Re: Perl versus UNIX Korn Shell

Chris Benson wrote:
> If you do want ammo, my war-story is: I'm doing some Perl courses at IBM
> in the UK, Perl is *the* scripting language used for writing tests and
> product builds for MQ, the SSA disk group ... and the Java development
> group.  Their main requirements are a common language across all
> platforms:  none of this :-
> 	case `echo "X\c"` in
> 	X?c)	ECHON=-n ;;
> 	*)	ECHOC='\c' ;;
> 	esac
> 	echo $ECHON "Some prompt: $ECHOC"
> or
> 	case `uname -o` in
> 	Solaris)  # ...
> 		;;
> 	AIX)	# ...
> 		;;
> 	HPUX)	# ...
> 		;;
> 	esac
> which doesn't work on OS/400, OS/2 and Win32 'cause there's no shell ...

Here's another war story. You want to find the home directory and shell
of user $myuname. $HOME and $SHELL environment variables are unreliable
(especially if running via "su"). The best I could come up with is:
  myhome=`csh -fc "echo ~$myuname"`
  myshell=`egrep "^$myuname:" /etc/passwd | sed -e 's/^..*:\(..*\) *\$/\1/'`
But some Linux systems don't have csh. And using /etc/passwd is unsound --
what if they are using NIS+, say? True, I'm not up-to-date with the latest
Korn shell (it may have a way to solve this); I tend to use /bin/sh if I
need high portability (i.e. Korn shell and/or Perl may not be installed)
and Perl for everything else. In Perl, this problem is easily and soundly
solved by calling the getpwnam() function. Larry summarizes it with:
"It is easier to port a shell than a shell script"

I have written many cross-platform shell scripts, but it is much easier
to do in Perl. Joseph N Hall sums it up in "Effective Perl Programming",
Introduction: "Can you write cross-platform shell scripts? Yes, but with
extreme difficulty. Most mere mortals should not attempt such things.
Can you write cross-platform Perl scripts? Yes, easily."

Another point not mentioned yet is that Perl is far superior to shell
for writing secure scripts: it relies much less on forking external
commands and has a unique "taint mode" feature.

Just curious: why do they prefer Korn shell over bash, say?

/-\


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