如何在C中使用char数组创建字符串？

Question

I am an Android and Java developer and I am not much familiar with C language. As well as you know there is not a String type in C. All I want is getting chars, putting them into an char array and writing these characters as a string. How can I take the whole string which is a array of characters and put it into a variable? This is my code but it does not work properly. The log which I get is:

I/        ( 2234): *********PROPERTY = 180000€¾Ü    €¾Ü €¾ 

It should have been 180000.

int c;
char output[1000];
int count = 0;
char *property;
FILE *file;
file = fopen("/cache/lifetime.txt", "r");
LOGI("****************FILE OPEN*************");
if (file) {
    LOGI("*****************FILE OPENED************");
    while ((c = getc(file)) != EOF) {
        putchar(c);
        output[count] = c;
        ++count;
        LOGI("******C = %c", c);
    }
    property = output;
    LOGI("*********PROPERTY = %s", property);
    fclose(file);
}

Answer 1

What you are missing is a '\\0' . All strings in C are just a sequence of characters ending with a '\\0' .

So, once your loop

while ((c = getc(file)) != EOF)

is done, you can add the statement

output[count] = '\0'

---

Below modifications are needed if you intend to return the property variable outside the local function and if output is a variable local to the function.

In the above below line will need modification

property = output; 

You should allocate memory for property using malloc and then use strcpy to copy the string in output to property or do a strdup as suggested by Joachim in the comment.

Using strdup, the statement will be like below

property = strdup(output); 

Answer 2

Determine whether the number of characters is known at compile time or runtime, then allocate the array either statically or dynamically:

char some_property [N+1]; // statically allocate room for N characters + 1 null termination

// or alternatively, dynamic memory allocation:
char* property = malloc (count + 1);

Then copy the data into the new variable:

memcpy(some_string, output, count); 

some_string[count] = '\0'; // null terminate

...
free(property); // clean up, if you used dynamic memory (and only then)

Or simply use the "output" variable already in place, by adding a null termination at the end of the input.