Thread: Having command line displayed in output

So what happens? Obviously not what you wanted, but you have to describe in more detail what actually happens.

Besides the missing '#' at the very beginning of the program:

Code:

  if (i < range[0] || i> range[1])
  printf("&#37;c", c);
  printf("%c", argv);

argv most certainly cannot be printed with %c. %c prints chars, and argv is a char **. I think that perhaps you're missing some curly braces around the statements of that if statement as well. Why are you printing argv there anyway? . . . .

Code:

while (scanf("%c",&c) != EOF)

scanf() returns EOF when the end of the file is reached, but it can return 0 as another error code (which is unlikely for %c, but still). It's best to compare the return value of scanf() against the number of format specifiers passed to it -- so if there's only one %c or %d or whatever, you'ld want something like this:

Code:

while(scanf("%c", &c) == 1)

Well that's probably because you never change i in your last while loop . . . you'll need to increment it for every character, and set it to 0 when you encounter a newline.

I told you before, you need to add curly braces to your if statement(s). Here's what it looks like when I do.

Code:

while (scanf("%c",&c) != EOF)//while the file is scanned
{
    // if the new number is less than the first number in range
    // or greater than the second number in range
    if (i <= range[0] || i > range[1]) {
        i++;
    }
    if(c == '\n') {
        i = 0;
    }
    printf("%c", c);  // print all the characters
}

Do you see the problem? You're only incrementing i when i is within the range you want to print -- and the printf() is always executed. Swap the i++ and the printf() statements and everything should be just fine.

Of course, you still need to handle more than one range . . . perhaps a for loop would be in order.

To find this sort of error yourself, it would help to indent properly at least, and preferably also add extra curly braces.

Let's have a look at your original code.

Code:

 for(i=1;i<argc;i++) 
 {
  token=strtok(argv[i]+1, "-");

  while (token != NULL)
  {
  range[j++] = atoi(token);
  token=strtok(NULL, "-");
  }
 }

You're tokenizing the string with "-"s as the separators. If you added "," to the list of separators -- making it "-," -- I think that would do exactly what you want.

A suggestion: consider using strtol() or even sscanf() instead of atoi(). atoi() has pretty bad error checking.

BTW -- I would get rid of the requirement for a "-" in front of the numbers. It makes the numbers look negative.

Oh, I see. Hmm. Well, unfortunately, your current code only handles one range, because all you use is this:

Code:

if (i < range[0] || i> range[1])

With a loop, you could loop over the elements of range[] to handle more than one range.

But to remove single columns -- in that case, you'd either need to specify ranges that start and being at the same place -- inefficient -- or invent a new array and add some code to handle it. Which would be wasteful as well.

That's assuming you can even parse the numbers separately. strtok() will let you do this, you just have to instruct it to.

I'm actually a little confused about the parameters of your program. In your first example, you used this:

Code:

cutchar - 2 -6 < theFileName

But with your current code, because the first "-" is separated, it only works by fluke. It simply takes all numbers that it can see and uses them as ranges. If you were to add blacklisted columns in addition to ranges, you'd need to modify that code.

I'll assume your initial example was meant to be "-2 -6". What are you going to do with something like "-2,4 -6"? Is that columns 2 and 4 eliminated, and the range from 4 to 6 as well? It doesn't make sense. Sucky syntax if you ask me. Or wait: was it meant to be "-2-6"? That makes sense.

If that's the case, you'll want to look for parameters that start with a "-", parse a number from them, check the next character to see if it's a '-' or a ',' or the end of the string, and continue doing this until you actually get to the end of the string. sscanf(), or better yet, strtol() would really help you in doing this. For example:

Code:

int n;
char *begin, *p;

/* ... */
begin = argv[x];  /* set begin to the beginning of the string */
n = strtol(begin, &p, 0);
if(begin == p) {  /* there was no number in begin */
    break;  /* we're done parsing this argument */
}
if(*p == ',') {
    /* ... */
}
begin = p + 1;
/* loop around again and start parsing begin . . . */

Maybe that was just confusing. Any questions?

So have you tried to implement support for multiple ranges yet? Did you get anywhere?