ENVPATH(1) User Contributed Perl Documentation ENVPATH(1)NAMEenvpath - 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 ALSOperl(1), "perldoc Env::Path"
perl v5.20.2 2003-10-10 ENVPATH(1)
