<p>How can I find out the size of a file I opened with an application written in C ? 
I would like to know the size, because I want to put the content of the loaded file into a string, which I allocate using <code>malloc()</code>. Just writing <code>malloc(10000*sizeof(char));</code> is IMHO a bad idea. </p>

You need to seek to the end of the file and then ask for the position:
```
```
fseek(fp, 0L, SEEK_END);
sz = ftell(fp);
```
```
You can then seek back, e.g.:
```
```
fseek(fp, 0L, SEEK_SET);
```
```
or (if seeking to go to the beginning)
```
```
rewind(fp);
```
```