Counting characters with unix utilities

[Bob McGowen x4312 dept208]

In article <1990Sep28.173033.292 at msi.umn.edu> haberman at msi.umn.edu (Joe Habermann) writes:
>george at hls0.hls.oz (George Turczynski) writes:
>
...
Deleted examples of awk scripts.
...

Original postings on this topic used tr and wc.  Following that line
I decided to try my hand at a script for counting characters.  In the
meantime things seem to have moved away from the "simple" solutions
into more esoteric (still interesting) ways to solve the problem.

Never the less I will present my script for commnent and feed back.
The basic design is to take advantage of the tr commands use of regular
expressions and provide a tool that will allow the user to count the
set of characters named or their inverse.  So:

	chrcnt abc file
	chrcnt -n abc file

will count all occurances of the letters a, b and c followed by a count
of all characters that are not a, b or c.  This will work with white
space as well and handles cases where there are no matches.  The use
of cat allows you to specify one or more files on the command line or
have the script read its standard input.  One final note is that if you
should want to look for dashes and n's, use n- as the pattern (or --n,
if you want).

------------script follows----------

#!/bin/sh

case $# in
   0)
      # the following is because cmd aliasing can produce absolute paths
      CMD=`basename $0`
      echo "$CMD:  usage:  $CMD [-n] reg_expression [files...]\n"\
	   "\twhere -n means not the following pattern characters." >&2
      exit 1
   ;;
   1) # if only one arg it must be the pattern
      TR_ARGS=-cd
      pattern="$1"
   ;;
   *) # all other cases may or may not have -n as the first arg
      case $1 in
	 -n)
	    TR_ARGS=-d
	    pattern="$2"
	    shift;shift
	    files="$*"    # if only two args, files is null
	 ;;
	 *)
	    TR_ARGS=-cd
	    pattern="$1"
	    shift
	    files="$*"
	 ;;
      esac
   ;;
esac

cat $files |
tr $TR_ARGS "$pattern" |
wc -c

Bob McGowan  (standard disclaimer, these are my own ...)
Product Support, Wyse Technology, San Jose, CA
..!uunet!wyse!bob
bob at wyse.com