Re: The shell and my scripts
More to the point, environment variables are part of every process (rather than just a login session). A process inherits variables with values from the environment of its parent when it starts. From then on they're independent of the parent. They're not a bolt-on but a fundamental part of the Unix process design. David Kim Helliwell [EMAIL PROTECTED] wrote: The environment variables have nothing to do with the shell. The only thing the shell does is give you a way to set environment variables, and different shells have different syntax for that. But environment variables are a property of your login session, not of the shell. So the short answer is: Perl does not need to know or care about what shell you're running in (although that's available as the environment variable SHELL). Perl scripts just get the environment variables for free as part of the startup. Hope that answers it. Kim Helliwell [EMAIL PROTECTED] Homepage: http://homepage.mac.com/kimgh On Jul 28, 2005, at 8:10 PM, John Horner wrote: Recently there was a change at work -- all http access now needs to go through a proxy. So if I have a script using LWP::UserAgent or similar, I have to add $UA-proxy( ['http'] , 'http://proxy.fake.com:8080' ); to all my scripts. Which is a big pain. So a *NIX guy said you shouldn't need to do that if you can add an environment variable to your shell. So, as I use tcsh, not bash, which is the default nowadays, I added this to .tcshrc: setenv http_proxy http://proxy.fake.com:8080 and it seemed to work, but leaving aside the specifics of the scripts, how would Perl know that I use tcsh, not bash? Isn't that a preference of the Terminal app, not of me as a user? A script run as a cron job, does it run using all the environment variables as if I'd typed its name into the Terminal? What about a script run from BBEdit? What if I su root and run it? I'd really appreciate someone explaining the relationship of script to shell and user.
Re: The shell and my scripts
On Jul 28, 2005, at 11:10 PM, John Horner wrote: and it seemed to work, but leaving aside the specifics of the scripts, how would Perl know that I use tcsh, not bash? As others have already said, Perl knows there's an environment variable, but it neither knows nor cares how that variable got set. Isn't that a preference of the Terminal app, not of me as a user? Actually, no. It's a preference of the user. If you log in by other means - X11's xterm, or remotely through ssh, for instance - the same preference will be used. A script run as a cron job, does it run using all the environment variables as if I'd typed its name into the Terminal? No. As it says in man 5 crontab, only LOGNAME (aka USER on some systems), HOME, and SHELL are set. You may set others by adding name=value pairs to your crontab file. See man 5 crontab for details. What about a script run from BBEdit? BBEdit is a GUI app, and GUI apps don't use your login shell. To define environment variables to be used by GUI apps, have a look at this QA from Apple: http://developer.apple.com/qa/qa2001/qa1067.html What if I su root and run it? It depends. If you simply su to root, you'll keep the same environment. But, if you su - (note the dash), it's like you're starting a separate new login session - root's own user login scripts are run, and nothing is inherited. Sudo begins with an inherited environment, but modifies it heavily - have a look at the Security Notes section in man sudo for details. sherm-- Cocoa programming in Perl: http://camelbones.sourceforge.net Hire me! My resume: http://www.dot-app.org
Re: The shell and my scripts
At 08:08 -0400 7/29/05, Sherm Pendley wrote: On Jul 28, 2005, at 11:10 PM, John Horner wrote: What about a script run from BBEdit? BBEdit is a GUI app, and GUI apps don't use your login shell. To define environment variables to be used by GUI apps, have a look at this QA from Apple: BBEdit also allows BBEdit worksheets which are a bit like Apple's MPW using ENTER to execute selected text as shell commands. If you are using one of those an instance of your selected shell, tcsh, is associated with each open worksheet. On opening a worksheet your ~/.tcshrc is sourced and you can set environment variables there. Your tcsh login script is NOT run. It's probably better to create a $HOME/.MacOSX/environment.plist file but watch out for the public tcsh startup files in /etc/. As delivered they can overwrite your selections in the plist especially for $PATH. The plist is read only at login-to-Aqua time. If you change it you must logout and login again to see the changes. Things are better now that it's UNIX underneath. Just ask Steve. -- -- Halloween == Oct 31 == Dec 25 == Christmas --
