Command Line Interface

Install the memlab command line tool with npm:

npm install -g memlab

COMMON Commands

memlab run

Find memory leaks in web apps

memlab run --scenario <TEST_SCENARIO_FILE>

examples

memlab run --scenario /tmp/test-scenario.js
memlab run --scenario /tmp/test-scenario.js --work-dir /tmp/test-1/

Options:

• --work-dir: set the working directory of the current run
• --headful: start the browser in headful mode, by default it is headless
• --full: take heap snapshot for every step in E2E interaction
• --skip-screenshot: skip taking screenshots
• --skip-gc: skip doing garbage collection in browser
• --skip-scroll: skip scrolling target page in browser
• --skip-extra-ops: skip doing extra interactions (e.g., scrolling and waiting) on target and final page
• --local-puppeteer: enable remote browser instance debugging via local puppeteer
• --scenario: set file path loading test scenario
• --chromium-binary: set the chromium binary for E2E run
• --protocol-timeout: set the protocol timeout for chromium connection (in ms). The current default value is 180000, you may want to increase the timeout via this flag when the heap snapshot is too big (e.g., over 1GB) and the Page crashed with error: 'ProtocolError: HeapProfiler.takeHeapSnapshot timed out'.
• --device: set the device type to emulate
• --user-agent: set the UserAgent string in browser (for E2E interaction), otherwise it uses the default UserAgent from Chromium
• --disable-xvfb: disable Xvfb (X virtual framebuffer) for simulating headful browser rendering
• --disable-web-security: disable web security in Chromium to enable cross domain requests; web security is enabled by default
• --rewrite-js: enable instrument JavaScript code in browser
• --log-script: enable intercepting and logging JavaScript code in browser
• --worker: set title of the target (worker) that needs to be selected and analyzed
• --leak-filter: specify a definition JS file for leak filter
• --trace-object-size-above: objects with retained size (bytes) bigger than the threshold will be considered as leaks
• --ignore-leak-cluster-size-below: ignore memory leaks with aggregated retained size smaller than the threshold (in bytes)
• --trace-all-objects: dump retainer trace for all allocated objects (ignore the leak filter), available option modes: --trace-all-objects=selected-js-objects, --trace-all-objects=default
• --save-trace-as-unclassified-cluster: dump each retainer trace as an unclassified trace cluster
• --ml-clustering: use machine learning algorithms for clustering leak traces (by default, traces are clustered by heuristics)
• --ml-linkage-max-dist: set linkage max distance value for clustering. The value should be between [0, 1] inclusive.
• --ml-clustering-max-df: set percentage based max document frequency for limiting the terms that appear too often
• --clean-up-snapshot: clean up heap snapshots after running
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab find-leaks

Find memory leaks in heap snapshots

There are three ways to specify inputs for the memlab find-leaks command:

1. --baseline, --target, --final specifies each heap snapshot input individually;
2. --snapshot-dir specifies the directory that holds all three heap snapshot files (MemLab will assign baseline, target, and final based on alphabetic order of the file);
3. --work-dir specifies the output working directory of the memlab run or the memlab snapshot command;

Please only use one of the three ways to specify the input.

You can also manually take heap snapshots in Chrome Devtools, save them to disk. Then process them using this command with the CLI flags (either option 1 or option 2 mentioned above).

# check memory leaks in the default working directory generated by
# memlab run (without setting the --work-dir option)
memlab find-leaks 

examples

# specify the baseline, target, and final heap snapshot file path separately
memlab find-leaks --baseline /tmp/baseline.heapsnapshot --target /tmp/target.heapsnapshot --final /tmp/final.heapsnapshot
# specifies the directory that holds all three heap snapshot files
memlab find-leaks --snapshot-dir /dir/containing/heapsnapshot/files/
# specifies the output working directory of the `memlab run` or the `memlab snapshot` command
memlab find-leaks --work-dir /memlab/working/dir/generated/by/memlab/

Options:

