5 IO::Handle - supply object methods for I/O handles
12 if ($fh->open "< file") {
17 $fh = new IO::Handle "> FOO";
23 $fh = new IO::Handle "file", "r";
26 undef $fh; # automatically closes the file
29 $fh = new IO::Handle "file", O_WRONLY|O_APPEND;
32 undef $fh; # automatically closes the file
38 $fh->setvbuf($buffer_var, _IOLBF, 1024);
44 C<IO::Handle> is the base class for all other IO handle classes.
45 A C<IO::Handle> object is a reference to a symbol (see the C<Symbol> package)
53 Creates a new C<IO::Handle> object.
55 =item new_from_fd ( FD, MODE )
57 Creates a C<IO::Handle> like C<new> does.
58 It requires two parameters, which are passed to the method C<fdopen>;
59 if the fdopen fails, the object is destroyed. Otherwise, it is returned
66 If the C function setvbuf() is available, then C<IO::Handle::setvbuf>
67 sets the buffering policy for the IO::Handle. The calling sequence
68 for the Perl function is the same as its C counterpart, including the
69 macros C<_IOFBF>, C<_IOLBF>, and C<_IONBF>, except that the buffer
70 parameter specifies a scalar variable to use as a buffer. WARNING: A
71 variable used as a buffer by C<IO::Handle::setvbuf> must not be
72 modified in any way until the IO::Handle is closed or until
73 C<IO::Handle::setvbuf> is called again, or memory corruption may
76 See L<perlfunc> for complete descriptions of each of the following
77 supported C<IO::Handle> methods, which are just front ends for the
78 corresponding built-in functions:
93 See L<perlvar> for complete descriptions of each of the following
94 supported C<IO::Handle> methods:
97 output_field_separator
98 output_record_separator
99 input_record_separator
102 format_lines_per_page
106 format_line_break_characters
110 Furthermore, for doing normal I/O you might need these:
116 This works like <$fh> described in L<perlop/"I/O Operators">
117 except that it's more readable and can be safely called in an
118 array context but still returns just one line.
122 This works like <$fh> when called in an array context to
123 read all the remaining lines in a file, except that it's more readable.
124 It will also croak() if accidentally called in a scalar context.
126 =item $fh->fdopen ( FD, MODE )
128 C<fdopen> is like an ordinary C<open> except that its first parameter
129 is not a filename but rather a file handle name, a IO::Handle object,
130 or a file descriptor number.
132 =item $fh->write ( BUF, LEN [, OFFSET }\] )
134 C<write> is like C<write> found in C, that is it is the
135 opposite of read. The wrapper for the perl C<write> function is
136 called C<format_write>.
140 Returns true if the object is currently a valid file descriptor.
144 Lastly, a special method for working under B<-T> and setuid/gid scripts:
150 Marks the object as taint-clean, and as such data read from it will also
151 be considered taint-clean. Note that this is a very trusting action to
152 take, and appropriate consideration for the data source and potential
153 vulnerability should be kept in mind.
159 A C<IO::Handle> object is a GLOB reference. Some modules that
160 inherit from C<IO::Handle> may want to keep object related variables
161 in the hash table part of the GLOB. In an attempt to prevent modules
162 trampling on each other I propose the that any such module should prefix
163 its variables with its own name separated by _'s. For example the IO::Socket
164 module keeps a C<timeout> variable in 'io_socket_timeout'.
169 L<perlop/"I/O Operators">,
174 Due to backwards compatibility, all filehandles resemble objects
175 of class C<IO::Handle>, or actually classes derived from that class.
176 They actually aren't. Which means you can't derive your own
177 class from C<IO::Handle> and inherit those methods.
181 Derived from FileHandle.pm by Graham Barr E<lt>F<bodg@tiuk.ti.com>E<gt>
187 use vars qw($VERSION @EXPORT_OK $AUTOLOAD @ISA);
199 output_field_separator
200 output_record_separator
201 input_record_separator
204 format_lines_per_page
208 format_line_break_characters
228 ################################################
229 ## Interaction with the XS.
233 @IO::ISA = qw(DynaLoader);
234 bootstrap IO $VERSION;
237 if ($AUTOLOAD =~ /::(_?[a-z])/) {
238 $AutoLoader::AUTOLOAD = $AUTOLOAD;
239 goto &AutoLoader::AUTOLOAD
241 my $constname = $AUTOLOAD;
242 $constname =~ s/.*:://;
243 my $val = constant($constname);
244 defined $val or croak "$constname is not a valid IO::Handle macro";
246 *$AUTOLOAD = sub { $val };
251 ################################################
252 ## Constructors, destructors.
256 my $class = ref($_[0]) || $_[0] || "IO::Handle";
257 @_ == 1 or croak "usage: new $class";
263 my $class = ref($_[0]) || $_[0] || "IO::Handle";
264 @_ == 3 or croak "usage: new_from_fd $class FD, MODE";
267 IO::Handle::fdopen($fh, @_)
275 # During global object destruction, this function may be called
276 # on FILEHANDLEs as well as on the GLOBs that contains them.
277 # Thus the following trickery. If only the CORE file operators
278 # could deal with FILEHANDLEs, it wouldn't be necessary...
