Check if a function exists before executing it in shell

Question

I want to check if a function exist or not before executing it in the shell script.

Does script shell support that? and how to do it?

Answer 1

As read in this comment, this should make it:

type -t function_name

this returns function if it is a function.

Test

$ type -t f_test
$ 
$ f_test () { echo "hello"; }
$ type -t f_test
function

Note that type provides good informations:

$ type -t ls
alias
$ type -t echo
builtin

Answer 2

POSIX does not specify any arguments for the type built-in and leaves its output unspecified. Your best bet, apart from a shell-specific solution, is probably

if type foo | grep -i function > /dev/null; then
   # foo is a function
fi