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Five Minute Lightning Talk: Perl's syscall Function

#11

sysfs

List supported filesystem types
If first argument is 3, returns total number of filesystem types
If first argument is 2, looks the filesystem name of the Nth filesystem

    my $num = syscall &SYS_sysfs, 3;
    die "sysfs: $!\n" if $num < 0;
    print "This system has support for $num file systems\n";

    for my $i (0..$num-1) {
        my $buf = "\0"x255;
        syscall(&SYS_sysfs, 2, $i, $buf) < 0 and die "sysfs: $!\n";
        print "$buf\n";
    }

Example output:

    This system has support for 21 file systems
    sysfs
    rootfs
    bdev
    proc
    ...

But this information is also avialable through /proc/filesystems

    [mct@ellesmere ~]$ perl -nle 'print +(split)[-1]' /proc/filesystems
    sysfs
    rootfs
    bdev
    proc
    ...

Not such a great example