Option parsing with getopts in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this getopts script?

Consider this bash script snippet using getopts to parse options. What will it print when run with arguments -a -b value -c?

Bash Scripting

#!/bin/bash
while getopts "ab:c" opt; do
  case $opt in
    a) echo "Option a set";;
    b) echo "Option b set with value $OPTARG";;
    c) echo "Option c set";;
    *) echo "Invalid option";;
  esac
done

A

Option a set
Option b set with value
Option c set

B

Option a set
Option b set with value value
Option c set

C

Option a set
Option b set with value value

D

Option a set
Option c set

💡 Hint

Remember that getopts processes options one by one and that options with a colon expect an argument.

The script defines options 'a', 'b:' (which requires an argument), and 'c'. Running with '-a -b value -c' triggers all three options. The 'b' option prints its argument stored in $OPTARG.

💻 Command Output

intermediate

What error does this getopts usage produce?

What error or output results from running this script with arguments -x?

Bash Scripting

#!/bin/bash
while getopts "ab:" opt; do
  case $opt in
    a) echo "Option a";;
    b) echo "Option b with $OPTARG";;
    *) echo "Unknown option: $opt";;
  esac
done

A Option b with x

B getopts: illegal option -- x

C Option a

D Unknown option: x

💡 Hint

Check how getopts handles options not defined in the option string.

When getopts encounters an unknown option, it sets the option variable to '?' and triggers the default case. The script prints 'Unknown option: x'.

📝 Syntax

advanced

Which option string correctly requires an argument for option 'f'?

You want to parse options where option 'f' requires an argument. Which option string is correct for getopts?

A "f:"

B "f"

C ":f"

D ":f:"

💡 Hint

In getopts, a colon after an option letter means it requires an argument.

The colon after 'f' in "f:" tells getopts that 'f' requires an argument. Without the colon, 'f' is treated as a flag without argument.

🚀 Application

advanced

How to correctly shift positional parameters after getopts?

After parsing options with getopts, you want to remove the processed options from the positional parameters. Which command correctly shifts the parameters?

A shift $((OPTIND - 1))

B shift $OPTIND

C shift $((OPTIND))

D shift $((OPTIND + 1))

💡 Hint

OPTIND points to the next argument to be processed, so subtract 1 to shift processed options.

OPTIND is the index of the next argument to be processed. To remove all processed options, shift by OPTIND minus 1.

🔧 Debug

expert

Why does this getopts script fail to parse option arguments correctly?

Given this script snippet, why does it fail to print the argument for option 'd' when run with -d value?

#!/bin/bash
while getopts "d" opt; do
  case $opt in
    d) echo "Option d with argument $OPTARG";;
    *) echo "Invalid option";;
  esac
done

A getopts does not support options with arguments

B OPTARG is not set because the script uses the wrong variable name

C Option 'd' is not marked to require an argument in the option string

D The script is missing a shift command after getopts

💡 Hint

Check the option string passed to getopts and how it indicates required arguments.

The option string "d" means option 'd' does not expect an argument. To accept an argument, it should be "d:". Without the colon, OPTARG is never set.