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pread(2) - pread, pwrite, pread, pwrite - read from or write to a file descriptor at a given offset - man 2 pread

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



NAME
       pread, pwrite - read(2,n,1 builtins) from or write(1,2) to a file(1,n) descriptor at a given off-
       set(7,n,1 builtins)

SYNOPSIS
       #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
       pread() reads up to count bytes from file(1,n) descriptor fd at offset  off-
       set(7,n,1 builtins)  (from the start of the file(1,n)) into the buffer starting at buf.  The
       file(1,n) offset is not changed.

       pwrite() writes up to count bytes from the buffer starting  at  buf  to
       the  file(1,n)  descriptor  fd  at  offset  offset.   The file(1,n) offset is not
       changed.

       The file(1,n) referenced by fd must be capable of seeking.

RETURN VALUE
       On success, the number of bytes read(2,n,1 builtins) or written is returned (zero indi-
       cates  that nothing was written, in(1,8) the case of pwrite, or end of file(1,n),
       in(1,8) the case of pread), or -1 on error(8,n), in(1,8) which case errno  is  set(7,n,1 builtins)  to
       indicate the error.

ERRORS
       pread  can  fail  and  set(7,n,1 builtins)  errno to any error(8,n) specified for read(2,n,1 builtins)(2) or
       lseek(2).  pwrite can fail and set(7,n,1 builtins) errno to  any  error(8,n)  specified  for
       write(1,2)(2) or lseek(2).

CONFORMING TO
       Unix98

HISTORY
       The  pread  and  pwrite  system  calls  were  added to Linux in(1,8) version(1,3,5)
       2.1.60; the entries in(1,8) the i386 system call table were added in(1,8) 2.1.69.
       The libc support (including emulation on older kernels without the sys-
       tem calls) was added in(1,8) glibc 2.1.

SEE ALSO
       lseek(2), read(2,n,1 builtins)(2), write(1,2)(2)



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

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