Option parsing with getopts in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of getopts in bash scripting?

getopts helps scripts read and handle command-line options (flags) easily and consistently.

It parses options like -a or -b value so your script can respond accordingly.

beginner

How do you specify that an option requires an argument in getopts?

In the options string passed to getopts, add a colon : right after the option letter.

For example, getopts "a:b" means -a needs an argument, -b does not.

intermediate

What variable does getopts use to store the current option letter?

getopts stores the current option letter in the shell variable given as its second argument (typically named opt).

OPTARG holds the argument value for options that require one, while OPTIND tracks the next index to process.

intermediate

What does the variable OPTIND represent in getopts usage?

OPTIND is the index of the next argument to be processed by getopts.

It starts at 1 and increments as options are parsed, helping your script know where options end and positional arguments begin.

beginner

Write a simple getopts loop to handle options -a (no argument) and -b (requires argument).

while getopts "ab:" opt; do
  case $opt in
    a) echo "Option a triggered" ;;
    b) echo "Option b with value: $OPTARG" ;;
    *) echo "Invalid option" ;;
  esac
done

In getopts, how do you indicate that an option requires an argument?

A Add a colon ':' after the option letter in the options string

B Add a semicolon ';' after the option letter

C Use uppercase letters for options with arguments

D Put the option letter inside square brackets

Adding a colon ':' after the option letter tells getopts that this option needs an argument.

Which variable holds the argument value for an option in getopts?

A OPTARG

B OPTIND

C OPTVAL

D OPTOPT

OPTARG stores the argument value for options that require one.

What does OPTIND represent in getopts?

A The total number of options parsed

B The current option letter

C The index of the next argument to process

D The exit status of the last command

OPTIND tracks the next argument index to be processed by getopts.

What happens if getopts encounters an unknown option?

A It throws a syntax error

B It stops the script immediately

C It ignores the option silently

D It sets the option variable to '?'

getopts sets the option variable to '?' when it finds an invalid option.

Which command correctly starts a getopts loop for options -x and -y with -y requiring an argument?

A while getopts "xy" opt; do ... done

B while getopts "xy:" opt; do ... done

C while getopts "x:y:" opt; do ... done

D while getopts "x:y" opt; do ... done

Option y requires an argument, so it is followed by a colon ':' in the options string.

Explain how to use getopts to parse command-line options in a bash script.

Think about how you tell the script which options need arguments and how you handle each option inside the loop.

Describe the roles of OPTARG and OPTIND when using getopts.

One stores values, the other tracks position.