fwrite(3) [x11r4 man page]

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

NAME

       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 https://www.kernel.org/doc/man-pages/.

GNU
								    2015-07-23								  FREAD(3)

fread(3)						     Library Functions Manual							  fread(3)

NAME

       fread, fread_unlocked, fwrite, fwrite_unlocked - Perform input/output operations

LIBRARY

       Standard C Library (libc.so, libc.a)

SYNOPSIS

       #include <stdio.h>

       size_t fread(
	       void *pointer,
	       size_t size,
	       size_t num_items,
	       FILE *stream);

       size_t fread_unlocked(
	       void *pointer,
	       size_t size,
	       size_t num_items,
	       FILE *stream);

       size_t fwrite(
	       const void *pointer,
	       size_t size,
	       size_t num_items,
	       FILE *stream);

       size_t fwrite_unlocked(
	       const void *pointer,
	       size_t size,
	       size_t num_items,
	       FILE *stream);

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       fread(), fwrite():  XPG4, XPG4-UNIX

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Points  to  an  array.	Specifies the size of the variable type of the array pointed to by the pointer parameter.  Specifies the number of
       items of data.  Specifies the input or output stream.

DESCRIPTION

       The fread() function copies num_items of data of length size from the input stream into an array beginning at the location  pointed  to	by
       the pointer parameter.

       The  fread() function stops copying bytes if an End-of-File or error condition is encountered while reading from the input specified by the
       stream parameter, or when the number of data items specified by the num_items parameter have been copied.  The  function  leaves  the  file
       pointer	of the stream parameter, if defined, pointing to the byte following the last byte read, if there is one. The fread() function does
       not change the contents of the stream parameter.

       The fwrite() function appends num_items of data of length size from the array pointed to by the pointer parameter to the output stream.

       The fwrite() function stops writing bytes if an error condition is encountered on the stream, or when the number of items of data specified
       by  the	num_items  parameter  have been written. The fwrite() function does not change the contents of the array pointed to by the pointer
       parameter.

       The fread_unlocked() and fwrite_unlocked() functions are functionally  identical  to  the  fread()  and	fwrite()  functions,  except  that
       fread_unlocked()  and fwrite_unlocked() may be safely used only within a scope that is protected by the flockfile() and funlockfile() func-
       tions used as a pair.  The caller must ensure that the stream is locked before using these functions.

NOTES

       If the stream parameter is invalid, the result of calling the fread(), fwrite(), fread_unlocked(), and fwrite_unlocked() functions is unde-
       fined.

RETURN VALUES

       Upon  successful  completion,  the fread(), fwrite(), fread_unlocked(), and fwrite_unlocked() functions return the number of items actually
       transferred. If the num_items parameter is negative or 0 (zero), no characters are transferred, and a value of 0 (zero) is returned.  If  a
       read or write error occurs, the error indicator for the stream is set, and errno is set to indicate the error.

ERRORS

       Refer to the fgetc(3) reference page for error codes returned by fread() and fread_unlocked().

       Refer to the fputc(3) reference page for error codes returned by fwrite() and fwrite_unlocked().

RELATED INFORMATION

       Functions: read(2), write(2), fopen(3), getc(3), gets(3), printf(3), putc(3), puts(3), scanf(3)

       Standards: standards(5) delim off

																	  fread(3)