NAME    [Toc]    [Back]

       pread, pwrite - read from or write to a file descriptor at a given offset

SYNOPSIS    [Toc]    [Back]

       #define _XOPEN_SOURCE 500

       #include <unistd.h>

       ssize_t pread(int fd, void *buf, size_t count, off_t offset);

       ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset);

DESCRIPTION    [Toc]    [Back]

       pread() reads up to count bytes from file descriptor fd at offset  off-
       set  (from the start of the file) into the buffer starting at buf.  The
       file offset is not changed.

       pwrite() writes up to count bytes from the buffer starting  at  buf  to
       the  file  descriptor  fd  at  offset  offset.	The file offset is not
       changed.

       The file referenced by fd must be capable of seeking.

RETURN VALUE    [Toc]    [Back]

       On success, the number of bytes read or written is returned (zero indicates
  that nothing was written, in the case of pwrite, or end of file,
       in the case of pread), or -1 on error, in which case errno  is  set  to
       indicate the error.

ERRORS    [Toc]    [Back]

       pread  can  fail  and  set  errno to any error specified for read(2) or
       lseek(2).  pwrite can fail and set errno to  any  error	specified  for
       write(2) or lseek(2).

CONFORMING TO    [Toc]    [Back]

       Unix98

HISTORY    [Toc]    [Back]

       The  pread  and	pwrite	system	calls  were  added to Linux in version
       2.1.60; the entries in the i386 system call table were added in 2.1.69.
       The libc support (including emulation on older kernels without the system
 calls) was added in glibc 2.1.

SEE ALSO    [Toc]    [Back]

       read(2), write(2), lseek(2)



Linux 2.2.0-pre9		  1999-01-21			      PREAD(2)