How can I use `scanf_s("%[^\n]s")` with a limit to the number of characters allowed? C

Question

How can I use scanf_s("%[^\n]s") with a limit to the number of characters allowed? C For example: scanf_s("%10s", ...); But how can i do this when theres [^\n] before the % ?

Answer 1

The s in format "%[^\n]s" serves no purpose. Delete that s .

---

Likely OP wants something like:

char buf[100];
...
//           v---- Consume all leading white-space
if (scanf_s(" %[^\n]", buf, XXX sizeofbuf) == 1) {
//                     ^^^  ^^^^^^^^^^^^^  2 arguments
  Success(); 
} else {
  Fail(); 
}

where XXX is either (int) (Visual) or (rsize_t) / nothing per the C standard.

• scanf_s() is not portable to systems that do not implement ..._s functions.

• scanf_s() may not read only one line as the " " reads white-space including multiple lines of only white-space.

• scanf_s() is a poor substitute to the preferable fgets() to read one line of user input. Recommend to never use scanf_s() nor scanf() until you know why there are bad.

Alternative:

char buf[100];
if (fgets(buf, sizeof buf, stdin)) {
  Success(); 
} else {
  Fail(); 
}