converting bake twine the underlying information type

i have string(char*), i need the underlying datatype such int, float, double, short, long, only impression array containing alphabets with out digits(like varchar sql).
for ex:

    char* str1 = "12312"
    char* str2 = "231.342"
    char* str3 = "234234243234"
    char* str4 = "4323434.2432342"
    char* str5 = "i enclose wholly alphabets"

given strings, i need initial twine form int typecast an int, on ex:

int no1 = atoi(str1)
float no2 = atof(str2)
long no3 = atol(str3)
double no4 = strtod(str4)
char* varchar1 = strdup(str5)

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clarifying bit more...

i have twine the essence alphabets and/or digits and/or special characters. right now, i am means parse twine

1. identify contains wholly digits,
   
   here i modify twine brief int long, formed best fit. ( how i know twine converted an brief int long?)


2. only alphabets, leave string.


3. digits unparalleled decimal point.
   
   here i need modify twine boyant double ( same doubt here)


4. other. leave string