Perl, system, backticks, and environment variables

Post #100,946 by admin 5/8/03 3:06:52 PM Reply	Perl, system, backticks, and environment variables Situation: Perl script needs to call a shell script (that is not under programmer control; ie. we can't change it to do our evil bidding). When that script is done, it will have set several environment variables. Is it possible to obtain those environment variables after the script runs, and how? Workaround is to run the script before the perl script, but in this situation that's a messy hack. I also made the suggestion to the guy working on it that he could call a script in the same system call after the initial script, and have the second script print out or otherwise return the environment variables in some fashion. That's a messy hack as well. Regards, -scott anderson "Welcome to Rivendell, Mr. Anderson..."
Post #101,066 by Yendor 5/9/03 10:49:05 AM Reply	Check out %ENV Quick check of [link\|http://www.perlmonks.org/index.pl?node_id=105795\|PerlMonks] uncovered this. Might help, might not... Check that after you call the other script, of course... And, IIRC, you can call the other script via the system() call... -YendorMike [link\|http://www.hope-ride.org/\|http://www.hope-ride.org/]
Post #101,072 by admin 5/9/03 11:16:38 AM Reply	%ENV not set by subprocesses. Which is exactly the problem. :-) Regards, -scott anderson "Welcome to Rivendell, Mr. Anderson..."
Post #101,123 by jake123 5/9/03 4:06:08 PM Reply	Re: %ENV not set by subprocesses. Why don't you just parse the other script and look for the set statements (setenv, export, whatever)? Dunno perl, but in rexx, you could do something like this: envsource = .stream~new(somescript.cmd)\nlines = envsource~makearray\ndo i = 1 to lines~lines\n if lines[i]~word(1) = "set"\n then do\n parse var lines[i] . envvar '=' newval\n value('OS2ENVIRONMENT', envvar, newval)\n end /* End if /\n else iterate\nend / End do loop /\ndrop lines\nenvsource~close Note that I haven't actually tested this, but should give you the general idea. It assumes you can read the file, of course, but if you can execute it I'm sure you can read it. Sure, it's an ugly hack, but it would work, and would permit you to let someone change the file without worrying about it breaking your program. --\n-------------------------------------------------------------------\n Jack Troughton jake at consultron.ca \n [link\|http://consultron.ca\|http://consultron.ca] [link\|irc://irc.ecomstation.ca\|irc://irc.ecomstation.ca] \n Kingston Ontario Canada [link\|news://news.consultron.ca\|news://news.consultron.ca] *\n-------------------------------------------------------------------
Post #101,127 by admin 5/9/03 4:21:58 PM Reply	That assumes the values aren't calculated. Regards, -scott anderson "Welcome to Rivendell, Mr. Anderson..."
Post #101,132 by Another Scott 5/9/03 4:58:40 PM Reply	Perhaps I'm dense. I'm just curious - ignore this if it requires TMI. As I understand the situation, you've got a script S that does some stuff and before exiting sets some environment variables. Those environment variables are persistent. You want to write a Perl script that calls S and be able to read those environment variables in the Perl script (or afterwards). But you can't do so with the Perl script because of subprocess limitations. Correct? But you say, Workaround is to run the script before the perl script, but in this situation that's a messy hack. How so? It seems to me that it's the best solution if you can't change script S. It sounds like the [link\|http://z.iwethey.org/forums/render/content/show?contentid=25831\|transparent aluminum mirror] problem again... ;-) Cheers, Scott.
Post #101,133 by admin 5/9/03 5:05:15 PM Reply	This is a CGI perl script Which means that we'd have to call another script first, which calls the environment variables script, and then calls the perl script. Regards, -scott anderson "Welcome to Rivendell, Mr. Anderson..."
