packed address of the appropriate type for the socket. See the examples in
L<perlipc/"Sockets: Client/Server Communication">.
-=item binmode FILEHANDLE, DISCIPLINE
+=item binmode FILEHANDLE, LAYER
=item binmode FILEHANDLE
taken as the name of the filehandle. Returns true on success,
C<undef> on failure.
-DISCIPLINE can be either of C<:bytes> for "binary" mode or C<:crlf>
-for "text" mode. If the DISCIPLINE is omitted, it defaults to
-C<:bytes>. To mark FILEHANDLE as UTF-8, use C<:utf8>. For backward
-compatibility C<binmode(FILEHANDLE)> also implicitly marks the
-filehandle as bytes.
-
-The C<:bytes>, C<:crlf>, and C<:utf8>, and any other directives of the
-form C<:...>, are called I/O I<disciplines>. The C<open> pragma can
-be used to establish default I/O disciplines. See L<open>.
-
-The C<:raw> discipline is deprecated. (As opposed to what Camel III
-said, it is not the inverse of C<:crlf>.) See L<perlrun> and the
-discussion about the PERLIO environment variable.
-
-In general, binmode() should be called after open() but before any I/O
-is done on the filehandle. Calling binmode() will flush any possibly
-pending buffered input or output data on the handle. The only
-exception to this is the C<:encoding> discipline that changes
-the default character encoding of the handle, see L<open>.
-The C<:encoding> discipline sometimes needs to be called in
-mid-stream, and it doesn't flush the stream.
+If LAYER is omitted or specified as C<:raw> the filehandle is made
+suitable for passing binary data. This includes turning off possible CRLF
+translation and marking it as bytes (as opposed to Unicode characters).
+Note that as desipite what may be implied in I<"Programming Perl">
+(the Camel) or elsewhere C<:raw> is I<not> the simply inverse of C<:crlf>
+-- other layers which would affect binary nature of the stream are
+I<also> disabled. See L<PerlIO>, L<perlrun> and the discussion about the
+PERLIO environment variable.
+
+I<The LAYER parameter of the binmode() function is described as "DISCIPLINE"
+in "Programming Perl, 3rd Edition". However, since the publishing of this
+book, by many known as "Camel III", the consensus of the naming of this
+functionality has moved from "discipline" to "layer". All documentation
+of this version of Perl therefore refers to "layers" rather than to
+"disciplines". Now back to the regularly scheduled documentation...>
On some systems (in general, DOS and Windows-based systems) binmode()
is necessary when you're not working with a text file. For the sake
and to never use it when it isn't appropriate.
In other words: regardless of platform, use binmode() on binary files
-(like for example images), and do not use binmode() on text files.
+(like for example images).
+
+If LAYER is present it is a single string, but may contain
+multiple directives. The directives alter the behaviour of the
+file handle. When LAYER is present using binmode on text
+file makes sense.
+
+To mark FILEHANDLE as UTF-8, use C<:utf8>.
+
+The C<:bytes>, C<:crlf>, and C<:utf8>, and any other directives of the
+form C<:...>, are called I/O I<layers>. The C<open> pragma can be used to
+establish default I/O layers. See L<open>.
+
+In general, binmode() should be called after open() but before any I/O
+is done on the filehandle. Calling binmode() will normally flush any
+pending buffered output data (and perhaps pending input data) on the
+handle. An exception to this is the C<:encoding> layer that
+changes the default character encoding of the handle, see L<open>.
+The C<:encoding> layer sometimes needs to be called in
+mid-stream, and it doesn't flush the stream.
The operating system, device drivers, C libraries, and Perl run-time
system all work together to let the programmer treat a single
Mac OS, all variants of Unix, and Stream_LF files on VMS use a single
character to end each line in the external representation of text (even
though that single character is CARRIAGE RETURN on Mac OS and LINE FEED
-on Unix and most VMS files). Consequently binmode() has no effect on
-these operating systems. In other systems like OS/2, DOS and the various
-flavors of MS-Windows your program sees a C<\n> as a simple C<\cJ>, but
-what's stored in text files are the two characters C<\cM\cJ>. That means
-that, if you don't use binmode() on these systems, C<\cM\cJ> sequences on
-disk will be converted to C<\n> on input, and any C<\n> in your program
-will be converted back to C<\cM\cJ> on output. This is what you want for
-text files, but it can be disastrous for binary files.
+on Unix and most VMS files). In other systems like OS/2, DOS and the
+various flavors of MS-Windows your program sees a C<\n> as a simple C<\cJ>,
+but what's stored in text files are the two characters C<\cM\cJ>. That
+means that, if you don't use binmode() on these systems, C<\cM\cJ>
+sequences on disk will be converted to C<\n> on input, and any C<\n> in
+your program will be converted back to C<\cM\cJ> on output. This is what
+you want for text files, but it can be disastrous for binary files.
Another consequence of using binmode() (on some systems) is that
special end-of-file markers will be seen as part of the data stream.
If you chomp a list, each element is chomped, and the total number of
characters removed is returned.
+Note that parentheses are necessary when you're chomping anything
+that is not a simple variable. This is because C<chomp $cwd = `pwd`;>
+is interpreted as C<(chomp $cwd) = `pwd`;>, rather than as
+C<chomp( $cwd = `pwd` )> which you might expect. Similarly,
+C<chomp $a, $b> is interpreted as C<chomp($a), $b> rather than
+as C<chomp($a, $b)>.
+
=item chop VARIABLE
=item chop( LIST )
Note that C<chop> returns the last character. To return all but the last
character, use C<substr($string, 0, -1)>.
+See also L</chomp>.
