Navigating: Home » Bash » Working With Variables In Bash Working With Variables In Bash Posted on by devsrealm Last Updated on: August 9, 2020 A variable is a value that can change depending on conditions or data passed to the program. To work with the variable in bash, here are what you need to know: A variable name cannot start with a number, and cannot contain spaces. It can be alphanumeric It can start with an underscore To declare a variable, type the name you want and set its value using the equals sign (=), make sure there is no space between the variable name and the equal sign or between the equals sign and the value, otherwise it would throw an error. For example: Copy Code Copied Use a different Browser #!/bin/bash b="How are You" c=15 To use this variable, you call it with a dollar sign in front of their name. E.g: Copy Code Copied Use a different Browser #!/bin/bash b="How are You" c=15 echo $b echo $c This is my output: Copy Code Copied Use a different Browser user@server:~/bin$ hw4.sh How are You 15 These variables can also work inside other variable or strings, just make sure they are double quoted, e.g: Copy Code Copied Use a different Browser #!/bin/bash b="How are You" c=15 echo "b! You are $c old." Output: Copy Code Copied Use a different Browser user@server:~/bin$ hw4.sh How are You! You are 15 old. Also, you can give variable a special attribute, e.g declaring it as an integer or as a read-only, meaning it can’t be modified later arithmetically or with stream manipulation. The one I find interesting is converting strings to a lowercase or uppercase: declare -i b=700 #b is an integer declare -r e=300 #e is read-only declare -l j=”Lowercase” #j would be converted to lowercase declare -u k=”Uppercase” #k would be converted to UPPERCASE Major Built-in Variable echo $PWD – Returns the current directory echo $HOME – User home directory echo $MACHTYPE – Returns the machine type, handy when working on a different platform echo $HOSTNAME – Returns system name Related posts:Using echo with Options in a Shell (With Examples)Script to Replace/substitute Multi Occurrences of A String in FilesCheck If Variable Is Not Empty [isset] (Bash)