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I wonder my code works perfectly fine either using strcmp or simply == in C++ for comparing 2 char arrays. Can any one justify the reason of using strcmp instead of ==;

herohuyongtao
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Fawad Nasim
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2 Answers2

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strcmp compares the actual C-string content, while using == between two C-string is asking if these two char pointers point to the same position.

If we have some C-string defined as following:

char string_a[] = "foo";
char string_b[] = "foo";
char * string_c = string_a;

strcmp(string_a, string_b) == 0 would return true, while string_a == string_b would return false. Only when "comparing" string_a and string_c using == would return true.

If you want to compare the actual contents of two C-string but not whether they are just alias of each other, use strcmp.

For a side note: if you are using C++ instead of C as your question tag shows, then you should use std::string. For example,

std::string string_d = "bar";
std::string string_e = "bar";

then string_d == string_e would return true. string_d.compare(string_e) would return 0, which is the C++ version of strcmp.

Marc.2377
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WiSaGaN
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  • note: this doesn't apply to std::string (in case ANYONE possibly doubted) –  Mar 22 '14 at 03:25
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    +1 beat me to it due to writing an example to show OP. No need to write another answer since you got it all already, just gonna leave the example [here](http://coliru.stacked-crooked.com/a/ce953c82def955ae) (with variables renamed to your versions). – AliciaBytes Mar 22 '14 at 03:42
1

One advantage of using strcmp is that....it will return < 0 if str1 is less than str2

0 if str1 is greater than str2 and 0 if they are equal.

but if you use simply == it will only return either true or false.

psj01
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