How to do a case-insensitive string comparison?

Question

I want to do a case-insensitive string comparison. What would be the easiest way to accomplish that? I have the below code which performs a case-sensitive operation.

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

int main(int argc, char *argv[])
{
    char *str1 = "String";
    char *str2 = "STRING";

    if (strncmp(str1, str2, 100) != 0)
    {
        printf("=(");
        exit(EXIT_FAILURE);
    }

    return 0;
}

convert [`toupper`](http://www.cplusplus.com/reference/cctype/toupper/) first then compare — amdixon, Jun 08 '15 at 05:51

score 4 · Accepted Answer · answered Jun 08 '15 at 05:52

4

If you can afford deviating a little from strict C standard, you can make use of strcasecmp(). It is a POSIX API.

Otherwise, you always have the option to convert the strings to a certain case (UPPER or lower) and then perform the normal comparison using strcmp().

answered Jun 08 '15 at 05:52

Sourav Ghosh

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you mean `strncasecmp`? – Aki Suihkonen Jun 08 '15 at 05:57
@AkiSuihkonen Upto you, you (almost) always have the length delimited version. Anyway, the man page I liked has both the version covered I guess. :-) – Sourav Ghosh Jun 08 '15 at 06:00
1

You meant *linked*.. – WedaPashi Jun 08 '15 at 06:05
@WedaPashi hah, my bad. yes right you are. (sorry, edit period is over) :-) – Sourav Ghosh Jun 08 '15 at 06:06

Sourav Kanta · Answer 2 · 2015-06-08T06:04:32.987

2

You can use strcmpi() function.

if(strcmpi(str1,str2)!=0)

only for Windows systems.

edited Jun 08 '15 at 06:04

answered Jun 08 '15 at 05:54

Sourav Kanta

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Pardon me, but isn't it windows specific? – Sourav Ghosh Jun 08 '15 at 05:59
man `strcmpi` --> no manual entry for strcmpi – Aki Suihkonen Jun 08 '15 at 06:00
@AkiSuihkonen Need to check [here](https://msdn.microsoft.com/en-us/library/windows/desktop/bb759942(v=vs.85).aspx). – Sourav Ghosh Jun 08 '15 at 06:02
Also, you could just mention to include `Shlwapi.h` – WedaPashi Jun 08 '15 at 06:03

How to do a case-insensitive string comparison?

2 Answers2