Bash Scripting

Examples:

1. [[example

   Basic Example]]

2. [[conditionals

   Example with Conditionals]]

3. [[check_file_has_w_permission

   Check if a file has write permission]]

A bash script always starts with:

#!/bin/bash

So your shell knows to run bash when you run the script

Debugging:

bash -x ./file.sh

And in the script:

echo "hi"

set -x

# this section will be debugged

set +x

Parameters

name=$1 # this will be the first argument given to the terminal when running the script

echo $name

It is possible to not supply them manually, but make it more interactive with read.

Check number of arguments supplied to the script:

$#

Arrays

@ - all arguments

• Delete an element:

unset array[1]

It removes the item but does not shift the others with one position, i.e if we echo array[1] we will get blank.

Conditionals

If statements:

if [ smth comparison smth else] then something else something different fi

If statements always use a pair of brackets and in the case of the [] we need to leave a space on both sides of the text(the bash syntax). We also always need to end the if statement with fi.

Comparison operators for integers:

-eq -ne -gt -lt -ge …