The joy of manual options parsing in C
It’s written, it compiles, but it’s not tested yet.
There’s something about this kind of repetitive code. Repetitive, wordy, lengthy, error-prone. You could use an API like getopt which provides a convenient abstraction, but if you do so you lose that very fine degree of control over things like error messages and conflict-handling.
You could try to identify the common code and extract it out into a function (or, ugh, a macro) without losing any of the flexibility and control, but you run the risk of increasing complexity (possibly adding bugs) and perhaps harming readability.
If you’re writing a tool like Git with jillions of subcommands and a zillion options then it probably makes sense to pursue this kind of abstraction, but for a write-once command-line tool then it’s probably best to just do the unpleasant work, write some tests to mark sure the darn thing actually works, and forget about it.
NSArray *parse_options_or_die(options_t *options, int argc, char *argv[])
{
int errors = 0;
BOOL scanning_paths = NO;
NSMutableArray *paths = [NSMutableArray array];
for (int i = 1; i < argc; i++)
{
if (scanning_paths)
[paths addObject:[NSString stringWithUTF8String:argv[i]]];
else if (!strcmp(argv[i], "--"))
scanning_paths = YES;
else if (!strcmp(argv[i], "-r") || !strcmp(argv[i], "--recurse"))
{
if (options->recurse == -1)
{
report_conflicting_options(argv[i], "no-recurse");
errors++;
}
else
options->recurse = 1;
}
else if (!strcmp(argv[i], "-R") || !strcmp(argv[i], "--no-recurse"))
{
if (options->recurse == 1)
{
report_conflicting_options(argv[i], "recurse");
errors++;
}
else
options->recurse = -1;
}
else if (!strcmp(argv[i], "-e") || !strcmp(argv[i], "--regular-expression"))
{
if (options->regex == -1)
{
report_conflicting_options(argv[i], "no-regular-expression");
errors++;
}
else
options->regex = 1;
}
else if (!strcmp(argv[i], "-E") || !strcmp(argv[i], "--no-regular-expression"))
{
if (options->regex == 1)
{
report_conflicting_options(argv[i], "regular-expression");
errors++;
}
else
options->regex = -1;
}
else if (!strcmp(argv[i], "-i") || !strcmp(argv[i], "--case-insensitive") ||
!strcmp(argv[i], "--no-case-sensitive"))
{
if (options->case_insensitive == -1)
{
report_conflicting_options(argv[i], "case-sensitive");
errors++;
}
else
options->case_insensitive = 1;
}
else if (!strcmp(argv[i], "-I") || !strcmp(argv[i], "--no-case-insensitive") ||
!strcmp(argv[i], "--case-sensitive"))
{
if (options->case_insensitive == 1)
{
report_conflicting_options(argv[i], "case-insensitive");
errors++;
}
else
options->case_insensitive = -1;
}
else if (!strcmp(argv[i], "-g") || !strcmp(argv[i], "--replace-all"))
{
if (options->global == -1)
{
report_conflicting_options(argv[i], "no-replace-all");
errors++;
}
else
options->global = 1;
}
else if (!strcmp(argv[i], "-G") || !strcmp(argv[i], "--no-replace-all"))
{
if (options->global == 1)
{
report_conflicting_options(argv[i], "replace-all");
errors++;
}
else
options->global = -1;
}
else if (!strcmp(argv[i], "-p") || !strcmp(argv[i], "--preview"))
{
if (options->preview == -1)
{
report_conflicting_options(argv[i], "no-preview");
errors++;
}
else
options->preview = 1;
}
else if (!strcmp(argv[i], "-P") || !strcmp(argv[i], "--no-preview"))
{
if (options->preview == 1)
{
report_conflicting_options(argv[i], "preview");
errors++;
}
else
options->preview = -1;
}
else if (!strcmp(argv[i], "-u") || !strcmp(argv[i], "--gui"))
{
if (options->gui == -1)
{
report_conflicting_options(argv[i], "no-gui");
errors++;
}
else
options->gui = 1;
}
else if (!strcmp(argv[i], "-U") || !strcmp(argv[i], "--no-gui"))
{
if (options->gui == 1)
{
report_conflicting_options(argv[i], "gui");
errors++;
}
else
options->gui = -1;
}
else if (!strcmp(argv[i], "-d") || !strcmp(argv[i], "--dry-run"))
{
if (options->dry_run == -1)
{
report_conflicting_options(argv[i], "no-dry-run");
errors++;
}
else
options->dry_run = 1;
}
else if (!strcmp(argv[i], "-D") || !strcmp(argv[i], "--no-dry-run"))
{
if (options->dry_run == 1)
{
report_conflicting_options(argv[i], "dry-run");
errors++;
}
else
options->dry_run = -1;
}
else if (!strcmp(argv[i], "-v") || !strcmp(argv[i], "--verbose"))
{
if (options->verbose == -1)
options->verbose = 1;
else
options->verbose++;
}
else if (!strcmp(argv[i], "-V") || !strcmp(argv[i], "--no-verbose"))
{
if (options->verbose == 1)
options->verbose = -1;
else
options->verbose--;
}
else if (!strcmp(argv[i], "-c"))
{
if (i + 1 == argc || argv[i + 1][0] == '-')
{
fprintf(stderr, "error: option -c requires an argument (-c file)\n");
errors++;
}
else if (options->skip_conf_files == 1)
{
report_conflicting_options(argv[i], "no-conf");
errors++;
}
else if (options->conf_path && strcmp(argv[i + 1], options->conf_path))
{
report_conflicting_options(argv[i], "conf");
errors++;
}
else
{
i++;
options->conf_path = argv[i];
}
}
else if (!strncmp(argv[i], "--conf", 6))
{
if (options->skip_conf_files == 1)
{
report_conflicting_options(argv[i], "no-conf");
errors++;
}
else if (argv[i][6] != '=' || strlen(argv[i]) < 8)
{
fprintf(stderr, "error: option --conf requires an argument (--conf=file)\n");
errors++;
}
else if (options->conf_path && strcmp(argv[i] + 7, options->conf_path))
{
report_conflicting_options(argv[i], "conf");
errors++;
}
else
options->conf_path = argv[i] + 7;
}
else if (!strcmp(argv[i], "-C") || !strcmp(argv[i], "--no-conf"))
{
if (options->conf_path)
{
report_conflicting_options(argv[i], "conf");
errors++;
}
else
options->skip_conf_files = 1;
}
else if (!strcmp(argv[i], "-h") || !strcmp(argv[i], "--help"))
show_usage_and_exit();
else if (!strcmp(argv[i], "--version"))
show_version_and_exit();
else if (argv[i][0] == '-')
{
fprintf(stderr, "error: unrecognized option or argument: %s\n", argv[i]);
errors++;
}
else
[paths addObject:[NSString stringWithUTF8String:argv[i]]];
}
if (errors)
{
fprintf(stderr, "For usage information see: %s --help\n", argv[0]);
exit(EXIT_FAILURE);
}
return paths;
}