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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  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
     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 repo-
     sition 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
     allbox;  lbw27  lb  lb  l  l  l.  Interface Attribute Value T{ fseek(),
     ftell(), rewind(),
     fgetpos(), fsetpos() T}   Thread safety  MT-Safe


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


     lseek(2), fseeko(3)


     This page is part of release 4.16 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)

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