6 IO::Handle - supply object methods for I/O handles
13 if ($io->fdopen(fileno(STDIN),"r")) {
19 if ($io->fdopen(fileno(STDOUT),"w")) {
20 $io->print("Some text\n");
23 # setvbuf is not available by default on Perls 5.8.0 and later.
24 use IO::Handle '_IOLBF';
25 $io->setvbuf($buffer_var, _IOLBF, 1024);
27 undef $io; # automatically closes the file if it's open
33 C<IO::Handle> is the base class for all other IO handle classes. It is
34 not intended that objects of C<IO::Handle> would be created directly,
35 but instead C<IO::Handle> is inherited from by several other classes
38 If you are reading this documentation, looking for a replacement for
39 the C<FileHandle> package, then I suggest you read the documentation
48 Creates a new C<IO::Handle> object.
50 =item new_from_fd ( FD, MODE )
52 Creates an 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 See L<perlfunc> for complete descriptions of each of the following
62 supported C<IO::Handle> methods, which are just front ends for the
63 corresponding built-in functions:
68 $io->format_write( [FORMAT_NAME] )
70 $io->read ( BUF, LEN, [OFFSET] )
72 $io->printf ( FMT, [ARGS] )
74 $io->sysread ( BUF, LEN, [OFFSET] )
75 $io->syswrite ( BUF, [LEN, [OFFSET]] )
78 See L<perlvar> for complete descriptions of each of the following
79 supported C<IO::Handle> methods. All of them return the previous
80 value of the attribute and takes an optional single argument that when
81 given will set the value. If no argument is given the previous value
82 is unchanged (except for $io->autoflush will actually turn ON
83 autoflush by default).
85 $io->autoflush ( [BOOL] ) $|
86 $io->format_page_number( [NUM] ) $%
87 $io->format_lines_per_page( [NUM] ) $=
88 $io->format_lines_left( [NUM] ) $-
89 $io->format_name( [STR] ) $~
90 $io->format_top_name( [STR] ) $^
91 $io->input_line_number( [NUM]) $.
93 The following methods are not supported on a per-filehandle basis.
95 IO::Handle->format_line_break_characters( [STR] ) $:
96 IO::Handle->format_formfeed( [STR]) $^L
97 IO::Handle->output_field_separator( [STR] ) $,
98 IO::Handle->output_record_separator( [STR] ) $\
100 IO::Handle->input_record_separator( [STR] ) $/
102 Furthermore, for doing normal I/O you might need these:
106 =item $io->fdopen ( FD, MODE )
108 C<fdopen> is like an ordinary C<open> except that its first parameter
109 is not a filename but rather a file handle name, an IO::Handle object,
110 or a file descriptor number.
114 Returns true if the object is currently a valid file descriptor, false
119 This works like <$io> described in L<perlop/"I/O Operators">
120 except that it's more readable and can be safely called in a
121 list context but still returns just one line.
125 This works like <$io> when called in a list context to read all
126 the remaining lines in a file, except that it's more readable.
127 It will also croak() if accidentally called in a scalar context.
129 =item $io->ungetc ( ORD )
131 Pushes a character with the given ordinal value back onto the given
132 handle's input stream. Only one character of pushback per handle is
135 =item $io->write ( BUF, LEN [, OFFSET ] )
137 This C<write> is like C<write> found in C, that is it is the
138 opposite of read. The wrapper for the perl C<write> function is
139 called C<format_write>.
143 Returns a true value if the given handle has experienced any errors
144 since it was opened or since the last call to C<clearerr>, or if the
145 handle is invalid. It only returns false for a valid handle with no
150 Clear the given handle's error indicator. Returns -1 if the handle is
151 invalid, 0 otherwise.
155 C<sync> synchronizes a file's in-memory state with that on the
156 physical medium. C<sync> does not operate at the perlio api level, but
157 operates on the file descriptor (similar to sysread, sysseek and
158 systell). This means that any data held at the perlio api level will not
159 be synchronized. To synchronize data that is buffered at the perlio api
160 level you must use the flush method. C<sync> is not implemented on all
161 platforms. Returns "0 but true" on success, C<undef> on error, C<undef>
162 for an invalid handle. See L<fsync(3c)>.
166 C<flush> causes perl to flush any buffered data at the perlio api level.
167 Any unread data in the buffer will be discarded, and any unwritten data
168 will be written to the underlying file descriptor. Returns "0 but true"
169 on success, C<undef> on error.
171 =item $io->printflush ( ARGS )
173 Turns on autoflush, print ARGS and then restores the autoflush status of the
174 C<IO::Handle> object. Returns the return value from print.
176 =item $io->blocking ( [ BOOL ] )
178 If called with an argument C<blocking> will turn on non-blocking IO if
179 C<BOOL> is false, and turn it off if C<BOOL> is true.
181 C<blocking> will return the value of the previous setting, or the
182 current setting if C<BOOL> is not given.
