6 IO::Handle - supply object methods for I/O handles
13 if ($fh->fdopen(fileno(STDIN),"r")) {
19 if ($fh->fdopen(fileno(STDOUT),"w")) {
20 $fh->print("Some text\n");
23 $fh->setvbuf($buffer_var, _IOLBF, 1024);
25 undef $fh; # automatically closes the file if it's open
31 C<IO::Handle> is the base class for all other IO handle classes. It is
32 not intended that objects of C<IO::Handle> would be created directly,
33 but instead C<IO::Handle> is inherited from by several other classes
36 If you are reading this documentation, looking for a replacement for
37 the C<FileHandle> package, then I suggest you read the documentation
40 A C<IO::Handle> object is a reference to a symbol (see the C<Symbol> package)
48 Creates a new C<IO::Handle> object.
50 =item new_from_fd ( FD, MODE )
52 Creates a C<IO::Handle> like C<new> does.
53 It requires two parameters, which are passed to the method C<fdopen>;
54 if the fdopen fails, the object is destroyed. Otherwise, it is returned
61 If the C function setvbuf() is available, then C<IO::Handle::setvbuf>
62 sets the buffering policy for the IO::Handle. The calling sequence
63 for the Perl function is the same as its C counterpart, including the
64 macros C<_IOFBF>, C<_IOLBF>, and C<_IONBF>, except that the buffer
65 parameter specifies a scalar variable to use as a buffer. WARNING: A
66 variable used as a buffer by C<IO::Handle::setvbuf> must not be
67 modified in any way until the IO::Handle is closed or until
68 C<IO::Handle::setvbuf> is called again, or memory corruption may
71 See L<perlfunc> for complete descriptions of each of the following
72 supported C<IO::Handle> methods, which are just front ends for the
73 corresponding built-in functions:
88 See L<perlvar> for complete descriptions of each of the following
89 supported C<IO::Handle> methods:
92 output_field_separator
93 output_record_separator
94 input_record_separator
101 format_line_break_characters
105 Furthermore, for doing normal I/O you might need these:
111 This works like <$fh> described in L<perlop/"I/O Operators">
112 except that it's more readable and can be safely called in an
113 array context but still returns just one line.
117 This works like <$fh> when called in an array context to
118 read all the remaining lines in a file, except that it's more readable.
119 It will also croak() if accidentally called in a scalar context.
121 =item $fh->fdopen ( FD, MODE )
123 C<fdopen> is like an ordinary C<open> except that its first parameter
124 is not a filename but rather a file handle name, a IO::Handle object,
125 or a file descriptor number.
127 =item $fh->write ( BUF, LEN [, OFFSET }\] )
129 C<write> is like C<write> found in C, that is it is the
130 opposite of read. The wrapper for the perl C<write> function is
131 called C<format_write>.
135 Returns true if the object is currently a valid file descriptor.
139 Lastly, a special method for working under B<-T> and setuid/gid scripts:
145 Marks the object as taint-clean, and as such data read from it will also
146 be considered taint-clean. Note that this is a very trusting action to
147 take, and appropriate consideration for the data source and potential
148 vulnerability should be kept in mind.
154 A C<IO::Handle> object is a GLOB reference. Some modules that
155 inherit from C<IO::Handle> may want to keep object related variables
156 in the hash table part of the GLOB. In an attempt to prevent modules
157 trampling on each other I propose the that any such module should prefix
158 its variables with its own name separated by _'s. For example the IO::Socket
159 module keeps a C<timeout> variable in 'io_socket_timeout'.
164 L<perlop/"I/O Operators">,
169 Due to backwards compatibility, all filehandles resemble objects
170 of class C<IO::Handle>, or actually classes derived from that class.
171 They actually aren't. Which means you can't derive your own
172 class from C<IO::Handle> and inherit those methods.
176 Derived from FileHandle.pm by Graham Barr E<lt>F<bodg@tiuk.ti.com>E<gt>
182 use vars qw($VERSION $XS_VERSION @EXPORT_OK $AUTOLOAD @ISA);
191 $XS_VERSION = "1.15";
195 output_field_separator
196 output_record_separator
197 input_record_separator
200 format_lines_per_page
204 format_line_break_characters
224 ################################################
225 ## Interaction with the XS.
229 @IO::ISA = qw(DynaLoader);
230 bootstrap IO $XS_VERSION;
233 if ($AUTOLOAD =~ /::(_?[a-z])/) {
234 $AutoLoader::AUTOLOAD = $AUTOLOAD;
235 goto &AutoLoader::AUTOLOAD
237 my $constname = $AUTOLOAD;
238 $constname =~ s/.*:://;
239 my $val = constant($constname);
240 defined $val or croak "$constname is not a valid IO::Handle macro";
242 *$AUTOLOAD = sub { $val };
247 ################################################
248 ## Constructors, destructors.
252 my $class = ref($_[0]) || $_[0] || "IO::Handle";
253 @_ == 1 or croak "usage: new $class";
259 my $class = ref($_[0]) || $_[0] || "IO::Handle";
260 @_ == 3 or croak "usage: new_from_fd $class FD, MODE";
263 IO::Handle::fdopen($fh, @_)
269 # There is no need for DESTROY to do anything, because when the
270 # last reference to an IO object is gone, Perl automatically
271 # closes its associated files (if any). However, to avoid any
272 # attempts to autoload DESTROY, we here define it to do nothing.
