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Annotation of coherent/a/usr/man/ALL/fseek, revision 1.1

1.1     ! root        1: 
        !             2: 
        !             3: fseek()                   STDIO Function                  fseek()
        !             4: 
        !             5: 
        !             6: 
        !             7: 
        !             8: Seek on file stream
        !             9: 
        !            10: #include <stdio.h>
        !            11: iinntt ffsseeeekk(_f_p, _w_h_e_r_e, _h_o_w)
        !            12: FFIILLEE *_f_p; lloonngg _w_h_e_r_e; iinntt _h_o_w;
        !            13: 
        !            14: fseek changes  where the next read or  write operation will occur
        !            15: within  the file  stream  fp.  It  handles any  effects the  seek
        !            16: routine might  have had on  the internal buffering  strategies of
        !            17: the system.  The arguments where and how specify the desired seek
        !            18: position.  where indicates the new seek position in the file.  It
        !            19: is measured from  the start of the file if  how equals zero, from
        !            20: the current seek position if how  equals one, and from the end of
        !            21: the file if how equals two.
        !            22: 
        !            23: fseek differs  from its cousin lseek in that  lseek is a COHERENT
        !            24: system call  and takes  a file number,  whereas fseek is  a STDIO
        !            25: function and takes a FILE pointer.
        !            26: 
        !            27: ***** Example *****
        !            28: 
        !            29: This  example opens  file  argv[1] and  prints  its last  argv[2]
        !            30: characters (default, 100).   It demonstrates the functions fseek,
        !            31: ftell, and fclose.
        !            32: 
        !            33: 
        !            34: #include <stdio.h>
        !            35: extern long atol();
        !            36: 
        !            37: 
        !            38: 
        !            39: void fatal(message)
        !            40: char *message;
        !            41: {
        !            42:         fprintf(stderr, "tail: %s\n", s);
        !            43:         exit(1);
        !            44: }
        !            45: 
        !            46: 
        !            47: 
        !            48: main(argc, argv)
        !            49: int argc; char *argv[];
        !            50: {
        !            51:         register FILE *ifp;
        !            52:         register int c;
        !            53:         long nchars, size;
        !            54: 
        !            55: 
        !            56: 
        !            57:         if (argc < 2 || argc > 3)
        !            58:                 fatal("Usage: tail file [ nchars ]");
        !            59:         nchars = (argc == 3) ? atol(argv[2]) : 100L;
        !            60: 
        !            61: 
        !            62: 
        !            63: 
        !            64: COHERENT Lexicon                                           Page 1
        !            65: 
        !            66: 
        !            67: 
        !            68: 
        !            69: fseek()                   STDIO Function                  fseek()
        !            70: 
        !            71: 
        !            72: 
        !            73: 
        !            74: 
        !            75:         if ((ifp = fopen(argv[1], "r")) == NULL)
        !            76:                 fatal("cannot open input file");
        !            77:         /* Seek to end */
        !            78:         if (fseek(ifp, 0L, 2) == -1)
        !            79:                 fatal("seek error");
        !            80: 
        !            81: 
        !            82: 
        !            83:         /* Find current size */
        !            84:         size = ftell(ifp);
        !            85:         size = (size < nchars) ? 0L : size - nchars;
        !            86: 
        !            87: 
        !            88: 
        !            89:         /* Seek to point */
        !            90:         if (fseek(ifp, size, 0) == -1)
        !            91:                 fatal("seek error");
        !            92:         while ((c = getc(ifp)) != EOF)
        !            93:                 /* Copy rest to stdout */
        !            94:                 putchar(c);
        !            95:         if (fclose(ifp) == EOF)
        !            96:                 fatal("cannot close");
        !            97:         exit(0);
        !            98: }
        !            99: 
        !           100: 
        !           101: ***** See Also *****
        !           102: 
        !           103: ftell(), lseek(), STDIO
        !           104: 
        !           105: ***** Diagnostics *****
        !           106: 
        !           107: For any diagnostic error, fseek returns -1; otherwise, it returns
        !           108: zero.  If  fseek goes  beyond the  end of the  file, it  will not
        !           109: return an error message  until the corresponding read or write is
        !           110: performed.
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        !           129: 
        !           130: COHERENT Lexicon                                           Page 2
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