How do I add input to a bash script?
How to write a bash script
- Open a new file: nano myscript.
- Write the shebang line: #!/usr/bin/env bash.
- Make the script executable. chmod +x myscript.
- Run the script. ./myscript # This should print HELLO!
- Add an input variable. #!/usr/bin/env bash NAME=${1?
- Now run it:
- Add an optional input variable.
- Now run it again:
What does echo $0 mean?
If the output of echo $0 command is -bash it means that bash was invoked as a login shell. If the output is only bash , then you are in a non-login shell. man bash says somewhere at line 126: A login shell is one whose first character of argument zero is a -, or one started with the –login option.
How are arguments processed in a bash script?
In this article, we looked at how arguments passed to a bash script during runtime can be processed inside the script in different ways: Positional parameters can be used when the input size is fixed and the order of the arguments in the input is known. With flags, the order of the arguments in the input doesn’t matter.
How to get input from the user in Bash?
So we now have 3 methods for getting input from the user: 1 Command line arguments 2 Read input during script execution 3 Accept data that has been redirected into the Bash script via STDIN
When to use shift with input arguments in Bash?
If your input arguments don’t expect a value then a shift is required near the end of the loop only. If you have a requirement to only collect 2-3 input arguments you can avoid shift if it feels too complicated for you. In this example we will use case statement with while loop to check for input arguments.
How to use command line arguments in a Linux script?
The getopts function reads the flags in the input, and OPTARG refers to the corresponding values: Let’s run this script with the same input as before, only this time, we’ll add flags to the input: The output is the same as before, though we have shifted the positions of the username and full name arguments: