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Programming-Idioms

  • C
  • Haskell

Idiom #107 Get folder containing current program

Assign to string dir the path of the folder containing the currently running executable.
(This is not necessarily the working directory, though.)

import System.Environment (getExecutablePath)
import System.FilePath.Windows
import System.IO.Unsafe (unsafePerformIO)
dir = unsafePerformIO (takeDirectory `fmap` getExecutablePath)

This uses unsafePerformIO which I assume to be safely used here because the executable path can be considered as constant.
import System.Environment (getExecutablePath)
import System.FilePath.Windows
dir <- takeDirectory `fmap` getExecutablePath

This uses the IO monad.
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <linux/limits.h>
#include <libgen.h>

int main()
{
    char exe[PATH_MAX], real_exe[PATH_MAX];
    ssize_t r;
    char *dir;

    if ((r = readlink("/proc/self/exe", exe, PATH_MAX)) < 0)
      exit(1);
    if (r == PATH_MAX)
	r -= 1;
    exe[r] = 0;
    if (realpath(exe, real_exe) == NULL)
	exit(1);
    dir = dirname(real_exe);
    puts(dir);
}

If the executable file that the current process is executing can be found searching $PATH, this is easier, but the general case can still be handled by examining where the symlink file /proc/self/exe points to.
dir = AppDomain.CurrentDomain.BaseDirectory;
New implementation...
< > ⌨
programming-idioms.org 
dir = unsafePerformIO (takeDirectory `fmap` getExecutablePath)
dir <- takeDirectory `fmap` getExecutablePath
int main()
{
    char exe[PATH_MAX], real_exe[PATH_MAX];
    ssize_t r;
    char *dir;

    if ((r = readlink("/proc/self/exe", exe, PATH_MAX)) < 0)
      exit(1);
    if (r == PATH_MAX)
	r -= 1;
    exe[r] = 0;
    if (realpath(exe, real_exe) == NULL)
	exit(1);
    dir = dirname(real_exe);
    puts(dir);
}

dir = AppDomain.CurrentDomain.BaseDirectory;

void main(string[] args) {
    string dir = args[0].dirName;
}
programPath := os.Args[0]
absolutePath, err := filepath.Abs(programPath)
if err != nil {
	return err
}
dir := filepath.Dir(absolutePath)
const dir = __dirname;
const dir = path.resolve();
dir = arg[1]
$dir = realpath(dirname(__FILE__));
dir := extractfilepath(paramstr(0));
dir := GetCurrentDir;
my $dir = path($EXECUTABLE_NAME)->parent;

dir = os.path.dirname(os.path.abspath(__file__))
dir = str(Path(__file__).parent)
dir = __dir__
let dir = std::env::current_exe()?
    .canonicalize()
    .expect("the current exe should exist")
    .parent()
    .expect("the current exe should be a file")
    .to_string_lossy()
    .to_owned();