Originální popis anglicky:
fflush - flush a stream
Návod, kniha: POSIX Programmer's Manual
#include <stdio.h>
int fflush(FILE *
stream);
If
stream points to an output stream or an update stream in which the
most recent operation was not input,
fflush() shall cause any unwritten
data for that stream to be written to the file, and the
st_ctime and
st_mtime fields of the underlying file shall be
marked for update.
If
stream is a null pointer,
fflush() shall perform this flushing
action on all streams for which the behavior is defined above.
Upon successful completion,
fflush() shall return 0; otherwise, it shall
set the error indicator for the stream, return EOF, and set
errno to indicate the error.
The
fflush() function shall fail if:
- EAGAIN
- The O_NONBLOCK flag is set for the file descriptor
underlying stream and the process would be delayed in the write
operation.
- EBADF
- The file descriptor underlying stream is not
valid.
- EFBIG
- An attempt was made to write a file that exceeds the
maximum file size.
- EFBIG
- An attempt was made to write a file that exceeds the
process' file size limit.
- EFBIG
- The file is a regular file and an attempt was made to write
at or beyond the offset maximum associated with the corresponding
stream.
- EINTR
- The fflush() function was interrupted by a
signal.
- EIO
- The process is a member of a background process group
attempting to write to its controlling terminal, TOSTOP is set, the
process is neither ignoring nor blocking SIGTTOU, and the process group of
the process is orphaned. This error may also be returned under
implementation-defined conditions.
- ENOSPC
- There was no free space remaining on the device containing
the file.
- EPIPE
- An attempt is made to write to a pipe or FIFO that is not
open for reading by any process. A SIGPIPE signal shall also be sent to
the thread.
The
fflush() function may fail if:
- ENXIO
- A request was made of a nonexistent device, or the request
was outside the capabilities of the device.
The following sections are informative.
The following example uses
printf() calls to print a series of prompts
for information the user must enter from standard input. The
fflush()
calls force the output to standard output. The
fflush() function is
used because standard output is usually buffered and the prompt may not
immediately be printed on the output or terminal. The
gets() calls read
strings from standard input and place the results in variables, for use later
in the program.
#include <stdio.h>
...
char user[100];
char oldpasswd[100];
char newpasswd[100];
...
printf("User name: ");
fflush(stdout);
gets(user);
printf("Old password: ");
fflush(stdout);
gets(oldpasswd);
printf("New password: ");
fflush(stdout);
gets(newpasswd);
...
None.
Data buffered by the system may make determining the validity of the position of
the current file descriptor impractical. Thus, enforcing the repositioning of
the file descriptor after
fflush() on streams open for
read() is
not mandated by IEEE Std 1003.1-2001.
None.
getrlimit() ,
ulimit() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<stdio.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
