#!/usr/bin/python3
import subprocess
# 执行外部命令 'date'
subprocess.call('date')
# 传递选项和参数给命令
print("\nToday is ", end="", flush=True)
subprocess.call(['date', '-u', '+%A'])
# 其他例子
print("\nSearching for 'hello world'", flush=True)
subprocess.call(['grep', '-i', 'hello world', 'hello_world.py'])
import
语句用于载入subprocess
模块,它是Python标准库[1]的一部分subprocess
模块中的call
函数是一种执行外部命令的方式True
给flush
参数(默认是False
),我们确保这个信息在subprocess.call
运行之前输出$ ./calling_shell_commands.py
Tue Jun 21 18:35:33 IST 2016
Today is Tuesday
Searching for 'hello world'
print("Hello World")
进一步阅读
#!/usr/bin/python3
import subprocess
# 不使用扩展调用Shell命令
print("No shell expansion when shell=False", flush=True)
subprocess.call(['echo', 'Hello $USER'])
# 使用Shell扩展调用Shell命令
print("\nshell expansion when shell=True", flush=True)
subprocess.call('echo Hello $USER', shell=True)
# 如果引号是命令的一部分则进行反义
print("\nSearching for 'hello world'", flush=True)
subprocess.call('grep -i \'hello world\' hello_world.py', shell=True)
subprocess.call
不会扩展shell 通配符[6],使用 command替换[7]等等shell
参数为True
进行重写shell=True
,否则会存在安全问题[8]$ ./shell_expansion.py
No shell expansion when shell=False
Hello $USER
shell expansion when shell=True
Hello learnbyexample
Searching for 'hello world'
print("Hello World")
# 像这样使用另一种引号
subprocess.call('grep -i "hello world" hello_world.py', shell=True)
# 或者这样
subprocess.call("grep -i 'hello world' hello_world.py", shell=True)
# 为了避免call函数字符串太常,我们使用变量先存储命令
cmd = "grep -h 'test' report.log test_list.txt > grep_test.txt"
subprocess.call(cmd, shell=True)
避开使用shell=True
>>> import subprocess, os
>>> subprocess.call(['echo', 'Hello', os.environ.get("USER")])
Hello learnbyexample
0
os.environ.get("USER")
返回环境变量USER
的值0
退出状态码,意味着成功执行了命令。#!/usr/bin/python3
import subprocess
# 输出也包含任何的错误信息
print("Getting output of 'pwd' command", flush=True)
curr_working_dir = subprocess.getoutput('pwd')
print(curr_working_dir)
# 获取命令执行的状态和输出
# 退出状态码不是“0”意味着有什么事情出错了
ls_command = 'ls hello_world.py xyz.py'
print("\nCalling command '{}'".format(ls_command), flush=True)
(ls_status, ls_output) = subprocess.getstatusoutput(ls_command)
print("status: {}\noutput: '{}'".format(ls_status, ls_output))
# 抑制出错信息
# subprocess.call()返回命令的状态码 returns status of command which can be used instead
print("\nCalling command with error msg suppressed", flush=True)
ls_status = subprocess.call(ls_command, shell=True, stderr=subprocess.DEVNULL)
print("status: {}".format(ls_status))
getstatusoutput()
的输出是元组数据类型,更多信息和例子在后续章节getstatusoutput()
和getoutput()
老式的函数$ ./shell_command_output_redirections.py
Getting output of 'pwd' command
/home/learnbyexample/Python/python_programs
Calling command 'ls hello_world.py xyz.py'
status: 2
output: 'ls: cannot access xyz.py: No such file or directory
hello_world.py'
Calling command with error msg suppressed
hello_world.py
status: 2
[1]Python标准库: https://docs.python.org/3/library/index.html
[2]Python文档 - subprocess: https://docs.python.org/3/library/subprocess.html
[3]Python文档 - os.system: https://docs.python.org/3/library/os.html#os.system
[4]os.system和subprocess.call的不同: https://www.quora.com/Whats-the-difference-between-os-system-and-subprocess-call-in-Python
[5]Python文档 - import语句: https://docs.python.org/3/reference/simple_stmts.html#import
[6]shell 通配符: https://github.com/ShixiangWang/Linux_command_line/blob/master/Shell.md#wildcards
[7]command替换: http://mywiki.wooledge.org/CommandSubstitution
[8]安全问题: https://stackoverflow.com/questions/3172470/actual-meaning-of-shell-true-in-subprocess
[9]Python文档 - subprocess.Popen: https://docs.python.org/3/library/subprocess.html#popen-constructor
[10]Shell命令重定向: https://github.com/ShixiangWang/Linux_command_line/blob/master/Shell.md#redirection
[11]Python文档 - subprocess.check_output: https://docs.python.org/3/library/subprocess.html#subprocess.check_output
[12]Python文档 - subprocess.run: https://docs.python.org/3/library/subprocess.html#subprocess.run