A free command replacement for macOS that displays memory usage information similar to the Linux free command.

macOS doesn't include a free command like Linux. This utility provides a familiar interface for checking memory usage, using native macOS APIs to gather accurate memory statistics.

• Display total, used, free, and available memory
• Show swap usage
• Multiple output formats (bytes, KiB, MiB, GiB, human-readable)
• Wide mode showing all macOS memory categories (active, inactive, wired, compressed)
• Continuous monitoring with configurable refresh interval
• Compatible with common free command options

• macOS 10.12 or later
• Xcode Command Line Tools (xcode-select --install)

make

make debug

git clone https://github.com/techquestsdev/mac-free.git
cd mac-free

# Build and install
make
sudo make install

# or use Homebrew
brew install techquestsdev/tap/mac-free

Installing from source will add free command to /usr/local/bin/. You can specify a different prefix:

sudo make install PREFIX=/opt/local

free [options]

$ free
              total        used        free      shared  buff/cache   available
Mem:       16777216     8388608     2097152           0     6291456     8388608
Swap:       2097152      524288     1572864

Human-readable format:

$ free -h
               total         used         free       shared   buff/cache    available
Mem:          16.0Gi        8.0Gi        2.0Gi           0B        6.0Gi        8.0Gi
Swap:          2.0Gi      512.0Mi        1.5Gi

Wide output with all memory categories:

$ free -w -h
              total        used        free      active    inactive       wired  compressed   available
Mem:         16.0Gi       8.0Gi       2.0Gi       4.0Gi       2.0Gi       2.0Gi       1.0Gi       8.0Gi
Swap:         2.0Gi     512.0Mi       1.5Gi

Monitor memory every 2 seconds:

free -h -s 2

Monitor memory 5 times with 1 second interval:

free -h -s 1 -c 5

Show macOS memory pressure (real kernel signal):

$ free -h -P
              total        used        free      shared  buff/cache   available
Mem:         16.0Gi       8.0Gi       2.0Gi          0B       6.0Gi       8.0Gi
Swap:         2.0Gi     512.0Mi       1.5Gi
Pressure: normal (50% available)

Show totals:

$ free -h -t
              total        used        free      shared  buff/cache   available
Mem:         16.0Gi       8.0Gi       2.0Gi          0B       6.0Gi       8.0Gi
Swap:         2.0Gi     512.0Mi       1.5Gi
Total:       18.0Gi       8.5Gi       3.5Gi

This utility uses macOS - specific APIs to gather memory information:

• host_statistics64() - Retrieves VM statistics including page counts for different memory states
• sysctl() - Gets total physical memory and swap usage
• sysctlbyname("kern.memorystatus_vm_pressure_level") - Real kernel memory-pressure level (for -P)
• vm_page_size - System page size for converting page counts to bytes

• Used Memory = Active + Wired + Compressed
• Available Memory = Free + Inactive + Purgeable + Speculative (approximation, as macOS can reclaim these pages)
• Shared Memory = reported as 0; macOS has no cheap system-wide shared-memory counter (unlike Linux Shmem). Deriving a real value would require summing the shared footprint across every task (as top/libtop do).

1. buff/cache: On Linux, this shows buffer and cache memory separately. On macOS, we sum the reclaimable file cache: inactive + purgeable + speculative pages.

2. shared: Linux tracks shared memory segments (Shmem). macOS exposes no equivalent system-wide counter, so this is reported as 0 rather than a misleading approximation.

3. available: Both systems estimate available memory, but the calculation differs due to different memory management strategies.

4. Wide mode: Shows macOS-specific categories (compressed memory is unique to macOS).

5. Memory pressure (-P): macOS relieves memory pressure with an in-RAM compressor before it touches swap, so the Linux-style free/swap columns can look healthy while the system is actually thrashing. -P prints the real kernel signal (kern.memorystatus_vm_pressure_level — the same one Activity Monitor uses): normal, warning, or critical.

sudo make uninstall

Or manually:

sudo rm /usr/local/bin/free

Use sudo for installation:

sudo make install

This is expected.Activity Monitor may use slightly different calculations or update at different intervals.The values should be close but not identical.

macOS uses dynamic swap. If no swap file has been created yet, total swap may show as 0. Swap files are created on - demand in /private/var/vm/.

Contributions are welcome! Please feel free to submit issues or pull requests.

# Build with debug symbols
make debug

# Run tests
make test

# Clean build artifacts
make clean

MIT License - See LICENSE file for details.