Question

We know some escape sequence ‘\n’ – new line but say we don’t know if \a, \b, \c …. \z is an escape sequence. How to write a program that allows us to test every character from a to z and/or A to Z in a printf statement or other way to identify an escape sequence and if it is, then print it’s value e.g. ouput may look like this:

‘\b’ is a special character and value of ‘\b’ = 8

This program may look silly but I am not able to find a solution for it…
Thanks in advance.

Answer 1

As Carl Norum pointed out, these are interpreted by the compiler. You can take an approach similar to autoconf (the program which generates configure scripts):

#!/bin/bash

for LETTER in {a..z}
do
    cat > letter.c <<EOF
#include <stdio.h>
int main() { printf("\\\\$LETTER has ASCII value %u\n", "\\$LETTER"[0]); }
EOF
    cc -Werror -o letter letter.c > /dev/null 2>&1 && ./letter
done

Output:

\a has ASCII value 7
\b has ASCII value 8
\e has ASCII value 27
\f has ASCII value 12
\n has ASCII value 10
\r has ASCII value 13
\t has ASCII value 9
\v has ASCII value 11

Notes: The reason for a string constant rather than a character constant is simply shell quoting. This relies on gcc‘s -Werror but you could solve that problem in other ways.