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Diffstat (limited to 'docs/freefeatures.rst')
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1 files changed, 194 insertions, 6 deletions
diff --git a/docs/freefeatures.rst b/docs/freefeatures.rst index 5c246798..d661e058 100644 --- a/docs/freefeatures.rst +++ b/docs/freefeatures.rst @@ -29,9 +29,9 @@ Simply include one command per line, typed exactly as you would inside a ``cmd2` Comments ======== -Any command line input where the first non-whitespace character is a # will be treated as a comment. -This means any # character appearing later in the command will be treated as a literal. The same -applies to a # in the middle of a multiline command, even if it is the first character on a line. +Any command line input where the first non-whitespace character is a `#` will be treated as a comment. +This means any `#` character appearing later in the command will be treated as a literal. The same +applies to a `#` in the middle of a multiline command, even if it is the first character on a line. Comments can be useful in :ref:`scripts`, but would be pointless within an interactive session. @@ -269,9 +269,198 @@ the readline history. .. automethod:: cmd2.cmd2.Cmd.__init__ -``cmd2`` makes a third type of history access available with the **history** command: +``cmd2`` makes a third type of history access available with the `history` command. Each time +the user enters a command, ``cmd2`` saves the input. The `history` command lets you do interesting +things with that saved input. The examples to follow all assume that you have entered the +following commands:: -.. automethod:: cmd2.cmd2.Cmd.do_history + (Cmd) alias create one !echo one + Alias 'one' created + (Cmd) alias create two !echo two + Alias 'two' created + (Cmd) alias create three !echo three + Alias 'three' created + (Cmd) alias create four !echo four + Alias 'four' created + +In it's simplest form, the `history` command displays previously entered commands. With no +additional arguments, it displays all previously entered commands:: + + (Cmd) history + 1 alias create one !echo one + 2 alias create two !echo two + 3 alias create three !echo three + 4 alias create four !echo four + +If you give a positive integer as an argument, then it only displays the specified command:: + + (Cmd) history 4 + 4 alias create four !echo four + +If you give a negative integer *N* as an argument, then it display the *Nth* last command. +For example, if you give `-1` it will display the last command you entered. If you give `-2` +it will display the next to last command you entered, and so forth:: + + (Cmd) history -2 + 3 alias create three !echo three + +You can use a similar mechanism to display a range of commands. Simply give two command numbers +separated by `..` or `:`, and you will see all commands between those two numbers:: + + (Cmd) history 2:3 + 2 alias create two !echo two + 3 alias create three !echo three + +If you omit the first number, it will start at the beginning. If you omit the last number, it +will continue to the end:: + + (Cmd) history :2 + 1 alias create one !echo one + 2 alias create two !echo two + (Cmd) history 2: + 2 alias create two !echo two + 3 alias create three !echo three + 4 alias create four !echo four + +You can use negative numbers as either the first or second number of the range (but not both). If +you want to display the last three commands entered:: + + (Cmd) history -- -3: + 2 alias create two !echo two + 3 alias create three !echo three + 4 alias create four !echo four + +Notice the double dashes. These are required because the history command uses `argparse` to parse +the command line arguments. For reasons I do not understand, `argparse` thinks `-3:` is an +option, not an argument, but it thinks `-3` is an argument. + +There is no zeroth command, so don't ask for it. If you are a python programmer, you've +probably noticed this looks a lot like the slice syntax for lists and arrays. It is, +with the exception that the first history command is 1, where the first element in +a python array is 0. + +Besides selecting previous commands by number, you can also search for them. You can use a simple +string search:: + + (Cmd) history two + 2 alias create two !echo two + +Or a regular expression search by enclosing your regex in slashes:: + + (Cmd) history '/te\ +th/' + 3 alias create three !echo three + +If your regular expression contains any characters that `argparse` finds +interesting, like dash or plus, you also need to enclose your regular expression +in quotation marks. + +This all sounds great, but doesn't it seem like a bit of overkill to have all +these ways to select