• --baseline: set file path of the baseline heap snapshot
• --target: set file path of the target heap snapshot
• --final: set file path of the final heap snapshot
• --snapshot-dir: set directory path containing all heap snapshots under analysis
• --engine: set the JavaScript engine (default to V8)
• --leak-filter: specify a definition JS file for leak filter
• --trace-object-size-above: objects with retained size (bytes) bigger than the threshold will be considered as leaks
• --ignore-leak-cluster-size-below: ignore memory leaks with aggregated retained size smaller than the threshold (in bytes)
• --trace-all-objects: dump retainer trace for all allocated objects (ignore the leak filter), available option modes: --trace-all-objects=selected-js-objects, --trace-all-objects=default
• --save-trace-as-unclassified-cluster: dump each retainer trace as an unclassified trace cluster
• --ml-clustering: use machine learning algorithms for clustering leak traces (by default, traces are clustered by heuristics)
• --ml-linkage-max-dist: set linkage max distance value for clustering. The value should be between [0, 1] inclusive.
• --ml-clustering-max-df: set percentage based max document frequency for limiting the terms that appear too often
• --clean-up-snapshot: clean up heap snapshots after running
• --work-dir: set the working directory of the current run
• --heap-parser-dict-fast-store-size: the size threshold for swtiching from fast store to slower store in the heap snapshot parser. The default value is 5,000,000. If you get the FATAL ERROR: invalid table size Allocation failed - JavaScript heap out of memory error, try to decrease the threshold here
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab diff-leaks

Find new memory leaks by diffing control and test heap snapshots

memlab diff-leaks 

Options:

• --control-snapshot: set the single (target) snapshot of control run
• --control-work-dir: set the working directory of the control run
• --treatment-snapshot: set the single (target) snapshot of treatment run
• --treatment-work-dir: set the working directory of the treatment run
• --engine: set the JavaScript engine (default to V8)
• --leak-filter: specify a definition JS file for leak filter
• --trace-object-size-above: objects with retained size (bytes) bigger than the threshold will be considered as leaks
• --ignore-leak-cluster-size-below: ignore memory leaks with aggregated retained size smaller than the threshold (in bytes)
• --trace-all-objects: dump retainer trace for all allocated objects (ignore the leak filter), available option modes: --trace-all-objects=selected-js-objects, --trace-all-objects=default
• --save-trace-as-unclassified-cluster: dump each retainer trace as an unclassified trace cluster
• --ml-clustering: use machine learning algorithms for clustering leak traces (by default, traces are clustered by heuristics)
• --ml-linkage-max-dist: set linkage max distance value for clustering. The value should be between [0, 1] inclusive.
• --ml-clustering-max-df: set percentage based max document frequency for limiting the terms that appear too often
• --max-cluster-sample-size: specify the max number of leak traces as input to leak trace clustering algorithm. Big sample size will preserve more complete inforrmation, but may risk out-of-memory crash.
• --trace-contains: set the node name or edge name to filter leak traces that contain the name
• --heap-parser-dict-fast-store-size: the size threshold for swtiching from fast store to slower store in the heap snapshot parser. The default value is 5,000,000. If you get the FATAL ERROR: invalid table size Allocation failed - JavaScript heap out of memory error, try to decrease the threshold here
• --work-dir: set the working directory of the current run
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab trace

Report retainer trace of a specific node, use with --nodeId

memlab trace --node-id=<HEAP_OBJECT_ID>

examples

memlab trace --node-id=@3123123
memlab trace --node-id=128127

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --snapshot-dir: set directory path containing all heap snapshots under analysis
• --engine: set the JavaScript engine (default to V8)
• --node-id: set heap node ID
• --heap-parser-dict-fast-store-size: the size threshold for swtiching from fast store to slower store in the heap snapshot parser. The default value is 5,000,000. If you get the FATAL ERROR: invalid table size Allocation failed - JavaScript heap out of memory error, try to decrease the threshold here
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze

Run heap analysis on heap snapshots.

