Parsing Function for Comma Separated String

Question

Suppose I have a string like "cmd,param1,param2" . String is an Arduino String type. https://www.arduino.cc/en/Reference/String

I want to extract each of the substrings separated by commas. I have successfully written code for a specific case like this. Here is the code;

 String = str_data('cmd,param1,param2'); int firstCommaIndex = str_data.indexOf(','); int secondCommaIndex = str_data.indexOf(',', firstCommaIndex+1); String cmd = str_data.substring(0, firstCommaIndex); String param1 = str_data.substring(firstCommaIndex+1, secondCommaIndex); String param2 = str_data.substring(secondCommaIndex+1); 

My problem is to have a function that solves the general case. A line can be divided into any number of commas. I would like to have a function that looks like this:

 String parserCommaDelimited(String input_delimited_str, int nth_param_num) { //implementation } 

Suppose input_delimited_str="cmd,param1,param2,param3,param4"

parserCommaDelimited(input_delimited_str, 1) returns "cmd" . parserCommaDelimited(input_delimited_str, 5) returns "param4" .

Answer 1

The following is a basic CSV parser:

 void readCSVline(char *line); char *readCSVfield(char *line, char *buf); void readCSVdemo(void) { char line[]= "0,,10004,10004,\"Albany Hwy After Galliers Av\",\"\",-32.13649428,116.0176090070,3"; readCSVline(line); } /* readCSVline is where you put your "intelligence" about fields to read * and what to do with them */ void readCSVline(char *line) { char field1[80], *lineptr=line; int nfields=0; while (*lineptr) { lineptr= readCSVfield(lineptr, field1); printf("%s\n", field1); nfields++; } printf("%d fields read.\n", nfields); } /* readCSVfield reads a field from a CSV line until the next comma or end-of-line. * It returns where the reading stopped. */ char *readCSVfield(char *line, char *buf) { int instr= FALSE; // track whether we are in a string char *cptr= line; while (*cptr) { if (instr) { if (*cptr=='"') { char cc= *++cptr; if (cc=='"') // escaped double quote *buf++ = '"'; else { *buf='\0'; cptr--; instr= FALSE; } } else *buf++ = *cptr; } else switch (*cptr) { case '"': instr= TRUE; break; case ',': cptr++; *buf= '\0'; return(cptr); case ' ': case '\t': case '\n': case '\r': break; default: *buf++ = *cptr; } cptr++; } *buf= '\0'; return(cptr); } 

Answer 2

You can split the string as shown below and get whatever you want.

 int split(char *result[], const char *str, char tok) { char buff[1024]; // it better to use length of str instead of 1024 int idx = 0; int len = 0; int ent_cnt = 0; int st = 0; // parse string while(1) { char ch = str[len++]; // need checking len to avoid overflow // end of string? if (ch == '\0') break; switch(st) { case 0: { if (ch == tok) st++; else buff[idx++] = ch; break; } case 1: { if (idx) { char *entry = malloc(idx + 1); int i; for (i = 0; i < idx; i++) entry[i] = buff[i]; entry[i] = '\0'; result[ent_cnt++] = entry; idx = 0; } // normal char? if (ch != tok) buff[idx++] = ch; st--; break; } default: break; } } // process last part if any if (idx) { char *entry = malloc(idx + 1); int i = 0; for (i = 0; i < idx; i++) entry[i] = buff[i]; entry[i] = '\0'; result[ent_cnt++] = entry; } return ent_cnt; } int main(int argc, char *argv[]) { char *result[10]; int cnt = split(result, "s,this,is,a,test,", ','); int i = 0; for (i = 0; i < cnt; i++) { printf("%s\n", result[i]); } if (cnt != 5) { printf("Fail!\n"); } return 0; } 

Answer 3

try with split, in C ++ there is strtok:

variable = strtok (variable, "separator"); converts a string to an array, in C ++ I do not know, I program php and javascript, but you can see it:

http://www.cplusplus.com/reference/cstring/strtok/

Hope this helps you!