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ENVPATH(1)	      User Contributed Perl Documentation	    ENVPATH(1)

NAME
       envpath - Advanced operations on	path variables

SYNOPSIS
       Run this	script with the	"-help"	option for usage details.

DESCRIPTION
       Parses the command line,	modifies the specified path variable(s), and
       execs the remaining arguments. There are	two modes, simple and
       advanced:

   SIMPLE MODE
       Simple mode presents an alternative, platform-independent syntax	for
       specifying paths	wherein	the path separator is "," and environment
       variables can be	expanded with @NAME@. For example

	   envpath PATH=@PATH@,/usr/ucb	-- printenv PATH

       appends "/usr/ucb" to $PATH and execs printenv PATH. The	"--" is
       optional.

       You can also specify prepending or appending by using "+=" or "=+"
       respectively:

	   # place /usr/ucb at the front
	   envpath PATH+=/usr/ucb -- printenv PATH

	   # place /usr/ucb at the back
	   envpath PATH=+/usr/ucb -- printenv PATH

       Simple mode requires only this script; it does not require Env::Path to
       be installed.

   ADVANCED MODE
       Advanced	mode basically provides	command-line access to the features of
       Env::Path (see),	which must be installed. The "-E" flag selects the
       path variable to	operate	on and other flags specify operations on it.
       E.g.

	   envpath -E MANPATH -A /tmp -R /usr/share/man	-N -U -- man ...

       would take MANPATH, append /tmp to it, remove any references to
       "/usr/share/man", remove	any dirs which don't exist ("-N") and remove
       redundant entries ("-U")	before running man.

       The -Whence option allows patterns. Thus

	   envpath -W "cat*"

       would find all programs on PATH which match cat*.

CLEARCASE WINKINS
       A big part of the motivation for	this script was	for use	with ClearCase
       builds; iff you know or care about ClearCase read on. Typically,	during
       builds (and not just with ClearCase), pathvars such as PATH, CLASSPATH,
       and LD_LIBRARY_PATH must	be strictly controlled.	 One choice is to
       force static values of these into the environment during	the build
       process,	another	is to simply require/expect users to set their paths
       appropriately. Each of these can	lead to	subtle build or	runtime
       errors, however,	and makes it hard for new users	to get up to speed
       since their personal environment	must be	just so.

       Another common choice is	to use only full pathnames within the
       Makefile, avoiding reliance on search paths at all. This	is often the
       best way	to go but can suppress ClearCase winkins.  For example,	say
       you're generating ascii files of	some type with a binary	executable you
       just built:

       $(INCDIR)/foo.h:	$(BINDIR)/foomaker	$(BINDIR)/foomaker ...

       The problem with	this is	that $(BINDIR) likely contains a platform part
       such as 'solaris' or 'hpux', which makes	it impossible to wink in the
       foo.h file on other platforms even though it's ascii. This same thing
       could come up even with a standard pre-built utility that's in
       different places	on different platforms;	"yacc",	for instance, is in
       /usr/bin	on Linux and /usr/ccs/bin on Solaris.

       You could modify	the path on the	fly:

       $(INCDIR)/foo.h:	$(BINDIR)/foomaker	PATH=$(BINDIR)$(SEP)$$PATH
       foomaker	...

       but this	suffers	from the same problem: since $(BINDIR) and $PATH are
       expanded	literally within the build script they'll suppress winkins.
       Here's a	solution using envpath:

       $(INCDIR)/foo.h:	$(BINDIR)/foomaker	envpath	PATH=@BINDIR@,@PATH@
       foomaker	...

       This hides the evaluation of BINDIR and PATH such that clearmake	never
       sees anything but the literals, thus clearing the field for winkins. Of
       course envpath is capable of doing more than this, but it's the
       original	reason it was written.

AUTHOR
       David Boyce <dsbperl AT boyski.com>

COPYRIGHT
       Copyright (c) 2000-2001 David Boyce. All	rights reserved.  This Perl
       program is free software; you may redistribute and/or modify it under
       the same	terms as Perl itself.

SEE ALSO
       perl(1),	"perldoc Env::Path"

perl v5.32.1			  2003-10-10			    ENVPATH(1)

NAME | SYNOPSIS | DESCRIPTION | CLEARCASE WINKINS | AUTHOR | COPYRIGHT | SEE ALSO

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