Question

I would like to run recursively myscript.sh, to execute all files in the directory:

It has been discussed here that I could do like this:

#!/bin/bash

for file in * ; do
    echo $file
done

But I would like myscript.sh to execute with this syntax, so that I could select only certain filetypes to be executed:

./myscript.sh *.dat

Thus I modify the script above:

#!/bin/bash

for file in $1 ; do
    echo $file
done

In which when executing, it only executes first occurrence, not all files with *.dat extensions.

What is wrong here?

Answer 1

The wildcard *.dat is expanded by the shell before your script ever sees it. So the filenames show up in your script as $1, $2, $3, etc.

You can work with them all at once by using the special $@ variable:

for file in "$@"; do
    echo $file
done

Note that the double quotes around "$@" is special. From man bash:

@  Expands to the positional parameters, starting from one.  When  the  expansion
   occurs  within double quotes, each parameter expands to a separate word.  That
   is, "$@" is equivalent to "$1" "$2" ...  If the double-quoted expansion occurs
   within  a word, the expansion of the first parameter is joined with the begin-
   ning part of the original word, and the expansion of  the  last  parameter  is
   joined  with the last part of the original word.  When there are no positional
   parameters, "$@" and $@ expand to nothing (i.e., they are removed).