Question

That is, prt("a \t\n") should print "a \t\n" literally,

is there any available function that does this?

Answer 1

I am assuming you want to escape special characters; that is, you want to print \n instead of a newline character.

Not in the standard library, as far as I know. You can easily write it yourself; the core of the function is something like this:

static char *escape_char(char *buf, const char *s) {
    switch (*s) {
        case '\n': return "\\n";
        case '\t': return "\\t";
        case '\'': return "\\\'";
        case '\"': return "\\\"";
        case '\\': return "\\\\";
        /* ... some more ... */
        default:
            buf[0] = *s;
            buf[1] = '\0';
            return buf;
    }
}

/* Warning: no safety checks -- buf MUST be long enough */
char *escape_string(char *buf, const char *s)
{
    char buf2[2];
    buf[0] = '\0';
    for (; *s != '\0'; s++) {
        strcat(buf, escape_char(buf2, s));
    }
    return buf;
}

Generating the function body is also an option, as it can get quite tedious and repetitive.

This is how you can test it:

int main()
{
    const char *orig = "Hello,\t\"baby\"\nIt\'s me.";
    char escaped[100];
    puts(orig);
    puts(escape_string(escaped, orig));
    return 0;
}