FSEEK Section: Linux Programmer's Manual (3) Updated: 29 November 2025 Index   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, 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 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 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, fsetpos return 0, and ftell returns 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. The function fgetpos, fseek, fsetpos, and ftell may also fail and set errno for any of the errors specified for the routines and   SEE ALSO   STANDARDS The fgetpos, fsetpos, fseek, ftell, and rewind functions conform to ANSI C3.159-1989 (``ANSI C'').   Index NAME SYNOPSIS DESCRIPTION RETURN VALUES ERRORS SEE ALSO STANDARDS This document was created by using the manual pages. Time: 11:58:03 GMT, March 24, 2025