Robert's Perl Tutorial

http://www.sthomas.net/roberts-perl-tutorial.htm


System

This runs an external command for you, then carries on with the script. It always returns, and the value it returns goes into $? . This means you can test to see if the program worked. Actually you are testing to see if it could be started, what the program does when it runs is outside your control if you use system .

This example demonstrates system in action. Run the 'vol' command from a command prompt first if you are not familiar with it. Then run the 'vole' command. I'm assuming you have no cute furry executables called vole on your system, or at least in the path. If you do have an executable called 'vole', be creative and change it.

system("vole");

print "\n\nResult: $?\n\n";

system("vol");

print "\n\nResult: $?\n\n";

As you can see, a successful system call returns 0. An unsuccessful one returns a value which you need to divide by 256 to get the real return value. Also notice you can see the output. And because system returns, the code after the first system call is executed. Not so with exec, which will terminate your perl script if it is successful. Perl's usual use of single and double quotes applies as per variable interpolation.