fseek

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



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

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,
       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 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 VALUE
       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
       error.

ERRORS
       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).

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       ┌────────────────────────────┬───────────────┬─────────┐
       │Interface                   Attribute     Value   │
       ├────────────────────────────┼───────────────┼─────────┤
       │fseek(), ftell(), rewind(), │ Thread safety │ MT-Safe │
       │fgetpos(), fsetpos()        │               │         │
       └────────────────────────────┴───────────────┴─────────┘

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

SEE ALSO
       lseek(2), fseeko(3)

COLOPHON
       This page is part of release 5.08 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
       https://www.kernel.org/doc/man-pages/.



GNU                                2018-04-30                           FSEEK(3)