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posix_fadvise: informace o souboru (POKROČILÝ REÁLNÝ ČAS)

Originální popis anglicky: posix_fadvise - file advisory information ( ADVANCED REALTIME)

Návod, kniha: POSIX Programmer's Manual

STRUČNĚ

#include <fcntl.h>
 
 
int posix_fadvise(int fd, off_t offset , size_t len, int advice);
 

POPIS / INSTRUKCE

The posix_fadvise() function shall advise the implementation on the expected behavior of the application with respect to the data in the file associated with the open file descriptor, fd, starting at offset and continuing for len bytes. The specified range need not currently exist in the file. If len is zero, all data following offset is specified. The implementation may use this information to optimize handling of the specified data. The posix_fadvise() function shall have no effect on the semantics of other operations on the specified data, although it may affect the performance of other operations.
The advice to be applied to the data is specified by the advice parameter and may be one of the following values:
POSIX_FADV_NORMAL
 
Specifies that the application has no advice to give on its behavior with respect to the specified data. It is the default characteristic if no advice is given for an open file.
POSIX_FADV_SEQUENTIAL
 
Specifies that the application expects to access the specified data sequentially from lower offsets to higher offsets.
POSIX_FADV_RANDOM
 
Specifies that the application expects to access the specified data in a random order.
POSIX_FADV_WILLNEED
 
Specifies that the application expects to access the specified data in the near future.
POSIX_FADV_DONTNEED
 
Specifies that the application expects that it will not access the specified data in the near future.
POSIX_FADV_NOREUSE
 
Specifies that the application expects to access the specified data once and then not reuse it thereafter.
 
These values are defined in <fcntl.h>.

NÁVRATOVÁ HODNOTA

Upon successful completion, posix_fadvise() shall return zero; otherwise, an error number shall be returned to indicate the error.

CHYBY / ERRORY

The posix_fadvise() function shall fail if:
EBADF
The fd argument is not a valid file descriptor.
EINVAL
The value of advice is invalid.
ESPIPE
The fd argument is associated with a pipe or FIFO.
 
The following sections are informative.

PŘÍKLADY POUŽITÍ

None.

APPLICATION USAGE

The posix_fadvise() function is part of the Advisory Information option and need not be provided on all implementations.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SOUVISEJÍCÍ

posix_madvise() , the Base Definitions volume of IEEE Std 1003.1-2001, <fcntl.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 .
2003 IEEE/The Open Group
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