Copyright (c) 1980 Regents of the University of California.
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@(#)write.2 6.5 (Berkeley) 5/14/86

C 4 write - write output

#include <sys/types.h>
#include <unistd.h>

ssize_t write(int d, const void *buf, size_t nbytes)

Write attempts to write nbytes of data to the object referenced by the descriptor d from the buffer pointed to by buf .

On objects capable of seeking, the write starts at a position given by the pointer associated with d , see lseek (2). Upon return from write , the pointer is incremented by the number of bytes actually written.

Objects that are not capable of seeking always write from the current position. The value of the pointer associated with such an object is undefined.

When using non-blocking I/O on objects such as TCP/IP channels that are subject to flow control, write may write fewer bytes than requested; the return value must be noted, and the remainder of the operation should be retried when possible.

Upon successful completion the number of bytes actually written is returned. Otherwise a -1 is returned and the global variable errno is set to indicate the error. Write will fail and the file pointer will remain unchanged if one or more of the following are true:

15 [EBADF] D is not a valid descriptor open for writing.

15 [EPIPE] An attempt is made to write to a pipe that is not open for reading by any process.

15 [EPIPE] An attempt is made to write to a TCP channel that is not connected to a peer socket.

15 [EFBIG] An attempt was made to write a file that exceeds the process's file size limit or the maximum file size.

15 [EFAULT] Part of the data to be written to the file points outside the process's allocated address space.

15 [ENOSPC] There is no free space remaining on the file system containing the file.

15 [EDQUOT] The user's quota of disk blocks on the file system containing the file has been exhausted. ..

15 [EIO] An I/O error occurred while reading from or writing to the file system.

15 [EAGAIN] The file was marked for non-blocking I/O, and no data could be written immediately.

fcntl (2), lseek (2), open (2), pipe (2), read (2).