CODEWITHSUNDEEP
cstringintegerc-strings
user981245
user981245

Reputation: 39

Store two integers from a String in C

I am trying to write a program that prints two numbers from a string.

For example, string = '20,66' I am trying to break this string apart so I can store '20' and '66' into two separate variables.

Here is the code I am working on:

#include <stdio.h>

char line[80];

int main(void)
{
    // Variables
    int start_number, end_number;
    int i, j;

    while(1)
    {
        printf("Enter a number: ");
        fgets( line, sizeof(line), stdin);

        // How to find Comma
        for( i=0; i < strlen(line); i++)
        {
            if(line[i]==',') break;
        }

        // How to find two numbers
        for(j = 0; j < i; j++)
        {
            printf("1: %c\n", line[j]);         
        }

        for(j = i + 1; j < strlen(line); j++)
        {
            printf("2: %c\n", line[j]);
        }

        if (strcmp(line, "quit\n") == 0)
        {
            printf("Now terminating program...");
            break;
        }       

    }   
}

So far, I am only able to store single digit variables and for some reason prints an extra line.

Any suggestions or advice will be appreciated.

Upvotes: 0

Views: 2081

Answers (5)

Ashok
Ashok

Reputation: 1952

#include <stdio.h>

char line[80];

int main(void)
{
    // Variables
    int start_number, end_number;
    int i, j;

    while(1)
    {
        printf("Enter a number: ");
        fgets( line, sizeof(line), stdin);
        for( i=0; i < strlen(line); i++)
        {
              char num[];
            if(line[i]!=','){
                num[j++] = line[i];  
            }
            else{
                for(int x =0 x<strlen(num); x++) 
                    printf("Number :%c", num[x]);
                j=0;
              }
        }
    }
}

Upvotes: 0

Arun
Arun

Reputation: 2523

Perhaps you dont want to have "1: " and/or a NEWLINE ("\n") printed within the for loop. Change this:

for(j = 0; j < i; j++)
{
    printf("1: %c\n", line[j]);
}

to this:

printf("1: "); 
for(j = 0; j < i; j++)
{
    printf("%c", line[j]);
}
printf("\n");

Upvotes: 0

derobert
derobert

Reputation: 51147

One of many approaches: Once you find the comma, you can change the comma to (char)0. Then you will have two strings, one will be line the other one will be at line+comma_offset+1. Both are just the numbers and can be passed to atoi.

This trick works due to the way C strings are implemented—the end of the string is a 0. So, you take a string:

'1'  '2'  ','  '3'  '4'  0x00
 |
line

and replace the comma with a null:

'1'  '2'  0x00 '3'  '4'  0x00
 |              |
line            str_2

then you have two C strings. This is how strtok and strtok_r work.

Upvotes: 2

Paul Rubel
Paul Rubel

Reputation: 27222

Look into scanf and its relatives:

#include <stdio.h>

int main() {
  int x, y;
  sscanf("22,33", "%d,%d", &x, &y);
  printf("Scanned vars: %i %i\n", x, y);
}
tmp]$ ./a.out 
Scanned vars: 22 33

It's possible to introduce security vulnerabilities so be sure to read and understand the section on security so that you have enough storage for the values you're trying to scan.

Upvotes: 2

Mario
Mario

Reputation: 36487

Quite simple:

const char *text = "20,30";
const char *rest = 0;
int first = strtol(text, &rest, 10); // input, pointer to remaining string, base (10 = decimal)
rest += 1; // skip the comma; this is error prone in case there are spaces!
int second = strtol(rest, NULL, 10); // not interested in remaining string, so pass NULL this time

Upvotes: 4

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