Question

At the end of the execution of the following script, I receive some errors like these:

filename.enc: No such file or directory
140347508795048:error:02001002:system library:fopen:No such file or directory:bss_file.c:398:fopen('filename.enc','r')
140347508795048:error:20074002:BIO routines:FILE_CTRL:system lib:bss_file.c:400: 

It seems like Popen is trying to close the file at the end of execution, although it was removed.

#!/usr/bin/python
import subprocess, os

infile = "filename.enc"
outfile = "filename.dec"
opensslCmd = "openssl enc -a -d -aes-256-cbc -in %s -out %s" % (infile, outfile)   
subprocess.Popen(opensslCmd, shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, close_fds=True)
os.remove(infile)

How can I close the file properly?

Thanks.

Answer 1

it sounds like your subprocess executes, but since it is non-blocking, your os.remove(infile) executes immediately after, deleting the file before the subprocess finishes.

you could use subprocess.call() instead, which will wait for the command to finish.

… or you could change your code to use wait():

p = subprocess.Popen(opensslCmd, shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, close_fds=True)
p.wait()
os.remove(infile)