HP 3000 Manuals HP 3000 Manuals
fflush
Flushes an I/O buffer to a file.
Syntax
#include <stdio.h>
int fflush (FILE *stream);
Parameters
stream A file pointer to an output stream.
Return Values
0 Success.
EOF An error occurred.
Description
The fflush function causes any information that was buffered by the
stream pointed to by the stream argument to be flushed out to the
associated file. The fflush function returns an EOF if the flush
operation caused a write error. It returns a zero if there was no error.
The fclose and exit functions automatically perform fflush(). Therefore,
there is often no need to call fflush() explicitly before closing a file
or terminating a program. However, it might be necessary to manually
fflush() a stream.
For example, data written to a terminal is line buffered by default.
This means the system waits for a newline character before writing the
buffer onto the terminal screen. There are times when you want whatever
has been written so far to be written to the screen without waiting for
the newline character. In such situations, you must use fflush.
Another situation when explicit use of the fflush function is needed is
when you have written less than a full buffer of data to a file, and you
want the contents of that file processed by another function. Because
less than a full buffer was written, the data is still in the buffer; the
file is still empty. Performing an fflush() causes the buffered data to
be written out to the file, enabling other functions or commands to
utilize the file's contents.
See Also
fopen(), exit(), setbuf(), ANSI C 4.9.5.2, POSIX.1 8.1