Bash shell script with $1 as variable with wildcards

Question

I have a basic bash script that currently looks for input of a specified file as a variable and if it is blank, processes the whole directory.

if i specify a file on execution such as script.sh file1.txt then it processes that file.

What I want and cannot figure out, is how to specify multiple files with wildcards. For example:

script.sh file*.txt

I guess it needs some simple loop, but I could not find any examples that matched this scenario.

When I try to do a loop, it only processes the first match.

#!/bin/bash
if [ $# -eq 0 ]; then
    echo "no argument supplied, pulling all file from tick_tock"

    for i in /var/tank/tick_tock/*.txt; do
        cp "$i" /var/tank/awaiting/
    done
fi
echo "you supplied $1"
cp "$1" /var/tank/awaiting/

Answer 1

If you invoke a script with:

$ script.sh file*.txt

and if there are matches, then the shell will expand that glob to the list of files matches. Assume, for instance, that you have file1.txt, file2.txt, and file3.txt, then the above command is equivalent to:

$ script.sh file1.txt file2.txt file3.txt

The order may differ, but that's not important here.

One option do handling the files in that case is a loop like:

while [[ $# -ne 0 ]]; do
    # process ${1}
    shift
done

The shift will discard the old ${1} and shift the remaining parameters "left" by one (2 becomes 1, 3 becomes 2, etc). The shift also updates $#.

For example:

#!/bin/bash

while [[ $# -ne 0 ]]; do
    echo ${1}
    shift
done

If I run that script, I see:

$ ./script.sh a b c
a
b
c
$

Answer 2

The thing here is that the wildcard pattern expands to multiple arguments, not just to a single argument at $1. The others are in $2, $3, etc. You can't index into those with standard shell features, but usually you don't need to: you can access the list of arguments to the script with "$@". So:

if [ "$#" -eq 0 ]; then
    echo "no arguments"
else
    echo "$# arguments:"
    for x in "$@"; do
        echo " $x"     # or do whatever with $x
    done
fi

Something like cp -- "$@" /var/tank/awaiting/ would in turn call cp with the files the script got as arguments. The -- there prevents any following arguments from being taken as options to cp.