I'm trying to write a script that runs in the background (&) The program names are entered as parameters on the command line. I want to use a loop without hard coding the number of iterations: I want it to execute an arbitary number of programs. Before executing, I need to verify that the program exists, is an ordinary file , and is executable. Could someone please help.....Thanks in advance.

To get the number of positional parameters
given on the command line you can use the
"$#" variable. You could also use a "while"
loop with "$*" (all positional parameters)
as it's input.

You can use the following conditional expressions
for "test" against the files...

-f evaluates true if file exists and is a
regular file.

-x evaluates true if file exists and is an
executable file.

You can "AND" ( && ) these conditions to check
for both in a single "test"

Here is the code I came up with. Any suggestions?
added code tags for readability --oombera

Well... I know Neo is going to bust my chops for this
but you did try somthing and you need a little
direction so here goes...

OK. The first thing you should do in all shell scripts is to
set up the execution environment. You do this by inserting
the following line as the very first line in your script
(without the comments)...
#!/bin/sh <- Bourne Shell (normally)
...or
#!/bin/ksh <- Korn Shell
...or
#!/bin/csh <- C Shell

...remember that $* expands to ALL the positional parameters.
You need to read each one into a variable...
for prog in $*
do

... now, each time through the loop, $prog contains the next
positional parameter. Next, you want to check $prog for
"ordinary file" AND "executable file"...
if [ -f $prog -a -x $prog ]
then
...
else
...
fi

...then end your "do/done" loop and exit
done
exit 0

...just FYI, it's good programming practice to return some
sort of value (0 = AOK, 255 = Error) although this is a personal
preference.

You can then run this script in the background...
myscript /bin/ls /usr/bin/stat /bin/df ./myprog &

...you get the picture.