Moving to zsh – part 7: Miscellanea

Apple has announced that in macOS 10.15 Catalina the default shell will be zsh.

In this series, I will document my experiences moving bash settings, configurations, and scripts over to zsh.

• Part 1: Moving to zsh
• Part 2: Configuration Files
• Part 3: Shell Options
• Part 4: Aliases and Functions
• Part 5: Completions
• Part 6: Customizing the zsh Prompt
• Part 7: Miscellanea (this article)
• Part 8: Scripting zsh

This series has grown into a book: reworked and expanded with more detail and topics. Like my other books, I plan to update and add to it after release as well, keeping it relevant and useful. You can order it on the Apple Books Store now.

As I have mentioned in the earlier posts, I am aware that there are many solutions out there that give you a pre-configured ‘shortcut’ into lots of zsh goodness. But I am interested in learning this the ‘hard way’ without shortcuts. Call me old-fashioned. (“Uphill! In the snow! Both ways!”)

We have covered the general aspects of configuring your zsh environment and enabling some of its features to make your work more productive. However, there are zsh features that didn’t quite fit in earlier posts, but also don’t warrant a post of their own. So I am gathering them here.

multiIO

Terminal commands can take input from a file or a previous command (stdin) and have two different outputs: stdout and stderr. In bash you can redirect each of these to a single other destination.

For example, you can redirect the output of a command to a file:

% system_profiler SPHardwareDataType >hardwareinfo.txt

In zsh you can redirect to (and from) multiple sources. In the simplest form you can write the output to two files:

% system_profiler SPHardwareDataType >hardwareinfo.txt >computerinfo.txt

This is of course not a very realistic case. Since the pipe | is a form of redirection, you can combine output to a file with a pipe:

% system_profiler SPHardwareDataType >hardwareprofile.txt | cat

Instead of piping to cat, you can also redirect to stdout (or &1) as well as to a file:

% system_profiler SPHardwareDataType >&1 >hardwareprofile.txt

Note that the order of doing this is important. The construct >file.txt >&1 would redirect the output to file.txt and then redirect the output again to where stdout or 1 is going, so it would be redundant.

When combined with pipes and other commands multiIO can become very useful:

% system_profiler SPHardwareDataType >hardwareprofile.txt | awk '/Serial Number/ { print $4 }' >&1 >serialnumber.txt

You can use multiIO for input as well:

% sort </usr/share/calendar/calendar.freebsd </usr/share/calendar/calendar.computer

And while this not directly related, but somewhat close, in zsh, this

% <hardwareinfo.txt

is equivalent to more hardwareinfo.txt.

Recursive Globbing with **

You can use the ** to denote an arbitrary string that can span multiple directories in a path.

For example:

% echo Library/Preferences/**/com.apple.screensaver.*plist
Library/Preferences/ByHost/com.apple.screensaver.BBCCDDEE-AABB-CCDD-ABCD-00AABBCCDDEE.plist Library/Preferences/com.apple.screensaver.plist

In this case the ** matches nothing as well as /ByHost/.

Note: when used on large folder structures this glob can take a while. So use with care.

Connected array Variables

We already encountered the fpath variable in earlier posts. You can see its contents with the echo command:

% echo $fpath
/Users/armin/Projects/mac-zsh-completions/completions/ /Users/armin/Projects/dotfiles/zshfunctions /usr/local/share/zsh/site-functions /usr/share/zsh/site-functions /usr/share/zsh/5.3/functions

Interestingly enough, zsh also has an FPATH variable, which is a colon-separated list of directories:

% echo $FPATH
/Users/armin/Projects/mac-zsh-completions/completions/:/Users/armin/Projects/dotfiles/zshfunctions:/usr/local/share/zsh/site-functions:/usr/share/zsh/site-functions:/usr/share/zsh/5.3/functions

Since the fpath variable is an array, I only changed the fpath variable in my zshrc.I never set or changed the FPATH, yet it reflects the changes made to the fpath variable.

When you see the type of both variables, you get an idea that something is going on:

% echo ${(t)fpath}
array-special
% echo ${(t)FPATH}
scalar-special

The fpath and FPATH are connected in zsh. Changes to one affect the other. This allows use of more flexible and powerful array operations through the fpath ‘aspect’ of the value, but also provides compatibility to tools that expect the traditional colon-separated format in FPATH.

You will not be surprised to hear that zsh uses the same ‘magic’ with the PATH variable and its array counterpart path.

This means that you can continue to use path_helper to get your PATH from the files in /etc/paths and /etc/paths.d. (Well, you don’t have to, because on macOS this is done for all users in /etc/zprofile.) But then you can manipulate the path variable with array functions, like:

path+=~/bin

You get the useful aspects of both syntaxes.

Suffix Aliases

I learnt this one after writing the aliases part.

Suffix aliases take effect on the last part of a path, so usually the file extension. A suffix alias will assign a command to use when you just type a file path in the command line.

For example, you can a suffix alias for the txt file extension:

alias -s txt="open -t"

When you then type a path ending with .txt and no command, zsh will execute open -t /path/to/file.txt.

The open -t command opens a file in the default application set for the txt file extension in Finder. You probably want to set the suffix alias to bbedit or atom or something like that rather than open -t.

You can use other command line tools for the suffix alias:

alias -s log="tail -f"

Then, typing /var/log/install.log will show the last lines of that file and update the output when the file changes. If you prefer the graphical user interface, you can use the open -a command to assign suffix aliases to applications:

alias -s log="open -a Console"

You can even create a suffix alias using a different alias:

alias pacifist="open -a Pacifist"
alias -s pkg=pacifist

Together with the AutoCD option, this can improve your application-shell interactions a lot.

Bindkey for History Search

Most of the keyboard shortcuts in zsh work the same way as they do in bash. I have found one change that has proven quite useful:

^[[A' up-line-or-search # up arrow bindkey

^[[B' down-line-or-search # down arrow 

These two commands will change the behavior of the up and down arrow keys from just switching to the previous command, to searching. This means that when you start typing a command and then hit the up key, rather than just replacing what you already typed with the previous command, the shell will instead search for the latest command in the history starting with what you already typed.

There are many commands or ‘widgets’ you can assign to keystrokes with the bindkey command. You can find a list of default ‘widgets’ in the documentation.

Conclusion

This concludes the part of the series about configuring zsh. When I set out I wanted to recreate the environment I had built in bash. Along the way I found a few features in zsh that seemed worth adding to my toolkit.

After nearly two months of working in zsh, there are already some features I would miss terribly when switching back to bash or a plain, unconfigured zsh. Most important is the powerful tab-completion. But features like AutoCD, MultiIO, and flexible aliases, are useful tools as well.

The dynamic loading of functions from files in the fpath was initially confusing, but it allows configurations and functions to be split out into their own, which simplifies “modularizing” and sharing.

In the next (and last) post, I will cover the changes when scripting with zsh vs bash.