hubcap heapsnapshot - Capture a V8 heap snapshot

When to use

Capture a V8 heap snapshot for memory analysis. Open the output file in Chrome DevTools Memory panel to inspect object allocations and track memory leaks. Use metrics for a quick heap size check without generating a full snapshot.

Usage

hubcap heapsnapshot --output <file>

Arguments

None.

Flags

Flag	Type	Default	Description
`--output`	string	`""`	Output file path (required)

Output

Field	Type	Description
`file`	string	Path to the written snapshot file
`size`	int	File size in bytes

{"file":"heap.json","size":12345}

Errors

Condition	Exit code	Stderr
Chrome not connected	2	`error: connecting to Chrome: ...`
Missing —output flag	1	`error: --output flag is required`
Cannot write to file	1	`error: cannot write to "<path>"`
Timeout during capture	3	`error: timeout`

Examples

Capture a heap snapshot:

hubcap heapsnapshot --output heap.json

Capture a snapshot and report its size:

hubcap heapsnapshot --output heap.json | jq '.size'

Compare heap size before and after an action:

hubcap heapsnapshot --output before.json
hubcap goto "https://example.com/heavy-page"
hubcap heapsnapshot --output after.json

Take a snapshot and check quick metrics in one pipeline:

hubcap heapsnapshot --output "heap-$(date +%s).json" && hubcap metrics | jq '.JSHeapUsedSize'