Check if string is valid enum in C

Question

I am trying to figure out if there is a better way to test if a string being entered at the command line is a valid enum entry for a C program.

Is there a better way to test the entries in an enum instead of saying:

if((!strcmp(string, "NUM0")) && (!strcmp(string, "NUM1")))
{
    printf("Invalid entry\n");
    return(EXIT_FAILURE);
}

A string cannot be an enum! And how to compare strings in C has been asked a million times already! Please do at least minimal research before asking. — too honest for this site
– too honest for this site, Commented Oct 30, 2016 at 14:14
No, all the answers are given in C#. I did do a search... for like 3 hours. Please see the answer below. He actually read my question and answered it brilliantly. — user2470057
– user2470057, Commented Oct 30, 2016 at 16:17

Community · Accepted Answer · 2017-05-23 12:19:20Z

4

I do it this way:

enum opt {NUM0, NUM1, NUM2, OPT_END};
static const char *opt_str[OPT_END] = {"NUM0", "NUM1", "NUM2"};

enum opt i;
for (i = 0; i < OPT_END; ++i)
   if (strcmp(string, opt_str[i]) == 0) break;

if (i == OPT_END) {
    puts("Invalid entry");
    return EXIT_FAILURE;
}
/* do something with i */

Additionally, you could employ x-macros to ensure your enums and strings are in sync: How to convert enum names to string in c.

edited May 23, 2017 at 12:19

CommunityBot

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answered Oct 30, 2016 at 13:48

a3f

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7 Comments

user2470057 Over a year ago

That's pretty slick, thank you. The list I have is pretty big, so this will make every a lot more compact. Thanks!

P.P Over a year ago

@user2470057 You can use x-macros to auto-generate if the list is long.

alk Over a year ago

For the sake of robustness I'd do ... char *opt_str[OPT_END] = ...

alk Over a year ago

Also why not make i of type enum opt?

a3f Over a year ago

@alk, thanks for the suggestions. Amended the answer.

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