问题描述
我正在尝试使用 Python 函数计算文件中的行数.在当前目录中，当 os.system("ls") 找到文件时，命令 subprocess.Popen(["wc -l filename"], stdout=subprocess.PIPE) 不起作用.
I am trying to count the number of lines in a file using Python functions. Within the current directory, while os.system("ls") finds the file, the command subprocess.Popen(["wc -l filename"], stdout=subprocess.PIPE) does not work.
这是我的代码:
>>> import os
>>> import subprocess
>>> os.system("ls")
sorted_list.dat
0
>>> p = subprocess.Popen(["wc -l sorted_list.dat"], stdout=subprocess.PIPE)File "<stdin>", line 1, in <module>
File "/Users/a200/anaconda/lib/python2.7/subprocess.py", line 710, in __init__
errread, errwrite)
File "/Users/a200/anaconda/lib/python2.7/subprocess.py", line 1335, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory
推荐答案
您应该将参数作为列表传递(推荐):
You should pass the arguments as a list (recommended):
subprocess.Popen(["wc", "-l", "sorted_list.dat"], stdout=subprocess.PIPE)
否则，如果要使用整个"wc -l sorted_list.dat"字符串作为命令，则需要传递shell=True(不推荐，可以是安全隐患).
Otherwise, you need to pass shell=True if you want to use the whole "wc -l sorted_list.dat" string as a command (not recommended, can be a security hazard).
subprocess.Popen("wc -l sorted_list.dat", shell=True, stdout=subprocess.PIPE)
详细了解 shell=True 安全问题 这里.
Read more about shell=True security issues here.
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