Pass a regular expression as a parameter to a shell script - regex

Question

How to pass a regular expression as a parameter to a shell script?
I need to write a shell script, which will take parameters and give them to unix commands. And I'd like to use regular expressions there. Is this possible at all?
Or reformulation - how to write the script equivalent to "cp" command, using only this command?
I'm trying to make a file "mycp"
#!/bin/bash -fx
cp $2 $1
and call it by
mycp myDir "*sh"
and want it to do the same as "cp *sh myDir".
But resulting bash interpretation is:
+ cp '*sh' myDir
cp: *sh: No such file or directory

Answer 1

Revised question
I'm trying to make a file "mycp"
#!/bin/bash -fx
cp $2 $1
and call it by
mycp myDir "*sh"
In that case, you still need eval, but you'd write:
#!/bin/bash -x
eval cp "$2" "$1"
You're running into problems because you have specified the -f option. man bash says (in part):
After word splitting, unless the -f option has been set, bash scans each word for the characters *, ?, and [.
Remove the f from the 'shebang' (first) line of the script.
Original question
Given that you want mycp "*sh*" aa to do shell expansion on the argument, you'll probably end up using eval in your script:
eval cp "$#"
However, the use of eval is dangerous; it can lead to unexpected side-effects. The use of "$#" is important; it preserves the number of arguments and spaces in them. Unfortunately, using eval then undoes that, but we can't have everything — or not easily.
For quite a long time (say 1987* to 1999), I used this script as a cover for cp:
: "#(#)$Id: cp.sh,v 1.3 1997/06/02 21:45:00 johnl Exp $"
#
# Alternative copy command
case $# in
0) /bin/cp ;;
1) /bin/cp $1 . ;;
2) /bin/cp "$#" ;;
*) if [ -d `la "$#"` ]
then /bin/cp "$#"
else /bin/cp "$#" .
fi;;
esac
It uses a very simple C program called la (for 'last argument') to get the last argument and checks whether the given last argument is a directory. More than 99% of the time, if I typed (by accident) 'cp /some/where/sh' rather than cp /some/where/*sh* ., the second was what I meant, and the script fixed things. I haven't used it for quite some time; it may have been in the last millennium, but was probably sometime earlier in this one that I gave up using it.
* Although the version string says '1997', the code is identical to the 1987 version. Version 1.1 and 1.2 were under SCCS and used different SCCS ID strings; the conversion to RCS made them identical. Version 1.3 reinstated the #(#) identifier string used by the SCCS what command to the RCS version handling. So, the script is ancient — 1987, really.

Answer 2

Try this: eval cp $1 $2
Bash reference manual: eval

Answer 3

If all you want to do is specify the directory first, look at the -t option to GNU cp:
alias mycp='cp -t'
mycp mydir *.sh
Otherwise:
mycp() {
local dir=$1
shift
cp "$#" "$dir"
}
mycp mydir *.sh
Either way, let the shell expand the wildcards and avoid the use of eval
(note, *.sh is not a regular expression, it's a shell "pattern", often referred to as a "glob pattern")