Path: utzoo!mnetor!uunet!mcvax!unido!ecrcvax!alan
From: alan@ecrcvax.UUCP (Alan P. Sexton)
Newsgroups: comp.unix.wizards
Subject: Re: Building Variable Names in Bourne Shell
Message-ID: <521@ecrcvax.UUCP>
Date: 24 Mar 88 11:32:45 GMT
References: <12565@brl-adm.ARPA>
Reply-To: alan@ecrcvax.UUCP (Alan P. Sexton)
Organization: ECRC, Munich 81, West Germany
Lines: 223

In article <12565@brl-adm.ARPA> kevinc@bearcat.lim.tek.com (Kevin Cosgrove 627-5212) writes:
>Anyone know how to build *accessible* variable names on the fly in Bourne
>shell?  Below is a do nothing script which, I hope, demonstrates what I
>want to do.
>
>#!/bin/sh
>onestring="A"			# set the values of arbitrary strings
>twostring="B"
>threestring="C"
>for string in one two three	# loop thru string sets
>do
>   var="${string}string"	# var contains the name of the string
>				# I wish to get access to
>
>   echo "\$$var = ${var}"	# how do I get the contents of the string
>				# "pointed to" by var?
>   echo
>done

Here is an example that I think will show how to do what you want.
I wrote it a looooong time ago to learn how to do shell
programming and kept it as a reference.
I make no claim that it is a `good' example of a sh script - merely
that it shows how to pretend that sh has dynamic array variables and the
like.

The script records a persons name, the number of hours of lectures and the
number of hours of tutorials he has given. It is very stupid and it
would be far easier to just edit a file to record the data.
a script of a sample is included.

I originally wrote this on a version 7 system (yes THAT long ago)
and I just fixed it so that it works on a bsd4.3 system so that I
could get the typescript.

Alan Sexton				ECRC, Arabellastr 17,
alan@ecrcvax.UUCP			8000 Muenchen 81, West Germany
mcvax!unido!ecrcvax!alan		tel. (089) 92699164

