int fseek ( FILE * stream, long int offset, int origin );

<cstdio>

Reposition stream position indicator

Sets the position indicator associated with the stream to a new position defined by adding offset to a reference position specified by origin.
The End-of-File internal indicator of the stream is cleared after a call to this function, and all effects from previous calls to ungetc are dropped.
When using fseek on text files with offset values other than zero or values retrieved with ftell, bear in mind that on some platforms some format transformations occur with text files which can lead to unexpected repositioning.
On streams open for update (read+write), a call to fseek allows to switch between reading and writing.

Parameters

stream

Pointer to a FILE object that identifies the stream.

offset

Number of bytes to offset from origin.

origin

Position from where offset is added. It is specified by one of the following constants defined in <cstdio>:

SEEK_SET	Beginning of file
SEEK_CUR	Current position of the file pointer
SEEK_END	End of file

Return Value

Example

/* fseek example */
#include <stdio.h>

int main ()
{
  FILE * pFile;
  pFile = fopen ( "myfile.txt" , "w" );
  fputs ( "This is an apple." , pFile );
  fseek ( pFile , 9 , SEEK_SET );
  fputs ( " sam" , pFile );
  fclose ( pFile );
  return 0;
}

After this code is successfully executed, the file example.txt contains:
This is a sample.

See also