fseek() function 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.
Declaration.
int fseek ( FILE * stream, long int offset, int origin );
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
If successful, the function returns a zero value.
Otherwise, it returns nonzero value.
Example
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13 | /* 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 ); // Go to 9th character of the file.
fputs ( " sam" , pFile ); // This is an sample.
fseek ( pFile , 0, SEEK_END); // Go to end of the file.
fputs ( " not end", pFile) // This is an sample.not end
fclose ( pFile );
return 0;
}
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