How make open function use bash instead of sh?

Question

I want to use bash instead of sh when I use the open function. For instance:

sub run_cmd {
    my ($cmd) = @_;
    my $fcmd;

    print("Run $cmd\n");

    open($fcmd, "$cmd |");
    while ( my $line = <$fcmd> ) {
        print "-> $line";
    }
    close $fcmd;
}

eval{run_cmd('ps -p $$')};

Here, the output is:

Run ps -p $$
->    PID TTY          TIME CMD
-> 189493 pts/6    00:00:00 sh

We can see sh is used by default.

I have some constraints and I need (1) to use the open function and (2) to call bash instead of sh. I tried simply to add bash at the beginning of my command but it doesn't work:

Run ps -p $$
/bin/ps: /bin/ps: cannot execute binary file

What can I do to use bash with the open function?

Answer 1

You can explicitly run bash instead.

open($fcd, "bash -c '$cmd' |");

The other answer indeed shows some important best practices for when cmd is not completely trivial, or not under your control.

Answer 2

Don't take your chances with quote injections:

open my $fcmd, '-|', qw(bash -c), $cmd;

(Also notice that you don't need to close $fcmd explicitly if you declared it with my; it will be automatically closed at the end of the block; perl is not java ;-))