python认识subprocess模块

外部链接

[1]subprocess
[2]python subprocess模块使用总结

subprocess

The subprocess module allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes.

0,subprocess.run()

使用参数运行命令并返回完整的进程实例

subprocess.run(args, *, stdin=None, input=None, stdout=None, stderr=None, capture_output=False, shell=False, cwd=None, timeout=None, check=False, encoding=None, errors=None, text=None, env=None, universal_newlines=None)

If capture_output is true, stdout and stderr will be captured. When used, the internal Popen object is automatically created with stdout=PIPE and stderr=PIPE. The stdout and stderr arguments may not be supplied at the same time as capture_output. If you wish to capture and combine both streams into one, use stdout=PIPE and stderr=STDOUT instead of capture_output.

result = subprocess.run(['ls' ,'/opt','-al'])
#print(resule):CompletedProcess(args=['ls', '/opt', '-al'], returncode=0)

**subprocess.PIPE:**可以为数据提供一个缓冲区，如果stdout输出在PIPE，则控制台上不会再次显示

返回的结果：class subprocess.CompletedProcess:

The return value from run(), representing a process that has finished.
args
The arguments used to launch the process. This may be a list or a string.
returncode
Exit status of the child process. Typically, an exit status of 0 indicates that it ran successfully.
A negative value -N indicates that the child was terminated by signal N (POSIX only).
stdout
Captured stdout from the child process. A bytes sequence, or a string if run() was called with an encoding, errors, or text=True. None if stdout was not captured.
If you ran the process with stderr=subprocess.STDOUT, stdout and stderr will be combined in this attribute, and stderr will be None.
stderr
Captured stderr from the child process. A bytes sequence, or a string if run() was called with an encoding, errors, or text=True. None if stderr was not captured.
check_returncode()
If returncode is non-zero, raise a CalledProcessError.

1，hight-level API

1.1,subprocess.call()

父进程等待子进程完成
返回退出信息(returncode，相当于Linux exit code)

1.2,subprocess.check_call()

父进程等待子进程完成
返回0
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，可用try…except…来检查

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。

使用示例：

import subprocess
result = str(subprocess.check_output('ls /opt -al',shell=True).decode('utf-8'))
print(result)

shell=False(default)时，采用下面list的方式。如果在shell=True的情况下列表，默认只运行第一个元素，后面几个并不会读进去。
以下面为例，过为True则返回当前的目录信息，对ls来说参数并没有读进来

import subprocess
result = str(subprocess.check_output(['ls' ,'/opt','-al']).decode('utf-8'))
print(result)

4,subprocess.Popen()

上面3个函数都是基于Popen()的封装.

class Popen(args, bufsize=0, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=False, shell=False, cwd=None, env=None, universal_newlines=False, startupinfo=None, creationflags=0)

数据的输入输出和CompletedProcess基本一致。