Test for a dot in bash

Question

How can I test if some string is dot in bash? I've tried this:

if [ "$var" = "." ]

and this:

if [ "$var" = "\." ]

But it doesn't work.

Answer 1

Try doubling the equals (==), comparing is not the same as assigning.

Answer 2

Works for me:

$ d=.
$ if [ $d = '.' ];then echo 'yes'; else echo 'no'; fi
yes
$ d=foo
$ if [ $d = '.' ];then echo 'yes'; else echo 'no'; fi
no

Answer 3

My code:

#!/bin/bash

var="."

[ $var = "." ] && echo "Yup, it equals '.'"

exit 0

Which prints:

Yup, it equals '.'

Debugged:

tpost@tpost-desktop:~$ /bin/bash -x ./foo.sh
+ var=.
+ '[' . = . ']'
+ echo 'Yup, it equals '\''.'\'''
Yup, it equals '.'
+ exit 0

You probably have some white space in $var (or perhaps $var is empty?), run it through /bin/sh -x ./yourscript.sh to see what its actually comparing.

Keep in mind, == is a bashism, it only works in Bash. Its there as a creature comfort for people who are used to a single = resulting in an assignment.This is fine if you are only using bash, but you never know what /bin/sh on some systems may point to. Its better to just use = and avoid the problem altogether.