Printf format parameter contains undefined escape character

Question

#include <stdio.h> int main() { printf("Hello\c!\n"); return 0; } 

Exit: Helloc!

So, when \[some_undifined_symbol] appeared in the printf format printf , it just ignores \ ?

Answer 1

\c not an escape sequence that is already defined, but it is better to avoid using it since it is reserved:

C99 §6.11.4 Escape sequences

Lowercase letters as escape sequences are reserved for future standardization. Other characters may be used in extensions.

Answer 2

You have the following escape sequences defined for c :

• \' single quote
• \" double quote
• \\ backslash
• \0 null character
• \a sound call
• \b backspace
• \f form feed - new page
• \n line feed - new line
• \r carriage return
• \t horizontal tab
• \v vertical tab
• \nnn arbitrary octal value
• \xnn arbitrary hex value