NAME

       fread - binary input

SYNOPSIS

       #include <stdio.h>

       size_t fread(void *restrict ptr, size_t size, size_t nitems,
              FILE *restrict stream);

DESCRIPTION

       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().

RETURN VALUE

       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.

ERRORS

       Refer to fgetc() .

       The following sections are informative.

EXAMPLES

   Reading from a Stream
       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);
              ...

APPLICATION USAGE

       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.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       feof()  ,  ferror() , fgetc() , fopen() , getc() , gets() , scanf() , the Base Definitions
       volume of IEEE Std 1003.1-2001, <stdio.h>

COPYRIGHT

       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 .