Terminal on Jake Worth

Overwrite vs. Append

Fri, 13 Mar 2026 16:01:22 -0400

I use the append >> and overwrite > redirection operators all the time. Today I’d like to share a simple mental model I’ve developed for remembering which is which.

Who Owns This Program?

Mon, 09 Feb 2026 10:36:33 -0500

I’ve got a command docker on my machine. I need to upgrade it. So, who owns it?

Calculating With Bc

Wed, 07 Jan 2026 09:48:26 -0500

Today I accidentally I found a calculator on my computer, bc. Let’s look at it!

pbcopy, no cat

Wed, 05 Mar 2025 10:07:24 -0500

My friend Josh recently wrote about a common mistake using pbcopy, Apple’s pasteboard utility.

Read Zsh Builtin Manual Pages

Wed, 22 May 2024 12:30:02 -0400

In Zsh, if you type man cd, instead of a manual page, you’ll get this:

See the built-in command description in the appropriate shell manual page.

To see Zsh’s implementation of cd, we need to view Zsh’s built-in man page:

man zshbuiltins

Append to a Write-Protected File

Thu, 22 Feb 2024 08:32:29 -0500

Suppose you want to append to a file that’s write-protected and can only be edited via sudo. Is that possible? It is!

A technique I discovered today is to use tee with sudo:

$ cat file.txt | sudo tee -a /etc/hosts

This lets me append the contents of file.txt to the write-protected /etc/hosts file by entering my password.

Create a File With `cat`

Tue, 12 Dec 2023 13:51:16 -0500

When you combine cat (concatenate) with > (output redirection), you can create and write to a file from the command line.

$ cat > test.txt

Hit enter after the file name, and your terminal will wait for input. End the file with CTRL + D.

$ cat > test.txt
one
two
three
$ cat test.txt
one
two
three

>> works, too; appending to the file as expected.

Override Autojump's Directory Rankings

Wed, 08 Mar 2023 10:12:50 -0500

Autojump is my tool of choice for navigating directories. If I enter the following into the terminal:

$ j til

Autojump will try to guess where I want to go among directories I’ve previously visited. It uses a database of directories and their relative rankings to do so.

But there’s a problem! These day I only want to visit ~/oss/til. In the past I’ve visited ~/oss/hr-til and ~/oss/tilex hundreds of times. Autojump always sends me there first. I don’t want that!

Force ASDF Reshim

Tue, 21 Jun 2022 09:49:59 -0400

When I upgrade ASDF, I sometimes get an error like this when I try to run a command:

/Users/jakeworth/.asdf/shims/jq: line 3:
/usr/local/Cellar/asdf/0.9.0/libexec/bin/asdf:
No such file or directory

The issue is that I’ve upgraded ADSF to v0.10.2, but the jq shim doesn’t know that and can’t find it in a directory called “0.9.0”. This issue persists even after running asdf reshim.

My solution is to force ASDF to rebuild shims directory by renaming it. A rename lets me get back to where I am now, in case I need to.

Ctags Dotfiles

Fri, 18 Mar 2022 12:11:25 -0400

Something I took for granted at Hashrocket was the file that configures Exhuberant Ctags. Without configuration, recursive tag generation will tag many things and cause problems. overindex badly.

Here’s how you configure Ctags to ignore things:

/ctags.cnf (on MSDOS, MSWindows only)
/etc/ctags.conf
/usr/local/etc/ctags.conf
$HOME/.ctags
$HOME/ctags.cnf (on MSDOS, MSWindows only)
.ctags
ctags.cnf (on MSDOS, MSWindows only)
If any of these configuration files exist, each will be expected to contain a
set of default options which are read in the order listed when ctags starts,
but before the CTAGS environment variable is read or any command line options
are read. This makes it possible to set up site-wide, personal or project-level
defaults.

Here’s the head of my root .ctags, which even this far in is excluding a lot:

Save Size Change to iTerm Profile

Sat, 13 Nov 2021 13:35:21 -0500

The longer I program (ahem), the bigger I want my terminal fonts. I think most programmers should be using a bigger font than they are. Complicating matters, the standard font for iTerm is miniscule on a computer monitor.

Today I discovered iTerm’s ‘View > Size Changes Update Profile’ feature. When enabled, changes to your font size via ⌘ + and ⌘ - will be applied to your iTerm profile. The next time you open iTerm, the new font size will persist.

Autojump and Open

Sat, 06 Nov 2021 13:39:32 -0400

I love autojump. I use it because I think that remembering my location in a directory structure relative to other directories, so I can navigate with cd, is mental energy I could be using for something else.

