Parsing Command Line Arguments in Bash

What are Command Line Arguments?

Command line arguments are parameters that are passed to a program when it is executed. They are used to provide additional information to the program, such as the name of a file to be processed or a configuration setting. In Bash, command line arguments are stored in the special array variable $@.

How to Parse Command Line Arguments in Bash

Parsing command line arguments in Bash is relatively straightforward. The most common way to parse command line arguments is to use the getopts built-in command. This command takes a single argument, which is a string containing all the valid options that can be passed to the program. For example, if you wanted to parse the command line arguments -f, -v, and -h, you would use the following command:

getopts "fvh" opt

The getopts command will then parse the command line arguments and store the value of each option in the variable $opt. For example, if the user passed the -f option, the value of $opt would be “f”. You can then use a case statement to process each option:

case $opt in
  f)
    # Process -f option
    ;;
  v)
    # Process -v option
    ;;
  h)
    # Process -h option
    ;;
esac

The getopts command also supports long options, such as –help. To parse long options, you need to use the getopt command instead. The syntax for the getopt command is slightly different from the getopts command. For example, to parse the long options –help, –version, and –file, you would use the following command:

getopt --name program --long help,version,file -- "$@"

The getopt command will then parse the command line arguments and store the value of each option in the variable $opt. For example, if the user passed the –help option, the value of $opt would be “–help”. You can then use a case statement to process each option:

case $opt in
  --help)
    # Process --help option
    ;;
  --version)
    # Process --version option
    ;;
  --file)
    # Process --file option
    ;;
esac

Summary

Parsing command line arguments in Bash is relatively straightforward. The getopts and getopt commands can be used to parse both short and long options, respectively. Once the command line arguments have been parsed, you can use a case statement to process each option