atof(S)                        6 January 1993                        atof(S)


 Name

    atof, atoi, atol - converts ASCII to numbers

 Syntax


    cc  . . .  -lc


    #include <stdlib.h>

    double atof (nptr)
    char *nptr;

    int atoi (nptr)
    char *nptr;

    long atol (nptr)
    char *nptr;


 Description

    These functions convert a string pointed to by nptr to double, integer,
    and long integer numbers respectively.  The first unrecognized character
    ends the string.

    The atof function converts a string to a double.  The string pointed to
    by nptr is converted up to the first character deemed to be inconsistent
    with the format of a floating-point number. Leading white-space charac-
    ters are ignored.  This call is analogous to:

       strtod(str, (char **) NULL)

    atof recognizes a string of the form:

       [ +|- ] digits[. digits ][ e|E [ +|- ] digits ]

    where the digits are contiguous decimal digits.  Any number of tabs and
    spaces may precede the string.  The ``+'' and ``-'' signs are optional.
    Either e or E may be used to mark the beginning of the exponent.  If the
    atof function fails due to overflow or underflow, errno is set to ERANGE.
    The maximum size of an exponent is set by DMAXEXP, which is defined in
    the /usr/include/values.h header file.

    The atoi function converts the string pointed to by nptr to an integer.
    Processing stops when up to the first character inconsistent with the
    format of a decimal integer is encountered. Leading white-space charac-
    ters is ignored. This call is analogous to the following except that an
    integer is returned.

       strtol(str, (char **) NULL, 10)

    atoi and atol recognize strings of the form:

       [ +|- ] digits

    where the digits are contiguous decimal digits.  Any number of tabs and
    spaces may precede the string.  The ``+'' and ``-'' signs are optional.
    If the atoi routine fails due to overflow or underflow, errno is set to
    ERANGE.

    The atol function converts the string pointed to by nptr up to the first
    character inconsistent with the format of a decimal integer, ignoring
    leading white-space characters, to a long.  This call is analogous to:

       strtol(str, (char **) NULL, 10)

    If the atoi function fails due to overflow or underflow, errno is set to
    ERANGE.

 Note

    If a value cannot be represented, the behavior is undefined.

 See also

    scanf(S)

 Standards conformance

    atof, atoi and atol are conformant with:
    AT&T SVID Issue 2;
    X/Open Portability Guide, Issue 3, 1989;
    Intel386 Binary Compatibility Specification, Edition 2 (iBCSe2);
    and ANSI X3.159-1989 Programming Language -- C.