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In order to run a bash script I need some arguments and flags, since the requirements are pretty tricky I've chosen to use a getopt function like this

while getopts ":s:g:r" o; do case "${o}" in s) # Variables that require value VALUE1=${OPTARG} ;; g) # Variables that require value MGROUP=${OPTARG} ;; r) # Variables that, if present, set just a flag ASROOT=1 ;; *) echo "Usage: ./myscript.sh -s value1 -g value2 -r" ;; esac done

I would like to have all parameters optional so I can write some conditions later in my code, and first two (s and g) with an arguments, the third (r) is only a optional flag. In the future I may need to add additional parametrers, always optional. Any advice?

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  • Firstly I'd suggest you to edit the title, as your ask is regarding getopts (bash builtin) and not getopt (gnu alternative). So, as optional parameter, you're saying that sometimes you gona use the options with an argument and sometimes you gona need to use it without argument? Like -s "optional argument"? Commented Aug 17, 2017 at 12:43
  • Voting to close as unclear. What are your actual requirements? Commented Aug 17, 2017 at 14:14
  • Ok, first of all the question is regarding getops, fine for me to edit the title. Second my question specifically regards this line: while getopts ":s:g:r" o; do - the question is: how to have all options not mandatory. An option that require an argument must have it, any option that is just a flag must remain this way. Apologise for ambiguity and hope this helps to clarify a bit more. Thanks to everyone Commented Aug 18, 2017 at 12:30

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Sample script illustrating optional arguments with bash getopts in a style similar to mysql client. "--" is also supported.

Usage: script.sh [-u ] [-p | -p] [--] arg1 arg2 ...

#!/bin/bash # # Sample script illustrating optional arguments with bash getopts in # a style similar to mysql client. "--" is also supported. # # [email protected] - 5-Oct-2019 - Distribute/use without restriction. # # Defaults username="$(whoami)" unset password while getopts ":u:p:" arg; do case $arg in u) # Username username="$OPTARG" ;; p) # Password thisarg=$((OPTIND - 1)); thisarg="${!thisarg}"; thisarg="${thisarg:2}" if [[ ! -z $OPTARG ]] && [[ "$OPTARG" != "$thisarg" ]]; then unset password OPTIND=$((OPTIND - 1)) else password="$thisarg" fi if [[ -z $password ]]; then read -s -p "Password: " password echo fi ;; \?) # Request Help echo "Sorry that I can be of no help." ;; *) # Deal with option at end of line OPTION=$((OPTIND - 1)); OPTION="${!OPTION}" case $OPTION in --) # Add support for -- break ;; -p) # Option with optional argument unset password read -s -p "Password: " password echo ;; *) # Invalid argument echo "Error; Invalid option \"$OPT\"." >&2 ;; esac ;; esac done shift $((OPTIND -1)) echo "Username: $username" echo "Password: $password" echo echo "Remaining arguments:$*" echo
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The optional parameter are optional to make mandatory check VALUE1 and MGROUP. For example:

[[ -n $VALUE1 && -n $MGROUP ]] || { echo "mandatory paramter missing" exit 1 }

getopts

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