How to call a function (defined in shell script) in a Perl script

Question

I have two scripts, namely shell_script.sh and perl_script.pl.

shell_script.sh : It has function definitions which, when invoked from Perl script, will execute certain commands on Linux in batch mode.

perl_script.pl : It has the code and logic to be implemented, which functions to invoke etc.

The content of shell_script.sh file is as under:

bash-4.2$ cat shell_script.sh

#!/bin/bash

# Function Definitions
func_1 ()
{
  echo "function definition"
}

func_2 ()
{
  echo "function definition"
}

The content of perl_script.pl file is as under:

bash-4.2$ cat perl_script.pl

#!/usr/bin/perl

use Getopt::Long;

my $var1;
my $var1;

GetOptions("var1=s"     => \$var1,
       "var2=s" => \$var2,
       "help|?" => \$help );

if ($help)
{
    HelpMenu();
}

print " Can I call the func_1 (defined in shell script) with arguments here..?? (in this perl script)";

How can i invoke the function func_1() (which is defined in shell_script.sh) in the perl script perl_script.pl ?

What do you want these functions to (actually) do from/in the Perl script? Return some values to Perl? Or just do their thing? — zdim
– zdim, Commented Jun 23, 2018 at 20:04
Your could possibly call a script that defined and called the function, but depending on what it does, it may be better to rewrite it as a Perl function. — Kusalananda
– Kusalananda, Commented Jun 23, 2018 at 20:05
You can invoke the function like this from the perl script: system 'bash', '-c', 'source shell_script.sh; func_1' — Håkon Hægland
– Håkon Hægland, Commented Jun 23, 2018 at 20:07

Håkon Hægland · Accepted Answer · 2018-06-23 20:16:17Z

10

To invoke a shell function, the shell needs to know its definition. One way to achieve that is to have the shell first source the file which defines the function. And then, without exiting the shell, call the function. From a Perl script, that would be for example:

system 'bash', '-c', 'source shell_script.sh; func_1';

answered Jun 23, 2018 at 20:16

Håkon Hægland

40.9k22 gold badges96 silver badges209 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

zdim · Accepted Answer · 2025-11-03 19:24:45Z

To use bash functions you need to be in bash. So that puts you inside backticks or system when in a Perl script, where you are inside a bash process^†. Then, inside that process, you can source the script with functions, what will bring them in, and execute them

funcs.sh

#!/bin/bash

function f1 {
    t1=$1
    u1=$2
    echo "f1: t1=$t1 u1=$u1"
}

function f2 {
    t2=$1
    u2=$2
    echo "f2: t2=$t2 u2=$u2"
}

and in Perl ("one-liner")

perl -wE'
    @r = qx(source funcs.sh; f1 a1 b1; f2 a2 b2); 
    print "got: $_" for @r
'

where qx is the operator for backticks, but perhaps clearer. I use backticks in case you need return from those functions. One can also call bash explicitly (but read on)

perl -wE'
    @r = qx(/bin/bash -c "source funcs.sh; f1 a1 b1; f2 a2 b2"); 
    print "got: $_" for @r
'

Assignment to an array puts qx in list context, in which it returns the STDOUT of what it ran as a list of lines. This can be used to separate return from different functions, if they return a single line each. The a1,b1 and a2,b2 are arguments passed to f1 and f2.

Prints

got: f1: t1=a1 u1=b1
got: f2: t2=a2 u2=b2

This makes some (reasonable) assumptions.

However, qx will pass this through a shell because it concatenates its input to a string which is then analyzed for shell meta-characters to decide whether to run a shell, and the " are shell meta-characters. Then on a system where sh isn't linked to bash (but, say, to dash) this may not work.

On such a system run commands in a way that ensures that no shell gets its fingers on them, best by using one of the good modules for running external commands. An example with IPC::Run

use IPC::Run qw(run); 

my @cmd = ('bash', '-c', 'source funcs.sh; f1 a1 b1; f2 a2 b2'); 

run \@cmd, \undef, \my $out, \my $err; 

say "out: $out" if $out; 
say "err: $err" if $err;

If there is no need for the return, but the functions only need to do their thing, you can use

system('/bin/bash', '-c', 'source ... ')

as in Håkon's answer. With system, supplying an argument list (as opposed to a string) ensures that no extra shell is called so this should work as it stands in any shell.

^† It is /bin/sh really, but that is often relegated to bash. Things may need to be run differently if sh links to another shell, read on.

mob · Accepted Answer · 2018-06-23 21:20:56Z

3

It's overkill for this problem, but Env::Modify provides a way to make shell functions available in Perl. With Env::Modify, you could, say, import the shell functions once and use them over and over again in subsequence system calls.

use Env::Modify qw(:bash system source qx);

# import the shell functions
system("source shell_script.sh ; export -f func_1 func_2");
# alternate: put  "export -f func_1 func_2"  at the end of shell_script.sh and call
source("shell_script.sh");

# use the shell functions
system("func_1");
$output = `func_2`;
...

answered Jun 23, 2018 at 21:20

mob

119k18 gold badges159 silver badges291 bronze badges

Collectives™ on Stack Overflow

How to call a function (defined in shell script) in a Perl script

3 Answers 3

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related