Question

Is there a way to control how scanf() separates input?

scanf("%10s %10s", array1, array2);

The above works fine, separating by space. But, can I use a different separation signal?

Because neither of these seem to work if I want to splice input with a comma rather than a space:

scanf("%10s,%10s", array1, array2);
scanf("%10s, %10s", array1, array2);

What gives? A book I am reading claims that one can separate input with scanf() using any character, but fails to explain how to do so. Furthermore, if alternate characters can be used, can a broader criteria than a single character be used, too? (i.e. value types, statements, etc.)

Answer 1

Using character classes:

#include <stdio.h>

int main(int argc, const char **argv) {
  char s1[10], s2[10];
  const char *str = "word1,word2";
  sscanf(str, "%[^,],%s", s1, s2);
  printf("%s -- %s\n", s1, s2);
  return 0;
}

Or you can be even more specific:

sscanf(str, "%[^,],%[^,]", s1, s2);

which will also capture white space in s2

To split on multiple characters you can use strstr:

#include <stdio.h>
#include <string.h>
int main(int argc, const char **argv) {
  const char *str = "word1fooword2fooword3", *foo = "foo", *ptr;
  const char *eofstr = str;
  for (ptr = str; eofstr; ptr = eofstr + strlen(foo)) {
    char word[10];
    eofstr = strstr(ptr, foo);
    if (eofstr) {
      size_t len = eofstr - ptr;
      strncpy(word, ptr, len);
      word[len] = 0;
      printf("%s\n", word);
    } else {
      strcpy(word, ptr);
      printf("%s\n", word);
    }   
  }
  return 0;
}