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19 May 2010 Tags: Bash, coding, dash, empty, language, linux, null, programming, script, scripting, The -n operator checks whether the string is not null. LearnShell.org is a free interactive Shell Programming tutorial for people who want to learn Shell STRING="to be or not to be" echo ${STRING[@]/be/eat} # to eat or not to be Delete all occurrences of substring (replace with empty string) Unix / Linux Shell String Operators Example - Learning fundamentals of UNIX in steps : A beginner's tutorial containing complete knowledge of Getting Started, Unix str, Checks if str is not the empty string; if it is empty, then it returns false. #!/usr/bin/env bash NAME="John" echo "Hello $NAME!" if [[ -z "$string" ]]; then echo "String is empty" elif [[ -n "$string" ]]; then echo "String is not empty" fi ${FOO:?message}, Show error message and exit if $FOO is not set Basic for loop. In the if condition give the $line in the double quotes it will work fine #!/bin/bash line="hello welcome " if [ -z "$line" ] ; then echo "String null" fi. 2 Jul 2015 The following bash script example we show some of the way how to check for an bash check_empty.sh hello Not Empty Variable 2 Not Empty As I think this can happen to others, I decided to convert the php empty function in bash. According to the php manual: a variable is considered empty if it doesn'tthen echo "Str is not null or space" fi if [ ! For checking the empty string in shell if [ "$str" See Shell Parameter Expansion and Pattern Matching in the Bash Manual. You can read more about string manipulation in bash shell scripting here. 11 Jul 2018 In bash at least the following command tests if $var is empty: See How to tell if a string is not defined in a bash shell script? . According to the php manual: 9 Aug 2018 Fig.01: Bash scripting various way to determine if a variable is empty Another option to check if bash shell variable is empty or not .. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML