How To Write and Use Custom Shell Functions and Libraries

If You Appreciate What We Do Here On TecMint, You Should Consider:

  1. Stay Connected to: Twitter | Facebook | Google Plus
  2. Subscribe to our email updates: Sign Up Now
  3. Get your own self-hosted blog with a Free Domain at ($3.95/month).
  4. Become a Supporter - Make a contribution via PayPal
  5. Support us by purchasing our premium books in PDF format.
  6. Support us by taking our online Linux courses

We are thankful for your never ending support.

Aaron Kili

Aaron Kili is a Linux and F.O.S.S enthusiast, an upcoming Linux SysAdmin, web developer, and currently a content creator for TecMint who loves working with computers and strongly believes in sharing knowledge.

Your name can also be listed here. Got a tip? Submit it here to become an TecMint author.

RedHat RHCE and RHCSA Certification Book
Linux Foundation LFCS and LFCE Certification Preparation Guide

You may also like...

2 Responses

  1. Cloud Consulting Services says:

    Create a function file called myfunctions.sh:

    #!/bin/bash
    # set variables
    declare -r TRUE=0
    declare -r FALSE=1
    declare -r PASSWD_FILE=/etc/passwd

    ##################################################################
    # Purpose: Converts a string to lower case
    # Arguments:
    # $1 -> String to convert to lower case
    ##################################################################
    function to_lower()
    {
    local str="$@"
    local output
    output=$(tr '[A-Z]' '[a-z]'<< Message
    # $2 -> Exit status (optional)
    ##################################################################
    function die()
    {
    local m="$1" # message
    local e=${2-1} # default exit status 1
    echo "$m"
    exit $e
    }
    ##################################################################
    # Purpose: Return true if script is executed by the root user
    # Arguments: none
    # Return: True or False
    ##################################################################
    function is_root()
    {
    [ $(id -u) -eq 0 ] && return $TRUE || return $FALSE
    }

    ##################################################################
    # Purpose: Return true $user exits in /etc/passwd
    # Arguments: $1 (username) -> Username to check in /etc/passwd
    # Return: True or False
    ##################################################################
    function is_user_exits()
    {
    local u="$1"
    grep -q "^${u}" $PASSWD_FILE && return $TRUE || return $FALSE
    }

    You can load myfunctions.sh into the current shell environment, enter:

    $ .myfunctions.sh
    OR
    $ ./path/to/myfunctions.sh
    

Got something to say? Join the discussion.

Your email address will not be published. Required fields are marked *