C Programming/C Reference/string.h/strxfrm

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strxfrm is a C Standard Library string function as defined in string.h. It transforms string according to the current locale setting.

The prototype of this function is:

  size_t strxfrm(char *str1 , const char *str2 , size_t num);



is the string which receives num characters of transformed string. If num is equal to zero then str1 contains only null character.


is the string which is to be transformed.


is the maximum number of characters which to be copied into str1.


strxfrm() function transforms str2 according to the current locale setting.For that LC_COLLATE category is used which is defined in locale.h. After transformation, the first num characters of the transformed string is copied into str1. strxfrm() function performs transformation in such a way that result of strcmp on two strings is the same as result of [[strcoll] on two original strings.

Return Value[edit]

strxfrm() function returns length of transformed string excluding terminating null character.

Example usage[edit]

#include <stdio.h>
#include <string.h>
int main(void)
    char str2[] = "Hello World";
    char str1[];
    printf("The length of str2 = %d\n",strxfrm(str1, str2, 4));
    printf("The content of str1 = %s\n", str1[]);
    printf("The content of str2 = %s\n", str2[]);
    return 0;


The length of str2 = 11
The content of str1 = Hell
The content of str2 = Hello World

External links[edit]