Creating an int value from multiple char array fields in C

Question

I'm working on a C program and i am struggling with it (I've been spoiled by the concept of object orientation).

What i want to do is this:

I want to put values in a char array into an int. So for example i have char[0] == '1' and char[1] == '2'. I want to put these values in an int variable so its value is 12. I have tried looking but I am not sure how to get this done.

I really am poor at explaining so please ask for more info if necessary.

your question shows the lack of personal research. there are tons of examples out there to solve this minor common problem. — Jason Hu, Aug 14 '15 at 16:53
possible duplicate of [How do you use atoi to assign individual elements of a char array?](http://stackoverflow.com/questions/3251401/how-do-you-use-atoi-to-assign-individual-elements-of-a-char-array) — dbush, Aug 14 '15 at 16:56
int foo = (char_array[0] & 0x0f)*10 + (char_array[0] & 0x0f). Don't call your characters char — Oleg Mazurov, Aug 14 '15 at 16:59
I think this will help: [atoi](http://www.cplusplus.com/reference/cstdlib/atoi/) — Milan Patel, Aug 14 '15 at 17:06
`int value = 0; for (int i = 0; i < lengthOfArray; ++i) { value *= 10; value += array[i]; }`. When someone can answer your question in one sentence, you have probably not given it enough thought and are doing yourself a learning disservice. — mah, Aug 14 '15 at 17:08

score 2 · Answer 1 · edited May 23 '17 at 11:51

2

If your char array is made with characters '1' and '2':

char a[2];
a[0] = '1';
a[1] = '2';
int b = (a[0]-'0')*10 + (a[1]-'0');

If your char array is made with numbers 1 and 2:

char a[2];
a[0] = 1;
a[1] = 2;
int b = a[0] * 10 + a[1];

also, see: Why does subtracting '0' in C result in the number that the char is representing?

edited May 23 '17 at 11:51

Community

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answered Aug 14 '15 at 17:09

orestisf

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Thanks alot. This also worked.Quite a simple solution actually. Not sure how i didn't think of this. – MrMalo Aug 14 '15 at 17:15

score 1 · Answer 2 · answered Aug 14 '15 at 17:18

If the character array contains a string that is if it is zero-terminated then you can apply standard C function atoi declared in header <stdlib.h>.

For example

char s[] = "12";
int x = atoi( s );

If the array is not zero-terminated as

char s[2] = "12";

then you can convert its content to an integer manually.

For example

int x = 0;

for ( size_t i = 0; i < sizeof( s ) / sizeof( *s ); i++ )
{
    x = 10 * x + s[i] - '0';
}

score 0 · Answer 3 · answered Aug 14 '15 at 17:19

0

What you are trying to do is called parsing. In c this can be done with the atoi() function like this:

 char s[] = "12";
 int num = atoi(s);

answered Aug 14 '15 at 17:19

Julius Naeumann

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Creating an int value from multiple char array fields in C

3 Answers3