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Path: utzoo!linus!decvax!decwrl!amd70!dual!proper!gam
From: gam@proper.UUCP (Gordon Moffett)
Newsgroups: net.unix
Subject: New uses for csh
Message-ID: <1403@proper.UUCP>
Date: Sat, 23-Jun-84 23:16:13 EDT
Article-I.D.: proper.1403
Posted: Sat Jun 23 23:16:13 1984
Date-Received: Wed, 27-Jun-84 03:22:25 EDT
Organization: Proper UNIX, Oakland, CA
Lines: 60
Keywords: csh,source,alias

It was begining to frustrate me that the csh ``alias'' command accepted
only one-line definitions; it is impossible to have an alias that uses
``if-then-else''.

My solution to this problem was using a combination of ``source''
and ``alias'' allow possibly lengthy alias-type commands using more
complex csh constructions.

This is particularly applicable in the following examples.  The UniSoft
port I am using does not support the ``pushd'' and ``popd'' commands
of csh, so I have implimented them thus:

[in my .cshrc]:
	alias	popd	'set argv = (\!*) ; source ~/csh/popd'
	alias	pushd	'set argv = (\!*) ; source ~/csh/pushd'

[~/csh/popd]:
	if (! $?_dirstack || $#_dirstack < 1) then
		echo "popd: Directory stack empty."
	else
		chdir $_dirstack[1]
		echo $_dirstack
		shift _dirstack
	endif

[~/csh/pushd]:
	if ($#argv != 1) then
		echo "pushd: Arg count."
	else
		if (! $?_dirstack) set $_dirstack = ()
		set _dirstack = (`pwd` $_dirstack)
		chdir $argv
		echo $argv $_dirstack
	endif

The advantages to this method are:
	o  More sophisticated (multi-line) csh constructs are allowed
	o  Operates on the current shell (qv, chdir)
	o  No overhead for reading .cshrc (as with an executable script)

The disadvantages are:
	o  Argv probably should be saved somewhere and restored
	o  No ``exit'' from ``if'' statements (other than -- ech --
	   ``goto'')
	o  Requires a file access

[ These scripts were derived from someone else's implimentation of
  pushd/popd for csh's lacking them; I don't recall who that is,
  but thank you anyway ]

[ Also do not use this as launch-point for another csh vs sh argument
  as it is not my intention to start one -- I shouldn't have to say
  this but I've been on the net for a while ... ]

Comments and discussion are encouraged.
-- 

Gordon A. Moffett

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