atoi Function

Converts a string to an integer.

Include

<stdlib.h>

Prototype

int atoi(const char *s);

Argument

s

string to be converted

Return Value

Returns the converted integer if successful; otherwise, returns 0.

Remarks

The number may consist of the following:

[whitespace] [sign] digits

Optional whitespace followed by an optional sign, then a sequence of one or more digits. The conversion stops when the first unrecognized character is reached. The conversion is equivalent to (int) strtol(s,0,10), except it does no error checking so errno will not be set.

Example

#include <stdio.h>
#include <stdlib.h>

int main(void)
{

  char a[] = " -127";
  char b[] = "Number1";
  int x;

  x = atoi(a);
  printf("String = \"%s\"\tint = %d\n", a, x);

  x = atoi(b);
  printf("String = \"%s\"\tint = %d\n", b, x);
}

Example Output

String = " -127"        int = -127
String = "Number1"      int = 0