fwrite

 

C

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Symbol index

 

File input/output

Types and objects
FILE fpos_t      stdinstdoutstderr
Functions
File access fopenfopen_s (C11) freopenfreopen_s (C11) fwide (C95) setbuf setvbuf fclose fflush Direct input/output fread fwrite Unformatted input/output fgetc fgets fputc fputs getchar getsgets_s (until C11)(C11) putchar puts ungetc fgetwcgetwc (C95)(C95) fgetws (C95) fputwcputwc (C95)(C95) fputws (C95) getwchar (C95) putwchar (C95) ungetwc (C95) Formatted input scanffscanfsscanfscanf_sfscanf_ssscanf_s (C11)(C11)(C11) wscanffwscanfswscanfwscanf_sfwscanf_sswscanf_s (C95)(C95)(C95)(C11)(C11)(C11)     vscanfvfscanfvsscanfvscanf_svfscanf_svsscanf_s (C99)(C99)(C99)(C11)(C11)(C11) vwscanfvfwscanfvswscanfvwscanf_svfwscanf_svswscanf_s (C99)(C99)(C99)(C11)(C11)(C11)	Formatted output printffprintfsprintfsnprintfprintf_sfprintf_ssprintf_ssnprintf_s (C99)(C11)(C11)(C11)(C11) wprintffwprintfswprintfwprintf_sfwprintf_sswprintf_ssnwprintf_s (C95)(C95)(C95)(C11)(C11)(C11)(C11)     vprintfvfprintfvsprintfvsnprintfvprintf_svfprintf_svsprintf_svsnprintf_s (C99)(C11)(C11)(C11)(C11) vwprintfvfwprintfvswprintfvwprintf_svfwprintf_svswprintf_svsnwprintf_s (C95)(C95)(C95)(C11)(C11)(C11)(C11) File positioning ftell fgetpos fseek fsetpos rewind Error handling clearerr feof ferror perror Operations on files remove rename tmpfiletmpfile_s (C11) tmpnamtmpnam_s (C11)

 

Defined in header <stdio.h>
size_t fwrite( const void          *buffer, size_t size, size_t count,                FILE          *stream );		(until C99)
size_t fwrite( const void *restrict buffer, size_t size, size_t count,                FILE *restrict stream );		(since C99)

Writes count of objects in the given array buffer to the output stream stream. Objects are not interpreted in any way.

Parameters

buffer	-	pointer to the first object object in the array to be written
size	-	size of each object
count	-	the number of the objects to be written

Return value

number of objects written successfully

Example

Run this code

#include <stdio.h>
 
int main()
{
    // write buffer to file
    FILE *f1;
    char buffer[] = { 'x' , 'y' , 'z' };
    f1 = fopen("file.bin", "wb");
    fwrite(buffer, sizeof(char), sizeof(buffer), f1);
    fclose(f1);
 
    // read the same data and print it to the standard output
    FILE *f2;
    char rbuf[10];
    f2 = fopen("file.bin", "rb");
    const char* res = fgets(rbuf, sizeof(rbuf), f2);
    fclose(f2);
 
    if (res) { // points to rbuf on read success, NULL on failure
        puts(res);
    }
}

Output:

xyz

See also

printffprintfsprintfsnprintfprintf_sfprintf_ssprintf_ssnprintf_s (C99)(C11)(C11)(C11)(C11)	prints formatted output to stdout, a file stream or a buffer (function)
fputs	writes a character string to a file stream (function)
fread	reads from a file (function)
C++ documentation for fwrite