184 If an error occurs C<blocking> will return undef and C<$!> will be set.
189 If the C functions setbuf() and/or setvbuf() are available, then
190 C<IO::Handle::setbuf> and C<IO::Handle::setvbuf> set the buffering
191 policy for an IO::Handle. The calling sequences for the Perl functions
192 are the same as their C counterparts--including the constants C<_IOFBF>,
193 C<_IOLBF>, and C<_IONBF> for setvbuf()--except that the buffer parameter
194 specifies a scalar variable to use as a buffer. You should only
195 change the buffer before any I/O, or immediately after calling flush.
197 WARNING: The IO::Handle::setvbuf() is not available by default on
198 Perls 5.8.0 and later because setvbuf() is rather specific to using
199 the stdio library, while Perl prefers the new perlio subsystem instead.
201 WARNING: A variable used as a buffer by C<setbuf> or C<setvbuf> B<must not
202 be modified> in any way until the IO::Handle is closed or C<setbuf> or
203 C<setvbuf> is called again, or memory corruption may result! Remember that
204 the order of global destruction is undefined, so even if your buffer
205 variable remains in scope until program termination, it may be undefined
206 before the file IO::Handle is closed. Note that you need to import the
207 constants C<_IOFBF>, C<_IOLBF>, and C<_IONBF> explicitly. Like C, setbuf
208 returns nothing. setvbuf returns "0 but true", on success, C<undef> on
211 Lastly, there is a special method for working under B<-T> and setuid/gid
218 Marks the object as taint-clean, and as such data read from it will also
219 be considered taint-clean. Note that this is a very trusting action to
220 take, and appropriate consideration for the data source and potential
221 vulnerability should be kept in mind. Returns 0 on success, -1 if setting
222 the taint-clean flag failed. (eg invalid handle)
228 An C<IO::Handle> object is a reference to a symbol/GLOB reference (see
229 the C<Symbol> package). Some modules that
230 inherit from C<IO::Handle> may want to keep object related variables
231 in the hash table part of the GLOB. In an attempt to prevent modules
232 trampling on each other I propose the that any such module should prefix
233 its variables with its own name separated by _'s. For example the IO::Socket
234 module keeps a C<timeout> variable in 'io_socket_timeout'.
239 L<perlop/"I/O Operators">,
244 Due to backwards compatibility, all filehandles resemble objects
245 of class C<IO::Handle>, or actually classes derived from that class.
246 They actually aren't. Which means you can't derive your own
247 class from C<IO::Handle> and inherit those methods.
251 Derived from FileHandle.pm by Graham Barr E<lt>F<gbarr@pobox.com>E<gt>
257 our($VERSION, @EXPORT_OK, @ISA);
261 use IO (); # Load the XS module
266 $VERSION = "1.21_00";
267 $VERSION = eval $VERSION;
271 output_field_separator
272 output_record_separator
273 input_record_separator
276 format_lines_per_page
280 format_line_break_characters
300 ################################################
301 ## Constructors, destructors.
305 my $class = ref($_[0]) || $_[0] || "IO::Handle";
306 @_ == 1 or croak "usage: new $class";
312 my $class = ref($_[0]) || $_[0] || "IO::Handle";
313 @_ == 3 or croak "usage: new_from_fd $class FD, MODE";
316 IO::Handle::fdopen($io, @_)
322 # There is no need for DESTROY to do anything, because when the
323 # last reference to an IO object is gone, Perl automatically
324 # closes its associated files (if any). However, to avoid any
325 # attempts to autoload DESTROY, we here define it to do nothing.
330 ################################################
334 sub _open_mode_string {
336 $mode =~ /^\+?(<|>>?)$/
337 or $mode =~ s/^r(\+?)$/$1</
338 or $mode =~ s/^w(\+?)$/$1>/
339 or $mode =~ s/^a(\+?)$/$1>>/
340 or croak "IO::Handle: bad open mode: $mode";
345 @_ == 3 or croak 'usage: $io->fdopen(FD, MODE)';
346 my ($io, $fd, $mode) = @_;
349 if (ref($fd) && "".$fd =~ /GLOB\(/o) {
350 # It's a glob reference; Alias it as we cannot get name of anon GLOBs
351 my $n = qualify(*GLOB);
354 } elsif ($fd =~ m#^\d+$#) {
355 # It's an FD number; prefix with "=".
359 open($io, _open_mode_string($mode) . '&' . $fd)
364 @_ == 1 or croak 'usage: $io->close()';
370 ################################################
371 ## Normal I/O functions.