Post #101,219 by kmself 5/10/03 5:24:36 PM Reply	Parent-child environment inheritence Parent don't inherit the child's environment. I'm assuming a Unix-like OS. \r\n\r\n Your options IMO are: \r\n\r\n \r\n Have the child report its environment to the parent. \r\n\r\n Determine the child's environment by other means. /proc/pid/env contains this information in Linux. \r\n\r\n Vague possibility: wrap the script in another process which manages it in a way that the environment is determinable. You'd probably have to intercept shell/system calls to do this. \r\n\r\n Make the script do your evil bidding. If it is indeed a shell script, you can modify the startup and/or exit via .bashrc and .bash_logout files. If you can control the effective userid of the script, you may be able to change its startup shell in /etc/passwd. Or you can require modules be run by whomever it is which writes the script. Or intercept the script and modify it prior to submission.... \r\n\r\n \r\n\r\n HTH --\r\n Karsten M. Self [link\|mailto:kmself@ix.netcom.com\|kmself@ix.netcom.com]\r\n [link\|http://kmself.home.netcom.com/\|http://kmself.home.netcom.com/]\r\n What part of "gestalt" don't you understand?\r\n [link\|http://twiki.iwethey.org/twiki/bin/view/Main/\|TWikIWETHEY] -- an experiment in collective intelligence. Stupidity. Whatever.\r\n \r\n Keep software free. Oppose the CBDTPA. Kill S.2048 dead.\r\n[link\|http://www.eff.org/alerts/20020322_eff_cbdtpa_alert.html\|http://www.eff.org/alerts/20020322_eff_cbdtpa_alert.html]\r\n
Post #101,518 by ben_tilly 5/12/03 5:36:35 PM Reply	In the script report ENV and parse that in the caller You might get some ideas on how to do that from [link\|http://www.perlmonks.org/index.pl?node_id=33628\|this hack] I wrote for figuring out your login environment. Cheers, Ben "good ideas and bad code build communities, the other three combinations do not" - [link\|http://archives.real-time.com/pipermail/cocoon-devel/2000-October/003023.html\|Stefano Mazzocchi]
Post #101,521 by admin 5/12/03 5:43:16 PM 5/12/03 5:46:50 PM Reply	Can't do that. We don't control the script that is being called. The rest looks good, though. Thanks, I'll pass it on. Regards, -scott anderson "Welcome to Rivendell, Mr. Anderson..." Edited by admin May 12, 2003, 05:46:50 PM EDT Expand All History
Post #106,473 by Arkadiy 6/18/03 5:49:29 PM Reply	How about writing a wrapper for the script that sources it? something along the lines of \n. origScript.sh\necho $env1\necho $env2\n -- Less Is More. In my book, About Face, I introduce over 50 powerful design axioms. This is one of them. --Alan Cooper. The Inmates Are Running the Asylum
Post #106,474 by admin 6/18/03 5:50:48 PM Reply	It's a CGI script that needs to call a setenv script. Regards, -scott anderson "Welcome to Rivendell, Mr. Anderson..."
Post #106,486 by Arkadiy 6/18/03 8:42:40 PM Reply	I guess I don't know CGI ... What is setenv script? -- Less Is More. In my book, About Face, I introduce over 50 powerful design axioms. This is one of them. --Alan Cooper. The Inmates Are Running the Asylum
Post #106,503 by ChrisR 6/19/03 12:28:18 AM Reply	bash script?
Post #106,522 by admin 6/19/03 10:22:19 AM Reply	Perl CGI calling base environment script. The idea is to use a standard system env. setup script in a cgi program to set up things like database SID, etc. I think he finished his work around a good month ago, though, so I'm a little bemused by the attention being lavished here now. :-) Regards, -scott anderson "Welcome to Rivendell, Mr. Anderson..."
Post #106,505 by boxley 6/19/03 12:36:32 AM Reply	WAG call a perl module calle expect, call it get what you want return processing to the shell\\ long way around thanx, bill will work for cash and other incentives [link\|http://home.tampabay.rr.com/boxley/resume/Resume.html\|skill set] questions, help? [link\|mailto:pappas@catholic.org\|email pappas at catholic.org] As the Poets have mournfully sung. Death takes the innocent young, The rolling in money, the screamingly funny, And those who are very well hung. W.H. Auden

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