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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 $
48 .Fn write "int d" "const void *buf" "size_t nbytes"
50 .Fn writev "int d" "const struct iovec *iov" "int iovcnt"
52 .Fn pwrite "int d" "const void *buf" "size_t nbytes" "off_t offset"
54 .Fn pwritev "int d" "const struct iovec *iov" "int iovcnt" "off_t offset"
59 of data to the object referenced by the descriptor
61 from the buffer pointed to by
66 perform the same action, but gather the output data
69 buffers specified by the members of the
71 array: iov[0], iov[1], ..., iov[iovcnt\|-\|1].
75 perform the same function, but write to the specified position in
76 the file without modifying the file pointer.
84 structure is defined as:
86 .Bd -literal -offset indent -compact
88 char *iov_base; /* Base address. */
89 size_t iov_len; /* Length. */
95 entry specifies the base address and length of an area
96 in memory from which data should be written.
100 will always write a complete area before proceeding
103 On objects capable of seeking, the
106 given by the pointer associated with
112 the pointer is incremented by the number of bytes which were written.
114 Objects that are not capable of seeking always write from the current
115 position. The value of the pointer associated with such an object
118 If the real user is not the super-user, then
120 clears the set-user-id bit on a file.
121 This prevents penetration of system security
124 a writable set-user-id file
125 owned by the super-user.
127 When using non-blocking I/O on objects such as sockets that are subject
132 may write fewer bytes than requested;
133 the return value must be noted,
134 and the remainder of the operation should be retried when possible.
136 Upon successful completion the number of bytes which were written
137 is returned. Otherwise a -1 is returned and the global variable
139 is set to indicate the error.
146 will fail and the file pointer will remain unchanged if:
150 is not a valid descriptor open for writing.
152 An attempt is made to write to a pipe that is not open
153 for reading by any process.
155 An attempt is made to write to a socket of type
157 that is not connected to a peer socket.
159 An attempt was made to write a file that exceeds the process's
160 file size limit or the maximum file size.
164 or data to be written to the file
165 points outside the process's allocated address space.
167 The pointer associated with
171 There is no free space remaining on the file system
174 The user's quota of disk blocks on the file system
175 containing the file has been exhausted.
177 An I/O error occurred while reading from or writing to the file system.
179 A signal interrupted the write before it could be completed.
181 The file was marked for non-blocking I/O,
182 and no data could be written immediately.
184 An attempt was made to write over a disk label area at the beginning
189 to enable writing on the disk label area.
196 may return one of the following errors:
198 .It Bq Er EDESTADDRREQ
199 The destination is no longer available when writing to a
201 domain datagram socket on which
203 had been used to set a destination address.
206 was less than or equal to 0, or greater than
219 array overflowed a 32-bit integer.
221 The mbuf pool has been completely exhausted when writing to a socket.
228 calls may also return the following errors:
231 The specified file offset is invalid.
233 The file descriptor is associated with a pipe, socket, or FIFO.
244 function call is expected to conform to
250 functions are expected to conform to
255 function call was added in
269 function call appeared in