Parse Command Line Arguments in Bash
Parse Command Line Arguments in Bash getopts getopts optstring opt [arg ...]
#!/bin/bash while getopts 'abc:h' opt; do case "$opt" in a) echo "Processing option 'a'" ;; b) echo "Processing option 'b'" ;; c) arg="$OPTARG" echo "Processing option 'c' with '${OPTARG}' argument" ;; ?|h) echo "Usage: $(basename $0) [-a] [-b] [-c arg]" exit 1 ;; esac done shift "$(($OPTIND -1))" optstring represents the supported options. The option expects an argument if there is a colon (:) after it. For instance, if option c expects an argument, then it would be represented as c: in the optstring When an option has an associated argument, then getopts stores the argument as a string in the OPTARG shell variable. For instance, the argument passed to option c would be stored in the OPTARG variable. opt contains the parsed option. #!/bin/bash while getopts ':abc:h' opt; do case "$opt" in a) echo "Processing option 'a'" ;; b) echo "Processing option 'b'" ;; c) arg="$OPTARG" echo "Processing option 'c' with '${OPTARG}' argument" ;; h) echo "Usage: $(basename $0) [-a] [-b] [-c arg]" exit 0 ;; :) echo -e "option requires an argument.\nUsage: $(basename $0) [-a] [-b] [-c arg]" exit 1 ;; ?) echo -e "Invalid command option.\nUsage: $(basename $0) [-a] [-b] [-c arg]" exit 1 ;; esac done shift "$(($OPTIND -1))" Note that we’ve updated optstring as well. Now it starts with the colon(:) character, which suppresses the default error message. The getopts function disables error reporting when the OPTERR variable is set to zero. Parsing Long Command-Line Options With getopt #!/bin/bash VALID_ARGS=$(getopt -o abg:d: --long alpha,beta,gamma:,delta: -- "$@") if [[ $? -ne 0 ]]; then exit 1; fi eval set -- "$VALID_ARGS" while [ : ]; do case "$1" in -a | --alpha) echo "Processing 'alpha' option" shift ;; -b | --beta) echo "Processing 'beta' option" shift ;; -g | --gamma) echo "Processing 'gamma' option. Input argument is '$2'" shift 2 ;; -d | --delta) echo "Processing 'delta' option. Input argument is '$2'" shift 2 ;; --) shift; break ;; esac done -o option represents the short command-line options --long option represents the long command-line options
