printing the contents of the c program as its output

Question

I came across this a few days ago.what i want to know is how to print the content of a C program as its output.consider the following small c code snipet:

#include<stdio.h>
#include<conio.h>
void main()
{
int a;
int b;
int sum;
}

how to modify the above code so that on executing it displays the same content of the code: the output should be:

#include<stdio.h>
#include<conio.h>
void main()
{
int a;
int b;
int sum;
}

I hope my question is not doubtful.

Read this: http://stackoverflow.com/questions/10238670/c-c-program-that-prints-its-own-source-code-as-its-output — 0xF1, Nov 20 '13 at 06:48
@Acme thanks for the comment will dig into quine,is it valid for java and c++ also? — R R, Nov 20 '13 at 06:50

score 2 · Answer 1 · answered Nov 20 '13 at 06:56

2

#include <stdio.h>
const char*s="#include <stdio.h>%cconst char*s=%c%s%c;%cint main(void){printf(s,10,34,s,34,10,10);}%c";
int main(void){printf(s,10,34,s,34,10,10);}

answered Nov 20 '13 at 06:56

Jonathan Leffler

730,956
141
904
1,278

2

I cheated; it's a copy of my answer from SO 10238670. I happened to keep a copy, so it didn't take any time to find. – Jonathan Leffler Nov 20 '13 at 07:04
@JonathanLeffler Oh, this is not a cheat. *I* cheated. :P – Nov 20 '13 at 07:05
@JonathanLeffler and H2CO3 :thanks a lot both of you :) – R R Nov 20 '13 at 07:07

score 2 · Accepted Answer · 2013-11-20T08:05:28.263

2

Here's how I would do it:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    FILE *f = fopen(__FILE__, "r");
    if (!f)
        exit(-1);

    fseek(f, 0, SEEK_END);
    long n = ftell(f);
    fseek(f, 0, SEEK_SET);

    char *buf = malloc(n + 1);
    if (!buf)
        exit(-1);

    if (fread(buf, n, 1, f) < 1)
        exit(-1);

    buf[n] = 0;
    puts(buf);

    free(buf);
    fclose(f);
    return 0;
}

edited Nov 20 '13 at 08:05

answered Nov 20 '13 at 07:00

@RishabhRaj Make sure to call your file "foo.c" :P – Nov 20 '13 at 07:04
change line with `fopen` to this one `FILE *f = fopen(__FILE__, "r");` and name file as you wish =) – JIghtuse Nov 20 '13 at 07:58

score 0 · Answer 3 · answered Nov 20 '13 at 06:48

0

The code you wrote will never compile to a program that produces that same code as its output: this should be clear, because that code doesn't print anything at all! So it definitely won't print the whole C file you want.

You are looking for this:

http://en.wikipedia.org/wiki/Quine_%28computing%29

answered Nov 20 '13 at 06:48

Andrey Mishchenko

3,986
2
19
37

i know that,i just gave an example :) – R R Nov 20 '13 at 06:50

printing the contents of the c program as its output

3 Answers3