An expression can be: String comparison, Numeric comparison, File operators and Logical operators and it is represented by [expression]: Number Comparisons: -eq - is equal to - if [ "$a" -eq "$b" ] -ne - is not equal to - if [ "$a" -ne "$b" ] -gt - is greater than - ...
Bash, short for "Bourne Again SHell," is a powerful scripting language used in Unix-based operating systems. One of the fundamental constructs in Bash programming is the if statement. The if statement allows you to control the flow of your script based on specific conditions. In this article,...
Now that you are aware of the various comparison expressions let's see them in action in various examples. Use if statement in bash Let's create a script that tells you if a given number is even or not. Here's my script namedeven.sh: #!/bin/bash read -p "Enter the number: " nu...
Compare the numbers:Theifstatement uses the-geoperator to check if the value ofnum1is greater than or equal tonum2. Execute the true condition:If the condition evaluates to true (the first number is greater than or equal), the script executes theechocommand to display the message"The first...
Another common error is using the wrong operator in the condition. For example, using ‘=’ instead of ‘-eq’ for numerical comparison can lead to unexpected results. a=5b=5# Incorrect syntaxif[$a=$b];thenecho'a is equal to b'fi# Output:# a is equal to b ...
If the shop is open, the nestedifstatement makes a second test. If the day is Wednesday, it tells us it is open in the morning only. #!/bin/bash # get the day as a number 1..7 day=$(date +"%u") if [ $day -le 6 ] ...
It then checks if the entered password ('$password') matches the correct password ('$correct_password') using an if statement with a string comparison ([[ ... ]]). If the passwords match, the script prints "Access granted" and exits the loop using the "break" statement. ...
This script is to demonstrate the usage of the case statement. $ cat signal.sh #!/bin/bash if [ $# -lt 2 ] then echo "Usage : $0 Signalnumber PID" exit fi case "$1" in 1) echo "Sending SIGHUP signal" kill -SIGHUP $2 ...
Later, I used the if-else twice to check each array. The first if statement will check for thearray1and the second one will verify thearray2. Once you execute the script, it will show you the following output: Check empty bash array with size comparison ...
A parameter is set if it has been assigned a value. The null string is a valid value. Once a variable is set, it may be unset only by using the unset builtin command (see SHELL BUILTIN COMMANDS below). A variable may be assigned to by a statement of the form ...