C program to reverse a string

strrev.c

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

void strrev(char *str) 
{
    char tmp, *end;

    if (str) {
        end = str + strlen(str) - 1;
        while (str < end) {
            tmp = *str;
            *str++ = *end;
            *end-- = tmp;
        }
    }
}

int main(int argc, char *argv[]) 
{
    char *str;
    int i;

    for (i = 1; i < argc; i++) {
        str = argv[i];
        strrev(str);
        printf("%s\n", str);
    }
    return 0;
}