memlab analyze <PLUGIN_NAME> [PLUGIN_OPTIONS]

Options:

• --analysis-plugin: specify the external heap analysis plugin file (must be a vanilla JS file ended with Analysis.js suffix)
• --heap-parser-dict-fast-store-size: the size threshold for swtiching from fast store to slower store in the heap snapshot parser. The default value is 5,000,000. If you get the FATAL ERROR: invalid table size Allocation failed - JavaScript heap out of memory error, try to decrease the threshold here
• --work-dir: set the working directory of the current run
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze unbound-collection

Check unbound collection growth (e.g., Map with growing number of entries)

memlab analyze unbound-collection 

Options:

• --snapshot-dir: set directory path containing all heap snapshots under analysis
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze collections-with-stale

Analyze collections holding stale objects

memlab analyze collections-with-stale 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --output: specify output format of the analysis (defaults to text)
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze detached-DOM

Get detached DOM elements

memlab analyze detached-DOM 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --output: specify output format of the analysis (defaults to text)
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze global-variable

Get global variables in heap

memlab analyze global-variable 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --output: specify output format of the analysis (defaults to text)
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze object

Get properties inside an object

memlab analyze object 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --node-id: set heap node ID
• --output: specify output format of the analysis (defaults to text)
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze object-fanout

Get objects with the most out-going references in heap

memlab analyze object-fanout 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --output: specify output format of the analysis (defaults to text)
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze object-shallow

Get objects by key and value, without recursing into sub-objects

memlab analyze object-shallow 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze shape

List the shapes that retained most memory

memlab analyze shape 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze object-size

Get the largest objects in heap

memlab analyze object-size 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --output: specify output format of the analysis (defaults to text)
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze unbound-object

Check unbound object growth (a single object with growing retained size)

memlab analyze unbound-object 

Options:

• --snapshot-dir: set directory path containing all heap snapshots under analysis
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze react-hooks

Show a memory breakdown of the most memory-consuming React components and their React hooks. This works best with unminified heap snapshots taken from React apps running in Dev mode. But also supports minified heap snapshots taken from React apps in production mode.

memlab analyze react-hooks 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze unbound-shape

Get shapes with unbound growth (a class of objects with growing aggregated retained size)

memlab analyze unbound-shape 

Options:

• --snapshot-dir: set directory path containing all heap snapshots under analysis
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze string

Find duplicated string instances in heap

memlab analyze string 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab analyze unmounted-fiber-node

Get unmounted React Fiber nodes

memlab analyze unmounted-fiber-node 

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --output: specify output format of the analysis (defaults to text)
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab heap

Interactive command to explore a single heap snapshot

memlab heap --snapshot <HEAP_SNAPSHOT_FILE>

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --engine: set the JavaScript engine (default to V8)
• --heap-parser-dict-fast-store-size: the size threshold for swtiching from fast store to slower store in the heap snapshot parser. The default value is 5,000,000. If you get the FATAL ERROR: invalid table size Allocation failed - JavaScript heap out of memory error, try to decrease the threshold here
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab view-heap

Interactive command to view a single heap snapshot

memlab view-heap --snapshot <HEAP_SNAPSHOT_FILE>

Options:

• --snapshot: set file path of the heap snapshot under analysis
• --engine: set the JavaScript engine (default to V8)
• --node-id: set heap node ID
• --ml-clustering: use machine learning algorithms for clustering leak traces (by default, traces are clustered by heuristics)
• --work-dir: set the working directory of the current run
• --heap-parser-dict-fast-store-size: the size threshold for swtiching from fast store to slower store in the heap snapshot parser. The default value is 5,000,000. If you get the FATAL ERROR: invalid table size Allocation failed - JavaScript heap out of memory error, try to decrease the threshold here
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

MISC Commands

memlab version

Show the versions of all memlab packages installed

memlab version 

Options:

• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab list

List all test scenarios

memlab list 

Options:

• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab reset

Reset and initialize all directories

memlab reset 

Options:

