atoi

atoi

Convert a String to Integer

Portability: ISO/ANSI C conforming, UNIX compatible

SYNOPSIS
DESCRIPTION
RETURN VALUE
CAUTION
DIAGNOSTICS
IMPLEMENTATION
EXAMPLE
RELATED FUNCTIONS
SEE ALSO

SYNOPSIS

#include <stdlib.h>

int atoi(const char *str);

DESCRIPTION

atoi converts the character string str to an integer. The string should consist of an optional plus or minus sign, followed by one or more decimal digits. Initial white-space characters are ignored.

RETURN VALUE

atoi returns the integer value represented by the character string up to the first unrecognized character. If no initial segment of the string is a valid integer, the return value is 0.

CAUTION

No indication of overflow or other error is returned, so you should validate the string before calling atoi .

DIAGNOSTICS

No indication is returned to the program to specify whether the string contains a valid integer.

If the correct value is too large to be stored in a 370 long , either LONG_MAX (2³¹-1) or LONG_MIN (-2³¹) is returned, depending on the sign of the value.

IMPLEMENTATION

atoi(x) is implemented as (int)atol(x) .

EXAMPLE

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

#define MAXLINE 25

main()
{
   int value;
   char *input;
   char line[MAXLINE];

   puts("Enter a number: ");
   input = gets(line);
      /* If string contains only digits, white space, or +/-,  */
      /*  convert. 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);
}

RELATED FUNCTIONS

strtol

SEE ALSO

String Utility Functions

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