C: split string to string array with delimiter "&&"

Question

I'm kinda new in C so i need help. I need to split a string to string array with the delimiter "&&", the thing is that i tried to use strtok, but when i use it, it looks like that the strtok can't handle correctly if the is '&' some where in the string.

I know that each part between the && is at max 256 chars and that there are at most 16 parts. so i need to create an array arr[16][256] or an array of size 16*256. in any case each time i try my code fail on the different between & and &&

example:

    char arr[16][255];
    char stringToSplit = "Hello World && How are u doing && more words & bla &";

output:

    arr[0] = "Hello World ";
    arr[1] = " How are u doing ";
    arr[2] = " more words & bla &";

Thanks ahead!

This is what i tried:

  int i;
  char *p;
  i = 0;
  p = strtok (stringToSplit ,"&&");
  while (p != NULL)
  {
    arr[i++] = p;
    p = strtok (NULL, "&&");
  }
  for (i=0;i<16; ++i)
    printf("%s\n", arr[i]);

`strtok` doesn't handle this because you are passing `stringToSplit` that pointing to string literal and `strtok` modifies string to which you pass. Read [this answer](http://stackoverflow.com/questions/17551665/strtok-causing-segfault-but-not-when-step-through-code/17551779#17551779) . — Grijesh Chauhan, Apr 28 '14 at 18:34
Another problem is that strtok only tokenizes using any single character within the given delimiter string. So passing it "&&" is no different than passing it "&". You may need to write your own tokenizing function, which is not that difficult. — ooga, Apr 28 '14 at 18:40
[check this](http://codepad.org/12Ap8HUK) or [this](http://codepad.org/JaXkmWXT) — Grijesh Chauhan, Apr 28 '14 at 19:00
See also [How to extract the string if we have more than one delimiters](http://stackoverflow.com/questions/22827998/how-to-extract-the-string-if-we-have-have-more-than-one-delimiters) [sic]. — Jongware, Apr 28 '14 at 21:29

score 0 · Answer 1 · answered Apr 28 '14 at 18:45

0

strtok() splits the string on characters.

You need strstr() to find a string inside a string then copy the relevant characters to the destination. Keep doing this until the source string is exhausted.

answered Apr 28 '14 at 18:45

pmg

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I tried that and it worked. but the problem was that I got some unknown chars at the end of each index. the arr[0] was "Hello world @H" – tubu13 Apr 28 '14 at 18:47
2

You need to properly terminate all strings by writing `'\0'` at the last position – pmg Apr 28 '14 at 18:48
how do i find the last index? the `strlen()` doesnt give the right length of the string... – tubu13 Apr 28 '14 at 18:49
The last index is the (relative) position of the next occurrence of `"&&"`. – pmg Apr 29 '14 at 08:09

score 0 · Answer 2 · answered Apr 28 '14 at 18:51

A simple double nested loop will do. check for "&&" and watch out for long sub-strings and too many sub-strings.

void  tubu13(void) {
  #define NUM (16)
  #define SIZ (255+1)

  char arr[NUM][SIZ];
  const char *stringToSplit = "Hello World && How are u doing && more words & bla &";

  const char *p = stringToSplit;
  int n, len;
  for (n = 0; n < NUM; n++) {
    for (len=0; len < SIZ-1; len++) {
      if (p[0] == '\0') {
        break;
      }
      if (p[0] == '&' && p[1] == '&') {
        p += 2;
        break;
      }
      arr[n][len] = *p;
      p++;
    }
    arr[n][len] = '\0';
    printf("  arr[%d] = \"%s\";\n", n, arr[n]);
  }
}

arr[0] = "Hello World ";
arr[1] = " How are u doing ";
arr[2] = " more words & bla &";
arr[3] = "";
...
arr[15] = "";

score 0 · Answer 3 · answered Apr 29 '14 at 08:06

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

char *strtokByWord_r(char *str, const char *word, char **store){
    char *p, *ret;
    if(str != NULL){
        *store = str;
    }
    if(*store == NULL) return NULL;
    p = strstr(ret=*store, word);
    if(p){
        *p='\0';
        *store = p + strlen(word);
    } else {
        *store = NULL;
    }
    return ret;
}
char *strtokByWord(char *str, const char *word){
    static char *store = NULL;
    return strtokByWord_r(str, word, &store);
}

int main(){
    char arr[16][255];
    char stringToSplit[] = "Hello World && How are u doing && more words & bla &";
    int i, n;
    char *p;
    i = 0;
    p = strtokByWord(stringToSplit, "&&");
    while (p != NULL){
        strcpy(arr[i++], p);
        p = strtokByWord(NULL, "&&");
    }
    n = i;
    for (i=0;i<n; ++i)
        printf("%s\n", arr[i]);
    return 0;
}

C: split string to string array with delimiter "&&"

3 Answers3