## jattach
### JVM Dynamic Attach utility
The utility to send commands to a JVM process via Dynamic Attach mechanism.
All-in-one **jmap + jstack + jcmd + jinfo** functionality in a single tiny program.
No installed JDK required, works with just JRE. Supports Linux containers.
This is the lightweight native version of HotSpot Attach API
https://docs.oracle.com/javase/8/docs/jdk/api/attach/spec/
[Supported commands](http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/file/812ed44725b8/src/share/vm/services/attachListener.cpp#l388):
- **load** : load agent library
- **properties** : print system properties
- **agentProperties** : print agent properties
- **datadump** : show heap and thread summary
- **threaddump** : dump all stack traces (like jstack)
- **dumpheap** : dump heap (like jmap)
- **inspectheap** : heap histogram (like jmap -histo)
- **setflag** : modify manageable VM flag
- **printflag** : print VM flag
- **jcmd** : execute jcmd command
### Download
Binaries are available on the [Releases](https://github.com/apangin/jattach/releases) page.
On some platforms, you can also [install](#installation) jattach with a package manager.
### Examples
#### Load native agent
$ jattach <pid> load <.so-path> { true | false } [ options ]
Where `true` means that the path is absolute, `false` -- the path is relative.
`options` are passed to the agent.
#### Load Java agent
Java agents are loaded by the special built-in native agent named `instrument`,
which takes .jar path and its arguments as a single options string.
$ jattach <pid> load instrument false "javaagent.jar=arguments"
#### List available jcmd commands
$ jattach <pid> jcmd "help -all"
### Installation
#### FreeBSD
On FreeBSD, you can use the following command to install `jattach` package:
$ pkg install jattach
#### Alpine Linux
On Alpine Linux, you can use the following command to install `jattach` package from the edge/community repository:
$ apk add --no-cache jattach --repository http://dl-cdn.alpinelinux.org/alpine/edge/community/
#### Archlinux
[jattach](https://aur.archlinux.org/packages/jattach/) package can be installed from [AUR](https://wiki.archlinux.org/index.php/Arch_User_Repository) using one of [AUR helpers](https://wiki.archlinux.org/index.php/AUR_helpers), e.g., `yay`:
$ yay -S jattach
#### Debian Linux
On Debian Linux, you can use the following command to install `jattach` from the [official repository](https://packages.debian.org/search?keywords=jattach):
$ apt install jattach
Packages are provided for **bullseye** (stable), **bookworm** (testing) and **sid** (unstable).