printf format parameter contain undefined escape character

问题

#include <stdio.h>

int main()
{
   printf("Hello\c!\n");
   return 0;
}

Output : Helloc!

So , when \[some_undifined_symbol] appeared in printf 's format string, it just ignore the \ ?

回答1:

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

C99 §6.11.4 Character escape sequences

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

回答2:

You have the following escape sequences defined for c:

• \' single quote
• \" double quote
• \\ backslash
• \0 null character
• \a audible bell
• \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 hexadecimal value

来源：https://stackoverflow.com/questions/18718787/printf-format-parameter-contain-undefined-escape-character