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.TH "JSHELL" "1" "2018" "JDK 13" "JDK Commands"

.hy

.SH NAME

.PP

jshell \- interactively evaluate declarations, statements, and

expressions of the Java programming language in a read\-eval\-print loop

(REPL)

.SH SYNOPSIS

.PP

\f[CB]jshell\f[R] [\f[I]options\f[R]] [\f[I]load\-files\f[R]]

.TP

.B \f[I]options\f[R]

Command\-line options, separated by spaces.

See \f[B]Options for jshell\f[R].

.RS

.RE

.TP

.B \f[I]load\-files\f[R]

One or more scripts to run when the tool is started.

Scripts can contain any valid code snippets or JShell commands.

.RS

.PP

The script can be a local file or one of following predefined scripts:

.TP

.B \f[CB]DEFAULT\f[R]

Loads the default entries, which are commonly used as imports.

.RS

.RE

.TP

.B \f[CB]JAVASE\f[R]

Imports all Java SE packages.

.RS

.RE

.TP

.B \f[CB]PRINTING\f[R]

Defines \f[CB]print\f[R], \f[CB]println\f[R], and \f[CB]printf\f[R] as

\f[CB]jshell\f[R] methods for use within the tool.

.RS

.RE

.PP

For more than one script, use a space to separate the names.

Scripts are run in the order in which they\[aq]re entered on the command

line.

Command\-line scripts are run after startup scripts.

To run a script after JShell is started, use the \f[CB]/open\f[R] command.

.PP

To accept input from standard input and suppress the interactive I/O,

enter a hyphen (\-) for \f[I]load\-files\f[R].

This option enables the use of the \f[CB]jshell\f[R] tool in pipe chains.

.RE

.SH DESCRIPTION

.PP

JShell provides a way to interactively evaluate declarations,

statements, and expressions of the Java programming language, making it

easier to learn the language, explore unfamiliar code and APIs, and

prototype complex code.

Java statements, variable definitions, method definitions, class

definitions, import statements, and expressions are accepted.

The bits of code entered are called snippets.

.PP

As snippets are entered, they\[aq]re evaluated, and feedback is

provided.

Feedback varies from the results and explanations of actions to nothing,

depending on the snippet entered and the feedback mode chosen.

Errors are described regardless of the feedback mode.

Start with the verbose mode to get the most feedback while learning the

tool.

.PP

Command\-line options are available for configuring the initial

environment when JShell is started.

Within JShell, commands are available for modifying the environment as

needed.

.PP

Existing snippets can be loaded from a file to initialize a JShell

session, or at any time within a session.

Snippets can be modified within the session to try out different

variations and make corrections.

To keep snippets for later use, save them to a file.

.SH OPTIONS FOR JSHELL

.TP

.B \f[CB]\-\-add\-modules\f[R] \f[I]module\f[R][\f[CB],\f[R]\f[I]module\f[R]...]

Specifies the root modules to resolve in addition to the initial module.

.RS

.RE

.TP

.B \f[CB]\-C\f[R]\f[I]flag\f[R]

Provides a flag to pass to the compiler.

To pass more than one flag, provide an instance of this option for each

flag or flag argument needed.

.RS

.RE

.TP

.B \f[CB]\-\-class\-path\f[R] \f[I]path\f[R]

Specifies the directories and archives that are searched to locate class

files.

This option overrides the path in the \f[CB]CLASSPATH\f[R] environment

variable.

If the environment variable isn\[aq]t set and this option isn\[aq]t

used, then the current directory is searched.

For Oracle Solaris, Linux, and macOS, use a colon (:) to separate items

in the path.

For Windows, use a semicolon (;) to separate items.

.RS

.RE

.TP

.B \f[CB]\-\-feedback\f[R] \f[I]mode\f[R]

Sets the initial level of feedback provided in response to what\[aq]s

entered.

The initial level can be overridden within a session by using the

\f[CB]/set\ feedback\f[R] \f[I]mode\f[R] command.

The default is \f[CB]normal\f[R].

.RS

.PP

The following values are valid for \f[I]mode\f[R]:

.TP

.B \f[CB]verbose\f[R]

Provides detailed feedback for entries.

Additional information about the action performed is displayed after the

result of the action.

The next prompt is separated from the feedback by a blank line.

.RS

.RE

.TP

.B \f[CB]normal\f[R]

Provides an average amount of feedback.

The next prompt is separated from the feedback by a blank line.

.RS

.RE

.TP

.B \f[CB]concise\f[R]

Provides minimal feedback.

