IO::Handle(3) IO::Handle(3)
NAME
IO::Handle - supply object methods for I/O handles
SYNOPSIS
use IO::Handle;
$fh = new IO::Handle;
if ($fh->fdopen(fileno(STDIN),"r")) {
print $fh->getline;
$fh->close;
}
$fh = new IO::Handle;
if ($fh->fdopen(fileno(STDOUT),"w")) {
$fh->print("Some text\n");
}
use IO::Handle '_IOLBF';
$fh->setvbuf($buffer_var, _IOLBF, 1024);
undef $fh; # automatically closes the file if it's open
autoflush STDOUT 1;
DESCRIPTION
IO::Handle is the base class for all other IO handle classes. It is not
intended that objects of IO::Handle would be created directly, but
instead IO::Handle is inherited from by several other classes in the IO
hierarchy.
If you are reading this documentation, looking for a replacement for the
FileHandle package, then I suggest you read the documentation for
IO::File
A IO::Handle object is a reference to a symbol (see the Symbol package)
CONSTRUCTOR
new ()
Creates a new IO::Handle object.
new_from_fd ( FD, MODE )
Creates a IO::Handle like new does. It requires two parameters,
which are passed to the method fdopen; if the fdopen fails, the
object is destroyed. Otherwise, it is returned to the caller.
METHODS
See the perlfunc manpage for complete descriptions of each of the
following supported IO::Handle methods, which are just front ends for the
corresponding built-in functions:
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IO::Handle(3) IO::Handle(3)
close
fileno
getc
eof
read
truncate
stat
print
printf
sysread
syswrite
See the perlvar manpage for complete descriptions of each of the
following supported IO::Handle methods:
autoflush
output_field_separator
output_record_separator
input_record_separator
input_line_number
format_page_number
format_lines_per_page
format_lines_left
format_name
format_top_name
format_line_break_characters
format_formfeed
format_write
Furthermore, for doing normal I/O you might need these:
$fh->fdopen ( FD, MODE )
fdopen is like an ordinary open except that its first parameter is
not a filename but rather a file handle name, a IO::Handle object,
or a file descriptor number.
$fh->opened
Returns true if the object is currently a valid file descriptor.
$fh->getline
This works like <$fh> described in the section on I/O Operators in
the perlop manpage except that it's more readable and can be safely
called in an array context but still returns just one line.
$fh->getlines
This works like <$fh> when called in an array context to read all
the remaining lines in a file, except that it's more readable. It
will also croak() if accidentally called in a scalar context.
$fh->ungetc ( ORD )
Pushes a character with the given ordinal value back onto the given
handle's input stream.
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IO::Handle(3) IO::Handle(3)
$fh->write ( BUF, LEN [, OFFSET }\] )
This write is like write found in C, that is it is the opposite of
read. The wrapper for the perl write function is called
format_write.
$fh->flush
Flush the given handle's buffer.
$fh->error
Returns a true value if the given handle has experienced any errors
since it was opened or since the last call to clearerr.
$fh->clearerr
Clear the given handle's error indicator.
If the C functions setbuf() and/or setvbuf() are available, then
IO::Handle::setbuf and IO::Handle::setvbuf set the buffering policy for
an IO::Handle. The calling sequences for the Perl functions are the same
as their C counterparts--including the constants _IOFBF, _IOLBF, and
_IONBF for setvbuf()--except that the buffer parameter specifies a scalar
variable to use as a buffer. WARNING: A variable used as a buffer by
setbuf or setvbuf must not be modified in any way until the IO::Handle is
closed or setbuf or setvbuf is called again, or memory corruption may
result! Note that you need to import the constants _IOFBF, _IOLBF, and
_IONBF explicitly.
Lastly, there is a special method for working under -T and setuid/gid
scripts:
$fh->untaint
Marks the object as taint-clean, and as such data read from it will
also be considered taint-clean. Note that this is a very trusting
action to take, and appropriate consideration for the data source
and potential vulnerability should be kept in mind.
NOTE
A IO::Handle object is a GLOB reference. Some modules that inherit from
IO::Handle may want to keep object related variables in the hash table
part of the GLOB. In an attempt to prevent modules trampling on each
other I propose the that any such module should prefix its variables with
its own name separated by _'s. For example the IO::Socket module keeps a
timeout variable in 'io_socket_timeout'.
SEE ALSO
the perlfunc manpage, the section on I/O Operators in the perlop manpage,
the IO::File manpage
BUGS
Due to backwards compatibility, all filehandles resemble objects of class
IO::Handle, or actually classes derived from that class. They actually
aren't. Which means you can't derive your own class from IO::Handle and
inherit those methods.
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IO::Handle(3) IO::Handle(3)
HISTORY
Derived from FileHandle.pm by Graham Barr <bodg@tiuk.ti.com>
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