE)
    >>> a.pid
    >>> a.kill()
    >>> a.pid   
    >>> a = subprocess.Popen('for i in $(seq 1 100);do sleep 1;echo $i >>sleep.log;done',shell=True,stdout=subprocess.PIPE)
    >>> a = subprocess.Popen('for i in $(seq 1 100);do sleep 1;echo $i >>sleep.log;done',shell=True,stdout=subprocess.PIPE)
    KeyboardInterrupt
    >>> a.pid
    >>> a.kill()
    KeyboardInterrupt
    >>> help(os.kill)
    Help on built-in function kill in module posix:
    
    kill(pid, signal, /)
        Kill a process with a signal.

    sys模块参考

     http://www.cnblogs.com/aland-1415/p/6613449.html

      

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  • 原文地址:https://www.cnblogs.com/joneylulu/p/10355892.html
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