getopts one liners

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The base-syntax for getopts is:

getopts OPTSTRING VARNAME [ARGS...]

where:

OPTSTRING - tells getopts which options to expect and where to expect arguments (see below)

VARNAME - tells getopts which shell-variable to use for option reporting

ARGS - tells getopts to parse these optional words instead of the positional parameters

The option-string tells getopts which options to expect and which of them must have an argument. The syntax is very simple — every option character is simply named as is, this example-string would tell getopts to look for -f, -A and –x

getopts fAx VARNAME

When you want getopts to expect an argument for an option, just place a : (colon) after the proper option flag. If you want -A to expect an argument (i.e. to become -A SOMETHING) just do:

getopts fA:x VARNAME

If the very first character of the option-string is a : (colon), which indicate getopts to switch to "silent error reporting mode". In productive scripts, this is helpful to handle errors yourself without being disturbed by annoying messages.

getopts :fA:x VARNAME

Example script getopts with only single mandatory argument

#!/bin/bash

while getopts ":a:" opt; do

  case $opt in

    a)

      echo "-a was triggered, Parameter: $OPTARG" >&2

      ;;

    \?)

      echo "Invalid option: -$OPTARG" >&2

      exit 1

      ;;

    :)

      echo "Option -$OPTARG requires an argument." >&2

      exit 1

      ;;

  esac

done

Executing script with below style will not give you any output as below,

# sh getops-01.sh

#

# sh getops-01.sh /etc/passwd

#

Executing script with option will show you various outputs as below,

# sh getops-01.sh -a

Option -a requires an argument.

# sh getops-01.sh -b

Invalid option: -b

# sh getops-01.sh -c

Invalid option: -c

# sh getops-01.sh -a 123

-a was triggered, Parameter: 123

# sh getops-01.sh -a 123 -a -a -c

-a was triggered, Parameter: 123

-a was triggered, Parameter: -a

Invalid option: -c

Example script getopts with two mandatory arguments

#!/bin/bash

while getopts ":a:b:" opt; do

  case $opt in

    a )

      echo "-a was triggered, Parameter: $OPTARG"

      ;;

    b )

      echo "-b was triggered, Parameter: $OPTARG"

      ;;

    \? )

      echo "Invalid option: -$OPTARG"

      exit 1

      ;;

    : )

      echo "Option -$OPTARG requires an argument."

      exit 1

      ;;

  esac

done

Executing script with below style will not give you any output as below,

# sh getops-02.sh

#

# sh getops-02.sh /etc/passwd

#

Executing script with option will show you various outputs as below,

# sh getops-02.sh -a

Option -a requires an argument.

# sh getops-02.sh -a -b

-a was triggered, Parameter: -b

# sh getops-02.sh -a 123

-a was triggered, Parameter: 123

# sh getops-02.sh -a 123 -b

-a was triggered, Parameter: 123

Option -b requires an argument.

# sh getops-02.sh -a 123 -b 234

-a was triggered, Parameter: 123

-b was triggered, Parameter: 234

# sh getops-02.sh -a 123 -b 234 -c

-a was triggered, Parameter: 123

-b was triggered, Parameter: 234

Invalid option: -c

References:-
http://wiki.bash-hackers.org/howto/getopts_tutorial

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