write - write to a file descriptor


SYNOPSIS

       #include <unistd.h>

       ssize_t write(int fd, const void *buf, size_t count);


DESCRIPTION

       write  writes  up to count bytes to the file referenced by
       the file descriptor fd from the buffer  starting  at  buf.
       POSIX  requires that a read() which can be proved to occur
       after a write() has returned returns the new  data.   Note
       that not all file systems are POSIX conforming.


RETURN VALUE

       On success, the number of bytes written are returned (zero
       indicates nothing was written).  On error, -1 is returned,
       and  errno is set appropriately.  If count is zero and the
       file descriptor refers  to  a  regular  file,  0  will  be
       returned  without causing any other effect.  For a special
       file, the results are not portable.


ERRORS

       EBADF  fd is not a valid file descriptor or  is  not  open
              for writing.

       EINVAL fd is attached to an object which is unsuitable for
              writing.

       EFAULT buf is outside your accessible address space.

       EFBIG  An attempt was made to write a  file  that  exceeds
              the implementation-defined maximum file size or the
              process' file size limit, or to write at a position
              past than the maximum allowed offset.

       EPIPE  fd  is  connected to a pipe or socket whose reading
              end is closed.  When this happens the writing  pro­
              cess  will receive a SIGPIPE signal; if it catches,
              blocks or ignores this the error EPIPE is returned.

       EAGAIN Non-blocking I/O has been selected using O_NONBLOCK
              and the write would block.

       EINTR  The call was interrupted by  a  signal  before  any
              data was written.

       ENOSPC The  device  containing  the file referred to by fd
              has no room for the data.

       EIO    A low-level I/O error occurred while modifying  the
              inode.

       to fd.


CONFORMING TO

       SVr4, SVID, POSIX, X/OPEN, 4.3BSD.  SVr4  documents  addi­
       tional  error  conditions  EDEADLK, ENOLCK, ENOLNK, ENOSR,
       ENXIO, EPIPE, or ERANGE.  Under SVr4 a write may be inter­
       rupted  and return EINTR at any point, not just before any
       data is written.


SEE ALSO

       open(2), read(2), fcntl(2), close(2), lseek(2), select(2),
       ioctl(2), fsync(2), fwrite(3)


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