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)