Problem with wildcard expansion in for loop range

Question

I'm having a problem here on a bash script I made. In a for loop, I iterate on all the arguments to construct a string variable that is later fed to an "eval" command:

    for arg in "$*"
    do
        if [ $arg != $lastArg ]; then
            findTarget+="-name $arg -o "
        else
            findTarget=$(echo $findTarget | sed 's/-o$//')
            break
        fi
    done

The problem stems from the "$*". For example when I enter "*.c" in the arguments, and the current folder contains files that match that pattern, the *.c argument is expanded into those files; I do not want that, I want findTarget to be concatenated with -name *.c -o, I have tried with and witout quotes, using eval, nothing seems to work. Any idea how to do this (simply if possible) ? Note: the total number of arguments can vary.

This is an example of how I run the script:

$ trouver.bash *.c *.f90 someString

At the end of my for loop, the variable findTarget should read -name *.c -o -name *.f90

This does not work if the *.c or *.f90 match files in the current folder...

Answer 1

The syntax to loop over the positional parameters is for arg do alone. "$*" is the concatenation of the positional parameters with the first character of $IFS, so you would be looping over one element only.

Also, if you want to build a list of arguments for the find command, you need an array, not a string. And don't forget to quote your variables!

So:

findTarget=()
or=()
for arg
do
    [ "$arg" = "$lastArg" ] && break
    findTarget+=("${or[@]}" -name "$arg")
    or=(-o)
done

find . \( "${findTarget[@]}" \)

Note that when you invoke your script, you need to quote the *.c... patterns as otherwise they would be expanded by the shell before being passed to the script.

trouver.bash '*.c' '*.f90' someString

If your interactive shell is zsh, you can define an alias for your command where globbing is disabled with:

alias trouver.bash='noglob trouver.bash'

That way, you can do:

trouver.bash *.c *.f90 someString

without the shell expanding those *.c *.f90 globs.

Answer 2

The use of "$*" means to join all arguments into a long one. Changing it to "$@" should give a list of arguments. But there is no real need to use for arg in "$@" as for arg is the correct idiom.

Then, to add a -o for each new argument we may use ${findTarget[@]+"-o "}.
It will be null if no value has been assigned to findTarget and will be the plain string -o if findTarget has any value assigned. In the first loop run it will collapse to nothing, in the next runs it will become -o.

(( $# < 1 )) && echo "please provide some argument(s)" && exit 1

unset  findTarget
for    arg
do     [[ "$arg" == "$lastArg" ]] && break
       findTarget+=("${findTarget[@]+"-o "}-name $arg")
done

find . \( "${findTarget[@]}" \)

You need to remember to run the script as this:

$ trouver.bash '*.c' '*.f90' someString

as you want that each argument gets not expanded by the shell (use single quotes. double quotes may work but do not express the intent to keep the arguments without expansion as clearly).

If you need to use the script without the "single quotes", you may remove the "Pathname expansion" (set -f) to avoid the expansion of *.

$ ( set -f; trouver.bash *.c *.f90 someString )

The () will avoid that the change to noglob affects the present running shell.

That works because the script will write the results to stdout, which also work printing from inside the sub-shell (…).