Can I open bash from a popen() stream?

If you want to use bash constructs in the snippet you pass to popen, you can call bash explicitly from sh.

f = popen("exec bash -c 'shopt -s dotglob; cat -- *'", "r");

If you need single quotes inside the bash snippet, pass them as '\''. All other characters are passed literally.

If you have an existing bash script that you want to run, simply specify its path, same as any script or other program. Make sure that the script is executable and begins with #!/usr/bin/env bash or #!/bin/bash. If you have a script that may be non-executable (for example because of Windows portability constraints), you can invoke bash explicitly:

f = popen("exec bash myscript.bash", "r");

Alternatively, write your own custom popen-like function that calls the program you want (but do that only if simpler solutions are not satisfactory, because it's more difficult to get right). See e.g. popen() alternative.

Probably the simplest is to have a small sh script which in turn invokes your bash script like so:

#!/bin/shexec bash yourscript.sh "$@"

Or you can forgo popen and implement your own popen with fork() and execl().