atoi example - Brave Search

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atoi() Function in C - GeeksforGeeks

October 13, 2025 - The atoi() function have different output for different input types. The following examples shown the behaviors of the atoi() function for different input values.

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C library - atoi() function

// use the atoi() function int number = atoi(concatenated); printf("The concatenated string is: %s\n", concatenated); printf("The integral number is: %d\n", number); // at the last free the alocated memory free(concatenated); return 0; } ... ...

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w3schools.com › c › ref_stdlib_atoi.php

C stdlib atoi() Function

The atoi() function is defined in the <stdlib.h> header file. Tip: If the number is not at the beginning of the string you can use a pointer to a different position in the string. See More Examples below for an example.

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r/learnprogramming on Reddit: How do you use 'atoi'? (C)

June 4, 2022 -

I want to assign an integer variable as a string. So if char *s = "123";, and int x;, I want to assign x to be whatever s is, so in this case "123". I asked a few hours ago and a lot of people said to use atoi. I tried researching it and from what I gathered it's a function that's in the header file stdlib.h, but no one really explained how to use it or what it does specifically. Also in every website I went to, they all said to use the syntax int atoi(const char *string), but if the function has already been declared in the header file, I don't see why there is a need to put a prototype. Can anyone explain this in a little more detail?

Thank you.

atoi will return the value of the integer stored in the string (assuming it contains an integer, if it doesn't you'll get a 0). So using the same basic code that you showed before: char* s = "123"; int x = atoi(s); Is how it is used. The examples on the atoi page show the result going straight to printf as a parameter to be printed, but it can be stored as well. If you use sscanf or sscanf_s you'd pass in the address of the variable x along with s and the format string: sscanf(s, "%d", &x); All the scanning functions return a number which is the number of matches and assignments (so if your s were "abcd" the return would be 0, but if it's a valid integer then 1) or EOF for some error conditions.

cppreference.com

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atoi, atol, atoll - cppreference.com

The name stands for “ASCII to integer”. Run this code · #include <stdio.h> #include <stdlib.h> int main(void) { printf("%i\n", atoi(" -123junk")); printf("%i\n", atoi(" +321dust")); printf("%i\n", atoi("0")); printf("%i\n", atoi("0042")); // treated as a decimal number with leading zeros ...

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Atoi in C++: An Ultimate Guide to atoi() Function

October 17, 2024 - Atoi in C++ accepts a string parameter that contains integer values and converts the passed string to an integer value. Learn all about the atoi() function!

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Microsoft Learn

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atoi, _atoi_l, _wtoi, _wtoi_l | Microsoft Learn

November 15, 2023 - This program shows how numbers stored as strings can be converted to numeric values using the atoi functions.

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C atoi Tutorial: String to Integer Conversion with Practical Examples

It's declared in stdlib.h and takes ... which provides error checking and supports different number bases. This example demonstrates converting a simple numeric string using atoi....

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atoi() function in C - Scaler Topics

October 14, 2022 - C language requires the following header file for atoi function: ... Let's see an example of converting a number in a string to an integer value using the atoi() function in C.

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How to use atoi() and how to make own atoi() ? - Aticleworld

October 17, 2022 - The atoi() function converts the numeric string to the int representation. It takes a string as an argument and returns its integer value.

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atoi() in C - Syntax, Use and Example - Codeforwin

July 20, 2025 - /** * C program to convert string to integer using atoi() library function. */ #include <stdio.h> #include <stdlib.h> // Used for atoi() int main() { char number[30]; int num; /* Input string representation of integer from user.

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C atoi() function

#include <stdlib.h> #include <stdio.h> int main(void) { int in_val; char *s; s = " -4938"; printf("String value: %s",s); in_val= atoi(s); printf("\nInteger value = %d\n",in_val); s = "+4938"; printf("\nString value: %s",s); in_val= atoi(s); printf("\nInteger value = %d\n",in_val); s = "4938"; printf("\nString value: %s",s); in_val= atoi(s); printf("\nInteger value = %d\n",in_val); s = "0038"; printf("\nString value: %s",s); in_val= atoi(s); printf("\nInteger value = %d\n",in_val); s = "003800"; printf("\nString value: %s",s); in_val= atoi(s); printf("\nInteger value = %d\n",in_val); }

cppreference.com

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std::atoi, std::atol, std::atoll - cppreference.com

#include <array> #include <cstdlib> #include <iostream> #include <locale> #include <numeric> int main() { std::cout.imbue(std::locale("en_US.UTF-8")); std::array<char, 8> arr; std::iota(arr.begin(), arr.begin() + arr.size() - 1, '1'); arr.back() = '\0'; const int num{std::atoi(arr.data())}; ...

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C++ Program To Write Your Own atoi() - GeeksforGeeks

July 23, 2025 - int atoi(const char strn) Parameters: The function accepts one parameter strn which refers to the string argument that is needed to be converted into its integer equivalent. Return Value: If strn is a valid input, then the function returns the ...

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String to Integer (atoi) - LeetCode

Note: You ... int(), parseInt, Number()). Perform the conversion manually. Example 1: Input: s = "42" Output: 42 · Explanation: The underlined characters are what is read in and the caret is the ...

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C++ atoi | How the atoi() method works in C++ with examples?

April 3, 2023 - Based on the requirement, we will ... built-in functions, and it will be used for converting the string data type values into the integer data type by using the function atoi()....

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C++ atoi() Function - Scaler Topics

June 10, 2024 - Explanation: In the above example, We have used the c++ atoi() function to convert the string into the int type. First, we declared the integer named variable val. Then we declared the character string char str whose size is 20.

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Function Descriptions : atoi

Note that the input may still not represent */ /* a valid integer. Consider +-14+5. **/ if (strspn(input, " +-0123456789") == strlen(input)){ value = atoi(input); printf(" The integer equivalent of given string is %d\n", value); } else printf("Invalid count value: %s\n", input); }

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String to Integer - Write your own atoi() - GeeksforGeeks

Write your own atoi() that takes a string (which represents a floating point value) as an argument and returns its value as double.

Published: April 14, 2026

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atoi() Function - C stdlib.h - Syntax, Parameters, Examples

February 21, 2025 - #include <stdio.h> #include <stdlib.h> int main() { char numStr[] = " -9876xyz"; int num = atoi(numStr); printf("Converted number: %d\n", num); return 0; } The function skips the leading spaces and detects the negative sign.