2.1. Pywbemcli command line interface

This section describes the command line interface of the pywbemcli command within the pywbemtools package.

Pywbemcli provides a command line interface(CLI) interaction with WBEM servers.

The command line can contain the following components:

  • COMMAND - A name of a command which may consist of:
    • <group name> <command name> for commands that are defined within groups (ex. class find).

    • <group name> (ex. class) to show group help including list of command within the group.

    • <command name> for those commands that are not part of a group. For example repl and help that are not in any command group.

  • ARGS - Arguments for a command.

  • COMMAND-OPTIONS - Options that apply only to a particular COMMAND.

Options are prefixed with the characters - for the short form or -- for the long form (ex. -n or --namespace). The other components do not begin with -.

Command groups are named after the objects the commands operate on (ex. class, instance, qualifier, server, connection, namespace, etc.). Executing:

$ pywbemcli --help
...
Commands:
  class       Command group for CIM classes.
...

returns the list of command groups under the title Commands.

Commands are named after actions on these objects (ex. get, create, delete). The list of commands for each group is listed with the command pywbemcli <group name> –help.

For example, the command:

$ pywbemcli --output-format mof class get CIM_ManagedElement --namespace interop

gets class CIM_ManagedElement in namespace interop and displays it in the MOF output format. The option --output-format is a general option and --namespace is a command option.

Pywbemcli supports several modes of tab-completion, auto-completion suggestions depending on whether it is in command or interactive mode. This is detailed in the following sections.

2.1.1. Modes of operation

Pywbemcli supports two modes of operation:

  • Command mode: Executing standalone non-interactive commands.

  • Interactive mode: Invoking an interactive pywbemcli shell for typing pywbemcli commands.

2.1.2. Command mode

In command mode, the pywbemcli command performs its task and terminates like any other standalone non-interactive command.

This mode is used when the pywbemcli command is invoked with a command or command group name and arguments/options:

$ pywbemcli [GENERAL-OPTIONS] COMMAND [COMMAND-OPTIONS] [ARGS]

The following example enumerates classes in the root/cimv2 namespace of the WBEM server on localhost:

$ pywbemcli --server http://localhost --default-namespace root/cimv2 --user username class enumerate
Enter password: <password>
. . .
<Returns MOF for the enumerated classes>

In command mode, tab completion is also supported for some command shells, but must be enabled specifically for each shell.

For example, with a bash shell, enter the following to enable tab completion of pywbemcli:

$ eval "$(_PYWBEMCLI_COMPLETE=source pywbemcli)"

Bash tab completion for pywbemcli is used like any other bash tab completion:

$ pywbemcli --<TAB><TAB>
... <shows the general options to select from>

$ pywbemcli <TAB><TAB>
... <shows the command groups to select from>

$ pywbemcli class <TAB><TAB>
... <shows the class commands to select from>

Pywbemcli uses the Python click package for its command line handling. See Bash Complete in the Click documentation for additional features of the Bash tab completion of pywbemcli.

2.1.3. Interactive mode

In interactive mode (also known as REPL mode), pywbem provides an interactive shell environment that allows typing pywbemcli commands, internal commands (for operating the pywbemcli shell), and external commands (that are executed in the standard shell of the user).

This pywbemcli shell is started when the pywbemcli command is invoked without specifying any command group or command:

$ pywbemcli [GENERAL-OPTIONS]
pywbemcli> _

Alternatively, the pywbemcli shell can also be started by specifying the repl command:

$ pywbemcli [GENERAL-OPTIONS] repl
pywbemcli> _

The pywbemcli shell uses the prompt pywbemcli>. The cursor is shown in the examples above as an underscore (_).

