Getting memory statistics from command line in MacOS

Getting memory statistics in MacOS from the command line is surprisingly difficult. Especially if you want to get the same information as provided by Activity Monitor.

Below is the script which I made after digging through lots of online forums, examples, support threads etc.

Compatibility

Manually tested on MacOS Monterey and MacOS Ventura

Code

⬇️ download

#!/bin/zsh
if [ ! $(command -v numfmt) ]; then
  echo "coreutils not installed. Please install it:\n\n    brew install coreutils\n" && exit 1
fi

VM_STAT=$(vm_stat | grep --ignore-case "pages")
PAGE_SIZE_BYTES=$(vm_stat | head -n 1 | grep -oE "[0-9]+")

function pages_to_bytes() {
    echo "$(($1 * PAGE_SIZE_BYTES))"
}

function bytes_to_human_readable() {
    echo "$1" | numfmt --to iec
}

function get_vm_stat_value_bytes() {
    pages_to_bytes "$(echo "$VM_STAT" | grep "$1" | grep -oE "[0-9]+")"
}

TOTAL_BYTES=$(sysctl hw.memsize | grep -oE "[0-9]+")

SWAP_USAGE_MB=$(sysctl vm.swapusage | grep -oE "used = [0-9,.]+." | grep -oE "[0-9]+" | head -n 1)
SWAP_USAGE_BYTES="$((SWAP_USAGE_MB * 1024))"

PAGEABLE_PAGES=$(sysctl vm.page_pageable_internal_count | grep -oE "[0-9]+")
PAGEABLE_BYTES=$(pages_to_bytes "$PAGEABLE_PAGES")

PURGEABLE_BYTES=$(get_vm_stat_value_bytes "Pages purgeable")

APP_MEMORY_BYTES=$((PAGEABLE_BYTES - PURGEABLE_BYTES))

WIRED_BYTES=$(get_vm_stat_value_bytes "Pages wired")
COMPRESSED_BYTES=$(get_vm_stat_value_bytes "Pages occupied by compressor")

USED_BYTES=$((APP_MEMORY_BYTES + WIRED_BYTES + COMPRESSED_BYTES))

FILE_BYTES=$(get_vm_stat_value_bytes "File-backed pages")

echo "Total memory: $(bytes_to_human_readable "$TOTAL_BYTES")"
echo "Used memory: $(bytes_to_human_readable "$USED_BYTES")"
echo " - App memory: $(bytes_to_human_readable "$APP_MEMORY_BYTES")"
echo " - Wired memory: $(bytes_to_human_readable "$WIRED_BYTES")"
echo " - Compressed memory: $(bytes_to_human_readable "$COMPRESSED_BYTES")"
echo "File-backed: $(bytes_to_human_readable "$FILE_BYTES")"
echo "Swap usage: $(bytes_to_human_readable "$SWAP_USAGE_BYTES")"

Sample output:

Total memory: 32G
Used memory: 24G
 - App memory: 17G
 - Wired memory: 5.0G
 - Compressed memory: 2.1G
File-backed: 7.5G
Swap usage: 659K

Correctness

I do not guarantee the response is 100% correct!

On my machine running MacOS Monterey, during my manual tests, the data correctness is as follows:

Gauge	Correctness
Total memory	100%
Used memory	96%
App memory	99%
Wired memory	97%
Compressed memory	100%
File-backed	66%
Swap usage	100%

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