How to convert a string to an integer in C
Educative Answers TeamIn C, the atoi() function converts a string to an integer.
Syntax
The syntax for the function is given below:
int atoi(const char *string)
Parameters
The function takes as input the string that is to be converted to an integer.
Return value
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If successfully executed, the function returns the integer value.
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If the string starts with an alphanumeric character or only contains alphanumeric characters, 0 is returned.
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In case the string starts with a numeric character but is followed by an alpha-numeric character, the string is converted to an integer until the occurrence of the first alphanumeric character
Note: The
stdlib.hlibrary must be included for theatoi()function to be executed
Example
Let’s look at an example to further understand the working of the atoi() function:
#include<stdio.h>
#include <stdlib.h>
int main() {
// Converting a numeric string
char str[10] = "122";
int x = atoi(str);
printf("Converting '122': %d\n", x);
// Converting an alphanumeric string
char str2[10] = "Hello!";
x = atoi(str2);
printf("Converting 'Hello!': %d\n", x);
// Converting a partial string
char str3[10] = "99Hello!";
x = atoi(str3);
printf("Converting '99Hello!': %d\n", x);
return 0;
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