问题
When using atoi in C I am trying to convert a char array of numbers to an int. I have leading 0's on my number though and they are not preserved when I print the number out later.
char num[] = "00905607";
int number;
number = atoi(num);
printf("%d", number);
The output from this will be 905607 and I would like it to be 00905607.
Any ideas?
回答1:
Use strtol instead. It allows you to specify the base.
回答2:
You can do padding on your printf() so if you wanted every output to be 8 characters long you would use
printf("%08d", number);
回答3:
That code is working properly, if it works at all. The integer is 905607... leading zeros don't exist in a mathematical sense.
You have a lot of issues with that code. You're declaring your string improperly, and you're not printing the converted number. Also, if you were doing printf(number); you'd need to use a format string. If you'd like to have leading spaces in that, you can use a width specifier.
回答4:
Don't use atoi. Use strtol with a base of 10.
In general, there's no reason to use atoi in modern code.
回答5:
Yes, when you want to display ints you have to format them as strings again. An integer is just a number, it doesn't contain any information on how to display it. Luckily, the printf-function already contains this, so that would be something like
printf( "%08d", num);
回答6:
Most answers assume you want 8 digits while this is not exactly what you requested.
If you want to keep the number of leading zeros, you're probably better keeping it as a string, and convert it with strtol for calculations.
回答7:
You could use sscanf, and provide '%d' as your format string.
回答8:
If you don't want that behavior; don't use atoi.
Perhaps sscanf with a %d format?
回答9:
You could also count the numbers of numbers in the string and create a new one with leading zeroes.
Or check out all the wonderful format tags for printf and use one to pad with zeroes. Here for example are lot of them: http://www.cplusplus.com/reference/clibrary/cstdio/printf/
来源：https://stackoverflow.com/questions/4694926/atoi-and-leading-0s-for-decimal-numbers