378 @_ == 1 or croak 'usage: $io->opened()';
379 defined fileno($_[0]);
383 @_ == 1 or croak 'usage: $io->fileno()';
388 @_ == 1 or croak 'usage: $io->getc()';
393 @_ == 1 or croak 'usage: $io->eof()';
398 @_ or croak 'usage: $io->print(ARGS)';
404 @_ >= 2 or croak 'usage: $io->printf(FMT,[ARGS])';
410 @_ == 1 or croak 'usage: $io->getline()';
412 return scalar <$this>;
415 *gets = \&getline; # deprecated
418 @_ == 1 or croak 'usage: $io->getlines()';
420 croak 'Can\'t call $io->getlines in a scalar context, use $io->getline';
426 @_ == 2 or croak 'usage: $io->truncate(LEN)';
427 truncate($_[0], $_[1]);
431 @_ == 3 || @_ == 4 or croak 'usage: $io->read(BUF, LEN [, OFFSET])';
432 read($_[0], $_[1], $_[2], $_[3] || 0);
436 @_ == 3 || @_ == 4 or croak 'usage: $io->sysread(BUF, LEN [, OFFSET])';
437 sysread($_[0], $_[1], $_[2], $_[3] || 0);
441 @_ >= 2 && @_ <= 4 or croak 'usage: $io->write(BUF [, LEN [, OFFSET]])';
443 $_[2] = length($_[1]) unless defined $_[2];
444 print { $_[0] } substr($_[1], $_[3] || 0, $_[2]);
448 @_ >= 2 && @_ <= 4 or croak 'usage: $io->syswrite(BUF [, LEN [, OFFSET]])';
449 if (defined($_[2])) {
450 syswrite($_[0], $_[1], $_[2], $_[3] || 0);
452 syswrite($_[0], $_[1]);
457 @_ == 1 or croak 'usage: $io->stat()';
461 ################################################
462 ## State modification functions.
466 my $old = new SelectSaver qualify($_[0], caller);
468 $| = @_ > 1 ? $_[1] : 1;
472 sub output_field_separator {
473 carp "output_field_separator is not supported on a per-handle basis"
476 $, = $_[1] if @_ > 1;
480 sub output_record_separator {
481 carp "output_record_separator is not supported on a per-handle basis"
484 $\ = $_[1] if @_ > 1;
488 sub input_record_separator {
489 carp "input_record_separator is not supported on a per-handle basis"
492 $/ = $_[1] if @_ > 1;
496 sub input_line_number {
498 my $tell = tell qualify($_[0], caller) if ref($_[0]);
500 $. = $_[1] if @_ > 1;
504 sub format_page_number {
505 my $old = new SelectSaver qualify($_[0], caller) if ref($_[0]);
507 $% = $_[1] if @_ > 1;
511 sub format_lines_per_page {
512 my $old = new SelectSaver qualify($_[0], caller) if ref($_[0]);
514 $= = $_[1] if @_ > 1;
518 sub format_lines_left {
519 my $old = new SelectSaver qualify($_[0], caller) if ref($_[0]);
521 $- = $_[1] if @_ > 1;
526 my $old = new SelectSaver qualify($_[0], caller) if ref($_[0]);
528 $~ = qualify($_[1], caller) if @_ > 1;
532 sub format_top_name {
533 my $old = new SelectSaver qualify($_[0], caller) if ref($_[0]);
535 $^ = qualify($_[1], caller) if @_ > 1;
539 sub format_line_break_characters {
540 carp "format_line_break_characters is not supported on a per-handle basis"
543 $: = $_[1] if @_ > 1;
547 sub format_formfeed {
548 carp "format_formfeed is not supported on a per-handle basis"
551 $^L = $_[1] if @_ > 1;
560 formline($picture, @_);
565 @_ < 3 || croak 'usage: $io->write( [FORMAT_NAME] )';
568 my $oldfmt = $io->format_name($fmt);
570 $io->format_name($oldfmt);
578 @_ == 3 || croak 'usage: $io->fcntl( OP, VALUE );';
580 return fcntl($io, $op, $_[2]);
585 @_ == 3 || croak 'usage: $io->ioctl( OP, VALUE );';
587 return ioctl($io, $op, $_[2]);
590 # this sub is for compatability with older releases of IO that used
591 # a sub called constant to detemine if a constant existed -- GMB
593 # The SEEK_* and _IO?BF constants were the only constants at that time
594 # any new code should just chech defined(&CONSTANT_NAME)
599 (($name =~ /^(SEEK_(SET|CUR|END)|_IO[FLN]BF)$/) && defined &{$name})
600 ? &{$name}() : undef;
604 # so that flush.pl can be deprecated
608 my $old = new SelectSaver qualify($io, caller) if ref($io);