C - Metric conversion strings

Question

I'm trying to be able to allow my program to recognize what is being entered in to the token string and compare it to the metric measurement so I can make multiple conversions like kilo, centi, etc. The problem im running into is I cant get the program to recognize milli right now.

Also note that there is a function for converting english into pig latin so ignore some of the pig latin variables

int i = 0;
int j = 0;
int command = 0, //Pig latin ints
    count = 0;
double tokenNum;
char name[50];
char *tokens[10];
char *englishLength[] = {"feet"};
char *metricLength[] = {"meter", "milli", "centi", "deci", "deka", "hecto", "kilo"};    
char sentence_ar[100], //Pig latin chars
     *array_of_pointers_to_strings[50],
     new_string1[50] = {'\0'},
     new_string2[50] = {'\0'};




printf ("Enter conversion in the following format\n -- How many meters are in X feet --:\n ");
            fflush (stdin);
            gets(name);

            printf ("Original name: %s\n", name);
            tokens[0] = strtok (name, " ");

            printf ("Token[0]: %s\n", tokens[0]);

            i++;

            while ((tokens[i] = strtok (NULL, " ")) != NULL)
            {
                printf ("Token[%d]: %s\n", i, tokens[i]);
                i++;
            }

            tokenNum = atof (tokens[5]);

            printf("%d\n", tokenNum);

            while (j < 1)
                {
                    if (strcmp(tokens[6],metricLength[0])==0);
                    {
                        // feet to meters
                        double result;

                        result = tokenNum * 0.3048;
                        j++;
                        printf("Feet to Meters %f\n", result);
                        // if you enter How many meters are in 5 feet, ANSWER: 1.524
                    }
                    // when token[6] = milli
                    if (strcmp(tokens[6],metricLength[1])==0)
                    {
                        //feet to millimeters
                        double result;

                        result = tokenNum * 304.8;
                        j++;
                        printf("Feet to Milli %f\n", result);
                        // if you enter How many milli are in 5 feet, ANSWER: 1524
                    }
            }

yeah my mistake, that was from last night when I was trying to get the program to recognize the p instead of m. i'm fairly new at programming and it didnt work haha — Joe Bray, Dec 08 '11 at 03:04
You have the potential to overflow your array here: `while ((tokens[i] = strtok (NULL, " ")) != NULL)` - no bounds checking on `i`. — AusCBloke, Dec 08 '11 at 03:09
You could also associate your array of measurement strings with a conversion multiplier, so that you don't have to create a separate `if` block for each type. — AusCBloke, Dec 08 '11 at 03:12
well it converts feet to meters even if i enter milli or before "pilli" lol. — Joe Bray, Dec 08 '11 at 03:12
@JoeBray: That's because there's a semicolon (`;`) after your first `if` statement - the feet to meters code will always be executed if you get into the `while` loop. — AusCBloke, Dec 08 '11 at 03:15
Someone has to say it: don't use `gets`, don't even think about it. — mu is too short, Dec 08 '11 at 03:15
@muistooshort just bet me too it, use `fgets(string, size, stdin)` instead. — AusCBloke, Dec 08 '11 at 03:16
@AusCBloke i'm in begining computer science (cpts 121), could you show me an example possibly? — Joe Bray, Dec 08 '11 at 03:18
The constant indexes 5 and 6 are suspicious (as in `tokens[5]` and `tokens[6]`). What are you typing before your length to make the number appear at index 5 and the units at index 6? — Jonathan Leffler, Dec 08 '11 at 03:19
@JonathanLeffler: I think he's wanting it to be: "How many meters are in VALUE UNITS" — AusCBloke, Dec 08 '11 at 03:22
Yeah i want "How many METRIC UNIT are in VALUE ENGLISH UNIT. Once I can figure that out than I can reverse it and do it for volume and weight as well later. — Joe Bray, Dec 08 '11 at 03:30
`stdin` is the standard input, that's what `scanf` and `gets` read from. — mu is too short, Dec 08 '11 at 03:52

score 2 · Answer 1 · edited May 23 '17 at 12:27

Here are few observations which you can use (This is more of a compilation of the comments above):
1. Don't use fflush(stdin). fflush is for output stream only.
2. Don't use gets. Its not safe. Use fgets as suggested.
3. Add bound checks to your array. In while ((tokens[i] = strtok (NULL, " ")) != NULL), you should check for the value of i so that is does not exceed the allocated array size of tokens
4. In the statement if (strcmp(tokens[6],metricLength[0])==0);, the semicolon makes this condition result in empty body. I think adding the semicolon was not intended so get rid of it.
5. As per your input requirement, you are checking the wrong token. If your input requires "How many METRIC_UNIT are in VALUE ENGLISH_UNIT", then you should compare the third token i.e. tokens[2]. If may be a good idea to validate the input as well.
6. Crank up the warnings on your compiler to the max & fix them all! Its a good practice.
Hope this helps!

C - Metric conversion strings

1 Answers1