PREAD(2)						     Linux Programmer's Manual							  PREAD(2)

NAME

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

SYNOPSIS

       #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);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       pread(), pwrite():
	   Since glibc 2.12:
	       _XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200809L
	   Before glibc 2.12:
	       _XOPEN_SOURCE >= 500

DESCRIPTION

       pread() reads up to count bytes from file descriptor fd at offset offset (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

       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

       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).

VERSIONS

       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.	C library support (including emulation using lseek(2) on older kernels without the system calls) was added in glibc 2.1.

CONFORMING TO

       POSIX.1-2001.

SEE ALSO

       lseek(2), read(2), write(2), feature_test_macros(7)

COLOPHON

       This page is part of release 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2010-09-20								  PREAD(2)