Why does subprocess.Popen() with shell=True work differently on Linux vs Windows?

by

Actually on Windows, it does use cmd.exe when shell=True – it prepends cmd.exe /c (it actually looks up the COMSPEC environment variable but defaults to cmd.exe if not present) to the shell arguments. (On Windows 95/98 it uses the intermediate w9xpopen program to actually launch the command).

So the strange implementation is actually the UNIX one, which does the following (where each space separates a different argument):

/bin/sh -c gcc --version

It looks like the correct implementation (at least on Linux) would be:

/bin/sh -c "gcc --version" gcc --version

Since this would set the command string from the quoted parameters, and pass the other parameters successfully.

From the sh man page section for -c:

Read commands from the command_string operand instead of from the standard input. Special parameter 0 will be set from the command_name operand and the positional parameters ($1, $2, etc.) set from the remaining argument operands.

This patch seems to fairly simply do the trick:

--- subprocess.py.orig  2009-04-19 04:43:42.000000000 +0200
+++ subprocess.py       2009-08-10 13:08:48.000000000 +0200
@@ -990,7 +990,7 @@
                 args = list(args)

             if shell:
-                args = ["/bin/sh", "-c"] + args
+                args = ["/bin/sh", "-c"] + [" ".join(args)] + args

             if executable is None:
                 executable = args[0]

More Related Contents:

  1. What is the subprocess.Popen max length of the args parameter?
  2. Running shell command and capturing the output
  3. Python subprocess/Popen with a modified environment
  4. Using sudo with Python script
  5. Popen waiting for child process even when the immediate child has terminated
  6. Execute terminal command from python in new terminal window?
  7. How do I pipe a subprocess call to a text file?
  8. Intercepting stdout of a subprocess while it is running
  9. Popen with conflicting executable/path
  10. How do I get ‘real-time’ information back from a subprocess.Popen in python (2.5)
  11. subprocess.Popen() error (No such file or directory) when calling command with arguments as a string
  12. How to write to stdout AND to log file simultaneously with Popen?
  13. How do I get all of the output from my .exe using subprocess and Popen?
  14. link several Popen commands with pipes
  15. Is it possible to run function in a subprocess without threading or writing a separate file/script.
  16. Process substitution not allowed by Python’s subprocess with shell=True?
  17. Keep a subprocess alive and keep giving it commands? Python
  18. Launch a shell command with in a python script, wait for the termination and return to the script
  19. How to get output from subprocess.Popen(). proc.stdout.readline() blocks, no data prints out
  20. python getoutput() equivalent in subprocess [duplicate]
  21. ‘yes’ reporting error with subprocess communicate()
  22. Understanding python subprocess.check_output’s first argument and shell=True [duplicate]
  23. real time subprocess.Popen via stdout and PIPE
  24. When to use Shell=True for Python subprocess module [duplicate]
  25. What’s the difference between subprocess Popen and call (how can I use them)?
  26. python subprocess Popen environment PATH?
  27. How do I eliminate Windows consoles from spawned processes in Python (2.7)? [duplicate]
  28. How can I specify working directory for a subprocess
  29. Opening a process with Popen and getting the PID
  30. subprocess.Popen in different console

Leave a Comment