Using type -t command in linux c.?

Question

I use popen to execute type -t type , this give me an error message -t not found. When I perform type -t type in the shell this gives me builtin . Why doesn't this work with popen ?

Answer 1

POSIX specifies that the shell used with popen is /bin/sh . Your interactive shell is probably bash . The behaviour of the type command is different for sh and bash . sh does not support -t .

Your system probably has /bin/sh symbolically linked to /bin/dash , but that's just an implementation detail.

If you need bash behaviour, run bash explicitly:

   popen("/bin/bash -c 'type -t type'", "r")

Live demo .