The next prompt immediately follows the code snippet or feedback.

.RS

.RE

.TP

.B \f[CB]silent\f[R]

Provides no feedback.

The next prompt immediately follows the code snippet.

.RS

.RE

.TP

.B \f[I]custom\f[R]

Provides custom feedback based on how the mode is defined.

Custom feedback modes are created within JShell by using the

\f[CB]/set\ mode\f[R] command.

.RS

.RE

.RE

.TP

.B \f[CB]\-\-help\f[R] or \f[CB]\-h\f[R] or \f[CB]\-?\f[R]

Prints a summary of standard options and exits the tool.

.RS

.RE

.TP

.B \f[CB]\-\-help\-extra\f[R] or \f[CB]\-X\f[R]

Prints a summary of nonstandard options and exits the tool.

Nonstandard options are subject to change without notice.

.RS

.RE

.TP

.B \f[CB]\-J\f[R]\f[I]flag\f[R]

Provides a flag to pass to the runtime system.

To pass more than one flag, provide an instance of this option for each

flag or flag argument needed.

.RS

.RE

.TP

.B \f[CB]\-\-module\-path\f[R] \f[I]modulepath\f[R]

Specifies where to find application modules.

For Oracle Solaris, Linux, and macOS, use a colon (:) to separate items

in the path.

For Windows, use a semicolon (;) to separate items.

.RS

.RE

.TP

.B \f[CB]\-\-no\-startup\f[R]

Prevents startup scripts from running when JShell starts.

Use this option to run only the scripts entered on the command line when

JShell is started, or to start JShell without any preloaded information

if no scripts are entered.

This option can\[aq]t be used if the \f[CB]\-\-startup\f[R] option is

used.

.RS

.RE

.TP

.B \f[CB]\-q\f[R]

Sets the feedback mode to \f[CB]concise\f[R], which is the same as

entering \f[CB]\-\-feedback\ concise\f[R].

.RS

.RE

.TP

.B \f[CB]\-R\f[R]\f[I]flag\f[R]

Provides a flag to pass to the remote runtime system.

To pass more than one flag, provide an instance of this option for each

flag or flag argument to pass.

.RS

.RE

.TP

.B \f[CB]\-s\f[R]

Sets the feedback mode to \f[CB]silent\f[R], which is the same as entering

\f[CB]\-\-feedback\ silent\f[R].

.RS

.RE

.TP

.B \f[CB]\-\-show\-version\f[R]

Prints version information and enters the tool.

.RS

.RE

.TP

.B \f[CB]\-\-startup\f[R] \f[I]file\f[R]

Overrides the default startup script for this session.

The script can contain any valid code snippets or commands.

.RS

.PP

The script can be a local file or one of the following predefined

scripts:

.TP

.B \f[CB]DEFAULT\f[R]

Loads the default entries, which are commonly used as imports.

.RS

.RE

.TP

.B \f[CB]JAVASE\f[R]

Imports all Java SE packages.

.RS

.RE

.TP

.B \f[CB]PRINTING\f[R]

Defines \f[CB]print\f[R], \f[CB]println\f[R], and \f[CB]printf\f[R] as

\f[CB]jshell\f[R] methods for use within the tool.

.RS

.RE

.PP

For more than one script, provide a separate instance of this option for

each script.

Startup scripts are run when JShell is first started and when the

session is restarted with the \f[CB]/reset\f[R], \f[CB]/reload\f[R], or

\f[CB]/env\f[R] command.

Startup scripts are run in the order in which they\[aq]re entered on the

command line.

.PP

This option can\[aq]t be used if the \f[CB]\-\-no\-startup\f[R] option is

used.

.RE

.TP

.B \f[CB]\-v\f[R]

Sets the feedback mode to \f[CB]verbose\f[R], which is the same as

entering \f[CB]\-\-feedback\ verbose\f[R].

.RS

.RE

.TP

.B \f[CB]\-\-version\f[R]

Prints version information and exits the tool.

.RS

.RE

.SH JSHELL COMMANDS

.PP

Within the \f[CB]jshell\f[R] tool, commands are used to modify the

environment and manage code snippets.

.TP

.B \f[CB]/drop\f[R] {\f[I]name\f[R]|\f[I]id\f[R]|\f[I]startID\f[R]\f[CB]\-\f[R]\f[I]endID\f[R]} [{\f[I]name\f[R]|\f[I]id\f[R]|\f[I]startID\f[R]\f[CB]\-\f[R]\f[I]endID\f[R]}...]

Drops snippets identified by name, ID, or ID range, making them

inactive.

