Chapter 12 External Programs and Commands
In Perl, backticks `` and the system() and exec()
functions run external programs. Shell escapes should be avoided, as they
impose needless security, portability, and maintainability problems.
Backticks run a command and returns the command's output
$A = `pwd`;
Backquotes provide a means of returning to the Perl process the value
generated by the child process that would have been written to STDOUT or
another file, had that process been launched through the system()
operator. Thus, this form of system call may be better suited in some
instances than the system() operator described below.
system() runs command and returns command's exit status.
$A = system("pwd");
The simplest form of Perl process operator is the system operator.
Just as a UNIX shell launches a new process to carry out a command, so the
system operator causes Perl to launch a new process to carry out the indicated
operation. It takes a single argument, the name of the process or command to be
executed, and it returns a success/failure code. However, unlike many other
operators, system normally returns a zero if successful and a nonzero value if
exec() runs command and never returns
The exec operator works much like the system operator except that when it
launches another process, the Perl program from which the launch originated