fseek C/C++

fseek

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

header:

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.

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

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

/* fseek example */
#include

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.