perl function setnetent

The setnetent function in Perl is used to rewind the networks file (/etc/networks) and start reading from the beginning. Here's an example of using setnetent in a script to read all the networks from the networks file:

while (my ($name, $aliases, $addrtype, $net) = getnetent()) {
    print "Network name: $name\n";
    print "Network aliases: ", join(',', @$aliases), "\n";
    print "Address type: $addrtype\n";
    print "Network address: $net\n";
}

# rewind the networks file and start again
setnetent();

# read the networks again
while (my ($name, $aliases, $addrtype, $net) = getnetent()) {
    print "Network name: $name\n";
    print "Network aliases: ", join(',', @$aliases), "\n";
    print "Address type: $addrtype\n";
    print "Network address: $net\n";
}

In this example, the getnetent function is used to read each network entry from the networks file in turn, and the details of each network are printed using print statements.

After reading all the networks from the networks file, the setnetent function is called to rewind the file pointer to the beginning of the file. This is necessary if we want to read the networks again from the beginning.

Finally, the getnetent function is called again in a loop to read each network entry from the beginning of the networks file, and the details of each network are printed again.

Note that the setnetent function is not necessary if you only need to read the networks file once, as the file pointer is automatically rewound to the beginning of the file when the end of the file is reached.