Hack 1 Get the Most Out of the Default Shell


figs/beginner.gif figs/hack1.gif

Become a speed daemon at the command line.

For better or for worse, you spend a lot of time at the command line. If you're used to administering a Linux system, you may be dismayed to learn that bash is not the default shell on a BSD system, for either the superuser or regular user accounts.

Take heart; the FreeBSD superuser's default tcsh shell is also brimming with shortcuts and little tricks designed to let you breeze through even the most tedious of tasks. Spend a few moments learning these tricks and you'll feel right at home. If you're new to the command line or consider yourself a terrible typist, read on. Unix might be a whole lot easier than you think.

NetBSD and OpenBSD also ship with the C shell as their default shell. However, it is not always the same tcsh, but often its simpler variant, csh, which doesn't support all of the tricks provided in this hack.

However, both NetBSD and OpenBSD provide a tcsh package in their respective package collections.


1.2.1 History and Auto-Completion

I hate to live without three keys: up arrow, down arrow, and Tab. In fact, you can recognize me in a crowd, as I'm the one muttering loudly to myself if I'm on a system that doesn't treat these keys the way I expect to use them.

tcsh uses the up and down arrow keys to scroll through your command history. If there is a golden rule to computing, it should be: "You should never have to type a command more than once." When you need to repeat a command, simply press your up arrow until you find the desired command. Then, press Enter and think of all the keystrokes you just saved yourself. If your fingers fly faster than your eyes can read and you whiz past the right command, simply use the down arrow to go in the other direction.

The Tab key was specifically designed for both the lazy typist and the terrible speller. It can be painful watching some people type out a long command only to have it fail because of a typo. It's even worse if they haven't heard about history, as they think their only choice is to try typing out the whole thing all over again. No wonder some people hate the command line!

Tab activates auto-completion. This means that if you type enough letters of a recognizable command or file, tcsh will fill in the rest of the word for you. However, if you instead hear a beep when you press the Tab key, it means that your shell isn't sure what you want. For example, if I want to run sockstat and type:

% so

then press my Tab key, the system will beep because multiple commands start with so. However, if I add one more letter:

% soc

and try again, the system will fill in the command for me:

% sockstat

1.2.2 Editing and Navigating the Command Line

There are many more shortcuts that can save you keystrokes. Suppose I've just finished editing a document. If I press my up arrow, my last command will be displayed at the prompt:

% vi mydocs/today/verylongfilename

I'd now like to double-check how many words and lines are in that file by running this command:

% wc mydocs/today/verylongfilename

I could pound on the backspace key until I get to the vi portion of the command, but it would be much easier to hold down the Ctrl key and press a. That would bring me to the very beginning of that command so I could replace the vi with wc. For a mnemonic device, remember that just as a is the first letter of the alphabet, it also represents the first letter of the command at a tcsh prompt.

I don't have to use my right arrow to go to the end of the command in order to press Enter and execute the command. Once your command looks like it should, you can press Enter. It doesn't matter where your cursor happens to be.

Sometimes you would like your cursor to go to the end of the command. Let's say I want to run the word count command on two files, and right now my cursor is at the first c in this command:

% wc mydocs/today/verylongfilename

If I hold down Ctrl and press e, the cursor will jump to the end of the command, so I can type in the rest of the desired command. Remember that e is for end.

Finally, what if you're in the middle of a long command and decide you'd like to start from scratch, erase what you've typed, and just get your prompt back? Simply hold down Ctrl and press u for undo.

If you work in the Cisco or PIX IOS systems, all of the previous tricks work at the IOS command line.


Did you know that the cd command also includes some built-in shortcuts? You may have heard of this one: to return to your home directory quickly, simply type:

% cd

That's very convenient, but what if you want to change to a different previous directory? Let's say that you start out in the /usr/share/doc/en_US.ISO8859-1/books/handbook directory, then use cd to change to the /usr/X11R6/etc/X11 directory. Now you want to go back to that first directory. If you're anything like me, you really don't want to type out that long directory path again. Sure, you could pick it out of your history, but chances are you originally navigated into that deep directory structure one directory at a time. If that's the case, it would probably take you longer to pick each piece out of the history than it would be to just type the command manually.

Fortunately, there is a very quick solution. Simply type:

% cd -

Repeat that command and watch as your prompt changes between the first and the second directory. What, your prompt isn't changing to indicate your current working directory? Don't worry, [Hack #2] will take care of that.

1.2.3 Learning from Your Command History

Now that you can move around fairly quickly, let's fine-tune some of these hacks. How many times have you found yourself repeating commands just to alter them slightly? The following scenario is one example.

Remember that document I created? Instead of using the history to bring up my previous command so I could edit it, I might have found it quicker to type this:

% wc !$   wc mydocs/today/verylongfilename         19        97        620 mydocs/today/verylongfilename

The !$ tells the shell to take the last parameter from the previous command. Since that command was:

% vi mydocs/today/verylongfilename

it replaced the !$ in my new command with the very long filename from my previous command.

The ! (or bang!) character has several other useful applications for dealing with previously issued commands. Suppose you've been extremely busy and have issued several dozen commands in the last hour or so. You now want to repeat something you did half an hour ago. You could keep tapping your up arrow until you come across the command. But why search yourself when ! can search for you?

For example, if I'd like to repeat the command mailstats, I could give ! enough letters to figure out which command to pick out from my history:

$ !ma

! will pick out the most recently issued command that begins with ma. If I had issued a man command sometime after mailstats command, tcsh would find that instead. This would fix it though:

% !mai

If you're not into trial and error, you can view your history by simply typing:

% history

If you're really lazy, this command will do the same thing:

% h

Each command in this history will have a number. You can specify a command by giving ! the associated number. In this example, I'll ask tcsh to reissue the mailstats command:

% h   165  16:51  mailstats   166  16:51  sockstat   167  16:52  telnet localhost 25   168  16:54  man sendmail % !165

1.2.4 Silencing Auto-Complete

The last tip I'll mention is for those of you who find the system bell irritating. Or perhaps you just find it frustrating typing one letter, tabbing, typing another letter, tabbing, and so on until auto-complete works. If I type:

% ls -l b

then hold down the Ctrl key while I press d:

backups/  bin/   book/  boring.jpg ls -l b

I'll be shown all of the b possibilities in my current directory, and then my prompt will return my cursor to what I've already typed. In this example, if I want to view the size and permissions of boring.jpg, I'll need to type up to here:

% ls -l bor

before I press the Tab key. I'll leave it up to your own imagination to decide what the d stands for.

1.2.5 See Also

  • man tcsh



BSD Hacks
BSD Hacks
ISBN: 0596006799
EAN: 2147483647
Year: 2006
Pages: 160
Authors: Lavigne

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