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Hi all,
im new to programming and new to C, just started with arrays and im somewhat stucked, where i have a .txt file which contains items and prices. I want the items and the prices split into 2 different arrays
The .txt looks like that:
orange 0.89
banana 0.79
apple 0.59
I now want to split the items in a char items[100][100] and float prices[100]. Can somebody show me how to split this, preferably with fscanf ?
Hi Zator. :)
What have you tried so far?
We are here to help but there are tons of solutions in these forums. I quick search for me for what you may be after was found here: http://cboard.cprogramming.com/windo...-function.html
so i have
Thats where im currently stucked. As you can see i am only using 1 array which presents the line. I have problems putting char[100][100] in, cause i dont know the notations for the while part then (gettin lots of errors etc.). Right now hes printing the completely .txt file likeCode:#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
int main() {
char filename[] = "test.txt";
FILE * file;
char items[100]; // [100][100];
// float prices[100]
file = fopen(filename,"r");
if (file == NULL){
perror(filename);
return 1;
}
while (fscanf(file,"%s", items) == 1){
printf("%s\n", items);
}
fclose(file);
}
orange
0.89
banana
0.79
apple
0.59
but i want it like this.
Dont want to print it tho (just looking if its okay).
He should give back the number of lines(=elements).
item array
orange
banana
apple
price array
0.89
0.79
0.59
Quote:
Originally Posted by Zator
This will only read individual items. You probably want to read pairs. For example your data file has this line:
orange 0.89
Then you want to read this into an item, price pair. I think the best way is to read individual lines and then process them with sscanf. For example, suppose you read in a line by using fgets into buf, then you could do the following:
This makes sure each line has the two tokens you need (item, price) and nothing else. The %99s ensures that item fits into a 100 byte buffer. If you declare your array as you said initially with char items[100][100] then you can simply copy them into your array at this point.Code:char item[100];
float price;
char c;
if (sscanf(buf, "%99s %f %c", item, &price, &c) != 2) {
printf("Line is not in correct format: expected item price\n");
exit(1);
}
Repeat this for all remaining lines. You should also add a check to stop reading lines as soon as nitems or nprices reaches 100.Code:strcpy(items[nitems++], item);
prices[nprices++] = price;
Well i want to do it with fscanf. Can you help me whats wrong here?
Code:#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#define MAX_LINES 100
#define MAX_LENGTH 100
int read_pricelist(const char* filename, char items[MAX_LINES][MAX_LENGTH], float prices[MAX_LINES]) {
FILE *file;
file = fopen("./prices.txt","r");
if (file == NULL){
perror("-1");
exit(1);
}
while(!feof(file)) {
fscanf(file, "%s %f", &items, &prices);
printf("read %s %f\n", items, prices);
}
fclose(file);
}
int main() {
}
i basically get this error for every: %s’ expects argument of type ‘char *’, but argument 3 has type ‘char (**)[100]’ and
‘%f’ expects argument of type ‘float *’, but argument 4 has type ‘float **’
It is error free now, but somehow its not printing anything.
Any help here?Code:#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#define MAX_LINES 100
#define MAX_LENGTH 100
void read_pricelist(const char* filename, char items[MAX_LINES][MAX_LENGTH], float prices[MAX_LINES]) {
int i;
FILE *file;
file = fopen("./prices.txt","r");
if (file == NULL){
perror("Reading from file prices.txt");
exit(1);
}
i = 0;
while(!feof(file)) {
fscanf(file, "%s %f", items[i], &prices[i]);
printf("%s %f\n", items[i], prices[i]);
i++;
}
fclose(file);
}
Perhaps you forgot to call the read_pricelist function?
Also, you should not use feof to control the loop in that way. Rather, use the return value of fscanf:
However, this is still problematic in that items[i] presumably can store a string at most MAX_LENGTH - 1 in length. You need to account for this when reading to avoid buffer overflow, e.g.,Code:i = 0;
while (fscanf(file, "%s %f", items[i], &prices[i]) == 2) {
printf("%s %f\n", items[i], prices[i]);
i++;
}
Also, it would probably be better to return an error code instead of exiting immediately if the file cannot be opened. Perhaps at some later point you might want to allow the user to try again with a different file name.Code:char scan_format[16];
sprintf(scan_format, "%%%ds %%f", MAX_LENGTH - 1);
i = 0;
while (fscanf(file, scan_format, items[i], &prices[i]) == 2) {
printf("%s %f\n", items[i], prices[i]);
i++;
}