280 if ($fh =~ /=FILEHANDLE\(/) {
283 if defined fileno(TMP);
287 if defined fileno($fh);
291 ################################################
295 sub _open_mode_string {
297 $mode =~ /^\+?(<|>>?)$/
298 or $mode =~ s/^r(\+?)$/$1</
299 or $mode =~ s/^w(\+?)$/$1>/
300 or $mode =~ s/^a(\+?)$/$1>>/
301 or croak "IO::Handle: bad open mode: $mode";
306 @_ == 3 or croak 'usage: $fh->fdopen(FD, MODE)';
307 my ($fh, $fd, $mode) = @_;
310 if (ref($fd) && "".$fd =~ /GLOB\(/o) {
311 # It's a glob reference; Alias it as we cannot get name of anon GLOBs
312 my $n = qualify(*GLOB);
315 } elsif ($fd =~ m#^\d+$#) {
316 # It's an FD number; prefix with "=".
320 open($fh, _open_mode_string($mode) . '&' . $fd)
325 @_ == 1 or croak 'usage: $fh->close()';
329 # This may seem as though it should be in IO::Pipe, but the
330 # object gets blessed out of IO::Pipe when reader/writer is called
331 waitpid(${*$fh}{'io_pipe_pid'},0)
332 if(defined ${*$fh}{'io_pipe_pid'});
337 ################################################
338 ## Normal I/O functions.
345 @_ == 1 or croak 'usage: $fh->opened()';
346 defined fileno($_[0]);
350 @_ == 1 or croak 'usage: $fh->fileno()';
355 @_ == 1 or croak 'usage: $fh->getc()';
360 @_ == 1 or croak 'usage: $fh->gets()';
366 @_ == 1 or croak 'usage: $fh->eof()';
371 @_ or croak 'usage: $fh->print([ARGS])';
377 @_ >= 2 or croak 'usage: $fh->printf(FMT,[ARGS])';
383 @_ == 1 or croak 'usage: $fh->getline';
385 return scalar <$this>;
389 @_ == 1 or croak 'usage: $fh->getline()';
391 croak 'Can\'t call $fh->getlines in a scalar context, use $fh->getline';
397 @_ == 2 or croak 'usage: $fh->truncate(LEN)';
398 truncate($_[0], $_[1]);
402 @_ == 3 || @_ == 4 or croak '$fh->read(BUF, LEN [, OFFSET])';
403 read($_[0], $_[1], $_[2], $_[3] || 0);
407 @_ == 3 || @_ == 4 or croak '$fh->sysread(BUF, LEN [, OFFSET])';
408 sysread($_[0], $_[1], $_[2], $_[3] || 0);
412 @_ == 3 || @_ == 4 or croak '$fh->write(BUF, LEN [, OFFSET])';
414 print { $_[0] } substr($_[1], $_[3] || 0, $_[2]);
418 @_ == 3 || @_ == 4 or croak '$fh->syswrite(BUF, LEN [, OFFSET])';
419 syswrite($_[0], $_[1], $_[2], $_[3] || 0);
423 @_ == 1 or croak 'usage: $fh->stat()';
427 ################################################
428 ## State modification functions.
432 my $old = new SelectSaver qualify($_[0], caller);
434 $| = @_ > 1 ? $_[1] : 1;
438 sub output_field_separator {
439 my $old = new SelectSaver qualify($_[0], caller);
441 $, = $_[1] if @_ > 1;
445 sub output_record_separator {
446 my $old = new SelectSaver qualify($_[0], caller);
448 $\ = $_[1] if @_ > 1;
452 sub input_record_separator {
453 my $old = new SelectSaver qualify($_[0], caller);
455 $/ = $_[1] if @_ > 1;
459 sub input_line_number {
460 my $old = new SelectSaver qualify($_[0], caller);
462 $. = $_[1] if @_ > 1;
466 sub format_page_number {
467 my $old = new SelectSaver qualify($_[0], caller);
469 $% = $_[1] if @_ > 1;
473 sub format_lines_per_page {
474 my $old = new SelectSaver qualify($_[0], caller);
476 $= = $_[1] if @_ > 1;
480 sub format_lines_left {
481 my $old = new SelectSaver qualify($_[0], caller);
483 $- = $_[1] if @_ > 1;
488 my $old = new SelectSaver qualify($_[0], caller);
490 $~ = qualify($_[1], caller) if @_ > 1;
494 sub format_top_name {
495 my $old = new SelectSaver qualify($_[0], caller);
497 $^ = qualify($_[1], caller) if @_ > 1;
501 sub format_line_break_characters {
502 my $old = new SelectSaver qualify($_[0], caller);
504 $: = $_[1] if @_ > 1;
508 sub format_formfeed {
509 my $old = new SelectSaver qualify($_[0], caller);
511 $^L = $_[1] if @_ > 1;
520 formline($picture, @_);
525 @_ < 3 || croak 'usage: $fh->write( [FORMAT_NAME] )';
528 my $oldfmt = $fh->format_name($fmt);
530 $fh->format_name($oldfmt);
537 @_ == 3 || croak 'usage: $fh->fcntl( OP, VALUE );';
538 my ($fh, $op, $val) = @_;
539 my $r = fcntl($fh, $op, $val);
540 defined $r && $r eq "0 but true" ? 0 : $r;
544 @_ == 3 || croak 'usage: $fh->ioctl( OP, VALUE );';
545 my ($fh, $op, $val) = @_;
546 my $r = ioctl($fh, $op, $val);
547 defined $r && $r eq "0 but true" ? 0 : $r;