Problems with fopen function on Mac

c, c++, fopen, macos

Solution

When you run `fopen` without full path, it uses the current working directory of the location where you ran the program from. So if your working directory (obtained by typing `pwd` in shell) where you execute your program from is `~/my_folder/` and `file.txt` happens to be in `~/my_folder/bin/` then even if your executable is inside `~/my_folder/bin/` it won't find `file.txt`. Because it will be looking for `~/my_folder/file.txt`.

So if you are running your program from a different directory than that of file.txt then you either have to provide absolute path or provide a path relative to the directory that you are running your program from.

For info on working directory see http://www.linfo.org/current_directory.html

Update

One workaround that can be used if you have access to the string array argument (`argv[]`) of `main` method. The first element of argv will contain the path (from working directory) that was used to execute your program. Following simple program simple prints that argument.

int main(int argc, char *argv[])
{
  printf("Path relative to the working directory is: %s\n", argv[0]);
  return 0;
}

This will print the relative path including the executable name. You can replace executable name with `file.txt` if that file is in the same location as executable. This way it will load in both scenarios: when run by double-clicking and also when run from command line by navigating to the location of the executable.

You may also have to take into account the possible `./` at the beginning of `argv[0]`. Hope it helps :)

Problem

I'm making a simple application on Mac (OSX Mavericks, compiling with clang). The problem is that when I try to open a file using the relative path, it doesn't work. It works if I use the absolute path. For example, if I try : `fp = fopen("file.txt", "r");` It returns `NULL`. It only works if I use: `fp = fopen(" User/UserName/Project_folder/file.txt", "r");` (project folder is the folder that I'm compiling in, and it has my file.txt) The file is in the exactly same directory. How I can solve this? Also the same code has worked well some time ago, and now this and other code that uses the `fopen` show the same problem.

Original source