Converting large string of numbers (14 digits) to integer or long in C

Question

I have a string that contains a 14-digit number.

I want to convert the string to an int.

When I use atoi(stringName), I get the max 32-bit in limitation.

Example:

String1 contains "201400000000"

long long tempNum1;
tempNum1 = atoi(String1);
printf("%d",tempNum1);

Output is: 2147483647

How can I turn this string into a number? I want to compare it to other strings of numbers and find which is the largest. (I have three strings of 14-digit numbers, I want to find which is the smallest, which is the largest).

I have to wonder what you were expecting `tempNum1 = sprintf(String1,NULL,10);` to do. — user253751, Oct 08 '15 at 08:01
As could be guess from it's name [`atoi`](http://en.cppreference.com/w/c/string/byte/atoi) only deals with `int`. You might want to use [`strtoll`](http://en.cppreference.com/w/c/string/byte/strtol) instead. — Some programmer dude, Oct 08 '15 at 08:02
it should be printf("%llu",tempNum1); and use strtoI for string to long conversion — user2979190, Oct 08 '15 at 08:10
`long` is still 32 bits on Windows and most 32-bit *nix OSes. Only `long long` is guaranteed to have at least 64 bits — phuclv, Oct 08 '15 at 08:16
Thanks all. strtoll works. Also thanks @user2979190 for mentioning the format specifier! — plc, Oct 08 '15 at 08:26

Bathsheba · Accepted Answer · 2015-10-08T08:21:02.850

3

atoi returns an int.

That int is assigned to a long long, but by then the limit has already been reached.

You want to use atoll which returns a long long.

And your printf format specifier is incorrect for your type.

edited Oct 08 '15 at 08:21

answered Oct 08 '15 at 08:01

Bathsheba

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Thank youThank youThank you – plc Oct 08 '15 at 08:17
And fix that format specifier else your compiler might eat your cat. – Bathsheba Oct 08 '15 at 08:21
[`atoi()` and `atoll()` shoudn't be used](https://stackoverflow.com/q/17710018/995714) – phuclv Feb 01 '20 at 02:15

score 3 · Answer 2 · answered Oct 08 '15 at 08:02

3

Since your target is a long long int, you can use the strtoll function:

#include <stdlib.h>

long long tempNum1 = strtoll(String1, NULL, 10);

answered Oct 08 '15 at 08:02

melpomene

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Rahul Tripathi · Answer 3 · 2015-10-08T08:06:24.017

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You can try like this using strol:

long strtol (const char *Str, char **EndPoint, int Base)

or

long long strtoll( const char *restrict str, char **restrict str_end, int base );

The atoi says:

The call atoi(str) shall be equivalent to:
(int) strtol(str, (char **)NULL, 10)
except that the handling of errors may differ. If the value cannot be represented, the behavior is undefined.

edited Oct 08 '15 at 08:06

answered Oct 08 '15 at 08:02

Rahul Tripathi

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That will fail on my 32-bit system. – melpomene Oct 08 '15 at 08:05

score 1 · Answer 4 · answered Oct 08 '15 at 08:21

1

try

 sscanf( String1, "%lld", &TempNum1);

Note that the format specifier %lld works for C99 , if not C99 please check the docs for the compiler

answered Oct 08 '15 at 08:21

Jibin Mathew

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Converting large string of numbers (14 digits) to integer or long in C

4 Answers4