Originální popis anglicky:
fread - binary input
Návod, kniha: POSIX Programmer's Manual
#include <stdio.h>
size_t fread(void *restrict
ptr, size_t
size , size_t
nitems,
FILE *restrict
stream );
The
fread() function shall read into the array pointed to by
ptr
up to
nitems elements whose size is specified by
size in bytes,
from the stream pointed to by
stream. For each object,
size
calls shall be made to the
fgetc() function and the results stored, in
the order read, in an array of
unsigned char exactly overlaying the
object. The file position indicator for the stream (if defined) shall be
advanced by the number of bytes successfully read. If an error occurs, the
resulting value of the file position indicator for the stream is unspecified.
If a partial element is read, its value is unspecified.
The
fread() function may mark the
st_atime field of the file
associated with
stream for update. The
st_atime field shall be
marked for update by the first successful execution of
fgetc(),
fgets(),
fgetwc(),
fgetws(),
fread(),
fscanf(),
getc(),
getchar(),
gets(), or
scanf() using
stream that returns data not supplied by a prior
call to
ungetc() or
ungetwc().
Upon successful completion,
fread() shall return the number of elements
successfully read which is less than
nitems only if a read error or
end-of-file is encountered. If
size or
nitems is 0,
fread() shall return 0 and the contents of the array and the state of
the stream remain unchanged. Otherwise, if a read error occurs, the error
indicator for the stream shall be set, and
errno shall be set
to indicate the error.
Refer to
fgetc() .
The following sections are informative.
The following example reads a single element from the
fp stream into the
array pointed to by
buf.
#include <stdio.h>
...
size_t bytes_read;
char buf[100];
FILE *fp;
...
bytes_read = fread(buf, sizeof(buf), 1, fp);
...
The
ferror() or
feof() functions must be used to distinguish
between an error condition and an end-of-file condition.
Because of possible differences in element length and byte ordering, files
written using
fwrite() are application-dependent, and possibly cannot
be read using
fread() by a different application or by the same
application on a different processor.
None.
None.
feof() ,
ferror() ,
fgetc() ,
fopen() ,
getc() ,
gets() ,
scanf() , 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
.
