Question :
I want to execute a script inside a subdirectory/superdirectory (I need to be inside this sub/super-directory first). I can’t get subprocess
to enter my subdirectory:
tducin@localhost:~/Projekty/tests/ve$ python
Python 2.7.4 (default, Sep 26 2013, 03:20:26)
[GCC 4.7.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import subprocess
>>> import os
>>> os.getcwd()
'/home/tducin/Projekty/tests/ve'
>>> subprocess.call(['cd ..'])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/subprocess.py", line 524, in call
return Popen(*popenargs, **kwargs).wait()
File "/usr/lib/python2.7/subprocess.py", line 711, in __init__
errread, errwrite)
File "/usr/lib/python2.7/subprocess.py", line 1308, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory
Python throws OSError and I don’t know why. It doesn’t matter whether I try to go into an existing subdir or go one directory up (as above) – I always end up with the same error.
Answer #1:
What your code tries to do is call a program named cd ..
. What you want is call a command named cd
.
But cd
is a shell internal. So you can only call it as
subprocess.call('cd ..', shell=True) # pointless code! See text below.
But it is pointless to do so. As no process can change another process’s working directory (again, at least on a UNIX-like OS, but as well on Windows), this call will have the subshell change its dir and exit immediately.
What you want can be achieved with os.chdir()
or with the subprocess
named parameter cwd
which changes the working directory immediately before executing a subprocess.
For example, to execute ls
in the root directory, you either can do
wd = os.getcwd()
os.chdir("/")
subprocess.Popen("ls")
os.chdir(wd)
or simply
subprocess.Popen("ls", cwd="/")
Answer #2:
To run your_command
as a subprocess in a different directory, pass cwd
parameter, as suggested in @wim’s answer:
import subprocess
subprocess.check_call(['your_command', 'arg 1', 'arg 2'], cwd=working_dir)
A child process can’t change its parent’s working directory (normally). Running cd ..
in a child shell process using subprocess won’t change your parent Python script’s working directory i.e., the code example in @glglgl’s answer is wrong. cd
is a shell builtin (not a separate executable), it can change the directory only in the same process.
Answer #3:
You want to use an absolute path to the executable, and use the cwd
kwarg of Popen
to set the working directory. See the docs.
If cwd is not None, the child’s current directory will be changed to
cwd before it is executed. Note that this directory is not considered
when searching the executable, so you can’t specify the program’s path
relative to cwd.
Answer #4:
subprocess.call
and other methods in the subprocess
module have a cwd
parameter.
This parameter determines the working directory where you want to execute your process.
So you can do something like this:
subprocess.call('ls', shell=True, cwd='path/to/wanted/dir/')
Check out docs subprocess.popen-constructor
Answer #5:
Another option based on this answer: https://stackoverflow.com/a/29269316/451710
This allows you to execute multiple commands (e.g cd
) in the same process.
import subprocess
commands = '''
pwd
cd some-directory
pwd
cd another-directory
pwd
'''
process = subprocess.Popen('/bin/bash', stdin=subprocess.PIPE, stdout=subprocess.PIPE)
out, err = process.communicate(commands.encode('utf-8'))
print(out.decode('utf-8'))
Answer #6:
I guess these days you would do:
import subprocess
subprocess.run(["pwd"], cwd="sub-dir")
Answer #7:
If you want to have cd functionality (assuming shell=True) and still want to change the directory in terms of the Python script, this code will allow ‘cd’ commands to work.
import subprocess
import os
def cd(cmd):
#cmd is expected to be something like "cd [place]"
cmd = cmd + " && pwd" # add the pwd command to run after, this will get our directory after running cd
p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=True) # run our new command
out = p.stdout.read()
err = p.stderr.read()
# read our output
if out != "":
print(out)
os.chdir(out[0:len(out) - 1]) # if we did get a directory, go to there while ignoring the newline
if err != "":
print(err) # if that directory doesn't exist, bash/sh/whatever env will complain for us, so we can just use that
return
Answer #8:
just use os.chdir
Example:
>>> import os
>>> import subprocess
>>> # Lets Just Say WE want To List The User Folders
>>> os.chdir("/home/")
>>> subprocess.run("ls")
user1 user2 user3 user4