Question

How to get the last N characters of a string in C

Answer 1

#include <stdio.h>
#include <string.h>
 
#define N 2
     
int main(int argc, char **argv) 
{ 
    char s[20] = "source.c";
    int len = strlen(s);
    
    const char *last_N = &s[len - N];
     
    puts(last_N);
      
    return 0;
}
     


/*
    
run:
     
.c
  
*/

 

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Answer 2

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

char *get_last_N_characters(char s[], int N) {
    char *last_N_chars = malloc(strlen(s) + 1);
    
    if (last_N_chars == NULL) {
        puts("malloc error");
        exit(1);
    }
      
    strncpy(last_N_chars, s + strlen(s) - N, N); 
    last_N_chars[N] = '\0';
    
    return last_N_chars;
}

int main(void) {
    char s[] = "java c c++ c# php python";
    int N = 12;
    
    char *p = get_last_N_characters(s, N);
    
    printf("%s", p);
      
    free(p);
}
  
  
  
  
/*
run:
  
# php python
  
*/

 

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