C pointer assignment going awry

[patricio2626]

Hello all,

I'm trying to create a simple routine where I transform the individual characters of a character string to uppercase. I'm trying to figure out why I can dereference individual elements, but can't assign to them. I must be committing some fundamental mistake, but my book pretty much has the same logic I'm using. Any hints? Thanks in advance, as usual!

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

int main(void){
	char *c = "hello!";
	int i;
	for( i = 0; *(c+i) != '\0'; i++){
				if(islower(*(c+i))){
				*(c+i) = toupper(*(c+i));  //boom!  Why?
				}
	}

}

[oogabooga]

You're trying to assign to a constant string "hello!" which c is pointing to. Instead, set aside some independent storage for c that is initialized with the string "hello!" like this:

char c[50] = "hello!";

[anduril462]

c is just a pointer, pointing to what appears to be unwritable memory. See if this helps: Question 6.2

[patricio2626]

Sho' nuff! The below works, thank you!

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

int main(void){
	char c1[888] = "hello!";
	char *c = c1;
	int i;
	for( i = 0; *(c+i) != '\0'; i++){

		if(islower(*(c+i))){
				*(c+i) = toupper(*(c+i));
				}
	}
	printf("%s",c);

}

[oogabooga]

The only difference between your code in post#4 and post#1 is the apparently useless fflush(stdout) !?

[patricio2626]

Yep, apparent improper use of ctrl + c