Thread: Error checking for is number or isdigit?

How would I go about checking for mishaps in typos that is suppose to be in a number format as such 3s or 3m or 3 if someone enters something like this,

Code:

userx@slackwhere\⚡/media/data/C-Projects/mhsetroot/mhsetroot/bin/Debug\⚡\ > 

./mhsetroot -over-ride   -z f3m  /media/data/wallpaper
f3m //that is what was typed in
0 // that is what what the value is in the var because nothing usable is returned.
defaults time settings // that is what gets called if value is zero,

therefore the function that sets the default time when -z option is not used is called due to var being zero.

Code:

int seconds_or_minutes(char *what_is_it)
{
  printf("%s\n",what_is_it);
    const char sec = 's';
    const char min = 'm';
    char str1[1+strlen(what_is_it)];

    strcpy(str1, what_is_it);

    if ( strrchr(what_is_it, sec) )
    {
        return (atoi( strtok(str1, "s") ));
    }
    if( strrchr(what_is_it, min) )
    {
        return (atoi(strtok(str1,"m")) * 60);
    }
    if (isdigit(what_is_it))
    {
        printf("is not a number\n");
        exit(1);
    }

    printf("%s",what_is_it);

    //defaults to seconds
    return atoi(what_is_it);
}

just to show how it calls for the value using getopts, and the other function that sets default time when option -z not used. So you'll know what is going on with that end of it.

Code:

  case 'z':
            if (optarg == NULL)
            printf("< %s >\n",optarg);
            else
            opts.ch_t =  seconds_or_minutes(optarg);

            printf("%d\n",opts.ch_t);
            break;

-------------------------------------

#ifndef DEFAULT_TIME
#define DEFAULT_TIME (5 * 60)
#endif // DEFAULT_TIME

void default_time_settings(void)
{
printf("defaults time settings\n");
    if(opts.ch_t == 0)
        opts.ch_t = DEFAULT_TIME;
}

So, what would, is a good way to accomplish this feet (feat) of getting it to stop the program if such a mishaps as that is preformed?