#! /bin/sh
# This is a shell archive, meaning:
# 1. Remove everything above the #! /bin/sh line.
# 2. Save the resulting text in a file.
# 3. Execute the file with /bin/sh (not csh) to create the files:
#	paycheck
#	typescript
# This archive created: Thu Mar 24 12:28:57 1988
export PATH; PATH=/bin:$PATH
echo shar: extracting "'paycheck'" '(1874 characters)'
if test -f 'paycheck'
then
	echo shar: will not over-write existing file "'paycheck'"
else
sed 's/^X//' << \SHAR_EOF > 'paycheck'
X#! /bin/sh
XN=1
Xif test -f "$1"
Xthen
X   exec <$1
X   while read NAME$N LECTS$N TUT$N
X   do
X      eval echo $"NAME$N" \\\	 $"LECTS$N" \\\	 $"TUT$N"
X      N=`expr $N + 1`
X   done
X   exec 0<&2
Xfi
XNUMBER=`expr $N - 1`
Xwhile true
Xdo
X   while true
X   do
X      echo -n "Name: "
X      if read name
X      then
X         N=1
X         while eval test $N -le $NUMBER -a \"$"NAME$N"\" != \""$name"\"
X         do
X            N=`expr $N + 1`
X         done
X         if test $N -gt $NUMBER
X         then
X            echo -n "New Lecturer? : "
X            read ANS
X            until test "$ANS" = "y" -o "$ANS" = "n"
X            do
X               echo -n "New Lecturer [y/n]? : "
X               read ANS
X            done
X            if test "$ANS" = "y"
X            then
X               eval NAME$N=$name
X               eval LECTS$N=0
X               eval TUT$N=0
X               NUMBER=$N
X            else
X               break
X            fi
X         fi
X         echo Name \	 Lects. \	 Tuts.
X         eval echo $"NAME$N" \\\	$"LECTS$N" \\\	 $"TUT$N"
X         echo -n "Number of Lectures ? : "
X         read LECTS$N
X         echo -n "Number of Tutorials ? : "
X         read TUT$N
X         echo Name \	 Lects. \	 Tuts.
X         eval echo $"NAME$N" \\\	 $"LECTS$N" \\\	 $"TUT$N"
X      fi
X      ANS=
X      echo -n "Finished ? : "
X      read ANS
X      until test "$ANS" = "y" -o "$ANS" = "n"
X      do
X         echo -n "Finished [y/n] ? : "
X         read ANS
X      done
X      if test "$ANS" = "n"
X      then
X         break
X      else
X         break 2
X      fi
X   done
Xdone
XN=1
Xwhile test $N -le $NUMBER
Xdo
X   eval echo $"NAME$N" \\\	 $"LECTS$N" \\\	 $"TUT$N"
X   N=`expr $N + 1`
Xdone
Xecho 'output file name (<EOT> to quit with no output) : '
Xread file || ( echo "no  output" ; exit 1 )
Xexec >$file
XN=1
Xwhile test $N -le $NUMBER
Xdo
X   eval echo $"NAME$N"\\\	$"LECTS$N"\\\	$"TUT$N"
X   N=`expr $N + 1`
Xdone
SHAR_EOF
if test 1874 -ne "`wc -c < 'paycheck'`"
then
	echo shar: error transmitting "'paycheck'" '(should have been 1874 characters)'
fi
chmod +x 'paycheck'
fi # end of overwriting check
echo shar: extracting "'typescript'" '(1025 characters)'
if test -f 'typescript'
then
	echo shar: will not over-write existing file "'typescript'"
else
sed 's/^X//' << \SHAR_EOF > 'typescript'
XScript started on Thu Mar 24 12:23:20 1988
X% paycheck
XName: alan
XNew Lecturer? : y
XName 	 Lects. 	 Tuts.
Xalan 	0 	 0
XNumber of Lectures ? : 2
XNumber of Tutorials ? : 3
XName 	 Lects. 	 Tuts.
Xalan 	 2 	 3
XFinished ? : n
XName: john
XNew Lecturer? : y
XName 	 Lects. 	 Tuts.
Xjohn 	0 	 0
XNumber of Lectures ? : 3
XNumber of Tutorials ? : 4
XName 	 Lects. 	 Tuts.
Xjohn 	 3 	 4
XFinished ? : y
Xalan 	 2 	 3
Xjohn 	 3 	 4
Xoutput file name (<EOT> to quit with no output) : 
Xtst
X% 
X% cat tst
Xalan	2	3
Xjohn	3	4
X% paycheck tst
Xalan 	 2 	 3
Xjohn 	 3 	 4
XName: john
XName 	 Lects. 	 Tuts.
Xjohn 	3 	 4
XNumber of Lectures ? : 4
XNumber of Tutorials ? : 6
XName 	 Lects. 	 Tuts.
Xjohn 	 4 	 6
XFinished ? : n
XName: fred
XNew Lecturer? : y
XName 	 Lects. 	 Tuts.
Xfred 	0 	 0
XNumber of Lectures ? : 1  
XNumber of Tutorials ? : 2
XName 	 Lects. 	 Tuts.
Xfred 	 1 	 2
XFinished ? : y
Xalan 	 2 	 3
Xjohn 	 4 	 6
Xfred 	 1 	 2
Xoutput file name (<EOT> to quit with no output) : 
Xtst
X% cat tst
Xalan	2	3
Xjohn	4	6
Xfred	1	2
X% ^D
Xscript done on Thu Mar 24 12:26:07 1988
SHAR_EOF
echo shar: 2 control characters may be missing from "'typescript'"
if test 1025 -ne "`wc -c < 'typescript'`"
then
	echo shar: error transmitting "'typescript'" '(should have been 1025 characters)'
fi
fi # end of overwriting check
#	End of shell archive
exit 0
-- 
Alan Sexton				ECRC, Arabellastr 17,
alan@ecrcvax.UUCP			8000 Muenchen 81, West Germany
mcvax!unido!ecrcvax!alan		tel. (089) 92699164