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

NAME
       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  con-
       forming.

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 implementa-
	      tion-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 process will also receive  a  SIG-
	      PIPE  signal.  (Thus, the	write return value is seen only	if the
	      program catches, blocks or ignores this signal.)

       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 writ-
	      ten.

       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.

       Other errors may	occur, depending on the	object connected to fd.

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

NOTES
       A successful return from	write does not make any	 guarantee  that  data
       has been	committed to disk.  In fact, on	some buggy implementations, it
       does not	even guarantee that space has successfully been	 reserved  for
       the  data.   The	 only way to be	sure is	to call	fsync(2) after you are
       done writing all	your data.

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

Linux 2.0.32			  2001-12-13			      WRITE(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO

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