FWRITE(3C) Standard C Library Functions FWRITE(3C)
NAME
fwrite - binary output
SYNOPSIS
#include <stdio.h>
size_t fwrite(
const void *ptr,
size_t size,
size_t nitems,
FILE *stream);
DESCRIPTION
The
fwrite() function writes, from the array pointed to by
ptr, up to
nitems elements whose size is specified by
size, to the stream
pointed to by
stream. For each object,
size calls are made to the
fputc(3C) function, taking the values (in order) from an array of
unsigned char exactly overlaying the object. The file-position
indicator for the stream (if defined) is advanced by the number of
bytes successfully written. If an error occurs, the resulting value
of the file-position indicator for the stream is unspecified.
The
st_ctime and
st_mtime fields of the file will be marked for
update between the successful execution of
fwrite() and the next
successful completion of a call to
fflush(3C) or
fclose(3C) on the
same stream or a call to
exit(2) or
abort(3C).
When using the
fwrite() function on a stream that was created with
open_wmemstream(3C), there are additional constraints on the binary
data that can be written due to the nature of the stream. Please see
open_wmemstream(3C) for additional information.
RETURN VALUES
The
fwrite() function returns the number of elements successfully
written, which might be less than
nitems if a write error is
encountered. If
size or
nitems is 0,
fwrite() returns 0 and the
state of the stream remains unchanged. Otherwise, if a write error
occurs, the error indicator for the stream is set and
errno is set to
indicate the error.
ERRORS
Refer to
fputc(3C).
USAGE
Because of possible differences in element length and byte ordering,
files written using
fwrite() are application-dependent, and possibly
cannot be read using
fread(3C) by a different application or by the
same application on a different processor.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+
SEE ALSO
write(2),
fclose(3C),
ferror(3C),
fopen(3C),
fread(3C),
getc(3C),
gets(3C),
open_wmemstream(3C),
printf(3C),
putc(3C),
puts(3C),
attributes(7),
standards(7) March 25, 2020 FWRITE(3C)
