Unix environment variables for exec process

GhodMode has asked for the wisdom of the Perl Monks concerning the following question:

Fellow Monks,
How can I set Unix environment variables that can be read by an exec'd process?

I'm trying to automate a backup process and I'm using Expect for some of the commands that prompt for information. This works perfectly when I execute it from the command line, but when I execute it from cron, I get something like the following error in the cron output:

Cannot exec(exp full=y statistics=none file=/home/ghodmode/runBackup/b
+ackup/13Mar2008_020502/oracle_data_13Mar2008_020502.dmp): No such fil
+e or directory
[download]

I realize this is probably related to the Unix PATH. The processes I'm trying to run need many other special environment variables set, too. I tried to take care of this by setting the variables via the %ENV hash before the spawn, but it's not working.

I've read Loading Environment Variables from a File, but that doesn't exactly meet my needs because I need to execute many processes with requirements defined in an external configuration file.

Until I figure this out, I'll use a shell script to set up the necessary environment variables and call the command, then run that script with expect, but I'd prefer an all-Perl solution.

Here's an example of the code that presents the problem:

#!/usr/bin/perl -w

use strict;
use warnings;

use Expect;

my $envscript = '/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/b
+in/oracle_env.sh';
open(ENV, "$envscript 2>&1 > expect.out; env |");

while ( <ENV> ) {
    chomp;
    my ($var, $value) = split( /=/, $_, 2 );
    next if ( !defined $var or !defined $value );
    $ENV{$var} = $value;
}

close ENV;


my $command = 'exp';
my @parameters = (
    'full=y',
    'statistics=none',
    'file=/home/ghodmode/runBackup/backup/oracle_data.dmp',
);

my $patidx;
my $pattern;

my $exp = new Expect;
$exp->raw_pty(1);

$exp->spawn($command, @parameters)
    or die "Cannot spawn $command: $!\n";

$pattern = '^Username:';
$patidx = $exp->expect( 5, ( '-re', $pattern) );
$exp->send( "me\n" );

$pattern = '^Password:';
$patidx = $exp->expect( 5, ('-re', $pattern) );
$exp->send( "my_password\n" );

$exp->soft_close();
[download]

Thank you,

--
-- Ghodmode

Blessed is he who has found his work; let him ask no other blessedness.
-- Thomas Carlyle

Comment on Unix environment variables for exec process Select or Download Code

Replies are listed 'Best First'.
Re: Unix environment variables for exec process by pc88mxer (Vicar) on Mar 13, 2008 at 14:56 UTC
Try specifying the full path to the `exp` command, e.g.: `my $command = '/full/path/to/exp';` [download] If you don't know where it is, just use the `which` command from your terminal: `$ which exp` [download] Update: This is very likely a `PATH` issue. When you run the command from the command line your PATH variable contains the directory that the `exp` resides in. When `cron` runs it begins with a very limited PATH. Even though you are modifying environement variables before invoking `exp`, note that it is being run in cron's context. So if `oracle_env.sh` does not explicitly modify the PATH variable to include the directory for `exp`, `cron` will not be able to find that program.	[reply] [d/l] [select]
Re: Unix environment variables for exec process by GhodMode (Pilgrim) on Mar 13, 2008 at 16:46 UTC
I think I found the problem. I probably should have read Loading Environment Variables from a File more carefully, too. When I started to write the shell script that would set up the environment and run the command, I realized that I needed to source the environment set-up script, not just run it. I put `source` in front of my environment script and now it's running from cron and seems to be working ok. Thank you, -- -- Ghodmode Blessed is he who has found his work; let him ask no other blessedness. -- Thomas Carlyle	[reply] [d/l]
Re: Unix environment variables for exec process by eyepopslikeamosquito (Archbishop) on Mar 13, 2008 at 20:14 UTC
Probably not related to your problem, but I noticed: `$envscript 2>&1 > expect.out;` [download] Assuming you want to fold stdout/stderr into file expect.out, you've got the order wrong. It should be written as: `$envscript > expect.out 2>&1;` [download] To see what I mean, run the following commands: `perl -le "print STDERR q{to-stderr};print STDOUT q{to-stdout}" 2>&1 >f +.tmp perl -le "print STDERR q{to-stderr};print STDOUT q{to-stdout}" >f.tmp +2>&1` [download] and note the difference.	[reply] [d/l] [select]