External programs
There are three ways to call external programs.
system() returns the exit status of the program
my $rc = system("/bin/cp $file1 $file2"); # returns exit status values
die "system() failed with status $rc" unless $rc == 0;
If possible, pass your arguments as a list, rather than a single string.
my $rc = system("/bin/cp", $file1, $file2 );
This makes sure that nothing goes wrong in the shell if $file1 or $file2 have spaces or other special characters.
The output from system() is not captured.
XXX Discuss lower 8-bits of return code.
XXX Discuss running through a pipe
Backticks (``) and qx() operator return the output of the program
When you want the output, use one of these.
my $output = `myprogram foo bar`.
You'll need to check the error code in $!.
If you're using backticks or qx(), prefer IPC::Open2 or IPC::Open3 instead, since they'll give you the same argument control and allow you to capture the output as well.
IPC::Open3 is the only way to capture STDERR in Perl without using shell commands.
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