Diff for "BashFAQ/035"

   1 #!/bin/sh
   2 # (POSIX shell syntax)
   3 
   4 set -o nounset
   5 # Reset all variables that might be set
   6 file=
   7 verbose=0
   8 
   9 while [ "$#" -gt 0 ]; do
  10     case $1 in
  11         -h|-\?|--help)   # Call a "show_help" function to display a synopsis, then exit.
  12             show_help
  13             exit
  14             ;;
  15         -f|--file)       # Takes an option argument, ensuring it has been specified.
  16             if [ "$#" -gt 1 ]; then
  17                 file=$2
  18                 shift 2
  19                 continue
  20             else
  21                 echo 'ERROR: Must specify a non-empty "--file FILE" argument.' >&2
  22                 exit 1
  23             fi
  24             ;;
  25         --file=?*)
  26             file=${1#*=} # Delete everything up to "=" and assign the remainder.
  27             ;;
  28         --file=)         # Handle the case of an empty --file=
  29             echo 'ERROR: Must specify a non-empty "--file FILE" argument.' >&2
  30             exit 1
  31             ;;
  32         -v|--verbose)
  33             verbose=$((verbose + 1)) # Each -v argument adds 1 to verbosity.
  34             ;;
  35         --)              # End of all options.
  36             shift
  37             break
  38             ;;
  39         -?*)
  40             printf 'WARN: Unknown option (ignored): %s\n' "$1" >&2
  41             ;;
  42         *)               # Default case: If no more options then break out of the loop.
  43             break
  44     esac
  45 
  46     shift
  47 done
  48 
  49 # Suppose --file is a required option. Check that it has been set.
  50 if [ ! "$file" ]; then
  51     echo 'ERROR: option "--file FILE" not given. See --help.' >&2
  52     exit 1
  53 fi
  54 
  55 # Rest of the program here.
  56 # If there are input files (for example) that follow the options, they
  57 # will remain in the "$@" positional parameters.

   1 #!/bin/sh
   2 
   3 # Usage info
   4 show_help() {
   5 cat << EOF
   6 Usage: ${0##*/} [-hv] [-f OUTFILE] [FILE]...
   7 Do stuff with FILE and write the result to standard output. With no FILE
   8 or when FILE is -, read standard input.
   9 
  10     -h          display this help and exit
  11     -f OUTFILE  write the result to OUTFILE instead of standard output.
  12     -v          verbose mode. Can be used multiple times for increased
  13                 verbosity.
  14 EOF
  15 }
  16 
  17 # Initialize our own variables:
  18 output_file=""
  19 verbose=0
  20 
  21 OPTIND=1 # Reset is necessary if getopts was used previously in the script.  It is a good idea to make this local in a function.
  22 while getopts "hvf:" opt; do
  23     case "$opt" in
  24         h)
  25             show_help
  26             exit 0
  27             ;;
  28         v)  verbose=$((verbose+1))
  29             ;;
  30         f)  output_file=$OPTARG
  31             ;;
  32         '?')
  33             show_help >&2
  34             exit 1
  35             ;;
  36     esac
  37 done
  38 shift "$((OPTIND-1))" # Shift off the options and optional --.
  39 
  40 printf 'verbose=<%d>\noutput_file=<%s>\nLeftovers:\n' "$verbose" "$output_file"
  41 printf '<%s>\n' "$@"
  42 
  43 # End of file