commands if all we can do is display them? Turns out, +displaying history commands is just the beginning. The history command can +perform many other actions: + +- running previously entered commands +- saving previously entered commands to a text file +- opening previously entered commands in your favorite text editor +- running previously entered commands, saving the commands and their output to a text file +- clearing the history of entered commands + +Each of these actions is invoked using a command line option. The `-r` or +`--run` option runs one or more previously entered commands. To run command +number 1:: + + (Cmd) history --run 1 + +To rerun the last two commands (there's that double dash again to make argparse +stop looking for options):: + + (Cmd) history -r -- -2: + +Say you want to re-run some previously entered commands, but you would really +like to make a few changes to them before doing so. When you use the `-e` or +`--edit` option, `history` will write the selected commands out to a text file, +and open that file with a text editor. You make whatever changes, additions, or +deletions, you want. When you leave the text editor, all the commands in the +file are executed. To edit and then re-run commands 2-4 you would:: + + (Cmd) history --edit 2:4 + +If you want to save the commands to a text file, but not edit and re-run them, +use the `-o` or `--output-file` option. This is a great way to create +:ref:`scripts`, which can be loaded and executed using the `load` command. To +save the first 5 commands entered in this session to a text file:: + + (Cmd) history :5 -o history.txt + +The `history` command can also save both the commands and their output to a text +file. This is called a transcript. See :doc:`transcript` for more information on +how transcripts work, and what you can use them for. To create a transcript use +the `-t` or `--transcription` option:: + + (Cmd) history 2:3 --transcript transcript.txt + +The `--transcript` option implies `--run`: the commands must be re-run in order +to capture their output to the transcript file. + +The last action the history command can perform is to clear the command history +using `-c` or `--clear`:: + + (Cmd) history -c + +In addition to these five actions, the `history` command also has some options +to control how the output is formatted. With no arguments, the `history` command +displays the command number before each command. This is great when displaying +history to the screen because it gives you an easy reference to identify +previously entered commands. However, when creating a script or a transcript, +the command numbers would prevent the script from loading properly. The `-s` or +`--script` option instructs the `history` command to suppress the line numbers. +This option is automatically set by the `--output-file`, `--transcript`, and +`--edit` options. If you want to output the history commands with line numbers +to a file, you can do it with output redirection:: + + (Cmd) history 1:4 > history.txt + +You might use `-s` or `--script` on it's own if you want to display history +commands to the screen without line numbers, so you can copy them to the +clipboard:: + + (Cmd) history -s 1:3 + +`cmd2` supports both aliases and macros, which allow you to substitute a short, +more convenient input string with a longer replacement string. Say we create an +alias like this, and then use it:: + + (Cmd) alias create ls shell ls -aF + Alias 'ls' created + (Cmd) ls -d h* + history.txt htmlcov/ + +By default, the `history` command shows exactly what we typed:: + + (Cmd) history + 1 alias create ls shell ls -aF + 2 ls -d h* + +There are two ways to modify that display so you can see what aliases and macros +were expanded to. The first is to use `-x` or `--expanded`. These options show +the expanded command instead of the entered command:: + + (Cmd) history -x + 1 alias create ls shell ls -aF + 2 shell ls -aF -d h* + +If you want to see both the entered command and the expanded command, use the +`-v` or `--verbose` option:: + + (Cmd) history -v + 1 alias create ls shell ls -aF + 2 ls -d h* + 2x shell ls -aF -d h* + +If the entered command had no expansion, it is displayed as usual. However, if +there is some change as the result of expanding macros and aliases, then the +entered command is displayed with the number, and the expanded command is +displayed with the number followed by an `x`. .. _`Readline Emacs editing mode`: http://readline.kablamo.org/emacs.html @@ -295,7 +484,6 @@ with automatically included ``do_`` methods. ( ``!`` is a shortcut for ``shell``; thus ``!ls`` is equivalent to ``shell ls``.) - Transcript-based testing ======================== |