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Running another app with a changed environment

Posted by enquirer (enquirer), 1 November 2002
I want to change an environment variable within my Perl, and have its new value seen within an appliaction that I shell off from witihn my Perl

Posted by admin (Graham Ellis), 1 November 2002
In Perl, the environment is present in the %ENV hash, and that's both readable and writable.   You'll find that if you change the environment like this, the new values are automatically exported to any shell commands you run in back quotes ... I've just done a couple of tests to confirm that this works because (quite honestly) I tought it was going to be much harder even though I knoew that it should work in theory.

Following codes tested on Linux and OSX (darwin). Changes the OSTYPE variable, uses backquotes to run another piece of Perl (our second app) to report on the value of that second variable.

$ ./demo
Operating system is : linux-gnu
Operating system is : jaguar
$ cat demo

# Example of changing an operating system environment variable
# for use in a command run by a Perl program.

print "Operating system is : ";
print `/home/graham/oct02/munch`;

print "Operating system is : ";
$ENV{OSTYPE} = "jaguar";
print `/home/graham/oct02/munch`;
$ cat munch

print "$ENV{OSTYPE}\n";
$ exit

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