Bash Shell Script Function Examples

function name(){
  Commands
}

name(){
 Commands
 return $TRUE
}

name

#!/bin/bash
# file.sh: a sample shell script to demonstrate the concept of Bash shell functions
# define usage function
usage(){
	echo "Usage: $0 filename"
	exit 1
}
 
# define is_file_exits function 
# $f -> store argument passed to the script
is_file_exits(){
	local f="$1"
	[[ -f "$f" ]] && return 0 || return 1
}
# invoke  usage
# call usage() function if filename not supplied
[[ $# -eq 0 ]] && usage
 
# Invoke is_file_exits
if ( is_file_exits "$1" )
then
 echo "File found"
else  
 echo "File not found"
fi

fname(){
  echo "Foo"
}
 
export -f fname

fname(){
  echo "Foo"
}
 
usage(){
  echo "Usage: $0 foo bar"
  exit 1
}
 
readonly -f usage
readonly -f fname

#!/bin/bash
# gloabal x and y
x=200
y=100
 
math(){
  # local variable x and y with passed args	
  local x=$1
  local y=$2
  echo $(( $x + $y ))
}
 
echo "x: $x and y: $y"
# call function 
 
echo "Calling math() with x: $x and y: $y"
math 5 10
 
# x and y are not modified by math()
echo "x: $x and y: $y after calling math()"
echo $(( $x + $y ))

#!/bin/bash
foo(){
  # do something
  # if not false call foo
  foo
}
 
# call foo
foo