|IO::Seekable(3perl)||Perl Programmers Reference Guide||IO::Seekable(3perl)|
NAME¶IO::Seekable - supply seek based methods for I/O objects
use IO::Seekable; package IO::Something; @ISA = qw(IO::Seekable);
DESCRIPTION¶"IO::Seekable" does not have a constructor of its own as it is intended to be inherited by other "IO::Handle" based objects. It provides methods which allow seeking of the file descriptors.
- Returns an opaque value that represents the current position of the IO::File, or "undef" if this is not possible (eg an unseekable stream such as a terminal, pipe or socket). If the fgetpos() function is available in your C library it is used to implements getpos, else perl emulates getpos using C's ftell() function.
- Uses the value of a previous getpos call to return to a previously visited position. Returns "0 but true" on success, "undef" on failure.
See perlfunc for complete descriptions of each of the following supported "IO::Seekable" methods, which are just front ends for the corresponding built-in functions:
- $io->seek ( POS, WHENCE )
- Seek the IO::File to position POS, relative to WHENCE:
- WHENCE=0 (SEEK_SET)
- POS is absolute position. (Seek relative to the start of the file)
- WHENCE=1 (SEEK_CUR)
- POS is an offset from the current position. (Seek relative to current)
- WHENCE=2 (SEEK_END)
- POS is an offset from the end of the file. (Seek relative to end)
The SEEK_* constants can be imported from the "Fcntl" module if you don't wish to use the numbers 0 1 or 2 in your code.
Returns 1 upon success, 0 otherwise.
- $io->sysseek( POS, WHENCE )
- Similar to $io->seek, but sets the IO::File's
position using the system call lseek(2) directly, so will confuse
most perl IO operators except sysread and syswrite (see perlfunc for full
Returns the new position, or "undef" on failure. A position of zero is returned as the string "0 but true"
- Returns the IO::File's current position, or -1 on error.
SEE ALSO¶perlfunc, "I/O Operators" in perlop, IO::Handle IO::File
HISTORY¶Derived from FileHandle.pm by Graham Barr <email@example.com>