Subcommands

Subcommands are space-delimited tokens that organize related operations. Typically, the final subcommand of a command is a verb that indicates the action to be performed. For example, commands related to managing breakpoints start with breakpoint, such as the breakpoint list and breakpoint disable commands, which list and disable breakpoints, respectively.

Arguments

A command may require one or more arguments. Arguments are space-delimited tokens that direct the action to be performed. For example, the breakpoint disable command requires a single argument to specify which breakpoint to disable, such as breakpoint disable 1, which disables the breakpoint with ID equal to 1.

Options

A command may also include one or more options. Options are space-delimited tokens beginning with a double dash (--) that may be used in different combinations to modify the action to be performed. Some options also provide a shorthand form that uses a single dash (-). For example, when the breakpoint set command specifies the --one-shot (-o) option, as in breakpoint set —one--shot, the breakpoint is deleted the first time it causes the program to stop.

Some options specify a single space-delimited value to act as a named parameter for the command. For example, the breakpoint set command can set a breakpoint on a particular function by passing the --name option with the name of the function as the option value.

Some commands may require options in certain combinations. For example, the breakpoint set command can set a breakpoint on a particular location in code by passing the --file and --line options with the corresponding file name and line number.

Command Forms

Equivalent LLDB commands can be represented in various different forms. For example, each of the following commands perform the same action of evaluating the object description of a variable someVariable and printing the result:

• The canonical form of a command acts as a descriptive representation of the action to be performed.

• The abbreviated form of a command uses short abbreviations of commands and subcommands, such as e for expression, and the short form of options, such as -O for --object-description.

• An alias can be created for any command subsequence, providing a convenient shorthand to perform common actions, such as po to evaluate and print an object expression.

For clarity, this document primarily refers to commands in their canonical form, followed by any abbreviated forms or aliases in parentheses. You’re encouraged to use the more convenient shorthand when debugging your own code.

Using Command-Line Help

LLDB provides extensive documentation within a debugger session through the help command.

Calling the help command without any arguments lists all of the available debugger commands, as well as the existing command aliases.

(lldb) help

Debugger commands:

  apropos           -- Find a list of debugger commands related to a particular word/subject.

  breakpoint        -- A set of commands for operating on breakpoints.

  ...

You can get information about the usage of a particular command or subcommand by passing it as the argument of the help command. For example, to get help for the breakpoint set command:

(lldb) help breakpoint set

     Sets a breakpoint or set of breakpoints in the executable.

Syntax: breakpoint set <cmd-options>

...

The help command works for any available form of a command, including an alias. For example, to determine the command aliased by po:

(lldb) help po

     Evaluate an expression (ObjC++ or Swift) in the current program context, using user defined variables and

     variables currently in scope.

...

'po' is an abbreviation for 'expression -O  -- '