Learning Perl, 5th Edition

The %ENV hash

Your Perl program, like any other program, runs in a certain environment, and your program can look at the environment to get information about its surroundings. Perl stores this information in the %ENV hash. For instance, you’ll probably see a PATH key in %ENV:

print "PATH is $ENV{PATH}\n";

Depending on your particular setup and operating system, you’ll see something like this:

PATH is /usr/local/bin:/usr/bin:/sbin:/usr/sbin

Most of these are set for you automatically, but you can add to the environment yourself. How you do this depends on your operating system and shell:

Bourne shell

  $ CHARACTER=Fred; export CHARACTER
  $ export CHARACTER=Fred

csh

  % setenv CHARACTER Fred

DOS or Windows command

  C:> set CHARACTER=Fred

Once you set these environment variables outside of your Perl program, you can access them inside your Perl program:

print "CHARACTER is $ENV{CHARACTER}\n";