IO::Handle - supply object methods for I/O handles
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 $fh; # automatically closes the file if it's open autoflush STDOUT 1;
IO::Handle is the base class for all other IO handle classes. It is not intended that objects of IO::Handle would be created directly, but instead IO::Handle is inherited from by several other classes in the IO hierarchy.
IO::Handle
If you are reading this documentation, looking for a replacement for the FileHandle package, then I suggest you read the documentation for IO::File
FileHandle
IO::File
A IO::Handle object is a reference to a symbol (see the Symbol package)
Symbol
Creates a new IO::Handle object.
Creates a IO::Handle like new does. It requires two parameters, which are passed to the method fdopen; if the fdopen fails, the object is destroyed. Otherwise, it is returned to the caller.
new
fdopen
See perlfunc for complete descriptions of each of the following supported IO::Handle methods, which are just front ends for the corresponding built-in functions:
close fileno getc eof read truncate stat print printf sysread syswrite
See perlvar for complete descriptions of each of the following supported IO::Handle methods:
autoflush output_field_separator output_record_separator input_record_separator input_line_number format_page_number format_lines_per_page format_lines_left format_name format_top_name format_line_break_characters format_formfeed format_write
Furthermore, for doing normal I/O you might need these:
fdopen is like an ordinary open except that its first parameter is not a filename but rather a file handle name, a IO::Handle object, or a file descriptor number.
open
Returns true if the object is currently a valid file descriptor.
This works like <$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.
Pushes a character with the given ordinal value back onto the given handle's input stream.
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.
write
format_write
Flush the given handle's buffer.
Returns a true value if the given handle has experienced any errors since it was opened or since the last call to clearerr.
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.
IO::Handle::setbuf
IO::Handle::setvbuf
_IOFBF
_IOLBF
_IONBF
setbuf
setvbuf
Lastly, there is 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'.
timeout
perlfunc, "I/O Operators" in perlop, IO::File
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>
To install lib, copy and paste the appropriate command in to your terminal.
cpanm
cpanm lib
CPAN shell
perl -MCPAN -e shell install lib
For more information on module installation, please visit the detailed CPAN module installation guide.