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copied!<p>Consider the following cut-down example. You'll notice that the <code>getFileLength</code> function (a) doesn't actually read anything from the file and (b) makes use of the <code>fseek</code> and <code>ftell</code> functions - fseek is the function that you use to reposition the file-pointer when it reaches EOF.</p> <p>Imagine that you weren't printing the data, but doing something else with it. What if the file is a billion bytes long? We sure don't want to read 1,000,000,000 times from it just to determine its length!</p> <p>As for the use of calloc - it zero initializes the data it allocates. Since you're reading text, you want to ensure that the text is NULL-terminated. (NULL generally = 0, though I've seen evil macros that change this) This NULL terminator is also why I allocate 1 byte more than the file contains.</p> <pre><code>#include <stdio.h> #include <stdlib.h> long getFileLength(FILE *input) { long result; long origPos = ftell(input); fseek(input, 0, SEEK_END); result = ftell(input); fseek(input, origPos, SEEK_SET); return result; } int main (void) { FILE *fp; long fileLen, numBytesRead; char *data; fp = fopen("main.cpp", "rb"); fileLen = getFileLength(fp); data = (char*)calloc(sizeof(char), fileLen+1); numBytesRead = fread(data, sizeof(char), fileLen, fp); if (numBytesRead != fileLen) printf("Error reading all bytes from file. Expected: %d, Read %d\n", fileLen, numBytesRead); else printf("%s", data); free(data); fclose(fp); } </code></pre>

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