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

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

       #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);

       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

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

       except that the error indicator for the stream is also cleared (see

       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.

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

       EINVAL The whence argument to fseek() was not SEEK_SET, SEEK_END, or
              SEEK_CUR.  Or: the resulting file offset would be negative.

       ESPIPE The file descriptor underlying stream is not seekable (e.g., it
              refers to a pipe, FIFO, or socket).

       The functions 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).

       For an explanation of the terms used in this section, see

       │Interface                   Attribute     Value   │
       │fseek(), ftell(), rewind(), │ Thread safety │ MT-Safe │
       │fgetpos(), fsetpos()        │               │         │

       POSIX.1-2001, POSIX.1-2008, C89, C99.

       lseek(2), fseeko(3)

       This page is part of release 5.02 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

GNU                               2018-04-30                          FSEEK(3)