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fread(3) [opendarwin man page]

FREAD(3)                                                     Linux Programmer's Manual                                                    FREAD(3)

fread, fwrite - binary stream input/output SYNOPSIS
#include <stdio.h> size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream); size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream); DESCRIPTION
The function fread() reads nmemb items of data, each size bytes long, from the stream pointed to by stream, storing them at the location given by ptr. The function fwrite() writes nmemb items of data, each size bytes long, to the stream pointed to by stream, obtaining them from the loca- tion given by ptr. For nonlocking counterparts, see unlocked_stdio(3). RETURN VALUE
On success, fread() and fwrite() return the number of items read or written. This number equals the number of bytes transferred only when size is 1. If an error occurs, or the end of the file is reached, the return value is a short item count (or zero). fread() does not distinguish between end-of-file and error, and callers must use feof(3) and ferror(3) to determine which occurred. ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). +------------------+---------------+---------+ |Interface | Attribute | Value | +------------------+---------------+---------+ |fread(), fwrite() | Thread safety | MT-Safe | +------------------+---------------+---------+ CONFORMING TO
POSIX.1-2001, POSIX.1-2008, C89. SEE ALSO
read(2), write(2), feof(3), ferror(3), unlocked_stdio(3) COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at GNU 2015-07-23 FREAD(3)

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fread(3C)						   Standard C Library Functions 						 fread(3C)

fread - binary input SYNOPSIS
#include <stdio.h> size_t fread(void *ptr, size_t size, size_t nitems, FILE *stream); DESCRIPTION
The fread() function reads 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 are made to the fgetc(3C) 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) is 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 ele- ment 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 will be marked for update by the first successful execution of fgetc(3C), fgets(3C), fgetwc(3C), fgetws(3C), fread(), fscanf(3C), getc(3C), getchar(3C), gets(3C), or scanf(3C) using stream that returns data not supplied by a prior call to ungetc(3C) or ungetwc(3C). RETURN VALUES
Upon successful completion, fread() returns 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() returns 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 is set and errno is set to indicate the error. ERRORS
Refer to fgetc(3C). EXAMPLES
Example 1 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); ... USAGE
The ferror() or feof() functions must be used to distinguish between an error condition and end-of-file condition. See ferror(3C). Because of possible differences in element length and byte ordering, files written using fwrite(3C) are application-dependent, and possibly cannot be read using fread() by a different application or by the same application on a different processor. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
read(2), fclose(3C), ferror(3C), fopen(3C), getc(3C), gets(3C), printf(3C), putc(3C), puts(3C), attributes(5), standards(5) SunOS 5.11 24 Jul 2002 fread(3C)
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