popen creates an extra sh process

Question

I am trying to execute (fork off) a command with popen and what I see is, there is an extra sh -c "my_command process" is also there.

I want to minimize number of processes so is it possible to get rid of it?

ps output:

root@home% ps awux | grep my_command
root 638  0.0  0.1  040  1424  ??  I    10:12PM   0:00.00 sh -c my_command /home/war
root 639  0.0  0.0  608   932  ??  S    10:12PM   0:00.01 my_command /home/war

After reading manpage, I know this is how popen() works.

Answer to problem above was provided by @R..

My requirement is as such, I need to dump output of the command into a file and read that file line by line and process the output. This is why I am using popen because, it returns output in a file. Can I achieve that via any exec call?

Answer 1

You should listen to the good folks who are advising you not to use popen - it's bad. But there is a simple fix for the issue you've encountered - add exec to the beginning of the command line you pass to popen. That is, instead of:

popen("my_command /home/war", ...

use:

popen("exec my_command /home/war", ...

Answer 2

popen uses sh to spawn the child process, like system does on POSIX systems.

If you want to avoid it, just use fork, close, mkpipe and exec (which is more or less what popen does internally). If you don't need the pipe you can just fork and exec.

Answer 3

As far as popen is concerned, it is supposed to invoke the shell (read the manpage)

To skip the shell process, you can do a fork/exec