CODEWITHSUNDEEP
pythonsubprocesspopen
user2105632
user2105632

Reputation: 781

subprocess.Popen() error (No such file or directory) when calling command with arguments as a string

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.

Here is my code:

>>> 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

Upvotes: 36

Views: 55945

Answers (2)

bakkal
bakkal

Reputation: 55448

You should pass the arguments as a list (recommended):

subprocess.Popen(["wc", "-l", "sorted_list.dat"], stdout=subprocess.PIPE)

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)

Read more about shell=True security issues here.

In this case, to use the command as a whole string and avoid the security issues of shell=True you can use shlex

import subprocess
import shlex

command = "wc -l sorted_list.dat"
subprocess.Popen(shlex.split(command), stdout=subprocess.PIPE)

Upvotes: 63

Antti Haapala -- Слава Україні
Antti Haapala -- Слава Україні

Reputation: 133919

The error occurs because you are trying to run a command named wc -l sorted_list.dat, that is, it is trying to find a file named like "/usr/bin/wc -l sorted dat".

Split your arguments:

["wc", "-l", "sorted_list.dat"]

Upvotes: 6

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