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Annotation of coherent/a/usr/man/MULTI/lseek, revision 1.1

1.1     ! root        1: 
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        !             3: lseek()                COHERENT System Call               lseek()
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        !             8: Set read/write position
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        !            10: lloonngg llsseeeekk(_f_d, _w_h_e_r_e, _h_o_w)
        !            11: iinntt _f_d, _h_o_w; lloonngg _w_h_e_r_e;
        !            12: 
        !            13: llsseeeekk changes the _s_e_e_k _p_o_s_i_t_i_o_n, or the point within a file where
        !            14: the next read or write  operation is performed.  fd is the file's
        !            15: file descriptor, which is returned by ooppeenn.
        !            16: 
        !            17: where and  how describe the  new seek position.   where gives the
        !            18: number of  bytes that you wish  to move the seek  position; it is
        !            19: measured from the beginning of the  file if how is zero, from the
        !            20: current seek position if how is  one, or from the end of the file
        !            21: if how is  two.  A successful call to lseek  returns the new seek
        !            22: position.  For example,
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        !            25:         position = lseek(filename, 100L, 0);
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        !            28: moves the seek position 100 bytes past the beginning of the file;
        !            29: whereas
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        !            32:         position = lseek(filename, 0L, 1);
        !            33: 
        !            34: 
        !            35: merely returns the current seek position, and does not change the
        !            36: seek position at all.
        !            37: 
        !            38: Sparse files may be created by seeking beyond the current size of
        !            39: the file  and writing.  The ``hole'' between the  end of the file
        !            40: and where  the write occurs  is read as  zero and will  occupy no
        !            41: disk space.  For example, if you llsseeeekk 10,000 bytes past the cur-
        !            42: rent end  of file and  write a string,  the data will  be written
        !            43: 10,000 bytes past the old  end of file and all intervening matter
        !            44: will be considered part of the file.
        !            45: 
        !            46: lseek differs  from its  cousin fseek in  that lseek is  a system
        !            47: call and  uses a file  descriptor, whereas fseek is  a C function
        !            48: and uses a FILE pointer.
        !            49: 
        !            50: ***** See Also *****
        !            51: 
        !            52: COHERENT system calls, STDIO
        !            53: 
        !            54: ***** Diagnostics *****
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        !            56: lseek  returns -1L  on an  error, such as  seeking to  a negative
        !            57: position.  If no error occurs, it returns the new seek position.
        !            58: 
        !            59: ***** Notes *****
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        !            61: llsseeeekk is permitted on character-special files, but drivers do not
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        !            64: COHERENT Lexicon                                           Page 1
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        !            69: lseek()                COHERENT System Call               lseek()
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        !            73: generally implement it.  As a result, seeking a terminal will not
        !            74: generate an error but will have no discernible effect.
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        !           130: COHERENT Lexicon                                           Page 2
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