How can we convert a string to int for very large integer values?

Question

I have used the function atoi to convert character strings to int and it\'s working fine but when I gave

num = atoi (argv[1]) ;

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Answer 1

You can use strtoull for very long numbers.

unsigned long long int strtoull(const char *nptr, char **endptr,
                                       int base);

Compile with C99 support -std=c99 or provide the defines in man strtoull to get the definition.