For a range of IDs, provide the starting ID and ending ID separated with

a hyphen.

To provide a list, separate the items in the list with a space.

Use the \f[CB]/list\f[R] command to see the IDs of code snippets.

.RS

.RE

.TP

.B \f[CB]/edit\f[R] [\f[I]option\f[R]]

Opens an editor.

If no option is entered, then the editor opens with the active snippets.

.RS

.PP

The following options are valid:

.TP

.B {\f[I]name\f[R]|\f[I]id\f[R]|\f[I]startID\f[R]\f[CB]\-\f[R]\f[I]endID\f[R]} [{\f[I]name\f[R]|\f[I]id\f[R]|\f[I]startID\f[R]\f[CB]\-\f[R]\f[I]endID\f[R]}...]

Opens the editor with the snippets identified by name, ID, or ID range.

For a range of IDs, provide the starting ID and ending ID separated with

a hyphen.

To provide a list, separate the items in the list with a space.

Use the \f[CB]/list\f[R] command to see the IDs of code snippets.

.RS

.RE

.TP

.B \f[CB]\-all\f[R]

Opens the editor with all snippets, including startup snippets and

snippets that failed, were overwritten, or were dropped.

.RS

.RE

.TP

.B \f[CB]\-start\f[R]

Opens the editor with startup snippets that were evaluated when JShell

was started.

.RS

.RE

.PP

To exit edit mode, close the editor window, or respond to the prompt

provided if the \f[CB]\-wait\f[R] option was used when the editor was set.

.PP

Use the \f[CB]/set\ editor\f[R] command to specify the editor to use.

If no editor is set, then the following environment variables are

checked in order: \f[CB]JSHELLEDITOR\f[R], \f[CB]VISUAL\f[R], and

\f[CB]EDITOR\f[R].

If no editor is set in JShell and none of the editor environment

variables is set, then a simple default editor is used.

.RE

.TP

.B \f[CB]/env\f[R] [\f[I]options\f[R]]

Displays the environment settings, or updates the environment settings

and restarts the session.

If no option is entered, then the current environment settings are

displayed.

If one or more options are entered, then the session is restarted as

follows:

.RS

.IP \[bu] 2

Updates the environment settings with the provided options.

.IP \[bu] 2

Resets the execution state.

.IP \[bu] 2

Runs the startup scripts.

.IP \[bu] 2

Silently replays the history in the order entered.

The history includes all valid snippets or \f[CB]/drop\f[R] commands

entered at the \f[CB]jshell\f[R] prompt, in scripts entered on the command

line, or scripts entered with the \f[CB]/open\f[R] command.

.PP

Environment settings entered on the command line or provided with a

previous \f[CB]/reset\f[R], \f[CB]/env\f[R], or \f[CB]/reload\f[R] command are

maintained unless an \f[I]option\f[R] is entered that overwrites the

setting.

.PP

The following options are valid:

.TP

.B \f[CB]\-\-add\-modules\f[R] \f[I]module\f[R][\f[CB],\f[R]\f[I]module\f[R]...]

Specifies the root modules to resolve in addition to the initial module.

.RS

.RE

.TP

.B \f[CB]\-\-add\-exports\f[R] \f[I]source\-module\f[R]\f[CB]/\f[R]\f[I]package\f[R]\f[CB]=\f[R]\f[I]target\-module\f[R][\f[CB],\f[R]\f[I]target\-module\f[R]]*

Adds an export of \f[I]package\f[R] from \f[I]source\-module\f[R] to

\f[I]target\-module\f[R].

.RS

.RE

.TP

.B \f[CB]\-\-class\-path\f[R] \f[I]path\f[R]

Specifies the directories and archives that are searched to locate class

files.

This option overrides the path in the \f[CB]CLASSPATH\f[R] environment

variable.

If the environment variable isn\[aq]t set and this option isn\[aq]t

used, then the current directory is searched.

For Oracle Solaris, Linux, and macOS, use a colon (\f[CB]:\f[R]) to

separate items in the path.

For Windows, use a semicolon (\f[CB];\f[R]) to separate items.

.RS

.RE

.TP

.B \f[CB]\-\-module\-path\f[R] \f[I]modulepath\f[R]

Specifies where to find application modules.

For Oracle Solaris, Linux, and macOS, use a colon (\f[CB]:\f[R]) to

separate items in the path.

For Windows, use a semicolon (\f[CB];\f[R]) to separate items.

.RS

.RE

.RE

.TP

.B \f[CB]/exit\f[R] [\f[I]integer\-expression\-snippet\f[R]]

Exits the tool.

