IO::Handle - supply object methods for I/O handles
use IO::Handle;
$fh = new IO::Handle;
if ($fh->open "< file") {
print <$fh>;
$fh->close;
}
$fh = new IO::Handle "> FOO";
if (defined $fh) {
print $fh "bar\n";
$fh->close;
}
$fh = new IO::Handle "file", "r";
if (defined $fh) {
print <$fh>;
undef $fh; # automatically closes the file
}
$fh = new IO::Handle "file", O_WRONLY|O_APPEND;
if (defined $fh) {
print $fh "corge\n";
undef $fh; # automatically closes the file
}
$pos = $fh->getpos;
$fh->setpos $pos;
$fh->setvbuf($buffer_var, _IOLBF, 1024);
autoflush STDOUT 1;
IO::Handle is the base class for all other IO handle classes. A IO::Handle object is a reference to a symbol (see the Symbol package)
Creates a new IO::Handle object.
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.
If the C function setvbuf() is available, then IO::Handle::setvbuf sets the buffering policy for the IO::Handle. The calling sequence for the Perl function is the same as its C counterpart, including the macros _IOFBF, _IOLBF, and _IONBF, except that the buffer parameter specifies a scalar variable to use as a buffer. WARNING: A variable used as a buffer by IO::Handle::setvbuf must not be modified in any way until the IO::Handle is closed or until IO::Handle::setvbuf is called again, or memory corruption may result!
See perlfunc for complete descriptions of each of the following supported IO::Handle methods, which are just front ends for the corresponding built-in functions:
close
fileno
getc
gets
eof
read
truncate
stat
print
printf
sysread
syswrite
See perlvar 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:
This works like <$fh> described in "I/O Operators" in perlop except that it's more readable and can be safely called in an array context but still returns just one line.
This works like <$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.
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.
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.
Returns true if the object is currently a valid file descriptor.
Lastly, a special method for working under -T and setuid/gid scripts:
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.
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'.
perlfunc, "I/O Operators" in perlop, "FileHandle" in POSIX
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.
Derived from FileHandle.pm by Graham Barr <bodg@tiuk.ti.com>
