fseek(3) - Linux man page

From: http://linux.die.net/man/3/fseek

Name

fgetpos, fseek, fsetpos, ftell, rewind - reposition a stream

Synopsis

 

#include <stdio.h>

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

long ftell(FILE *stream);

void rewind(FILE *stream);

int fgetpos(FILE *stream, fpos_t *pos);
int fsetpos(FILE *stream, fpos_t *pos);

Description

The fseek() function sets the file position indicator for the stream pointed to bystream. The new position, measured in bytes, is obtained by adding offset bytes to the position specified bywhence. If whence is set to SEEK_SET, SEEK_CUR, or SEEK_END, the offset is relative to the start of the file, the current position indicator, or end-of-file, respectively. A successful call to thefseek() function clears the end-of-file indicator for the stream and undoes any effects of theungetc(3) function on the same stream.

The ftell() function obtains the current value of the file position indicator for the stream pointed to bystream.

The rewind() function sets the file position indicator for the stream pointed to bystream to the beginning of the file. It is equivalent to:

(void) fseek(stream, 0L, SEEK_SET)

except that the error indicator for the stream is also cleared (see clearerr(3)).

The fgetpos() and fsetpos() functions are alternate interfaces equivalent toftell() and fseek() (with whence set toSEEK_SET), setting and storing the current value of the file offset into or from the object referenced bypos. On some non-UNIX systems, an fpos_t object may be a complex object and these routines may be the only way to portably reposition a text stream.

Return Value

The rewind() function returns no value. Upon successful completion,fgetpos(), fseek(), fsetpos() return 0, andftell() returns the current offset. Otherwise, -1 is returned anderrno is set to indicate the error.

Errors

EBADF

The stream specified is not a seekable stream.

EINVAL

The whence argument to fseek() was not SEEK_SET,SEEK_END, or SEEK_CUR.

The functions fgetpos(), fseek(), fsetpos(), andftell() may also fail and set errno for any of the errors specified for the routinesfflush(3),fstat(2),lseek(2), andmalloc(3).