FSEEK(3)

NAME
fgetpos, fseek, fseeko, fsetpos, ftell, ftello, rewind - reposition a stream

LIBRARY
libc

SYNOPSIS
#include <stdio.h>
int
fseek(FILE *stream, long offset, int whence);
long
ftell(FILE *stream);
void
rewind(FILE *stream);
int
fgetpos(FILE *stream, fpos_t *pos);
int
fsetpos(FILE *stream, const fpos_t *pos);
#include <sys/types.h>
int
fseeko(FILE *stream, off_t offset, int whence);
off_t
ftello(FILE *stream);

DESCRIPTION
The fseek() function sets the file position indicator for the stream pointed to by stream. The new position, measured in bytes, is obtained by adding offset bytes to the position specified by whence. 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 the fseek() function clears the end-of-file indicator for the stream and undoes any effects of the ungetc(3) function on the same stream.

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

The rewind() function sets the file position indicator for the stream pointed to by stream 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 fseeko() function is identical to fseek(), except it takes an off_t argument instead of a long. Likewise, the ftello() function is identical to ftell(), except it returns an off_t.

The fgetpos() and fsetpos() functions are alternate interfaces equivalent to ftell() and fseek() (with whence set to SEEK_SET), setting and storing the current value of the file offset into or from the object referenced by pos. 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 VALUES
The rewind() function returns no value. Upon successful completion, fgetpos(), fseek(), fseeko(), and fsetpos() return 0, and ftell() and ftello() return the current offset. Otherwise, -1 is returned and the global variable errno 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.

[EOVERFLOW]
    For ftell(), the resulting file offset would be a value which cannot be represented correctly in an object of type long.

The functions fgetpos(), fseek(), fseeko(), fsetpos(), ftell(), and ftello() may also fail and set errno for any of the errors specified for the routines fflush(3), fstat(2), lseek(2), and malloc(3).

SEE ALSO
lseek(2)

STANDARDS
The fgetpos(), fsetpos(), fseek(), ftell(), and rewind() functions conform to ansiC.

The fseeko() and ftello() functions conform to susv2.