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Annotation of coherent/a/usr/man/MULTI/open, revision 1.1.1.1

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                      2: 
                      3: open()                 COHERENT System Call                open()
                      4: 
                      5: 
                      6: 
                      7: 
                      8: Open a file
                      9: 
                     10: iinntt ooppeenn(_f_i_l_e, _t_y_p_e) cchhaarr *_f_i_l_e; iinntt _t_y_p_e;
                     11: 
                     12: open opens  a file  to receive  data, or to  have its  data read.
                     13: When it  opens file, open  returns a file descriptor,  which is a
                     14: small, positive integer  that identifies the open file for subse-
                     15: quent calls to read, write, close, dup, or dup2.  type determines
                     16: how the file is opened, as follows:
                     17: 
                     18: 
                     19:              00       Read only
                     20:              11       Write
                     21:              22       Read and write
                     22: 
                     23: 
                     24: After file is opened, reading or writing begins at byte 0.
                     25: 
                     26: ***** Example *****
                     27: 
                     28: This example copies the file named in argv[1] to the one named in
                     29: argv[2] by using COHERENT system calls.  It demonstrates the sys-
                     30: tem calls open, close, read, write, and creat.
                     31: 
                     32: 
                     33: #include <stdio.h>
                     34: #define BUFSIZE (20*512)
                     35: char buf[BUFSIZE];
                     36: 
                     37: 
                     38: 
                     39: void fatal(s)
                     40: char *s;
                     41: {
                     42:         fprintf(stderr, "copy: %s\n", s);
                     43:         exit(1);
                     44: }
                     45: 
                     46: 
                     47: 
                     48: main(argc, argv)
                     49: int argc; char *argv[];
                     50: {
                     51:         register int ifd, ofd;
                     52:         register unsigned int n;
                     53: 
                     54: 
                     55: 
                     56:         if (argc != 3)
                     57:                 fatal("Usage: copy source destination");
                     58:         if ((ifd = open(argv[1], 0)) == -1)
                     59:                 fatal("cannot open input file");
                     60:         if ((ofd = creat(argv[2], 0666)) == -1)
                     61:                 fatal("cannot open output file");
                     62: 
                     63: 
                     64: COHERENT Lexicon                                           Page 1
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                     67: 
                     68: 
                     69: open()                 COHERENT System Call                open()
                     70: 
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                     72: 
                     73: 
                     74: 
                     75: 
                     76:         while ((n = read(ifd, buf, BUFSIZE)) != 0) {
                     77:                 if (n == -1)
                     78:                         fatal("read error");
                     79:                 if (write(ofd, buf, n) != n)
                     80:                         fatal("write error");
                     81:         }
                     82: 
                     83: 
                     84: 
                     85:         if (close(ifd) == -1 || close(ofd) == -1)
                     86:                 fatal("cannot close");
                     87:         exit(0);
                     88: }
                     89: 
                     90: 
                     91: ***** See Also *****
                     92: 
                     93: COHERENT system calls, fopen()
                     94: 
                     95: ***** Diagnostics *****
                     96: 
                     97: open returns  -1 if the file is nonexistent,  if the caller lacks
                     98: permission, or if a system resource is exhausted.
                     99: 
                    100: ***** Notes *****
                    101: 
                    102: open is  a low-level call that passes  data directly to COHERENT.
                    103: It  should not  be mixed  with high-level  calls, such  as fread,
                    104: fwrite, or fopen.
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                    130: COHERENT Lexicon                                           Page 2
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