The commands and options that can be typed in the pywbemcli shell are the rest of the command line that would follow the pywbemcli command in command mode, as well as internal commands (for operating the pywbemcli shell), and external commands (that are executed in the standard shell of the user):

pywbemcli> [GENERAL-OPTIONS] COMMAND [ARGS] [COMMAND-OPTIONS]

    where: COMMAND can be either a group name and
           a command (ex. class find or repl)

pywbemcli> :INTERNAL-COMMAND

pywbemcli> !EXTERNAL-COMMAND

The general options may be included on the interactive command line to override the general options entered in the initial command line for pywbemcli. Thus, a user can define a server on the command line and override elements of that definition with commands in the interactive mode.

NOTE: The effects of any general option entered in the interactive mode exists only for that command and the original definition from the command line is restored for the next command. Any changes to the connections file defined in the interactive mode and executed in the same command are retained (ex. setting the default connection).

Thus:

pywbemcli --server http://blah
pywbemcli> class get CIM_ManagedObject
# The timeout change below only applies to the command on that line
pywbemcli> --timeout 90 class get CIM_ManagedObject.
# The --verbose mode only applies to the command on the same line.
pywbemcli> --verbose class get CIM_ManagedObject

The following example starts a pywbemcli shell in interactive mode, executes several commands, and exits the shell:

$ pywbemcli -s http://localhost -d root/cimv2 -u username

pywbemcli> class enumerate --no
. . . <Enumeration of class names in the default namespace>

pywbemcli> class get CIM_System
. . . <Class CIM_System in the default namespace in MOF format>

pywbemcli> :q

The pywbemcli shell command class get CIM_System in the example above has the same effect as the standalone command:

$ pywbemcli -s http://localhost -d root/cimv2 -u username class get CIM_System
. . . <Class CIM_System in the default namespace in MOF format>

The internal commands :?, :h, or :help display general help information for external and internal commands:

> :help
REPL help:

  External Commands:
    prefix external commands with "!"

  Internal Commands:
    prefix internal commands with ":"
    :?, :h, :help     displays general help information
    :exit, :q, :quit  exits the REPL

In addition to using one of the internal exit commands shown in the help text above, you can also exit the pywbemcli shell by typing Ctrl-D (on Linux, OS-X and UNIX-like environments on Windows), or Ctrl-C (on native Windows).

Typing --help or -h in the pywbemcli shell displays general help information for the pywbemcli commands which includes general options and a list of the supported command groups and commands without command group.

$ pywbemcli
pywbemcli> --help
Usage: pywbemcli [GENERAL-OPTIONS] COMMAND [ARGS] [COMMAND-OPTIONS]
. . .

General Options:
  -n, --name NAME                 Use the WBEM server ...
  . . .

Commands:
  class       Command group for CIM classes.
  connection  Command group for WBEM connection definitions.
  . . .

The usage line in this help text shows the usage in command mode. In interactive mode, the pywbemcli word is omitted.

Typing COMMAND --help, or COMMAND -h in the pywbemcli shell displays help information for the specified pywbemcli command group, for example:

pywbemcli> class --help
Usage: pywbemcli [GENERAL-OPTIONS] class COMMAND [ARGS] [COMMAND-OPTIONS]
. . .

Command Options:
  -h, --help  Show this message and exit.

Commands:
  associators   List the classes associated with a class.
  . . .

The pywbemcli shell in the interactive mode supports popup help text while for commands, arguments, and options typing, where the valid choices are shown based upon what was typed so far, and where an item from the popup list can be picked with <TAB> or with the cursor keys. It can be used to select from the list of general options. In the following examples, an underscore _ is shown as the cursor:

pywbemcli> --_
--name               Use the WBEM server defined by the WBEM connection ...
--mock-server        Use a mock WBEM server that is automatically ...
--server             Use the WBEM server at the specified URL with ...
. . .

pywbemcli> cl_
              class

The pywbemcli shell supports history across multiple invocations of the shell using <UP_ARROW>, <DOWN-ARROW> to step through the history line by line.

