WRITE

write − write to a file descriptor

#include <unistd.h>

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

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.

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.

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.

EPIPE

fd is connected to a pipe or socket whose reading end is closed. When this happens the writing process 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 there was no room in the pipe or socket connected to fd to write the data immediately.

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.

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

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

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