Shell Cheatsheet

Table of contents

• Useful Snippets
  • Project Header
  • Good start
  • To take arguments when running script
  • Add help usage if arg1 == -h
  • Second way to take arguments (maybe more proper?)
  • Check For Dependencies
  • Ask for user confirmation to continue
  • Command or something else if it fails
  • Print success or non success

---

Useful Snippets

Project Header

#!/bin/bash
#-------------------------------------------------------------------------------
#-------------------------------------------------------------------------------
#  
# Tyler(UnclassedPenguin) PROJECT TITLE 2022
#  
# Author: Tyler(UnclassedPenguin)
#    URL: https://unclassed.ca
# GitHub: https://github.com/UnclassedPenguin
#
#-------------------------------------------------------------------------------
#-------------------------------------------------------------------------------

Good start

Gives you the function “warn” that leads with the name of script.

SCRIPTNAME="${0##*/}"  
  
warn() {  
    printf >&2 "$SCRIPTNAME: $*\n"  
}  
usage: warn $"Something to warn about"  

To take arguments when running script

ARG1=${1}  
ARG2=${2:somedefault}  
  
echo "$ARG1"  

Add help usage if arg1 == -h

if [ "$ARG1" == "-h" ] || [ "$ARG1" == "" ]; then  
    echo "This is the help usage"  
    exit 0  
fi  

Second way to take arguments (maybe more proper?)

Help(){  
    echo "This is help usage"  
}  

(If multiple options do it like optspec=":huv:")

optspec=":h"  
while getopts "$optspec" option; do  
  case $option in  
    h) # print help usage  
      Help  
      exit;;  
  esac  
done  

Check For Dependencies

iscmd() {
    command -v >&- "$@"
}

checkdeps() {
    local -i not_found
    for cmd; do
        iscmd "$cmd" || {
            warn $"$cmd is not found"
            let not_found++
        }
    done
    (( not_found == 0 )) || {
        warn $"Install dependencies listed above to use $SCRIPTNAME"
        exit 1
    }
}

# If you need to check more, just add here i.e.:
# checkdeps curl cmd cmd1 cmd2
checkdeps curl

Ask for user confirmation to continue

read -r -p "Continue? [Y/n]" response  
response=${response,,} # tolower  
if [[ $response =~ ^(yes|y| ) ]] || [[ -z $response ]]; then  
    dosomethingifyes  
else  
    dosomethingelse  
fi  

Command or something else if it fails

some command || {  
    echo "Something went wrong"  
    exit 1  
}  

Print success or non success

if some command ; then  
    echo "command succeed"  
else  
    echo "command failed"  
fi