fseek


function
<cstdio> 
int fseek ( FILE * stream, long int offset, int origin );

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_SETBeginning of file
SEEK_CURCurrent position of the file pointer
SEEK_ENDEnd of file


Return Value

If successful, the function returns a zero value.
Otherwise, it returns nonzero value.

Example

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

int main ()
{
  FILE * pFile;
  pFile = fopen ( "example.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

ftell Get current position in stream (function)
fsetpos Set position indicator of stream (function)
rewind Set position indicator to the beginning (function)