Question

Consider the following simple C program that read a file into a buffer and displays that buffer to the console:

#include<stdio.h>  main() {   FILE *file;     char *buffer;     unsigned long fileLen;     //Open file     file = fopen('HelloWorld.txt', 'rb');     if (!file)     {         fprintf(stderr, 'Unable to open file %s', 'HelloWorld.txt');         return;     }     //Get file length     fseek(file, 0, SEEK_END);     fileLen=ftell(file);     fseek(file, 0, SEEK_SET);     //Allocate memory     buffer=(char *)malloc(fileLen+1);     if (!buffer)     {         fprintf(stderr, 'Memory error!');         fclose(file);         return;     }     //Read file contents into buffer     fread(buffer, fileLen, 1, file);     //Send buffer contents to stdout     printf('%s\n',buffer);         fclose(file); } 

The file it will read simply contains:

Hello World!

The output is:

Hello World!²²²²▌▌▌▌▌▌▌↔☺

It has been a while since I did anything significant in C/C++, but normally I would assume the buffer was being allocated larger than necessary, but this does not appear to be the case.

fileLen ends up being 12, which is accurate.

I am thinking now that I must just be displaying the buffer wrong, but I am not sure what I am doing wrong.

Can anyone clue me in to what I am doing wrong?

Answer 1

You need to NUL-terminate your string. Add

buffer[fileLen] = 0; 

before printing it.