How to print special characters from string literal as their "backslash" symbol?

Question

I have regular string literal and want to print it as it is - raw, similar how repr() function in Python does.

For example:

char* text = "this thing\n";
printf("%s", text);

How do I get C to print

this thing\n

instead of

this thing

Your question seems to have nothing to do with the repr special method in Python, could you either elaborate on the repr relationship or take it out of the title? — Andrew Holmgren, Jul 20 '20 at 21:11

Jorengarenar · Accepted Answer · 2020-07-20T21:28:17.390

2

There are few solutions:

Prepend \n with \, so backslash before n is recognized as normal symbol, and therefore n isn't included to special symbol: printf("This thing\\n");
If your compiler supports GNU extensions, use raw string: printf(R"(This thing\n)");
Write own function:

void myRepr(const char* str)
{
    while (*str != '\0') {
        switch (*str) {
            case '\n':
                fputs("\\n", stdout);
                break;
            case '\t':
                fputs("\\t", stdout);
                break;
            // case ...
            default:
                fputc(*str, stdout);
        }
        ++str;
    }
}

edited Jul 20 '20 at 21:28

answered Jul 20 '20 at 21:08

Jorengarenar

2,705
5
23
60

Clearly more work to do on #3 but that's what I think OP wants. – Joshua Jul 20 '20 at 21:14
[C does not have "raw strings"](https://stackoverflow.com/questions/24850244/does-c-support-raw-string-literals). That's a C++ feature that C has not (yet) adopted, and I'm inclined to doubt that C ever will adopt it. – John Bollinger Jul 20 '20 at 21:27
@JohnBollinger Thanks, I forgot to mention it's GNU extension – Jorengarenar Jul 20 '20 at 21:34
Is it? I'm having trouble finding it documented in [the GCC manual's list of extensions](https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html), and my GCC 8.3.1 rejects the syntax, at least by default. – John Bollinger Jul 20 '20 at 21:36
@JohnBollinger GCC 10.1.0 with `-std=gnu99` compiles – Jorengarenar Jul 20 '20 at 21:38
So, not a genuine option for most people. Ok. – John Bollinger Jul 20 '20 at 21:39
@Jorengarenar This was what I was looking for, thanks! – cdpp Jul 20 '20 at 21:54

score 0 · Answer 2 · answered Jul 20 '20 at 21:01

0

Full solution:

#include <stdio.h>

int main () {
    printf("This thing\\n");
    return 0;
}

answered Jul 20 '20 at 21:01

AnthonyHein

131
4

1

The question is not completely clear, but I would imagine that although the input string is hard-coded as a constant in this example, it is intended as a more general question about how to convert a string containing newlines, rather than simply a question of how to hard-code a literal backslash. – alani Jul 20 '20 at 21:08

tibi · Answer 3 · 2020-07-20T21:37:03.353

You can use "\\n" to print \n u can also use it with \t.

int main(){
    char* text = "this thing\\n";
    printf("%s", text);
}

or you can do it like this:

#include <stdio.h>
#include <string.h>

void newline(char* str){
    int i;
    for(i=0; i<strlen(str); i++){ // iterate through the string
        // 10 == the ascii code for new line
        if(str[i] != 10){ 
            printf("%c", str[i]);
        }
        else if (str[i] == 10){
            printf("\\n");
        }
    }
}

void newline2(char* str){ // same function useing in line if
    int i;
    for(i=0; i<strlen(str); i++){
        str[i] != 10 ? printf("%c", str[i]) : printf("\\n");
    }
}

int main(){
    char* text = "this \n thing\n";
    newline(text);
    newline2(text);
}

How to print special characters from string literal as their "backslash" symbol?

3 Answers3