+
=item chown LIST
Changes the owner (and group) of a list of files. The first two
=item glob
-Returns the value of EXPR with filename expansions such as the
-standard Unix shell F</bin/csh> would do. This is the internal function
-implementing the C<< <*.c> >> operator, but you can use it directly.
-If EXPR is omitted, C<$_> is used. The C<< <*.c> >> operator is
-discussed in more detail in L<perlop/"I/O Operators">.
+In list context, returns a (possibly empty) list of filename expansions on
+the value of EXPR such as the standard Unix shell F</bin/csh> would do. In
+scalar context, glob iterates through such filename expansions, returning
+undef when the list is exhausted. This is the internal function
+implementing the C<< <*.c> >> operator, but you can use it directly. If
+EXPR is omitted, C<$_> is used. The C<< <*.c> >> operator is discussed in
+more detail in L<perlop/"I/O Operators">.
Beginning with v5.6.0, this operator is implemented using the standard
C<File::Glob> extension. See L<File::Glob> for details.
=item lock THING
-This function places an advisory lock on a shared variable, or referenced
+This function places an advisory lock on a shared variable, or referenced
object contained in I<THING> until the lock goes out of scope.
lock() is a "weak keyword" : this means that if you've defined a function
In the 2-arguments (and 1-argument) form opening C<'-'> opens STDIN
and opening C<< '>-' >> opens STDOUT.
-You may use the three-argument form of open to specify
-I<I/O disciplines> that affect how the input and output
-are processed: see L</binmode> and L<open>. For example
+You may use the three-argument form of open to specify IO "layers"
+(sometimes also referred to as "disciplines") to be applied to the handle
+that affect how the input and output are processed (see L<open> and
+L<PerlIO> for more details). For example
open(FH, "<:utf8", "file")
will open the UTF-8 encoded file containing Unicode characters,
-see L<perluniintro>.
+see L<perluniintro>. (Note that if layers are specified in the
+three-arg form then default layers set by the C<open> pragma are
+ignored.)
Open returns nonzero upon success, the undefined value otherwise. If
the C<open> involved a pipe, the return value happens to be the pid of
character, and which encode that character in C as C<"\n">, do not
need C<binmode>. The rest need it.
-In the three argument form MODE may also contain a list of IO "layers"
-(see L<open> and L<PerlIO> for more details) to be applied to the
-handle. This can be used to achieve the effect of C<binmode> as well
-as more complex behaviours.
-
When opening a file, it's usually a bad idea to continue normal execution
if the request failed, so C<open> is frequently used in connection with
C<die>. Even if C<die> won't do what you want (say, in a CGI script,
Note the I<characters>: depending on the status of the filehandle,
either (8-bit) bytes or characters are read. By default all
filehandles operate on bytes, but for example if the filehandle has
-been opened with the C<:utf8> discipline (see L</open>, and the C<open>
+been opened with the C<:utf8> I/O layer (see L</open>, and the C<open>
pragma, L<open>), the I/O will operate on characters, not bytes.
=item readdir DIRHANDLE
Note the I<characters>: depending on the status of the socket, either
(8-bit) bytes or characters are received. By default all sockets
operate on bytes, but for example if the socket has been changed using
-binmode() to operate with the C<:utf8> discipline (see the C<open>
+binmode() to operate with the C<:utf8> I/O layer (see the C<open>
pragma, L<open>), the I/O will operate on characters, not bytes.
=item redo LABEL
Note the I<in bytes>: even if the filehandle has been set to
operate on characters (for example by using the C<:utf8> open
-discipline), tell() will return byte offsets, not character offsets
+layer), tell() will return byte offsets, not character offsets
(because implementing that would render seek() and tell() rather slow).
If you want to position file for C<sysread> or C<syswrite>, don't use
Note the I<characters>: depending on the status of the socket, either
(8-bit) bytes or characters are sent. By default all sockets operate
on bytes, but for example if the socket has been changed using
-binmode() to operate with the C<:utf8> discipline (see L</open>, or
+binmode() to operate with the C<:utf8> I/O layer (see L</open>, or
the C<open> pragma, L<open>), the I/O will operate on characters, not
bytes.
Note the I<characters>: depending on the status of the filehandle,
either (8-bit) bytes or characters are read. By default all
filehandles operate on bytes, but for example if the filehandle has
-been opened with the C<:utf8> discipline (see L</open>, and the C<open>
+been opened with the C<:utf8> I/O layer (see L</open>, and the C<open>
pragma, L<open>), the I/O will operate on characters, not bytes.
An OFFSET may be specified to place the read data at some place in the
negative).
Note the I<in bytes>: even if the filehandle has been set to operate
-on characters (for example by using the C<:utf8> discipline), tell()
+on characters (for example by using the C<:utf8> I/O layer), tell()
will return byte offsets, not character offsets (because implementing
that would render sysseek() very slow).
Note the I<characters>: depending on the status of the filehandle,
either (8-bit) bytes or characters are written. By default all
filehandles operate on bytes, but for example if the filehandle has
-been opened with the C<:utf8> discipline (see L</open>, and the open
+been opened with the C<:utf8> I/O layer (see L</open>, and the open
pragma, L<open>), the I/O will operate on characters, not bytes.
=item tell FILEHANDLE
Note the I<in bytes>: even if the filehandle has been set to
operate on characters (for example by using the C<:utf8> open
-discipline), tell() will return byte offsets, not character offsets
+layer), tell() will return byte offsets, not character offsets
(because that would render seek() and tell() rather slow).
The return value of tell() for the standard streams like the STDIN
=item untie VARIABLE
Breaks the binding between a variable and a package. (See C<tie>.)
+Has no effect if the variable is not tied.
=item unshift ARRAY,LIST
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