lk/basics/conditionals.md

title	tags
conditionals	Documentation Basics

If statements

Test statement equality as so:

read t1
read t2
if test $t1 != $t2; then
	echo 'variables do not match'
else
	echo 'variables match'
fi
exit 0

Case Structure

These deal with multiple states rather than forking conditions.

Example:

#!/bin/bash

# Simple case demonstration

echo "What's your favourite creature?"
read CRE
case $CRE in
        human | humanoids ) echo "Why is $CRE always standard?"
;;
        troll | monsters ) echo "Not exactly known for their character ..."
;;
        owlbears | monsters ) echo "Really you're a wizard fan"
;;
esac

# While and Until
This prints from 1 until 9.

> COUNTER=1

> while [ $COUNTER -lt 2 ]; do

        > ((COUNTER++))

        > echo $COUNTER

> done

There's also 'until', which stops when something is true, rather than keeping going when something is true.

For

for i in $( ls ); do du -sh $i done

Sequences

The sequences tool counts up from X in jumps of Y to number Z.

Count from 1 to 10.

seq 10

Count from 4 to 11.

seq 4 11

Count from 1 to 100 in steps of 5.

seq 1 5 100