Diff for "BashFAQ/035"

   1 #!/bin/sh
   2 # POSIX
   3 
   4 # Reset all variables that might be set
   5 file=
   6 verbose=0 # Variables to be evaluated as shell arithmetic should be initialized to a default or validated beforehand.
   7 
   8 while :; do
   9     case $1 in
  10         -h|-\?|--help)   # Call a "show_help" function to display a synopsis, then exit.
  11             show_help
  12             exit
  13             ;;
  14         -f|--file)       # Takes an option argument, ensuring it has been specified.
  15             if [ -n "$2" ]; then
  16                 file=$2
  17                 shift
  18             else
  19                 printf 'ERROR: "--file" requires a non-empty option argument.\n' >&2
  20                 exit 1
  21             fi
  22             ;;
  23         --file=?*)
  24             file=${1#*=} # Delete everything up to "=" and assign the remainder.
  25             ;;
  26         --file=)         # Handle the case of an empty --file=
  27             printf 'ERROR: "--file" requires a non-empty option argument.\n' >&2
  28             exit 1
  29             ;;
  30         -v|--verbose)
  31             verbose=$((verbose + 1)) # Each -v argument adds 1 to verbosity.
  32             ;;
  33         --)              # End of all options.
  34             shift
  35             break
  36             ;;
  37         -?*)
  38             printf 'WARN: Unknown option (ignored): %s\n' "$1" >&2
  39             ;;
  40         *)               # Default case: If no more options then break out of the loop.
  41             break
  42     esac
  43 
  44     shift
  45 done
  46 
  47 # if --file was provided, open it for writing, else duplicate stdout
  48 if [ -n "$file" ]; then
  49     exec 3> "$file"
  50 else
  51     exec 3>&1
  52 fi
  53 
  54 # Rest of the program here.
  55 # If there are input files (for example) that follow the options, they
  56 # will remain in the "$@" 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