Bash – How to shift arguments while arguments start with –

bashshell-script

Say I have a bash function, which is supposed to remove all arguments that start with "-" until it gets to an argument that does not start with "-".

gmx(){

  local options=( );

  while [ "${1:0:1}" == "-"  ]; do
    options+=("${1}")
    shift 1;
  done

  echo "first legit arg: $1"
  "$@" # omg will be executed here, like `omg --rolo`
}

gmx -a -f -c omg --rolo

this seems to work, but I am wondering if this is a good generic solution to always get 'omg' to be the first "legit" argument. Are there any edge cases that might fail?

In other words -a, -f, -c are all arguments to gmx. Whereas omg and everything that follows, will be run in a child process.

Best Answer

The official and best way is t use the getopts builtin to parse the command line options.

See the man page for more information.

A note may be important: bash does not support long options.

If you like scripts to deal with long options, you have two shells that support them: ksh93 and bosh. Both shells support long options the way they are supported by the getopt(3) function in libc on Solaris. See the bosh man page (currently starting at page 43:

http://schilytools.sourceforge.net/man/man1/bosh.1.html

getopts "f:(file)(input-file)o:(output-file)" OPT

supports e.g an option -f with an argument and that option has a long option alias --file and a second alias for this option --input-file

ksh93 supports this as well, even though it is not documented in the ksh93 man page.

Related Solutions

shell-script command-line arguments – Get First CLI Argument After Options in Shell Script

Your requirements are logically contradictory. Given input like gitploy up -t 2.0.0 test_repo, you need to parse the options, and in particular notice the presence of the -t option and the fact that it takes one argument, in order to identify that the first non-option argument is test_repo.

So first parse the options normally. Then you can know what the first operand is. At that point, process the options. Store the information you need about the options in variables.

action="$1"
shift
unset t_arg
while getopts "zhvdurqw:c:i:e:o:b:t:f:p:g" opt; do
  case "$opt" in
    c) c_arg="$OPTARG";;
    …
  esac
done
shift "$((OPTIND-1))"
root_arg="$1"

if [ -n "${c_arg+1}" ]; then
  queue_callback "$OPTARG"
  echo "$root_arg was here"
fi

Bash – How to pass files found by find as arguments

Use arrays.

If you don't need to handle the possibility of newlines in your filenames, then you could get away with

mapfile -t ABC_FILES < <(find -L some/dir -name \*.abc | sort)
mapfile -t XYZ_FILES < <(find -L other/dir -name \*.xyz | sort)

then

./program --abc-files "${ABC_FILES[@]}" --xyz-files "${XYZ_FILES[@]}"

If you do need to handle newlines within filenames, and have bash >= 4.4, you can use -print0 and -d '' to null-terminate the names during array construction:

mapfile -td '' ABC_FILES < <(find -L some/dir -name \*.abc -print0 | sort -z)

(and similarly for the XYZ_FILES). If you don't have the newer bash, then you could use a null-terminated read loop to append filenames to the arrays e.g.

ABC_FILES=()
while IFS= read -rd '' f; do ABC_FILES+=( "$f" ); done < <(find -L some/dir -name \*.abc -print0 | sort -z)

Best Answer

Related Solutions

shell-script command-line arguments – Get First CLI Argument After Options in Shell Script

Bash – How to pass files found by find as arguments

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