mike@turing.UNM.EDU.unm.edu (Michael I. Bushnell) (08/21/87)
How can I determine if an environment variable is set using csh? (I.e., in a script) The manual doesn't seem to say. Michael I. Bushnell a/k/a Bach II mike@turing.UNM.EDU --- I just had a NOSE JOB!! -- Zippy the Pinhead
roy@phri.UUCP (Roy Smith) (08/25/87)
In <626@unmvax.unm.edu> mike@turing.UNM.EDU.UUCP (Michael I. Bushnell) writes: > How can I determine if an environment variable is set using csh? > (I.e., in a script) After a bit of experimentation, I came up with the following ---------------- #!/bin/csh if (`printenv FOO`X == X) then echo FOO is not set else echo FOO is set endif if (`printenv TERM`X == X) then echo TERM is not set else echo TERM is set endif ---------------- which gives me: FOO is not set TERM is set This works, but is a bit grotty. I suspect there has to be a prettier way to do it, but I don't see any. -- Roy Smith, {allegra,cmcl2,philabs}!phri!roy System Administrator, Public Health Research Institute 455 First Avenue, New York, NY 10016
tim@brspyr1.BRS.Com (Tim Northrup) (08/26/87)
in article <626@unmvax.unm.edu>, Michael I. Bushnell says: + | How can I determine if an environment variable is set using csh? | (I.e., in a script) | Michael I. Bushnell | a/k/a Bach II + mike@turing.UNM.EDU if ( $?variable ) then VARIABLE IS SET TO SOMETHING else IT AIN'T endif -- Tim "The Enchanter" Northrup ========================================++===================================== " ... for death awaits you all || tim@brspyr1.BRS.Com with big, sharp, pointy teeth!" || uunet!steinmetz!brspyr1!tim
dupuy@amsterdam.columbia.edu (Alexander Dupuy) (08/26/87)
In article <2876@phri.UUCP> roy@phri.UUCP (Roy Smith) writes: >In <626@unmvax.unm.edu> mike@turing.UNM.EDU.UUCP (Michael I. Bushnell) writes: >> How can I determine if an environment variable is set using csh? >> (I.e., in a script) > > After a bit of experimentation, I came up with the following > [c-shell script using `printenv` deleted] maybe this is a stupid answer, but have you tried $?VARIABLE ? % echo $?TERM 1 % echo $?FOO 0 I know I have a ( hacked) version of the 4.3 csh, but it does work for me. @alex --- arpanet: dupuy@columbia.edu uucp: ...!seismo!columbia!dupuy
rsalz@bbn.com (Richard Salz) (08/26/87)
The problem is in distinguishing between "set var value" and "setenv var value" -- in most cases, the C shell hides any difference between them -- $var will get the value of the "var" variable, be it a shell variable or an environment variable. With that caveat in mind: % if ( $?TERM ) echo TERM is set TERM is set % if ( $?FOO ) echo FOO is set % set FOO=yow % if ( $?FOO ) echo FOO is now set FOO is now set % if ( $?BAR ) echo BAR is set % setenv BAR value % if ( $?BAR ) echo BAR is now set BAR is now set Roy's idea of using printenv is probably better, but his method will probably cause quoting problems if you try to see if TERMCAP is set after using tset(1); this seems to do it: % if ( `printenv TERMCAP | wc -l` == 1 ) echo TERMCAP is set TERMCAP is set % if ( `printenv CAP | wc -l` == 1 ) echo CAP is set % Hope this helps, /r$ -- For comp.sources.unix stuff, mail to sources@uunet.uu.net.
mkhaw@teknowledge-vaxc.ARPA (Mike Khaw) (08/26/87)
->>> How can I determine if an environment variable is set using csh?
...
-> maybe this is a stupid answer, but have you tried $?VARIABLE ?
->
-> % echo $?TERM
-> 1
-> % echo $?FOO
-> 0
This isn't quite right if you are unfortunate enough to have done:
% set TERM = whatever # a csh var., not an env. var.
