PerlBench

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consistency.

A named array in scalar context is quite different from what would at
first glance appear to be a list in scalar context.  You can't get a list
like C<(1,2,3)> into being in scalar context, because the compiler knows
the context at compile time.  It would generate the scalar comma operator
there, not the list construction version of the comma.  That means it
was never a list to start with.

In general, functions in Perl that serve as wrappers for system calls
of the same name (like chown(2), fork(2), closedir(2), etc.) all return
true when they succeed and C<undef> otherwise, as is usually mentioned
in the descriptions below.  This is different from the C interfaces,
which return C<-1> on failure.  Exceptions to this rule are C<wait>,
C<waitpid>, and C<syscall>.  System calls also set the special C<$!>
variable on failure.  Other functions do not, except accidentally.

=head2 Perl Functions by Category

Here are Perl's functions (including things that look like
functions, like some keywords and named operators)

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C<readdir>, C<rewinddir>, C<seek>, C<seekdir>, C<select>, C<syscall>,
C<sysread>, C<sysseek>, C<syswrite>, C<tell>, C<telldir>, C<truncate>,
C<warn>, C<write>

=item Functions for fixed length data or records

C<pack>, C<read>, C<syscall>, C<sysread>, C<syswrite>, C<unpack>, C<vec>

=item Functions for filehandles, files, or directories

C<-I<X>>, C<chdir>, C<chmod>, C<chown>, C<chroot>, C<fcntl>, C<glob>,
C<ioctl>, C<link>, C<lstat>, C<mkdir>, C<open>, C<opendir>,
C<readlink>, C<rename>, C<rmdir>, C<stat>, C<symlink>, C<sysopen>,
C<umask>, C<unlink>, C<utime>

=item Keywords related to the control flow of your Perl program

C<caller>, C<continue>, C<die>, C<do>, C<dump>, C<eval>, C<exit>,
C<goto>, C<last>, C<next>, C<redo>, C<return>, C<sub>, C<wantarray>

=item Keywords related to scoping

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=back

=head2 Portability

Perl was born in Unix and can therefore access all common Unix
system calls.  In non-Unix environments, the functionality of some
Unix system calls may not be available, or details of the available
functionality may differ slightly.  The Perl functions affected
by this are:

C<-X>, C<binmode>, C<chmod>, C<chown>, C<chroot>, C<crypt>,
C<dbmclose>, C<dbmopen>, C<dump>, C<endgrent>, C<endhostent>,
C<endnetent>, C<endprotoent>, C<endpwent>, C<endservent>, C<exec>,
C<fcntl>, C<flock>, C<fork>, C<getgrent>, C<getgrgid>, C<gethostbyname>,
C<gethostent>, C<getlogin>, C<getnetbyaddr>, C<getnetbyname>, C<getnetent>,
C<getppid>, C<getpgrp>, C<getpriority>, C<getprotobynumber>,
C<getprotoent>, C<getpwent>, C<getpwnam>, C<getpwuid>,
C<getservbyport>, C<getservent>, C<getsockopt>, C<glob>, C<ioctl>,
C<kill>, C<link>, C<lstat>, C<msgctl>, C<msgget>, C<msgrcv>,
C<msgsnd>, C<open>, C<pipe>, C<readlink>, C<rename>, C<select>, C<semctl>,
C<semget>, C<semop>, C<setgrent>, C<sethostent>, C<setnetent>,

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You can actually chop anything that's an lvalue, including an assignment.

If you chop a list, each element is chopped.  Only the value of the
last C<chop> is returned.

Note that C<chop> returns the last character.  To return all but the last
character, use C<substr($string, 0, -1)>.

See also L</chomp>.

=item chown LIST

Changes the owner (and group) of a list of files.  The first two
elements of the list must be the I<numeric> uid and gid, in that
order.  A value of -1 in either position is interpreted by most
systems to leave that value unchanged.  Returns the number of files
successfully changed.

    $cnt = chown $uid, $gid, 'foo', 'bar';
    chown $uid, $gid, @filenames;

On systems that support fchown, you might pass file handles among the
files.  On systems that don't support fchown, passing file handles
produces a fatal error at run time.

Here's an example that looks up nonnumeric uids in the passwd file:

    print "User: ";
    chomp($user = <STDIN>);
    print "Files: ";
    chomp($pattern = <STDIN>);

    ($login,$pass,$uid,$gid) = getpwnam($user)
	or die "$user not in passwd file";

    @ary = glob($pattern);	# expand filenames
    chown $uid, $gid, @ary;

On most systems, you are not allowed to change the ownership of the
file unless you're the superuser, although you should be able to change
the group to any of your secondary groups.  On insecure systems, these
restrictions may be relaxed, but this is not a portable assumption.
On POSIX systems, you can detect this condition this way:

    use POSIX qw(sysconf _PC_CHOWN_RESTRICTED);
    $can_chown_giveaway = not sysconf(_PC_CHOWN_RESTRICTED);

=item chr NUMBER

=item chr

Returns the character represented by that NUMBER in the character set.
For example, C<chr(65)> is C<"A"> in either ASCII or Unicode, and
chr(0x263a) is a Unicode smiley face.  Note that characters from 128
to 255 (inclusive) are by default not encoded in UTF-8 Unicode for
backward compatibility reasons (but see L<encoding>).