When we can or cannot modify String Literals [duplicate]

Question

This question already has an answer here:

• Segmentation fault when modifying a string [duplicate] 2 answers

#include<stdio.h>

int main ()
{
    char *s="FIGHT" ;
    printf("\n Whole string is %s ", s );            // Printing FIGHT -- this is fine
    s[0]='L' ;
    printf ("\n Now whole string is %s", s );  // Printing LIGHT -- My Question is how string literal constant is getting modified when it is being stored in read only memory .
}

Above Code is working fine on my system.

Answer 1

TL;DR -- Never.

Any attempt to modify a string literal invokes undefined behavior.

To quote the C11 standard, chapter §6.4.5, String literals

[...]. If the program attempts to modify such an array, the behavior is undefined.

§ "Above Code is working fine on my system".

Yes, welcome to the world of undefined behavior, which includes working as (wrongly) expected.