A incremental search of the history can be initiated by entering <CTRL-r> followed by one or more characters that define the search. The search displays the last command containing the search string. This search string can be modified in place to change the search, returning the last command in the command history that contains the the string. <UP_ARROW>, <DOWN-ARROW> will find other commands in the history containing the same string.

pywbemcli> <CTRL-r>
(reverse-i-search)`':
                                                    ENTER Characters CIM
(reverse-i-search)`CIM': class get CIM_ManagedElement
                                                    <UP-ARROW> and <DOWN-ARROW> find
                                                    other commands containing of "CIM"

<DOWN_ARROW>
(i-search)`get': instance get CIM_ComputerSystem.?
                                                    Hit <ENTER> selects current found command
pywbemcli> instance get CIM_ComputerSystem.?

The pywbemcli history is stored in the user home directory, ~/.pywbemcli_history.

The pywbemcli interactive mode also supports automated parameter suggestions based on the pywbemcli history file which works with the auto completion described above. The input is compared to the history and when there is another entry starting with the given text, the completion will be shown as gray text behind the current input. Pressing the right arrow → or c-e will insert this suggestion.

General options can be entered in the interactive mode but they generally only apply to the current command defined in the same command input as the general option. Thus, to modify the output format for a particular command, enter the –output-format general option before the command. The following command sets the output format to table before executing the command and then restores it to the original value.:

pywbemcli> --output-format table instance enumerate CIM_Foo

A particular difference between general options in the interactive mode and the command line mode is the ability to set general options back to their default value in the interactive mode. In the command mode this is not required. However, in the interactive mode, it could be useful to reset a general option to its default value for a command. Thus, if the log was set on startup (–log all), it could be disabled for a command or the user name (–user) could be set back to None. However, normally the default value is only set by not including that general option with the command line input

To reset selected string type general options in the interactive, the string value of "" (an empty string) is provided as the value which causes pywbemcli to set the default value of that general option.

The following code defines a server with –user and password in interactive mode. Then it attempts to modify the user and password to their default values of None and execute the class enumerate again. This command would be executed without using the user and password because they have been reset for that command.

pywbemcli -s https:blah --user fred --pasword blah
pywbemcli> class enumerate
pywbemcli> --user "" --pasword "" class enumerate

2.1.4. Error handling

Pywbemcli terminates with one of the following program exit codes:

  • 0 - Success: The pywbemcli command has succeeded.

  • 1 - Error: In such cases, pywbemcli aborts the requested operation and displays one or more human readable error messages on standard error.

    If this happens for a command entered in interactive mode, the pywbemcli shell is not terminated; only the command that failed is terminated.

    Examples for errors reported that way:

    • Local system issues, e.g. pywbemcli history file or term:connections file cannot be written to.

    • WBEM server access issues, e.g. pywbemcli cannot connect to or authenticate with the WBEM server. This includes CIM errors about failed authentication returned by the server.

    • WBEM server operation issues, e.g. pywbemcli attempts to retrieve an instance that does not exist, or the WBEM server encountered an internal error. This will mostly be caused by CIM errors returned by the server, but can also be caused by the pywbemcli code itself.

    • Programming errors in mock Python scripts (see: Mock support overview); the error message includes a Python traceback of the error.

  • 1 - Python traceback: In such cases, pywbemcli terminates during its processing, and displays the Python stack traceback on standard error.

    If this happens for a command entered in interactive mode, the pywbemcli shell also terminates with a program exit code of 1.

    These Python tracebacks should never happen and are always considered a reason to open a bug in the pywbemtools issue tracker.

    Note that an error message with a traceback from a mock Python script does not fall into this category and is an issue in that Python script and not in pywbemcli.

  • 2 - User error: In such cases, pywbemcli terminates without even attempting to perform the requested operation, and displays one or more human readable error messages on standard error.

    If this happens for a command entered in interactive mode, the pywbemcli shell is not terminated; only the command that failed is terminated.

    Examples for user errors are a missing required command argument, the use of an invalid option, or an invalid option argument.

  • 2 - Help: When help is requested (--help/-h option or help command), pywbemcli displays the requested help text on standard output and terminates.

    If this happens for a command entered in interactive mode, the pywbemcli shell is not terminated; only the command that displayed the help is terminated.