Bash Functions

About bash functions

• Also called Shell Functions
• Once a function is defined, it is used like a "regular" command
• Shell functions are executed in the current shell context; no new process is created to interpret them.

Function Syntax

• Functions are declared using this syntax:

1fname () compound-command [ redirections ]
2
3or
4
5function fname [()] compound-command [ redirections ]

• Examples:

1hello () {
2   printf "1: %s\n"  $1
3   printf "2: %s\n"  $2
4}
5
6function hello2 {
7   printf "This is hello2"
8}

• Create those functions by using source command
• Call your functions as if it was a "regular" command:

1hello Dave Jane
2hello2

• If you omit the parentheses and you don't use the function keyword, bash cannot understand you are creating a new function.
  So this is not good:

1hello  {
2   printf "1: %s\n"  $1
3   printf "2: %s\n"  $2
4}

• You cannot specify parameters inside the function parentheses.
• Delete your function by using unset command

Complete funcionts example

 1$ cat func1 
 2#!/usr/bin/bash
 3#
 4
 5hello () {
 6   printf "1: %s\n"  $1
 7   printf "2: %s\n"  $2
 8}
 9
10function hello2 {
11   printf "This is hello2"
12}
13
14$ source func1 
15$ 
16$ hello Dave Jane
171: Dave
182: Jane
19$ hello
201: 
212: 
22$ hello2
23This is hello2$ 
24$