Wednesday, 26 April 2017

c - Capture quoted strings separated with commas from a file




let's say I want to take an input from a file like this :-



"8313515769001870,GRKLK,03/2023,eatcp,btlzg"
"6144115684794523,ZEATL,10/2033,arnne,drrfd"


for a structure I made as follows



typedef struct{
char Card_Number[20];

char Bank_Code[6];
char Expiry_Date[8];
char First_Name[30];
char Last_Name[30];
}Card;


This is my attempt to read the input from a file named 'file' in the reading mode, the str in fgets is storing the right string but it isn't getting absorbed c[i]:



FILE * fptr;

int count=0;
fptr= fopen("file","r");
Card *c = (Card*)calloc(10,sizeof(Card));
printf("StartAlloc\n");
int i=0;
char str[1000];
fgets(str,80,fptr);
if(fptr==NULL)
{return 0;}
do{

sscanf(str,"\"%[^,],%[^,],%[^,],%[^,],%[^,]\" \n",c[i].Card_Number,c[i].Bank_Code,c[i].Expiry_Date,c[i].First_Name,c[i].Last_Name);
i++;

}while(fgets(str,80,fptr)!=NULL);


I do not understand why the regex %[^,] is not capturing the individual elements, I have wasted a lot of time, and help would be greatly appreciated.


Answer



Using fscanf() with the proper format you can retrieve the desired elements from each line :




"\"%[^,]%*c %[^,]%*c %[^,]%*c %[^,]%*c %[^\"]%*c\n" 



With the previous format, the opening quote is ignored (\"), and the strings separated by commas are captured (%[^,]%*c). Finally the the closing quote is discarded (%[^\"]%*c), and the line break considered (\n), to let next line to be read.




This is how you can integrate it in your code :



while (fscanf(file, "\"%[^,]%*c %[^,]%*c %[^,]%*c %[^,]%*c %[^\"]%*c\n", c[i].Card_Number, c[i].Bank_Code, c[i].Expiry_Date, c[i].First_Name, c[i].Last_Name) != -1 ) i++;



Complete code snippet for testing purposes :



#include 
#include

typedef struct{
char Card_Number[20];
char Bank_Code[6];

char Expiry_Date[8];
char First_Name[30];
char Last_Name[30];
}Card;

int main(){
FILE *file;
file = fopen("data.csv", "r");
int i=0;
Card *c = (Card*)calloc(10,sizeof(Card));


while (fscanf(file, "\"%[^,]%*c %[^,]%*c %[^,]%*c %[^,]%*c %[^\"]%*c\n", c[i].Card_Number, c[i].Bank_Code, c[i].Expiry_Date, c[i].First_Name, c[i].Last_Name) != -1 ) {
printf("%s | %s | %s | %s | %s \n", c[i].Card_Number, c[i].Bank_Code, c[i].Expiry_Date, c[i].First_Name, c[i].Last_Name);
i++;
}
fclose(file);
return 0;
}

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