subprocess.Popen引发子异常

Question

I put an operation in my python file :

 subprocess.Popen(['notify-send', message])

and the error on terminal is :

subprocess.Popen(['notify-send', message])
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 710, in __init__ errread, errwrite)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1335, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory

how to prevent this error?

Answer 1

Popen uses default no environment, so not PATH. There are several solutions:

• Use an env in Popen subprocess.Popen(args=['notify-send', message], env={'PATH': os.getenv('PATH')}
• Use the full path to notify-send subprocess.Popen(['/full/path/here/notify-send', message])

Answer 2

By design, programs starting other programs do not use the PATH environment variable by default. It used to be a common attack way to subvert a legit program by changing the PATH or by installing a rogue program with a higher priority in normal PATH than the real child. As a result, the rogue program could be executed on behalf on the user without any abnormal action from him/her.

There are tons of ways of forcing the use of the PATH and it is fine for simple operations (parameter shell = TRUE is one of them). But for more serious scripts it gives the same difference as using the frowned upon system instead of fork + exec in C or C++ languages.

TL/DR: the most correct way is to pass the full PATH of the child program.