fseek(3S)           (C Programming Language Utilities)            fseek(3S)


   NAME
         fseek, rewind, ftell - reposition a file pointer in a stream

   SYNOPSIS
         #include <stdio.h>

         int fseek (FILE *stream, long offset, int ptrname);

         void rewind (FILE *stream);

         long ftell (FILE *stream);

   DESCRIPTION
         fseek sets the position of the next input or output operation on the
         stream [see intro(3)].  The new position is at the signed distance
         offset bytes from the beginning, from the current position, or from
         the end of the file, according to a ptrname value of SEEKSET,
         SEEKCUR, or SEEKEND (defined in stdio.h) as follows:

         Name        Description

         SEEKSET    set position equal to offset bytes.

         SEEKCUR    set position to current location plus offset.

         SEEKEND    set position to EOF plus offset.

         fseek allows the file position indicator to be set beyond the end of
         the existing data in the file.  If data is later written at this
         point, subsequent reads of data in the gap will return zero until
         data is actually written into the gap.  fseek, by itself, does not
         extend the size of the file.

         rewind (stream) is equivalent to:

               (void) fseek (stream, 0L, SEEKSET).

         except that rewind also clears the error indicator on stream.

         fseek and rewind clear the EOF indicator and undo any effects of
         ungetc on stream.  After fseek or rewind, the next operation on a
         file opened for update may be either input or output.

         If stream is writable and buffered data has not been written to the
         underlying file, fseek and rewind cause the unwritten data to be
         written to the file.

         ftell returns the offset of the current byte relative to the
         beginning of the file associated with the named stream.




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   fseek(3S)           (C Programming Language Utilities)            fseek(3S)


   SEE ALSO
         lseek(2), write(2), fopen(3S), popen(3S), stdio(3S), ungetc(3S).

   DIAGNOSTICS
         fseek returns -1 for improper seeks, otherwise zero.  An improper
         seek can be, for example, an fseek done on a file that has not been
         opened via fopen; in particular, fseek may not be used on a terminal
         or on a file opened via popen(3S).  After a stream is closed, no
         further operations are defined on that stream.

   NOTES
         Although on the UNIX system an offset returned by ftell is measured
         in bytes, and it is permissible to seek to positions relative to that
         offset, portability to non-UNIX systems requires that an offset be
         used by fseek directly.  Arithmetic may not meaningfully be performed
         on such an offset, which is not necessarily measured in bytes.





































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