fseek(3) - NetBSD Manual Pages

FSEEK(3)                  NetBSD Programmer's Manual                  FSEEK(3)


NAME

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


LIBRARY

     Standard C Library (libc, -lc)


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);


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, re-
     spectively.  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 indi-
     cator 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 fgetpos() and fsetpos() functions are alternative interfaces equiva-
     lent 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 ref-
     erenced by pos.  On systems other than UNIX, an ``fpos_t'' object may be
     a complex object and these routines may be the only way to portably repo-
     sition a text stream.


RETURN VALUES

     The rewind() function returns no value.  Upon successful completion,
     fgetpos(), fseek(), fsetpos() return 0, and ftell() returns the current
     offset.  Otherwise, fseek() and ftell() return -1 and the others return a
     nonzero value 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.

     The function fgetpos(), fseek(), fsetpos(), and ftell() 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 con-
     form to ANSI X3.159-1989 (``ANSI C'').

NetBSD 1.5                       June 4, 1993                                2