Shell script assistance required..

TheEngineer · 10-25-2006, 04:37 PM

Hi.

I have been using Linux for a few years now and want to
learn how to program/write shell scripts.

So I decided to try and write a simple shell script that will process the arguments on a command line. It must:

(1) display the number of arguments.
(2) show if an argument is only numeric
(3) show if an argument is only alphabetic
(4) show if an argument is only alphanumeric
(5) exit with an error message if an argument is invalid

This is what I have done so far:

Code:

#!/bin/sh

echo -e "\nNumber of parameters: $#\n"

while test $# -gt 0; do
  case "$1" in
    [0-9]*)  echo -e "Numeric: $1\n"
	     shift;;

 [A-Za-z]*)  echo -e "Alphabetic: $1\n"
	     shift;;

  	 *)  echo -e "Error: $1 is an invalid option.\n"
	     exit 1;;

  esac	
done

exit 0

I am having trouble with (4), how to detect an alphanumeric string.

Code:

[A-Za-z0-9]*

would work to some extent, but it seems to pattern match the obvious.

I would appreciate any help.

Thanks,

J.

pixellany · 10-25-2006, 04:55 PM

I don't have my Regex dictionary in front of me, so I don't know the exact syntax, but I think you want:
((A-Z)OR(a-z))AND(0-9)

ie match a pattern that has either LC or UC letters AND at least one number

chrism01 · 10-25-2006, 08:56 PM

If you want it to match only if there is an alpha AND a numeric, you'll need the '1 or more' regex modifer '+' .
I think it's

[A-Za-z]+[0-9]+

this code is untested ... derived from this page: http://www.tldp.org/LDP/abs/html/x14890.html

johndoe0028 · 10-26-2006, 12:16 AM

Here, this works.(A little messy, but...)

Code:

#!/bin/sh

echo -e "\nNumber of parameters: $#\n"

while test $# -gt 0; do
	case "$1" in
		[A-Za-z]*[0-9]* | [0-9]*[A-za-z]*) echo -e "Alphanumeric: $1\n"
		shift;;
		[0-9]*)  echo -e "Numeric: $1\n"
		shift;;
		[A-Za-z]*)  echo -e "Alphabetic: $1\n"
		shift;;
		*)  echo -e "Error: $1 is an invalid option.\n"
	     exit 1;;
	esac
done
exit 0

For alphanumeric, I used "OR" characters, and the range of digits and letters to test it. Alphanumeric comes first, because it is the most complex. (It may pass the numeric test, and switch before it goes through the alphanumeric test. [0-9] doesn't test for letters, so it should go after the one the does)

It doesn't care about non-digit characters or non-letter characters if they are padded by digits or letters, though. 7.5 returns as numeric, 5.a returns as alphanumeric, and a.b returns as alphabetic.

Hope this helps

TheEngineer · 10-26-2006, 06:42 AM

Thanks to all of you who replied.

I shall look at the A.B.S. Guide - it looks very good indeed.

Best regards,

J.