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28 .\" @(#)write.2 8.5 (Berkeley) 4/2/94
29 .\" $FreeBSD: src/lib/libc/sys/write.2,v 1.12.2.8 2002/10/13 17:42:14 schweikh Exp $
30 .\" $DragonFly: src/lib/libc/sys/write.2,v 1.5 2006/04/27 16:01:33 swildner Exp $
50 .Fn write "int d" "const void *buf" "size_t nbytes"
52 .Fn writev "int d" "const struct iovec *iov" "int iovcnt"
54 .Fn pwrite "int d" "const void *buf" "size_t nbytes" "off_t offset"
56 .Fn pwritev "int d" "const struct iovec *iov" "int iovcnt" "off_t offset"
58 .Fn extpwrite "int d" "const void *buf" "size_t nbytes" "int flags" "off_t offset"
60 .Fn extpwritev "int d" "const struct iovec *iov" "int iovcnt" "int flags" "off_t offset"
65 of data to the object referenced by the descriptor
67 from the buffer pointed to by
72 perform the same action, but gather the output data
75 buffers specified by the members of the
77 array: iov[0], iov[1], ..., iov[iovcnt\|-\|1].
81 perform the same function, but write to the specified position in
82 the file without modifying the file pointer.
90 structure is defined as:
92 .Bd -literal -offset indent -compact
94 char *iov_base; /* Base address. */
95 size_t iov_len; /* Length. */
101 entry specifies the base address and length of an area
102 in memory from which data should be written.
106 will always write a complete area before proceeding
116 extend the specification further by allowing a flags argument
117 to also be passed in, controlling blocking/non-blocking and other features
118 on a call-by-call basis, ignoring the related default for the descriptor.
122 Force the system call to operate in a blocking fashion.
124 Force the system call to operate in a non-blocking fashion.
126 Force append mode for the operation.
128 Force offset mode for the operation.
130 Force the system call to issue the write synchronously.
132 Force the system call to issue the write asynchronously.
135 On objects capable of seeking, the
138 given by the pointer associated with
144 the pointer is incremented by the number of bytes which were written.
146 Objects that are not capable of seeking always write from the current
147 position. The value of the pointer associated with such an object
150 If the real user is not the super-user, then
152 clears the set-user-id bit on a file.
153 This prevents penetration of system security
156 a writable set-user-id file
157 owned by the super-user.
159 When using non-blocking I/O on objects such as sockets that are subject
164 may write fewer bytes than requested;
165 the return value must be noted,
166 and the remainder of the operation should be retried when possible.
168 Upon successful completion the number of bytes which were written
169 is returned. Otherwise a -1 is returned and the global variable
171 is set to indicate the error.
178 will fail and the file pointer will remain unchanged if:
182 is not a valid descriptor open for writing.
184 An attempt is made to write to a pipe that is not open
185 for reading by any process.
187 An attempt is made to write to a socket of type
189 that is not connected to a peer socket.
191 An attempt was made to write a file that exceeds the process's
192 file size limit or the maximum file size.
196 or data to be written to the file
197 points outside the process's allocated address space.
199 The pointer associated with
203 There is no free space remaining on the file system
206 The user's quota of disk blocks on the file system
207 containing the file has been exhausted.
209 An I/O error occurred while reading from or writing to the file system.
211 A signal interrupted the write before it could be completed.
213 The file was marked for non-blocking I/O,
214 and no data could be written immediately.
216 An attempt was made to write over a disk label area at the beginning
221 to enable writing on the disk label area.
228 may return one of the following errors:
230 .It Bq Er EDESTADDRREQ
231 The destination is no longer available when writing to a
233 domain datagram socket on which
235 had been used to set a destination address.
238 was less than or equal to 0, or greater than
251 array overflowed a 32-bit integer.
253 The mbuf pool has been completely exhausted when writing to a socket.
260 calls may also return the following errors:
263 The specified file offset is invalid.
265 The file descriptor is associated with a pipe, socket, or FIFO.
276 function call is expected to conform to
282 functions are expected to conform to
287 function call was added in
301 function call appeared in