The Chronicle

of a ColdFusion Expatriate

Why You Should Give Zsh Another Try

November 19, 2013

If you’re already a fan of “the Z shell” (zsh), you may not need to read any further. If, however, you’re like me and have spent years in the Bourne Again shell (bash), it might be time to re-evaluate your choice.

I have used bash for a long time and reached a fair proficiency level in it. I was doing things like looping over program output, filtering it, using utilities like seq and wc all the time. I could re-run commands from my history in more than one way and reverse-search them with Ctrl-R. None of this was news to me.

But then someone told me about this Z shell configuration package called “oh my zsh,” and I decided to dangle my toes into the waters of the Z shell and see what it’s all about. After all, the OS X terminal drops you into zsh by default; there must be something to it.

I’m never going back.

To begin, here are some specific reasons you should drop bash or tcsh or csh and use the Z shell:

  1. The number one reason to consider zsh as a replacement for the shell you already use is ubiquity. You’re going to be much more likely to actually find zsh on any given machine than newfangled shells like “fish.” If you only ever use your own single personal computer this doesn’t matter as much.
  2. The features, oh the features! The bulk of this post will be about these features so I will leave it at this for now. Suffice it to say, there are a couple of options that are so killer that I can never go back to bash.
  3. The “oh my zsh” system provides a further ecosystem of themes and extensions that other people maintain, giving you some awesome off-the-shelf capabilities as well as a very reasonable framework in which to create your own, if you wish.

Curious? Let’s dig in.

Get Started Right Now

If you’re like me, you’re more of a doer than a reader. If you want to see what all the fuss is about, here is how you can do that right now:

  1. Make sure you have zsh installed. It is the default shell in OS X and sometimes CentOS; other flavors of Linux may need a quick install. For Ubuntu, sudo apt-get install zsh, for Gentoo sudo emerge zsh zsh-completion.
  2. If you want to try “oh my zsh”, get it on the oh-my-zsh Github page. I highly recommend it, but be prepared to read another README and follow more installation instructions.

Oh, the Features!

As a long-time bash user, perhaps the single most game-changing feature that zsh offers is insanely good command completion. What do I mean by “good?” Well, zsh sometimes unexpectedly completes things that I’ve accidentally typed using the wrong case, its menu completion is (to my mind) easier to use because it highlights the selected item. On top of those, it’s all configurable (the Linux user’s dream).

There are straightforward options for whether to ring the terminal bell when starting an ambiguous completion and whether to use menu completion immediately or attempt a regular inline completion first. Let’s talk about these options now.

First, you can see a list of all of the options on this handy webpage maintained by a Hungarian University. This is the page I used as a reference; I’m not sure why it’s in English or why it’s so highly ranked by Google, but here it is: ZSH options.

In zsh, you set and unset options using the commands setopt and unsetopt. Zsh has a semi-unique way of dealing with options: the names themselves are not case-sensitive and the underscores don’t even matter. In other words, APPEND_HISTORY is the same as Ap_pEND_hIs_t_ory or just appendhistory.

Similar to Vim, you can negate an option by prepending “no” to it. Thus, setopt noautomenu is the same as unsetopt automenu.

With me so far? Excellent. Here are the options that I have set and why:

When you press tab to try to autocomplete your entry, if the completion is ambiguous (what you have typed is not unique), immediately display the list of possible completions.

Note that if you like the behavior of menucomplete described below, you probably won’t need to set this option, as menucomplete supersedes it.

Zsh has a really neat feature where you can “name” directories and then use the name instead of the full directory path anywhere where a normal path would be accepted. This option tells zsh that if you set an environment variable to a literal path, that environment variable should also be accepted as a name for that path when preceded by the ~ (tilde), which is how zsh normally identifies the names of named directories. I’ll dig into this a bit more later on.
This basically says that if an argument is expected to be a directory and all other shell expansion has failed to produce a directory, also try to expand it as though it were the name of a named directory, even though it doesn’t begin with the ~ character.
Don’t record duplicate commands in the history. Because honestly, did you need to know how many times you had to repeat the same command? It’s just embarrassing.
This causes the menu completion display to include characters indicating the types of the items (symbolic links, executables, etc.)
When attempting a completion on an ambiguous match, instead of simply appending all remaining characters shared by all possible matches and waiting (which is the usual behavior in most shells), immediately insert the entire first possible match and display the completion menu. This is better experienced than described, so try it out and see if you like it. I do.
Zsh will emit a terminal bell when you attempt to do an ambiguous completion… Unless you set this option. Which I strongly recommend.

These are the options that I’m pretty happy with so far, although I’m still tweaking things here and there. Now let’s get into the serious stuff!

Since I wrote this, I have decided that menucomplete is kind of annoying. When menucomplete is turned on, you can’t drill down into partial completions by adding disambiguating characters because the menu appears immediately. So, give it a try, but I turned it back off.

What’s in a Name?

Zsh has this pretty fantastic feature called named directories. If you are familiar with Linux shells at all, you are probably by now quite used to using ~ to stand in for the path to your home directory. This is supremely convenient when you want to, for example, copy a file from your current directory to your home directory, like this:

$ cp some_file.txt ~

Much easier than having to type out /home/myusername/ or whatever it may be. So that’s swell, but what if you could create your own symbols for long directory names that you use often? In zsh you can!

The whole concept of “named directories” is based on zsh’s “expansion” system, which you can read about in detail on this page. Essentially, if any word entered at the zsh prompt begins with a tilde (~), zsh attempts to expand it in a few ways. Note that you can force this expansion “live” on the prompt by pressing tab (which is sometimes really helpful and cool).

To name your own directory, all you need to do is define a shell variable (in zsh they call these “parameters;” I’m not sure why) that begins with a forward slash. Obviously named directories must be absolute, so that might be slightly limiting, but let’s look at an example.

Let’s say you run an Apache webserver and the root of your main website is located at /var/www/awesomesite. Even with tab completion it can be annoying to type that over and over, so let’s create a very short name for it:

$ export wroot=/var/www/awesomesite

In the above example, I have used the export command at the prompt to immediately add this variable to my environment. You can add that exact line to your .zshrc so that it is permanent (without the dollar sign prompt obviously). Now, if you want to change directories to your web root, you type:

$ cd ~wr<tab>

When you press tab, if there are no other named directories starting with “wr,” it will expand your command line to cd ~wroot/. You saved at least six or seven keystrokes even accounting for tab completion with the original full path. You can also use the ~wroot shorthand anywhere where zsh expects a path and it will work. For example, touch ~wroot/foo.txt will work. Think of the possibilities.

So what if you wind up with a whole bunch of named directories? No problem, zsh will continue to use your various completion options to disambiguate what you have typed, including the same menu it uses for normal commands and paths as described above.

Named directories is one of my favorite zsh tricks.

What Else?

There are obviously a lot of options available and I have only scratched the surface here. I am still learning which combination of options I really like, but maybe you have some experience or ideas as well; feel free to share them! Remember, sharing is caring.