• --work-dir: set the working directory of the current run
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab measure

Run test scenario in measure mode

In some web apps, the heap size can show considerable variability across various runs. This fluctuation can often make it hard to understand the impact of memory leaks. The introduction of the measure mode aims to address this challenge by executing the same scenario repetitively, therefore getting multiple data points of JavaScript heap sizes. This can help understand if the heap size movements during specific runs come from memory-related issues or just noise.

memlab measure --scenario <TEST_SCENARIO_FILE>

examples

memlab measure --scenario /tmp/test-scenario.js
memlab measure --scenario /tmp/test-scenario.js --work-dir /tmp/test-1/

Options:

• --headful: start the browser in headful mode, by default it is headless
• --run-num: set number of runs
• --app: set name for onboarded web application
• --interaction: set name for onboarded interaction
• --full: take heap snapshot for every step in E2E interaction
• --skip-snapshot: skip taking heap snapshots
• --skip-screenshot: skip taking screenshots
• --skip-gc: skip doing garbage collection in browser
• --skip-scroll: skip scrolling target page in browser
• --skip-extra-ops: skip doing extra interactions (e.g., scrolling and waiting) on target and final page
• --run-mode: set running mode
• --local-puppeteer: enable remote browser instance debugging via local puppeteer
• --scenario: set file path loading test scenario
• --chromium-binary: set the chromium binary for E2E run
• --protocol-timeout: set the protocol timeout for chromium connection (in ms). The current default value is 180000, you may want to increase the timeout via this flag when the heap snapshot is too big (e.g., over 1GB) and the Page crashed with error: 'ProtocolError: HeapProfiler.takeHeapSnapshot timed out'.
• --device: set the device type to emulate
• --user-agent: set the UserAgent string in browser (for E2E interaction), otherwise it uses the default UserAgent from Chromium
• --disable-xvfb: disable Xvfb (X virtual framebuffer) for simulating headful browser rendering
• --disable-web-security: disable web security in Chromium to enable cross domain requests; web security is enabled by default
• --rewrite-js: enable instrument JavaScript code in browser
• --log-script: enable intercepting and logging JavaScript code in browser
• --work-dir: set the working directory of the current run
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab warmup

Warm up the target app

memlab warmup --scenario <TEST_SCENARIO_FILE>

examples

memlab warmup --scenario /tmp/test-scenario.js

Options:

• --headful: start the browser in headful mode, by default it is headless
• --app: set name for onboarded web application
• --interaction: set name for onboarded interaction
• --run-mode: set running mode
• --local-puppeteer: enable remote browser instance debugging via local puppeteer
• --scenario: set file path loading test scenario
• --chromium-binary: set the chromium binary for E2E run
• --protocol-timeout: set the protocol timeout for chromium connection (in ms). The current default value is 180000, you may want to increase the timeout via this flag when the heap snapshot is too big (e.g., over 1GB) and the Page crashed with error: 'ProtocolError: HeapProfiler.takeHeapSnapshot timed out'.
• --device: set the device type to emulate
• --user-agent: set the UserAgent string in browser (for E2E interaction), otherwise it uses the default UserAgent from Chromium
• --disable-xvfb: disable Xvfb (X virtual framebuffer) for simulating headful browser rendering
• --disable-web-security: disable web security in Chromium to enable cross domain requests; web security is enabled by default
• --skip-warmup: skip warming up web server
• --rewrite-js: enable instrument JavaScript code in browser
• --log-script: enable intercepting and logging JavaScript code in browser
• --work-dir: set the working directory of the current run
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab help

List all MemLab CLI commands or print helper text for a specific command

memlab help <COMMAND> [SUB-COMMANDS]

Options:

• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab get-default-work-dir

Query the default working directory

memlab get-default-work-dir 

Options:

• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab snapshot

Interact with web app and take heap snapshots

memlab snapshot --scenario <TEST_SCENARIO_FILE>

examples

memlab snapshot --scenario /tmp/test-scenario.js
memlab snapshot --scenario /tmp/test-scenario.js --work-dir /tmp/test-1/

