`rewind`

Artikkeli
12/02/2022

Repositions the file pointer to the beginning of a file.

Syntax

void rewind(
   FILE *stream
);

Parameters

stream
Pointer to FILE structure.

Remarks

The rewind function repositions the file pointer associated with stream to the beginning of the file. A call to rewind is similar to

(void) fseek(stream, 0L, SEEK_SET );

However, unlike fseek, rewind clears both the error indicators for the stream and the end-of-file indicator. Also, unlike fseek, rewind doesn't return a value to indicate whether the pointer was successfully moved.

To clear the keyboard buffer, use rewind with the stream stdin, which is associated with the keyboard by default.

If stream is a NULL pointer, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, this function returns, and errno is set to EINVAL.

For information on these and other error codes, see errno, _doserrno, _sys_errlist, and _sys_nerr.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

Routine	Required header
`rewind`	<stdio.h>

For more compatibility information, see Compatibility.

Libraries

All versions of the C run-time libraries.

Example

// crt_rewind.c
/* This program first opens a file named
* crt_rewind.out for input and output and writes two
* integers to the file. Next, it uses rewind to
* reposition the file pointer to the beginning of
* the file and reads the data back in.
*/
#include <stdio.h>

int main( void )
{
   FILE *stream;
   int data1, data2;

   data1 = 1;
   data2 = -37;

   fopen_s( &stream, "crt_rewind.out", "w+" );
   if( stream != NULL )
   {
      fprintf( stream, "%d %d", data1, data2 );
      printf( "The values written are: %d and %d\n", data1, data2 );
      rewind( stream );
      fscanf_s( stream, "%d %d", &data1, &data2 );
      printf( "The values read are: %d and %d\n", data1, data2 );
      fclose( stream );
   }
}

Output

The values written are: 1 and -37
The values read are: 1 and -37

Jaa