Tips Tricks

Error-Proof Your Variables

export somedir="/home/user/somedir"
rm -rf /$somedir
# IF $somedir is unset or null then it will wipe out root "/"
#
# The failsafe
rm -rf /${somedir:?}

Skip the Long if-else Statements

# INSTEAD of

#!/bin/bash
rsync -azP somefile server1:/tmp
if [ ! $? -eq 0 ]
then
  echo "error with rsync"
  exit 1
fi
echo "continuing next step"

# USE THIS

[ ! $? -eq 0 ] && { echo "error with rsync"; exit 1; } 

The {} braces are basically your then statements separated by ;.

Don’t Rely on Passing Arguments

# Instead of assuming the order of the values was provided as desired like `args` in python
# Rely on `"${@}"1 like kwargs in python

#!/bin/bash
## reads in name and age, has boolean flag "--reset" which changes age to be 1
source functions.sh
get_params "${@}"

# Each of thuese results in the below

./main.sh --name joe --reset --age 25
./main.sh --age 25 --name joe --reset

#> NAME="joe"
#> AGE="25"
#> RESET="true"

Easily Check Your Positional Arguments

name=${1:?"Error: parameter missing Name"}
age=${2:?"Error: parameter missing Age"}

./main joe
#> Error: parameter missing Age

Create a Default Value for a Variable

echo "enter your name"
read name
name=${name:-Unknown}

If a user enters blank, your $name will be set to Unknown. The dash after the colon provides a default fallback value.