Need shell script help - processing the same option multiple times

Question

So I've ran into a bit of a wall, I have an option in my script that calls a function which allows me to specify a file/directory and then I want to parse that output into a menu tool (using dmenu in this case) to select which file is the one I want specifically and continue working with that selection as a variable in the same script. This works fine if it's just one file or directory, but I want to be able to use the option multiple times and then parse all of that output at once to dmenu. Here's a snippet

fileSelection () { if [ -d "${OPTARG}" ]; then find "${OPTARG}" -type f; fi; if [ -f "${OPTARG}" ]; then printf '%s\n' "${OPTARG}"; fi; } while getopts "f:" option; do case "${option}" in f) file="$(fileSelection|dmenu)";; esac done 

And like I said this works if I do:

myscript -f file 

or

myscript -f directory 

but I was hoping to also be able to do this:

myscript -f file1 -f file2 

The problem is, since the function is called consecutively I can't parse the output into dmenu like that, because it doesn't invoke dmenu with options file1 and file2, but first with file1 and then with file2, I hope this makes sense.

There might be some really simple solution I am missing, I've thought about simply writing the output into a file and then parsing that which might work, but I'd like to avoid piping to files if possible. I am also trying to keep it POSIX compliant, and would appreciate answers that follow that.

Answer 1

You can collect the values derived from your -f and pass them all together to dmenu. Here's an example that will work for most directories and files - but not those containing an embedded newline:

#!/bin/bash # if ! type dmenu >/dev/null 2>&1 then # Demonstration code in case dmenu is not installed dmenu() { echo "This is a fake implementation of dmenu" >&2 sed 's/^/> /' >&2 } fi # List of files from the -f option files=() # Loop across the command line while getopts "f:" OPT do case $OPT in f) # Disable globbing OIFS="$IFS" IFS=$'\n' noglob=$(set -o | awk '$1=="noglob"{print $2}') set -o noglob # Capture the specified set of files files+=( $(find "$OPTARG" -type f) ) # Reenable globbing IFS="$OIFS" [ "$noglob" = 'off' ] && set +o noglob ;; esac done # If we have some files then pass them to dmenu [ "${#files[@]}" -gt 0 ] && printf '%s\n' "${files[@]}" | dmenu 

Since you want a POSIX solution, and you're already assuming file names cannot contain newlines, you could build up a single string of newline-terminated values and use that. Actually, in this case I'd probably build the set of starting points and then use find | dmenu across them rather than build the set of results like I have in my first approach.

#!/bin/sh # List of source files from the -f option files= # Loop across the command line nl=' ' while getopts "f:" OPT do case $OPT in f) # Capture the source file name files="$files$OPTARG$nl" ;; esac done # If we have some files then pass them to dmenu if [ -n "$files" ] then while [ -n "$files" ] do file=${files%%$nl*} # get first NL-terminated entry files=${files#*$nl} # strip it off the list find "$file" -type f # generate the set of files done | dmenu fi 

Answer 2

Your fileSelection|dmenu assumes file paths don't contain newline characters anyway, so you can make $file a newline separated/delimited list:

NL=' ' files= ... (f) files=$files$(fileSelection|dmenu)$NL;; ... # to use $files, like pass each file as separate arguments to a # command, use split+glob with glob disabled IFS=$NL; set -o noglob cmd -- $files 

An alternative is to generate the set -- ... shell code to set the list of positional parameters to the list of files

sh_quote() { LC_ALL=C sed "s/'/'\\\\''/g; 1s/^/'/; \$s/\$/'/" } files= ... (f) files="$files $(fileSelection|dmenu|sh_quote)";; ... # and to use either eval "cmd -- $files" # or eval "set -- $files" cmd -- "$@" 

POSIXly, that's still dangerous as sed is not required to work correctly with lines exceeding LINE_MAX bytes in length and the output of find is not guaranteed to have lines as short (not even shorter than PATH_MAX itself not guaranteed to be shorted than LINE_MAX).

Answer 3

Make the option-parsing while-loop output the found names, and pass the output of it to dmenu. I.e., move the piping to dmenu from the output from fileSelection to the output of the while-loop.

To do this correctly, we first need to be certain that there actually are at least one -f option on the command line. This means having to parse the options twice: once to handle any other option and to detect a -f, and once more to act on the -f options and to get the file list and let the user pick filename into our file variable.

#!/bin/sh usage () { echo 'use with "-h" or "-f somepath" (optionally repeated)' } fileSelection () { if [ -d "${OPTARG}" ]; then find "${OPTARG}" -type f; fi; if [ -f "${OPTARG}" ]; then printf '%s\n' "${OPTARG}"; fi; } # Parse command line options and set a flag # if we have any -f options to deal with. f_flag=false while getopts hf: opt; do case $opt in h) usage; exit ;; f) f_flag=true ;; *) echo 'error' >&2; exit 1 esac done if "$f_flag"; then # Now parse all options again, # but only care about the -f options. OPTIND=1 file=$( while getopts hf: opt; do case $opt in (f) fileSelection; esac done | dmenu ) fi 

Answer 4

I have maybe found a solution after looking more into the POSIX way of doing arrays

#!/bin/sh fileSelection () { printf '%s\n' "${OPTARG}" } while getopts "f:" option; do case "${option}" in f) set -- "$@" "$(fileSelection)";; esac done printf '%s\n' "$@" | sed "/^-/ d;" 

this is a very simplified version of the script but simply parsing from sed into dmenu should produce what I want. I'll double check once I am home. Thanks to Chris Davies for pointing me in the right direction.