Parsing house number from street address represented as a char[] - c

Question

Suppose I have a street address stored as a char[]. Examples of valid values:
1600 Pennsylvania Ave
1 Infinite Loop
221 Baker Street
As you can see, the house number can be of any length.
In C, what is an efficient way of separating the house number into its own int? I'm thinking I need to write a while loop to check for each char c if isdigit(c), but I don't know if I'm on the right track here in terms of implementation.

Answer 1

You can use strtok to break up the string into tokens and use isdigit() to figure out if that token is numeric.
#include <string.h>
#include <stdio.h>
int main()
{
const char str1[80] = "1600 Pennsylvania Ave";
int houseNumber = 0;
const char s[2] = " ";
char *token;
/* get the first token */
token = strtok(str, s);
/* walk through other tokens */
while( token != NULL ) {
printf( " %s\n", token );
if (isdigit(str1[0])) {
houseNumber = atoi (token);
}
token = strtok(NULL, s);
}
return(0);
}
Alternatively, you can use sscanf to read the entire string and automatically parse everything:
#include <string.h>
#include <stdio.h>
int main()
{
const char str1[80] = "1600 Pennsylvania Ave";
int houseNumber = 0;
char streetName[50];
char streetExt[20];
sscanf (str1,"%d %s %s", &houseNumber, streetName, streetExt);
return(0);
}
This last method depends on the format of the strings being exactly the same in all cases, meaning that it's always a number followed by 2 strings. The strtok method will be a little more fault tolerant if there's more other stuff.

Answer 2

Consider the following solution:
#include <stdio.h>
#include <string.h>
int main(void)
{
char address[255];
char * ptr;
int number;
char strnumber[100];
char strstreet[255];
// ask adress
printf("Please, enter the addres: ");
// put end of string replacing newline
fgets(address, 255, stdin);
ptr = strchr(address, '\n');
if(ptr)
{
*ptr = '\0';
}
else
{
address[254] = '\0';
}
// try to read whole number from the beggining of the string
if( 1 == sscanf(address, "%d", &number) )
{
// make number as a string (if it is needed)
sprintf(strnumber, "%d", number);
// take streat to separate string
ptr = strchr(address + strlen(strnumber), ' '); // find the firs space
if( ptr )
{
strcpy(strstreet, ptr + 1); // +1 just to skip the found space
}
}
else
{ // if no number at the beginning of address string
number = 0;
strnumber[0] = '\0';
strstreet[0] = '\0';
}
// show the results
printf("You have entered a string:\n%s\n", address);
printf("The found number is:\n%d\n", number);
printf("The found number as a string:\n%s\n", strnumber);
printf("The address without number is:\n%s\n", strstreet);
}

Answer 3

I would use strstr and atoi like this
char someAddress[80] = "1600 Pennsylvania Ave";
char* p = strstr(someAddress, " ");
if (p)
{
*p = 0; // Terminate string, i.e. cheat for a moment
int number = atoi(someAddress);
*p = " "; // Restore someAddress
}
else
{
// Handle illegal format in someAddress
}
This method shall only be used when you know it is safe to modify someAddress for a short period.

Answer 4

This is one situation with the numbers first, where it is much easier just to use a simple pointer and an if statement to parse the line:
#include <stdio.h>
#define ADDL 64
int main (void) {
char address[ADDL] = {0};
char street[16] = {0};
while (fgets (address, ADDL-1, stdin) != NULL)
{
char *ap = address;
char *sp = street;
while (*ap >= '0' && *ap <= '9') /* while the char is a number */
{
*sp = *ap++; /* copy to street number */
sp++;
}
*sp = 0; /* null-terminate */
printf (" Address: %s Number : %s\n\n", address, street);
}
return 0;
}
Output
$ ./bin/split_address < dat/houses.txt
Address: 1600 Pennsylvania Ave
Number : 1600
Address: 1 Infinite Loop
Number : 1
Address: 221 Baker Street
Number : 221
Note: the printf statement above makes use to the embedded newline at the end of address rather than stripping it as you would normally do. Also note that if you want the number as an integer, long, or unsigned, simply call atoi, strtol or strtoul on street.