Joy Ram Sen Gupta Joy Ram Sen Gupta - 9 days ago 3x
C Question

How does scanf(" %[^\n]", str); work in C Programming?

Encountered this in a C program.

char str[100];
scanf(" %[^\n]", str);

Please explain how it works and why?


This scanf format string consists of two parts:

  • a space character, which skips space characters (' ', '\t', '\n', etcetera) in the input, and
  • the %[^\n] conversion specification, which matches a string of all characters not equal to the new line character ('\n') and stores it (plus a terminating '\0' character) in str.

Note however that if the input (after the leading spaces, and before the first newline character) is longer than 99 characters, this function exhibits undefined behaviour, because str can only hold 100 chars including the terminating '\0' character. A safer alternative is:

scanf(" %99[^\n]", str);