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pread (2)
PREAD(2) Linux Programmer's Manual PREAD(2)
NAME
pread, pwrite - read from or write to a file descriptor at a given off-
set
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 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
On success, the number of bytes read or written is returned (zero indi-
cates 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.
The libc support (including emulation on older kernels without the sys-
tem calls) was added in glibc 2.1.
CONFORMING TO
POSIX.1-2001.
SEE ALSO
lseek(2), read(2), write(2), feature_test_macros(7)
Linux 1999-01-21 PREAD(2)
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