Explicit conversion C

Question

If i have the following :

char id[5]="1";

and I want to use the id as a integer,i have to convert it first or is enough (int)id to use the value from that string ?

This question should help. http://stackoverflow.com/questions/3420629/convert-string-to-integer-sscanf-or-atoi — FreeNickname, Apr 11 '13 at 17:54
Especially note that `(int)id` will compile and is valid C, but does not do what you think it would. It will return the (first) memory address of the string, i.e. the value of the pointer itself. — Kninnug, Apr 11 '13 at 17:57

K Scott Piel · Answer 1 · 2013-04-11T19:12:22.817

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No... you would need to convert it using a function call such as int n = atoi( id )

A char array is just that... an array of char... it is not a number in the sense that you're thinking. You need to use a function call to convert it from the string representation of a value to the actual numerical integer value you're looking for.

edited Apr 11 '13 at 19:12

answered Apr 11 '13 at 17:52

K Scott Piel

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well, technically it is a number, an ASCII character code, but it doesn't map to the numeral. – metalhead Apr 11 '13 at 18:04
Fair enough -- edited to clarify – K Scott Piel Apr 11 '13 at 19:13

score 1 · Answer 2 · answered Apr 11 '13 at 17:52

1

You can use atoi to convert the string to an integer:

char id[5] = "1";
int n = atoi(id); // n = 1

answered Apr 11 '13 at 17:52

Paul R

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score 1 · Answer 3 · answered Apr 11 '13 at 17:53

C does not provide type conversions between strings and numerical data.

To convert from a string to an int, you need to use atoi or (better) strtol. strtol is better, because it does not result in undefined behaviour if the input string is not convertable to a number, and it allows you to detect cases like "42xyz" and react correctly.

Explicit conversion C

3 Answers3