strtol

来源： https://stackoverflow.com/questions/63537391/strtoll-not-setting-errno-to-erange-upon-overflow

来源： https://stackoverflow.com/questions/63537391/strtoll-not-setting-errno-to-erange-upon-overflow

来源： https://stackoverflow.com/questions/2024648/convert-a-string-to-int-but-only-if-really-is-an-int

问题 I can use the strtol function for turning a base36 based value (saved as a string) into a long int : long int val = strtol("ABCZX123", 0, 36); Is there a standard function that allows the inversion of this? That is, to convert a long int val variable into a base36 string, to obtain "ABCZX123" again? 回答1: There's no standard function for this. You'll need to write your own one. Usage example: https://godbolt.org/z/MhRcNA const char digits[] =

问题 I've been trying to properly convert a char array to a long with strtol , check if there was an overflow or underflow and then do an int cast on the long. Along the way, I've noticed a lot of code that looks like this if ((result == LONG_MAX || result == LONG_MIN) && errno == ERANGE) { // Handle the error } Why can you not just say if(errno == ERANGE) { // Handle the error } From my understanding, if an underflow or overflow occur, errno is set to ERANGE in both cases. So is the former really

问题 This code seems to work as expected, populates an array of numbers using a single pointer #include <stdio.h> #include <ctype.h> #include <stdlib.h> int main(void) { int arr[4], count = 0, i; char *p, s[32] = " \t 10, 15 \n ,20, 25 , "; p = s; do { arr[count++] = (int)strtol(p, &p, 10); while (isspace(*p) || *p == ',') p++; } while (*p); for (i = 0; i < count; i++) { printf("%d\n", arr[i]); } return 0; } My question is: It is valid to use p as param1 (source) and &p as param 2 (address of the

问题 How does the second argument of strtol work? Here is what I tried: strtol(str, &ptr, 10) where ptr is a char * and str is a string. Now, If I pass in str as '34EF' , and print *ptr , it correctly gives me E , and *(ptr+1) gives me F , however if I print ptr , it gives me EF! Shouldn't printing ptr just result in a rubbish value like a hex address or something? 回答1: ptr is a pointer to the interior of a null terminated string. So given "34EF" it ends up pointing to the character 'E' and the

问题 What is the difference between atol() & strtol()? According to their man pages, they seem to have the same effect as well as matching arguments: long atol(const char *nptr); long int strtol(const char *nptr, char **endptr, int base); In a generalized case, when I don't want to use the base argument (I just have decimal numbers), which function should I use? 回答1: strtol provides you with more flexibility, as it can actually tell you if the whole string was converted to an integer or not. atol

问题 This question already has answers here : Keep Leading zeros C (2 answers) keeping leading zeros in C [duplicate] (3 answers) Closed last year . I am wondering as to why when converting strings to int with either atoi or strtol it does not print the number 0 if its the first index, take this code for example char s[] = "0929784"; long temp = strtol(s, NULL, 10); printf("%li", temp); OUTPUT: 929784 is there a way to have the 0 print? 回答1: Use char s[] = "0929784"; size_t len = strlen(s); long

问题 I am new to programming and to C in general and am currently studying it at university. This is for an assignment so I would like to avoid direct answers but are more after tips or hints/pushes in the right direction. I am trying to use strtol to validate my keyboard input, more specifically, test whether the input is numeric. I have looked over other questions on here and other sites and I have followed instructions given to other users but it hasn't helped me. From what I have read/