How to check if a string is in an array of strings in C?

Question

How to write below code in C? Also: is there any built in function for checking length of an array?

Python Code

x = ['ab', 'bc' , 'cd']
s = 'ab'

if s in x:
  //Code

possible duplicate of http://stackoverflow.com/questions/8848940/search-a-string-in-an-array-of-strings — Cacho Santa, Dec 03 '12 at 05:57
This post is Python translating to C, so it can't be a duplicate of a question posed in C. — Carey Gregory, Dec 03 '12 at 06:29
@CareyGregory Why not? The OP has to rewrite the whole program to C, the original Python code is not helpful. — Lundin, Dec 03 '12 at 07:37
Yes it is helpful. It specifies exactly what task the questioner is looking to accomplish. — conjectures, Feb 16 '15 at 21:53

user93353 · Accepted Answer · 2012-12-03T06:04:11.380

18

There is no function for checking length of array in C. However, if the array is declared in the same scope as where you want to check, you can do the following

int len = sizeof(x)/sizeof(x[0]);

You have to iterate through x and do strcmp on each element of array x, to check if s is the same as one of the elements of x.

char * x [] = { "ab", "bc", "cd" };
char * s = "ab";
int len = sizeof(x)/sizeof(x[0]);
int i;

for(i = 0; i < len; ++i)
{
    if(!strcmp(x[i], s))
    {
        // Do your stuff
    }
}

edited Dec 03 '12 at 06:04

answered Dec 03 '12 at 05:57

user93353

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@CareyGregory - my original post wasn't incorrect - this way isn't a function. And it works only if the array is declared in the same scope. – user93353 Dec 03 '12 at 06:01
2

I didn't say your post was incorrect; it wasn't. It was simply less than it could have been, but you fixed it. So all is well, yes? :-) – Carey Gregory Dec 03 '12 at 06:05
This is not exactly what OP wants as the conditional code would execute multiple times if the target string appears more than once in the array of strings, right? – Matheus Santana Mar 21 '18 at 18:12

score 12 · Answer 2 · edited Feb 10 '18 at 11:30

12

Something like this??

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

int main() {
    char *x[] = {"ab", "bc", "cd", 0};
    char *s = "ab";
    int i = 0;
    while(x[i]) {
        if(strcmp(x[i], s) == 0) {
            printf("Gotcha!\n");
            break;
        }
        i++;
    }
}

edited Feb 10 '18 at 11:30

Morgoth

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answered Dec 03 '12 at 05:59

nvlass

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score 3 · Answer 3 · answered Mar 21 '18 at 18:11

A possible C implementation for Python's in method could be

#include <string.h>

int in(char **arr, int len, char *target) {
  int i;
  for(i = 0; i < len; i++) {
    if(strncmp(arr[i], target, strlen(target)) == 0) {
      return 1;
    }
  }
  return 0;
}

int main() {
  char *x[3] = { "ab", "bc", "cd" };
  char *s = "ab";

  if(in(x, 3, s)) {
    // code
  }

  return 0;
}

Note that the use of strncmp instead of strcmp allows for easier comparison of string with different sizes. More about the both of them in their manpage.

score 1 · Answer 4 · answered Dec 03 '12 at 06:57

1

There is a function for finding string length. It is strlen from string.h

And then you could use the strcmp from the same header to compare strings, just as the other answers say.

answered Dec 03 '12 at 06:57

Dimitar Slavchev

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How to check if a string is in an array of strings in C?

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