Mike Khaw
--
internet: mkhaw@teknowledge-vaxc.arpa
usenet: {hplabs|sun|ucbvax|decwrl|sri-unix}!mkhaw%teknowledge-vaxc.arpa
USnail: Teknowledge Inc, 1850 Embarcadero Rd, POB 10119, Palo Alto, CA 94303mlandau@bbn.com (Matt Landau) (08/26/87)
In <626@unmvax.unm.edu> mike@turing.UNM.EDU.UUCP (Michael I. Bushnell) writes: > How can I determine if an environment variable is set using csh? Well, under 4BSD and Sun csh, this works: if ($?VAR) then echo "VAR is set" else echo "VAR is not set" endif I would assume it works the same way in SysV, but I don't have one handy to check. -- Matt Landau A rock feels no pain... mlandau@bbn.com ...and an island never cries
dan@rose3.Rosemount.COM (Dan Messinger) (08/26/87)
In article <626@unmvax.unm.edu> mike@turing.UNM.EDU.UUCP (Michael I. Bushnell) writes: > >How can I determine if an environment variable is set using csh? >(I.e., in a script) The following (as described in my manual) works fine. However, it does not differentiate between environment variables and shell variables. # if ( $?xxx ) then echo its set else echo not set endif Dan Messinger dan@rose3.rosemount.com
mikep@ism780c.UUCP (Michael A. Petonic) (08/27/87)
In article <2876@phri.UUCP> roy@phri.UUCP (Roy Smith) writes: >In <626@unmvax.unm.edu> mike@turing.UNM.EDU.UUCP (Michael I. Bushnell) writes: >> How can I determine if an environment variable is set using csh? >> (I.e., in a script) > > After a bit of experimentation, I came up with the following > [...] A better was is to use printenv and the "status" variable, like this: printenv FOO > /dev/null if ( $status == 1 ) then variable is not set else variable is set fi or something like that. Look at the man page near the bottom for the return values of printenv. MikeP
guy%gorodish@Sun.COM (Guy Harris) (08/27/87)
> I would assume it works the same way in SysV, but I don't have one handy > to check. It definitely doesn't work the same way in vanilla SysV, since it doesn't have "csh". If a System V system offers the 4BSD "csh", it should work the same way, although there is no absolute guarantee of this; somebody may have changed or broken it. (The same is true of 4BSD-derived systems. BTW, before anybody pipes up with this, Sun did *not* change the C shell in recent releases not to change the "term" shell variable if the "TERM" environment variable is changed, as has been claimed elsewhere. That behavior is exhibited by straight 4.3BSD, and I believe by straight 4.2BSD as well.) Guy Harris {ihnp4, decvax, seismo, decwrl, ...}!sun!guy guy@sun.com
henry@garp.mit.edu (Henry Mensch) (08/27/87)
roy@phri.UUCP (Roy Smith) wrote:
->In <626@unmvax.unm.edu> mike@turing.UNM.EDU.UUCP (Michael I. Bushnell) writes:
->> How can I determine if an environment variable is set using csh?
->> (I.e., in a script)
->
-> After a bit of experimentation, I came up with the following
->
-> . . . (shell script removed here)
->
-> This works, but is a bit grotty. I suspect there has to be a
->prettier way to do it, but I don't see any.
Yeah; try this:
61 garp /users/henry --> printenv PRINTER ; set in my .{login,cshrc}
ln03-bldge40-2
62 garp /users/henry --> printenv DEADLY ; some random name
63 garp /users/henry --> echo ${?PRINTER} ${?DEADLY}
1 0
64 garp /users/henry -->
${?variablename} returns 1 if set and 0 if not set. Oh yeah; this was
described in the manual page for csh that I have.
# Henry Mensch / <henry@garp.mit.edu> / E40-379 MIT, Cambridge, MA
# {ames,cca,rochester,harvard,mit-eddie}!garp!henrymouse@mcgill-vision.UUCP (09/06/87)
In article <159@papaya.bbn.com>, rsalz@bbn.com (Richard Salz) writes: > The problem is in distinguishing between "set var value" and > "setenv var value" [...]. > Roy's idea of using printenv is probably better, but his method will > probably cause quoting problems if you try to see if TERMCAP is set > after using tset(1); this seems to do it: > % if ( `printenv TERMCAP | wc -l` == 1 ) echo TERMCAP is set > TERMCAP is set > % if ( `printenv CAP | wc -l` == 1 ) echo CAP is set > % Or even just if { printenv TERMCAP >& /dev/null } then .... endif WARNING if you try this: The following does NOT work correctly. if { printenv TERMCAP >& /dev/null } echo TERMCAP is set This will print nothing regardless of whether TERMCAP is set or not, becuase, believe it or not, the echo command gets its output redirected by the redirection in the {}! (Verified by changing /dev/null to /tmp/foo - system is mtXinu 4.3+NFS, though the bug is present in a local derivative of the 4.2 csh as well, and therefore is presumably present in the 4.2 csh.) The version using then and endif does not suffer from the same problem. der Mouse (mouse@mcgill-vision.uucp)