Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ames!lll-winken!scooter!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.att
Subject: Re: Anyone running cnews on a 3b1?  (inews problem)
Summary: slight differences between sh and ksh
Message-ID: <1873@neoucom.UUCP>
Date: 15 Jan 90 14:56:12 GMT
References: <1990Jan11.023127.13866@ntvax.uucp> <1990Jan14.055820.24@stb.uucp>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 58


I agree.  It sounds like the errors from the egrep in the inews
script are due to ksh instead of sh running the script.

There are a couple of ways to ensure that a shell program is run
under sh instead of ksh.  Note that ksh is the usual default shell
on the 3b1 for users, and shell programs will normally exeucute
under ksh for users.  To assure that sh is used, a colon by itself
on the very first line indicates that this is an sh program.  If
the script is being invoked from crontab or some other place, you
can put "/bin/sh program" to ensure that you get sh.

There is a $SHELL environment variable, but it isn't terribly
useful for shell programs run by users.  I set my defualt shell to
ksh and did "sh test" (see below) and got ksh as the answer.

	:
	#"/u/wtm/programs/test"
	#SHELL variable test program
	echo Your shell is $SHELL.


There is a slight difference in the say the Korn and Bourne shells
parse strings apparently.  It seems that the Kron shell
automatically does an eval as it parses the comand, so ksh scripts
require fewer escaped characters than sh scripts.  The way around
the difference is to assign grep, sed, etc. strings to variables so
that the shell only makes one pass on the string and does a clean
substitution.

Here is an example programming fragment.  For sh, you'd have to
have:

	echo Enter news group: \\c
	read NEWSGROUP
	DIR=/usr/spool/news/`echo $NEWSGROUP | sed -e s+\\\\.+g`
	echo News directory is $DIR

For ksh you need:

	echo Enter news group: \\c
	read NEWSGROUP
	DIR=/usr/spool/news/`echo $NEWSGROUP | sed -e s+\\.+g`
	echo News directory is $DIR

The following works in either shell:

	echo Enter news group: \\c
	read NEWSGROUP
	SEDSTR="s+\\.+g"
	DIR=/usr/spool/news/`echo $NEWSGROUP | sed -e $SEDSTR`
	echo News directory is $DIR

Try these these examples in ksh and sh and note the difreent
results for fun and amusement.


Bill