write writes up to 'count' bytes to the file referenced by the file descriptor 'fileDescriptor' from the buffer starting at 'buf'.
See Also
Parameters
- fd
- Documentation for this section has not yet been entered.
- buf
- Documentation for this section has not yet been entered.
- count
- Documentation for this section has not yet been entered.
Returns
Upon successful completion the number of bytes which were written is returned. Otherwise a -1 is returned and the global variable Stdlib.GetLastError is set to indicate the error.
Usage
The write(), writev(), and pwrite() system calls will fail and the file pointer will remain unchanged if:
Error Details Errno.EBADF The d argument is not a valid descriptor open for writing.
Errno.EPIPE An attempt is made to write to a pipe that is not open for reading by any process.
Errno.EPIPE An attempt is made to write to a socket of type Errno.SOCK_STREAM that is not connected to a peer socket.
Errno.EFBIG An attempt was made to write a file that exceeds the process's file size limit or the maximum file size.
Errno.EFAULT Part of iov or data to be written to the file points outside the process's allocated address space.
Errno.EINVAL The pointer associated with d was negative.
Errno.ENOSPC There is no free space remaining on the file system containing the file.
Errno.EDQUOT The user's quota of disk blocks on the file system containing the file has been exhausted.
Errno.EIO An I/O error occurred while reading from or writing to the file system.
Errno.EINTR A signal interrupted the write before it could be completed.
Errno.EAGAIN The file was marked for non-blocking I/O, and no data could be written immediately.
Errno.EROFS An attempt was made to write over a disk label area at the beginning of a slice. Use disklabel(8) Fl W to enable writing on the disk label area.
In addition, writev() may return one of the following errors:
Error Details Errno.EDESTADDRREQ The destination is no longer available when writing to a Ux domain datagram socket on which Syscall.connect(2) had been used to set a destination address.
Errno.EINVAL The iovcnt argument was less than or equal to 0, or greater than TODO.IOV_MAX .
Errno.EINVAL One of the iov_len values in the iov array was negative.
Errno.EINVAL The sum of the iov_len values in the iov array overflowed a 32-bit integer.
Errno.ENOBUFS The mbuf pool has been completely exhausted when writing to a socket.
The pwrite() system call may also return the following errors:
Error Details Errno.EINVAL The offset value was negative.
Errno.ESPIPE The file descriptor is associated with a pipe, socket, or FIFO.
Remarks
The write() system call attempts to write nbytes of data to the object referenced by the descriptor d from the buffer pointed to by buf . The writev() system call performs the same action, but gathers the output data from the iovcnt buffers specified by the members of the iov array: iov[0], iov[1], ..., iov[iovcnt|-|1]. The pwrite() system call performs the same function, but writes to the specified position in the file without modifying the file pointer.
For writev(), the iovec structure is defined as:
Usage
struct iovec {
};
Each iovec entry specifies the base address and length of an area in memory from which data should be written. The writev() system call will always write a complete area before proceeding to the next.
On objects capable of seeking, the write() starts at a position given by the pointer associated with d , see Syscall.lseek(2) . Upon return from write(), the pointer is incremented by the number of bytes which were 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.
If the real user is not the super-user, then write() clears the set-user-id bit on a file. This prevents penetration of system security by a user who captures a writable set-user-id file owned by the super-user.
When using non-blocking I/O on objects such as sockets that are subject to flow control, write() and writev() may write fewer bytes than requested; the return value must be noted, and the remainder of the operation should be retried when possible.
Requirements
Namespace: Mono.Unix.Native
Assembly: Mono.Posix (in Mono.Posix.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0