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How can I open files mentioned on the command line, and parse option flags?

April 26, 2017Command files flags line mentioned option parse

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How can I open files mentioned on the command line, and parse option flags?

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Here is a skeleton which implements a traditional Unix-style argv parse, handling option flags beginning with -, and optional filenames. (The two flags accepted by this example are -a and -b; -b takes an argument.) #include #include #include main(int argc, char *argv[]) { int argi; int aflag = 0; char *bval = NULL; for(argi = 1; argi < argc && argv[argi][0] == '-'; argi++) { char *p; for(p = &argv[argi][1]; *p != '\0'; p++) { switch(*p) { case 'a': aflag = 1; printf("-a seen\n"); break; case 'b': bval = argv[++argi]; printf("-b seen (\"%s\")\n", bval); break; default: fprintf(stderr, "unknown option -%c\n", *p); } } } if(argi >= argc) { /* no filename arguments; process stdin */ printf(“processing standard input\n”); } else { /* process filename arguments */ for(; argi < argc; argi++) { FILE *ifp = fopen(argv[argi], "r"); if(ifp == NULL) { fprintf(stderr, "can't open %s: %s\n", argv[argi], strerror(errno)); continue; } printf("processing %s\n", argv[argi]