在char数组中存储多个整数

Question

I've been looking online for a few hours to find this, but haven't found anything yet that's exactly what I need. I have multiple integers that I need to put into a char* (separated by a space) to be later written to a .txt file. My best attempt until now has been this:

char* temp = (char)input.Z_pos_Camera_Temperature;

Where input.Z_pos_Camera_Temperature is a member of a struct. I tried

char* temp = (char)input.Z_pos_Camera_Temperature + ' ' + input.Z_neg_Camera_Temperature;

but that only added the values of the three chars individually. Can someone help me figure this out?

Answer 1

In C, you cannot concatenate characters into a string using the + operator like you can in higher level languages, nor can you concatenate several strings into a larger, separate string using the + operator.

You can, however, use the function sprintf to build a string, like so:

char buffer[100]; // adjust per your needs
sprintf(buffer, "%d %d", input.Z_pos_Camera_Temperature, input.Z_neg_Camera_Temperature);

Answer 2

您可能要使用snprintf。

char buf[32]; snprintf(buf, 32, "%d %d", input.Z_pos_Camera_Temperature, input.Z_neg_Camera_Temperature);

Answer 3

This isn't really intended as an answer because you have already got that. I'm posting to help you understand what you tried actually does. Looking at the first sample:

char* temp = (char)input.Z_pos_Camera_Temperature;

First of all, you should have gotten a warning when you compiled this line. Something like:

warning C4047: 'initializing': 'char *' differs in levels of indirection from 'char'

This is an indication that something bad is going on. So what happens when this line is executed?

If input.Z_pos_Camera_Temperature has a value of 32, the 4-byte integer is truncated to 1 byte by your cast to char and assigned to the char* temp . temp now contains the address 0x00000020.

If input.Z_pos_Camera_Temperature is 450 (maybe the camera is in an oven?) the value would be truncated to from 0x000001C2 to 0xC2, sign extended when assigned, and `temp' would now contain the address 0xffffffC2;

The second attempt is the same except that there is integer addition before the cast and assignment:

char* temp = (char)450 + 32 + -5; // NOTE: the 32 here is the ASCII value for ' '

Answer 4

另一个选择是使用来自string.h lib的strcat函数。

Answer 5

You have to make the char* large enough to be able to store all the numbers. Then you can use something like the following in order to convert the number to string:

int n[10] = {1, 2, 3, 4, 5888, 6, 7, 8, 9, 10};
char final[1000]; //adjust to acoomodate all the digits and spaces
int len = 0;
for (int i = 0; i < 10; i++) {
    char str[64];
    sprintf(str, "%d", n[i]);
    strcpy(final + len, str); //copy the ith number 
    len += strlen(str); //take a note of the number of digits used
    final[len] = ' '; //add a space
    len++;

}
final[len] = '\0'; //terminate the string

Try online