cwd vs exe mode

dir-cpu can attribute CPU usage to a process in two ways. Choosing the right one depends on what you're trying to monitor.

The fundamental problem

The OS identifies processes by PID, not by project. A single python3 process running your web app and another python3 process running an unrelated cron job look identical by name. dir-cpu solves this by using the filesystem path instead.

But there are two paths that could represent a process:

• Where it's running from — the working directory (cwd)
• What binary is running — the executable path (exe)

These are different, and each has a different sweet spot.

cwd mode (default)

Path used: /proc/[pid]/cwd

This is the directory the process was launched from — typically the project root when you run python app.py or node server.js from a terminal.

/home/user/projects/myapp$ python app.py

In this case cwd = /home/user/projects/myapp, which is exactly where you want the cost attributed.

Best for:

• Python scripts
• Node.js apps
• Ruby, PHP, shell scripts
• Any interpreted language where the binary (/usr/bin/python3) is shared but the project directory distinguishes them

Limitation:
If a process changes its working directory after startup (e.g., a daemon that does chdir("/") on launch), the initial project context is lost. System daemons often do this.

exe mode

Path used: /proc/[pid]/exe

This is the path to the actual binary being executed — resolved through the symlink in /proc.

/usr/local/bin/myapp
/home/user/go/bin/server
/opt/app/bin/worker

Best for:

• Compiled Go, Rust, C, C++ programs
• Binaries installed to a specific project or environment path
• Identifying processes by where their binary lives, not where they were launched

Limitation:
For interpreted languages (/usr/bin/python3, /usr/bin/node), all Python or Node processes roll up to /usr/bin — completely losing project context. Use cwd instead.

Side-by-side comparison

Scenario	Recommended mode
Python/Node/Ruby project	cwd
Go/Rust/C binary	exe
Mix of both	Run two terminals with each mode
Daemon monitoring	exe (daemons often chdir /)
Security scan for rogue processes	exe (surfaces unusual binary locations)
Monorepo with multiple services	cwd

Example: monorepo

/home/user/monorepo/
  frontend/    ← npm dev server
  backend/     ← go run .
  worker/      ← python worker.py

With cwd mode, each service costs roll up correctly to their subdirectory and then aggregate at /home/user/monorepo.

With exe mode, the frontend rolls to /home/user/.nvm/..., the backend to /home/user/go/bin/..., and the worker to /usr/bin/ — the monorepo structure is invisible.

Mixing both modes

There's no combined mode, but you can run two instances in split panes:

# pane 1
dir-cpu -base=cwd

# pane 2
dir-cpu -base=exe