Fseek

fseek is a C function belonging to the ANSI C standard library, and included in the file stdio.h. Its purpose is to change the file position indicator for the specified stream. Because fseek uses 32 bit values on many platforms it has a limitation of maximum 2 gigabyte seeks [http://www.codeproject.com/file/64-bit_fileio.asp] .

Function prototype

:int fseek(FILE "*stream_pointer", long "offset", int "origin");

Argument meaning:
* "stream_pointer" is a pointer to the stream "FILE" structure of which the position indicator should be changed;
* "offset" is a "long" integer which specifies the number of bytes from "origin" where the position indicator should be placed;
* "origin" is an integer which specifies the origin position. It can be:
**SEEK_SET : origin is the start of the stream ;
**SEEK_CUR : origin is the current position ;
**SEEK_END : origin is the end of the stream ;

Return value

The return value is an "integer" which mean:
* "0" (zero) : function performed successfully in the stream
* "nonzero" : an error occurred
* On devices incapable of seeking, the return value is undefined.

Notes that each error number has a distinct meaning. The meaning can be revealed by checking "errno.h".

Example

#include

int main(int argc, char **argv) { FILE *file_pointer; file_pointer = fopen("text.txt","r"); if(fseek(file_pointer, 0, SEEK_SET)) { puts("An error occurred"); } else { char buffer [100] ; fgets(buffer, 100, file_pointer); puts("The first line of the file is:"); puts(buffer); } fclose(file_pointer); return 0;}This program code opens a file called "text.txt" in read-only mode, tries to force the file pointer to the beginning of the file, and outputs the first line of the file.