277 ################################################
281 sub _open_mode_string {
283 $mode =~ /^\+?(<|>>?)$/
284 or $mode =~ s/^r(\+?)$/$1</
285 or $mode =~ s/^w(\+?)$/$1>/
286 or $mode =~ s/^a(\+?)$/$1>>/
287 or croak "IO::Handle: bad open mode: $mode";
292 @_ == 3 or croak 'usage: $fh->fdopen(FD, MODE)';
293 my ($fh, $fd, $mode) = @_;
296 if (ref($fd) && "".$fd =~ /GLOB\(/o) {
297 # It's a glob reference; Alias it as we cannot get name of anon GLOBs
298 my $n = qualify(*GLOB);
301 } elsif ($fd =~ m#^\d+$#) {
302 # It's an FD number; prefix with "=".
306 open($fh, _open_mode_string($mode) . '&' . $fd)
311 @_ == 1 or croak 'usage: $fh->close()';
317 ################################################
318 ## Normal I/O functions.
325 @_ == 1 or croak 'usage: $fh->opened()';
326 defined fileno($_[0]);
330 @_ == 1 or croak 'usage: $fh->fileno()';
335 @_ == 1 or croak 'usage: $fh->getc()';
340 @_ == 1 or croak 'usage: $fh->gets()';
346 @_ == 1 or croak 'usage: $fh->eof()';
351 @_ or croak 'usage: $fh->print([ARGS])';
357 @_ >= 2 or croak 'usage: $fh->printf(FMT,[ARGS])';
363 @_ == 1 or croak 'usage: $fh->getline';
365 return scalar <$this>;
369 @_ == 1 or croak 'usage: $fh->getline()';
371 croak 'Can\'t call $fh->getlines in a scalar context, use $fh->getline';
377 @_ == 2 or croak 'usage: $fh->truncate(LEN)';
378 truncate($_[0], $_[1]);
382 @_ == 3 || @_ == 4 or croak '$fh->read(BUF, LEN [, OFFSET])';
383 read($_[0], $_[1], $_[2], $_[3] || 0);
387 @_ == 3 || @_ == 4 or croak '$fh->sysread(BUF, LEN [, OFFSET])';
388 sysread($_[0], $_[1], $_[2], $_[3] || 0);
392 @_ == 3 || @_ == 4 or croak '$fh->write(BUF, LEN [, OFFSET])';
394 print { $_[0] } substr($_[1], $_[3] || 0, $_[2]);
398 @_ == 3 || @_ == 4 or croak '$fh->syswrite(BUF, LEN [, OFFSET])';
399 syswrite($_[0], $_[1], $_[2], $_[3] || 0);
403 @_ == 1 or croak 'usage: $fh->stat()';
407 ################################################
408 ## State modification functions.
412 my $old = new SelectSaver qualify($_[0], caller);
414 $| = @_ > 1 ? $_[1] : 1;
418 sub output_field_separator {
419 my $old = new SelectSaver qualify($_[0], caller);
421 $, = $_[1] if @_ > 1;
425 sub output_record_separator {
426 my $old = new SelectSaver qualify($_[0], caller);
428 $\ = $_[1] if @_ > 1;
432 sub input_record_separator {
433 my $old = new SelectSaver qualify($_[0], caller);
435 $/ = $_[1] if @_ > 1;
439 sub input_line_number {
440 my $old = new SelectSaver qualify($_[0], caller);
442 $. = $_[1] if @_ > 1;
446 sub format_page_number {
447 my $old = new SelectSaver qualify($_[0], caller);
449 $% = $_[1] if @_ > 1;
453 sub format_lines_per_page {
454 my $old = new SelectSaver qualify($_[0], caller);
456 $= = $_[1] if @_ > 1;
460 sub format_lines_left {
461 my $old = new SelectSaver qualify($_[0], caller);
463 $- = $_[1] if @_ > 1;
468 my $old = new SelectSaver qualify($_[0], caller);
470 $~ = qualify($_[1], caller) if @_ > 1;
474 sub format_top_name {
475 my $old = new SelectSaver qualify($_[0], caller);
477 $^ = qualify($_[1], caller) if @_ > 1;
481 sub format_line_break_characters {
482 my $old = new SelectSaver qualify($_[0], caller);
484 $: = $_[1] if @_ > 1;
488 sub format_formfeed {
489 my $old = new SelectSaver qualify($_[0], caller);
491 $^L = $_[1] if @_ > 1;
500 formline($picture, @_);
505 @_ < 3 || croak 'usage: $fh->write( [FORMAT_NAME] )';
508 my $oldfmt = $fh->format_name($fmt);
510 $fh->format_name($oldfmt);
517 @_ == 3 || croak 'usage: $fh->fcntl( OP, VALUE );';
518 my ($fh, $op, $val) = @_;
519 my $r = fcntl($fh, $op, $val);
520 defined $r && $r eq "0 but true" ? 0 : $r;
524 @_ == 3 || croak 'usage: $fh->ioctl( OP, VALUE );';
525 my ($fh, $op, $val) = @_;
526 my $r = ioctl($fh, $op, $val);
527 defined $r && $r eq "0 but true" ? 0 : $r;