If no snippet is entered, the exit status is zero.

If a snippet is entered and the result of the snippet is an integer, the

result is used as the exit status.

If an error occurs, or the result of the snippet is not an integer, an

error is displayed and the tool remains active.

.RS

.RE

.TP

.B \f[CB]/history\f[R]

Displays what was entered in this session.

.RS

.RE

.TP

.B \f[CB]/help\f[R] [\f[I]command\f[R]|\f[I]subject\f[R]]

Displays information about commands and subjects.

If no options are entered, then a summary of information for all

commands and a list of available subjects are displayed.

If a valid command is provided, then expanded information for that

command is displayed.

If a valid subject is entered, then information about that subject is

displayed.

.RS

.PP

The following values for \f[I]subject\f[R] are valid:

.TP

.B \f[CB]context\f[R]

Describes the options that are available for configuring the

environment.

.RS

.RE

.TP

.B \f[CB]intro\f[R]

Provides an introduction to the tool.

.RS

.RE

.TP

.B \f[CB]shortcuts\f[R]

Describes keystrokes for completing commands and snippets.

See \f[B]Input Shortcuts\f[R].

.RS

.RE

.RE

.TP

.B \f[CB]/imports\f[R]

Displays the current active imports, including those from the startup

scripts and scripts that were entered on the command line when JShell

was started.

.RS

.RE

.TP

.B \f[CB]/list\f[R] [\f[I]option\f[R]]

Displays a list of snippets and their IDs.

If no option is entered, then all active snippets are displayed, but

startup snippets aren\[aq]t.

.RS

.PP

The following options are valid:

.TP

.B {\f[I]name\f[R]|\f[I]id\f[R]|\f[I]startID\f[R]\f[CB]\-\f[R]\f[I]endID\f[R]} [{\f[I]name\f[R]|\f[I]id\f[R]|\f[I]startID\f[R]\f[CB]\-\f[R]\f[I]endID\f[R]}...]

Displays the snippets identified by name, ID, or ID range.

For a range of IDs, provide the starting ID and ending ID separated with

a hyphen.

To provide a list, separate the items in the list with a space.

.RS

.RE

.TP

.B \f[CB]\-all\f[R]

Displays all snippets, including startup snippets and snippets that

failed, were overwritten, or were dropped.

IDs that begin with \f[CB]s\f[R] are startup snippets.

IDs that begin with \f[CB]e\f[R] are snippets that failed.

.RS

.RE

.TP

.B \f[CB]\-start\f[R]

Displays startup snippets that were evaluated when JShell was started.

.RS

.RE

.RE

.TP

.B \f[CB]/methods\f[R] [\f[I]option\f[R]]

Displays information about the methods that were entered.

If no option is entered, then the name, parameter types, and return type

of all active methods are displayed.

.RS

.PP

The following options are valid:

.TP

.B {\f[I]name\f[R]|\f[I]id\f[R]|\f[I]startID\f[R]\f[CB]\-\f[R]\f[I]endID\f[R]} [{\f[I]name\f[R]|\f[I]id\f[R]|\f[I]startID\f[R]\f[CB]\-\f[R]\f[I]endID\f[R]}...]

Displays information for methods identified by name, ID, or ID range.

For a range of IDs, provide the starting ID and ending ID separated with

a hyphen.

To provide a list, separate the items in the list with a space.

Use the \f[CB]/list\f[R] command to see the IDs of code snippets.

.RS

.RE

.TP

.B \f[CB]\-all\f[R]

Displays information for all methods, including those added when JShell

was started, and methods that failed, were overwritten, or were dropped.

.RS

.RE

.TP

.B \f[CB]\-start\f[R]

Displays information for startup methods that were added when JShell was

started.

.RS

.RE

.RE

.TP

.B \f[CB]/open\f[R] \f[I]file\f[R]

Opens the script specified and reads the snippets into the tool.

The script can be a local file or one of the following predefined

scripts:

.RS

.TP

.B \f[CB]DEFAULT\f[R]

Loads the default entries, which are commonly used as imports.

.RS

.RE

.TP

.B \f[CB]JAVASE\f[R]

Imports all Java SE packages.

.RS

.RE

.TP

.B \f[CB]PRINTING\f[R]

Defines \f[CB]print\f[R], \f[CB]println\f[R], and \f[CB]printf\f[R] as

\f[CB]jshell\f[R] methods for use within the tool.

.RS

.RE

.RE

.TP

.B \f[CB]/reload\f[R] [\f[I]options\f[R]]