atoi [C++ Reference]
Keywords: c,string,atoi
Date: 2009-02-18T14:51:07-0800

## atoi

Syntax:

        #include <cstdlib>
        int atoi( const char *str );

The atoi function converts `str` into an integer, and returns that integer. `str` should start with whitespace or some sort of number, and atoi will stop reading from `str` as soon as a non-numerical character has been read. For example:

        int i;
        i = atoi( "512" );
        i = atoi( "512.035" );
        i = atoi( "   512.035" );
        i = atoi( "   512+34" );
        i = atoi( "   512 bottles of beer on the wall" );

All five of the above assignments to the variable `i` would result in it being set to 512.

If the conversion cannot be performed, then atoi will return zero:

        int i = atoi( " does not work: 512" );  // results in i == 0

You can use sprintf to convert a number into a string.

Related Topics: atof, atol, sprintf