atoi() -- General Function (libc)

Convert ASCII strings to integers
#include <stdlib.h>
int atoi(string) char *string;

atoi()  converts  string  into the  binary  representation  of an  integer.
string may contain a leading sign and any number of decimal digits.  atoi()
ignores leading  blanks and tabs; it stops scanning  when it encounters any
non-numeral other than the leading sign, and returns the resulting int.

Example

The following demonstrates atoi(). It takes a string typed at the terminal,
turns it into an integer, then prints that integer on the screen.  To exit,
type <ctrl-C>.

#include <stdlib.h>

main()
{
    extern char *gets();
    extern int atoi();
    char string[64];

    for(;;) {
        printf("Enter numeric string: ");
        if(gets(string))
            printf("%d\n", atoi(string));
        else
            break;
    }
}

See Also

libc
ANSI Standard, §7.10.1.2
POSIX Standard, §8.1

Notes

atoi does not check to see if the number represented by string fits into an
int.  It returns zero if you hand it a string that it cannot interpret.

© 2012 by Stephen A. Ness