Edit: In c++17 or later from_chars is preferred. See here for more: https://topanswers.xyz/cplusplus?q=724#a839 For a given string str there are several ways to accomplish this each with advantages and disadvantages. I’ve written a live example here: https://ideone.com/LO2Qnq and discuss each below: strtol As suggested here strtol‘s out-parameter can be used to get the number of … Read more
It means Ascii to Integer. Likewise, you can have atol for Ascii to Long, atof for Ascii to Float, etc. A Google search for ‘atoi “ascii to integer”‘ confirms this on several pages. I’m having trouble finding any official source on it… but in this listing of man pages from Third Edition Unix (1973) collected … Read more
atoi() converts a string representation of an integer into its value. It will not convert arbitrary characters into their decimal value. For instance: int main(void) { const char *string=”12345″; printf(“The value of %s is %d\n”, string, atoi(string)); return 0; } There’s nothing in the standard C library that will convert “A” to 65 or “Z” … Read more
1). Are there any other differences between the two? I find std::atoi() a horrible function: It returns zero on error. If you consider zero as a valid input, then you cannot tell whether there was an error during the conversion or the input was zero. That’s just bad. See for example How do I tell … Read more
The proper function (as long as you are insisting on using C-style functions) is strtol and the conversion code might look as follows const char *number = “10”; /* for example */ char *end; long value = strtol(number, &end, 10); if (end == number || *end != ‘\0’ || errno == ERANGE) /* ERROR, abort … Read more
That’s one of the reasons atoi is sometimes considered unsafe. Use strtol / strtoul instead. And if you have it use strtonum. The function atoi is more dangerous than you might think. The POSIX standard says: If the value cannot be represented, the behavior is undefined. The C99 standard says this also: 7.20.1 The functions … Read more
You have 3 choices: atoi This is probably the fastest if you’re using it in performance-critical code, but it does no error reporting. If the string does not begin with an integer, it will return 0. If the string contains junk after the integer, it will convert the initial part and ignore the rest. If … Read more
There is strtol which is better IMO. Also I have taken a liking in strtonum, so use it if you have it (but remember it’s not portable): long long strtonum(const char *nptr, long long minval, long long maxval, const char **errstr); You might also be interested in strtoumax and strtoimax which are standard functions in … Read more