Options:

• --headful: start the browser in headful mode, by default it is headless
• --app: set name for onboarded web application
• --interaction: set name for onboarded interaction
• --full: take heap snapshot for every step in E2E interaction
• --skip-snapshot: skip taking heap snapshots
• --skip-screenshot: skip taking screenshots
• --skip-gc: skip doing garbage collection in browser
• --skip-scroll: skip scrolling target page in browser
• --skip-extra-ops: skip doing extra interactions (e.g., scrolling and waiting) on target and final page
• --run-mode: set running mode
• --local-puppeteer: enable remote browser instance debugging via local puppeteer
• --scenario: set file path loading test scenario
• --chromium-binary: set the chromium binary for E2E run
• --protocol-timeout: set the protocol timeout for chromium connection (in ms). The current default value is 180000, you may want to increase the timeout via this flag when the heap snapshot is too big (e.g., over 1GB) and the Page crashed with error: 'ProtocolError: HeapProfiler.takeHeapSnapshot timed out'.
• --device: set the device type to emulate
• --user-agent: set the UserAgent string in browser (for E2E interaction), otherwise it uses the default UserAgent from Chromium
• --disable-xvfb: disable Xvfb (X virtual framebuffer) for simulating headful browser rendering
• --disable-web-security: disable web security in Chromium to enable cross domain requests; web security is enabled by default
• --rewrite-js: enable instrument JavaScript code in browser
• --log-script: enable intercepting and logging JavaScript code in browser
• --worker: set title of the target (worker) that needs to be selected and analyzed
• --work-dir: set the working directory of the current run
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output

memlab warmup-and-snapshot

Warm up server and take heap snapshots

This is equivalent to running memlab warmup and memlab snapshot.

# specify a test scenario file, memlab will warm up the server and take heap snapshots
memlab warmup-and-snapshot --scenario <TEST_SCENARIO_FILE>

examples

memlab warmup-and-snapshot --scenario /tmp/test-scenario.js
# set the working directory of the current run
memlab warmup-and-snapshot --scenario /tmp/test-scenario.js --work-dir /tmp/test-1/

Options:

• --work-dir: set the working directory of the current run
• --headful: start the browser in headful mode, by default it is headless
• --app: set name for onboarded web application
• --interaction: set name for onboarded interaction
• --run-mode: set running mode
• --local-puppeteer: enable remote browser instance debugging via local puppeteer
• --scenario: set file path loading test scenario
• --chromium-binary: set the chromium binary for E2E run
• --protocol-timeout: set the protocol timeout for chromium connection (in ms). The current default value is 180000, you may want to increase the timeout via this flag when the heap snapshot is too big (e.g., over 1GB) and the Page crashed with error: 'ProtocolError: HeapProfiler.takeHeapSnapshot timed out'.
• --device: set the device type to emulate
• --user-agent: set the UserAgent string in browser (for E2E interaction), otherwise it uses the default UserAgent from Chromium
• --disable-xvfb: disable Xvfb (X virtual framebuffer) for simulating headful browser rendering
• --disable-web-security: disable web security in Chromium to enable cross domain requests; web security is enabled by default
• --skip-warmup: skip warming up web server
• --rewrite-js: enable instrument JavaScript code in browser
• --log-script: enable intercepting and logging JavaScript code in browser
• --full: take heap snapshot for every step in E2E interaction
• --skip-snapshot: skip taking heap snapshots
• --skip-screenshot: skip taking screenshots
• --skip-gc: skip doing garbage collection in browser
• --skip-scroll: skip scrolling target page in browser
• --skip-extra-ops: skip doing extra interactions (e.g., scrolling and waiting) on target and final page
• --worker: set title of the target (worker) that needs to be selected and analyzed
• --help, -h: print helper text
• --verbose, -v: show more details
• --sc: set to continuous test mode
• --debug: enable manual debugging
• --silent, -s: mute all terminal output