A.P. Lawrence

Best of the Newsgroups: sh vs. ksh

If this isn't exactly what you wanted, please try our Search (there's a LOT of techy and non-techy stuff here about Linux, Unix, Mac OS X and just computers in general!):

From: Bela Lubkin <belal@sco.com>
Subject: Re: Shell Programming: IFS variable
Date: Thu, 7 Aug 2003 22:11:29 GMT References: <hwqYa.40450$I_3.19987@twister.nyroc.rr.com>

Doc wrote:

> I'm having a strange little problem that MUST have an answer but I can't
> seem to figure it out!  I'm using a Bourne shell on SCO Openserver 5.0.5 and
> have the following problem:
> 
> I'm trying to set the IFS (Internal Field Seperator) variable to a newline
> character so I can properly loop thru each line of a command output.  Here's
> a snip of my code:
>    IFS='\n'
>    dex=0
>    for nxt in `ps`
>    do
>       dex=`expr $dex + 1`
>       e=`echo $nxt|cut -f1 -d' '`
>       eval jbid_$dex=$e
>       echo "$dex) $nxt"
>    done
> 
> The problem is that the shell is seperating my lines at each "n" instead of
> each newline.  It seems evident that my problem is that I'm not actually
> setting IFS to a newline character as I'd like.  But am instead setting it
> to "\" and "n".
> 
> Anyone know how to set IFS to a true newline character?

Others have showed you:

  IFS='
'   # actual newline in quotes

My usual idiom for what you're doing is:

  ps | while read nxt; do
    ...
  done

But there's a gotcha here.  The Bourne shell forks a separate shell for
a set of shell commands that are being piped to.  It does a decent job
of hiding this fact, but your:

  eval jbid_$dex=$e

statements won't come through.  The variables $jbid_xxx will get set in
the sub-shell, but they won't exist by the time you come to try to use
them, back in the parent shell.

The Korn shell does not fork a separate shell in this situation; running
the same script under `ksh` would make it work.  It was a design goal of
ksh to eliminate these language oddities where the scope of a variable
is constrained by forces outside your control.

>Bela<

Enter your email address for automatic notification of new posts here
(be sure to whitelist 'feedburner.com' if you use spam filtering)

/Bofcusm/2273.html copyright 1997-2004 Bela Lubkin All Rights Reserved

Have you tried Searching this site?

Unix/Linux/Mac OS X support by phone, email or on-site: Support Rates

This is a Unix/Linux resource website. It contains technical articles about Unix, Linux and general computing related subjects, opinion, news, help files, how-to's, tutorials and more. We appreciate comments and article submissions.

Publishing your articles here