56 lines
1.6 KiB
Bash
56 lines
1.6 KiB
Bash
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#!/bin/sh
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# POSIX
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# Reset all variables that might be set
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file=
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verbose=0 # Variables to be evaluated as shell arithmetic should be initialized to a default or validated beforehand.
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while :; do
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case $1 in
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-h|-\?|--help) # Call a "show_help" function to display a synopsis, then exit.
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show_help
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exit
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;;
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-f|--file) # Takes an option argument, ensuring it has been specified.
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if [ -n "$2" ]; then
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file=$2
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shift
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else
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printf 'ERROR: "--file" requires a non-empty option argument.\n' >&2
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exit 1
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fi
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;;
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--file=?*)
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file=${1#*=} # Delete everything up to "=" and assign the remainder.
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;;
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--file=) # Handle the case of an empty --file=
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printf 'ERROR: "--file" requires a non-empty option argument.\n' >&2
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exit 1
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;;
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-v|--verbose)
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verbose=$((verbose + 1)) # Each -v argument adds 1 to verbosity.
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;;
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--) # End of all options.
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shift
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break
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;;
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-?*)
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printf 'WARN: Unknown option (ignored): %s\n' "$1" >&2
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;;
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*) # Default case: If no more options then break out of the loop.
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break
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esac
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shift
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done
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# if --file was provided, open it for writing, else duplicate stdout
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if [ -n "$file" ]; then
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exec 3> "$file"
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else
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exec 3>&1
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fi
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# Rest of the program here.
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# If there are input files (for example) that follow the options, they
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# will remain in the "$@" positional parameters.
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