CODEWITHSUNDEEP
cscanf
Liftoff
Liftoff

Reputation: 25392

C more arguments than required scanf

I have a while loop with scanf() that reads in a single char* value:

char c[9];

while(c != 'q')
{
    scanf("%s", c);
}

c is then compared with multiple one-character strings to determine which operation should be performed.

This scanf can receive multiple arguments and I need to know when only one argument is provided to the function or if there are multiple arguments, but whenever I type in more than one argument, the while loop is run separately for each argument entered.

Edit:

So say I enter something like "a b c d", the while loop will process c="a", c="b", c="c", and c="d", which is fine, but I need to know that I entered 4 non-white-space elements in the last scan.

So the first argument is the command I am going to run which is a letter, followed by between 0 and 3 arguments for that command, which are strings or numbers:

Example:

"a box 1 2"

When the number of arguments are fixed, I just used a boolean value to know that the next x values of c are supposed to be the arguments, but I have one function which can accept 0 or 1 arguments, e.g.

"b" is acceptable.
"b 25" is acceptable.

b is basically a search function where the optional argument is the query to check against. If no argument is provided, it lists all items. So a boolean value won't work in this case because the number of arguments is not fixed.

So I need to know that if I enter:

"a 1 2 3"  x=4
"a 1"      x=2
"a"        x=1

Upvotes: 1

Views: 2223

Answers (2)

chux
chux

Reputation: 154305

Separate IO from scanning/parsing.

char buf[100];
fgets(buf, sizeof buf, stdin);
int count = 0;  // Count of arguments.
char *p = buf;

while (*p) {
  if (!isspace((unsigned char) *p)) {
    count++;
    // Do something, if desired with *p
  }
  else {
    Handle_UnexpectedWhiteSpaceChar();
  }
  if (isspace((unsigned char) *p)) {
    p++;
  }
  else {
    Handle_UnexpectedTwoNonSpaceChar();
  }

Upvotes: 1

Barmar
Barmar

Reputation: 781716

This will allow you to type a series of numbers on each line, until you enter q.

char line[1024] = "";
int nums[MAXNUMS];
int counter = 0;
while (strcmp(line, "q\n") != 0) {
    fgets(line, sizeof(line), stdin);
    while (counter < MAXNUMS && sscanf("%d", &nums[counter])) {
        counter++;
    }
}

Upvotes: 0

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