strings in C- is char *str is really equivalent to char str []?

Question

Possible Duplicates:
Difference between char *str="STRING" and char str[] = "STRING"?
Need some help with C programming

while this snip gets segmentation fault

int main(void) {

    char*  str ="abcde";
    str[strlen(str)-1] ='\0';
    printf("%s",str);
    return 0;
}

If I put char str [] ="abcde"; instead of the pointer that works perfectly, do you have an idea why so?

The title of your question and its body ask different things. — Bertrand Marron, Aug 27 '11 at 09:38
By the way, this gets asked every week. Please do some research before posting here. — Bertrand Marron, Aug 27 '11 at 09:48
@Bertrand - I looked for a dupe before answering, but couldn't find anything good enough to vote to close for. Can you link to the "definitive" answer on this? — Flexo, Aug 27 '11 at 09:58
http://stackoverflow.com/questions/3862842/difference-between-char-str-string-and-char-str-string http://stackoverflow.com/questions/1880573/c-difference-between-char-var-and-char-var http://stackoverflow.com/questions/3268292/need-some-help-with-c-programming There is not much to say for such a question. — Bertrand Marron, Aug 27 '11 at 10:02
The answers are good on the proposed duplicate, but the code example is needlessly complex — Flexo, Aug 27 '11 at 10:07
Please close this, really. Or close the others as a dupe of this ;) — n0nChun, Aug 27 '11 at 10:45

Flexo · Accepted Answer · 2011-08-27T09:53:04.480

When you write char *str = "abcde"; you make a char pointer to a string literal, which you are not allowed to modify.

When you write char str[] = "abcde"; you make a char array and copy a string literal into it. This is just a normal char array so you are free to modify it.

It is undefined behaviour to modify a string literal. This is a deliberate design decision that allows string literals to be placed in special read only sections of the output program. In practice many compliers and platforms do this (marking it read only means you need only one copy of the strings in memory, even if there is more than one instance of the program running). This leads to the behaviour you observed on your platform.

Bertrand Marron · Answer 2 · 2011-08-27T09:49:34.617

2

char *str = "abcde";

str is a pointer to char that points to a string literal. String literals are stored in read only memory. You can't modify them.

char str[] = "abcde";

The string literal "abcde" is copied into the array str. So you can modify it.

edited Aug 27 '11 at 09:49

answered Aug 27 '11 at 09:40

Bertrand Marron

21,501
8
58
94

1

string literals **can** stored in read only memory – user411313 Aug 27 '11 at 10:17

score 1 · Answer 3 · answered Aug 27 '11 at 09:41

1

char * is pointer to char (string literal) and char [] is an array of char. You can't modify string literal but you can modify char array.

answered Aug 27 '11 at 09:41

hari

9,439
27
76
110

strings in C- is char *str is really equivalent to char str []?

3 Answers3