Today I learned that autojump has a jo command, which jumps to a directory and opens it in your file explorer.

jo Desktop

This might be a throwaway lesson if I wasn’t regularly sidetracked by the MacOS file explorer. Finding a file using the file explorer is a routine operation I have yet to do fluidly on a Mac. This helps!

Command Line Subshell

Mon, 02 Aug 2021 11:34:14 -0400

When chaining commands in the terminal, you may need to do things that affect the shell’s environment, like change directories. Here’s an example:

$ yarn install && cd ios && pod install && cd .. && yarn build

These cd’s can clutter up a script, and they’re incidental. My solution is to use a subshell (here’s the explanation from man bash):

(list) list is executed in a subshell environment (see COMMAND EXECUTION ENVIRONMENT below). Variable assignments and builtin commands that affect the shell’s environment do not remain in effect after the command completes. The return status is the exit status of list.

Directional Commands

Wed, 21 Apr 2021 16:50:27 -0400

You can move the cursor without arrow keys. Here is the keyboard equivalent for each.

Up (‘previous’): CTRL + P
Down (’next’): CTRL + N
Left (‘back’): CTRL + B
Right (‘forward’): CTRL + F

Mapping caps lock to CTRL makes these combinations very accessible.

Finding Getters

Wed, 21 Apr 2021 16:50:27 -0400

After writing the other day about why you might not want to use simple getters, I decided that I wanted to eliminate all such methods from a project.

Here is the regex I wrote to isolate the pattern:

ag 'def (\w+);?\s+@\1;?\s+end'

The semicolon catches one-line getter methods as well as the more common three-line.

MD5 File Signatures

Wed, 21 Apr 2021 16:50:27 -0400

The command md5 <file> generates a unique 32-digit hexadecimal number. This can serve as a signature for a file in its particular state, letting you know when it has changed.

Example usage:

$ touch test.txt
$ md5 test.txt
 MD5 (test.txt) = d41d8cd98f00b204e9800998ecf8427e
$ echo 'some content' > test.txt
$ md5 test.txt
 MD5 (test.txt) = eb9c2bf0eb63f3a7bc0ea37ef18aeba5

Printing with lpr

Wed, 21 Apr 2021 16:50:27 -0400

Recently while trying to fix a printer I used lpr a bunch of times. It’s not exactly new to me, but never fails to surprise people when I use it.

lpr submits files for printing to your default printer in OSX.

Print a file:

lpr README.md

Print the current file in your Vim session, with a cool job name:

:! lpr -T 'cool job name' %

Print two copies to a specific printer:

Reverse a String

Wed, 21 Apr 2021 16:50:27 -0400

Reverse a string with the rev command.

$ echo 'test' | rev
tset

It also works with files.

$ rev Procfile
br.amup/gifnoc C- amup cexe eldnub :bew

Run Previous Command

Wed, 21 Apr 2021 16:50:27 -0400

Previously run commands can be viewed with the history command.

$ history
10048 git checkout master
10049 gpr
10050 rake

With this list, you can rerun any command using !n:

$ !10048
Already on 'master'

The command !! prints the last command you ran, then runs it. Here is an example:

$ ls
LICENSE.md README.md bash cucumber rails
$ !!
ls
LICENSE.md README.md bash cucumber rails

Replace the second ! with the first few letters of a command you have previously run, and bash will search for, print, and run the most recent instance.

Screen Flashing in OSX

Wed, 21 Apr 2021 16:50:27 -0400

I like a quiet computer. But I also like tab-completing commands in the terminal, which produces a necessary alert from time to time.

A solution I found today is to use OSX Accessibility features to add a screen flash on alerts, then disable the sounds.

System Preferences > Accessibility > Hearing menu, choose ‘Audio’ > Check ‘Flash the screen when an alert occurs’

Send Processes to the Background

Wed, 21 Apr 2021 16:50:27 -0400

Processes on any POSIX-compliant computer can be sent to the background with CTRL-Z (<prefix> + Z for the tmux-ers) and returned to the foreground with fg.

Here is an example:

user@computer:~% ping www.google.com
PING www.google.com (74.125.228.212): 56 data bytes
64 bytes from 74.125.228.212: icmp_seq=0 ttl=52 time=41.574 ms
64 bytes from 74.125.228.212: icmp_seq=1 ttl=52 time=42.836 ms
64 bytes from 74.125.228.212: icmp_seq=2 ttl=52 time=53.527 ms
^Z
zsh: suspended ping www.google.com
user@computer:~% fg
[1] + continued ping www.google.com
64 bytes from 74.125.228.212: icmp_seq=3 ttl=52 time=42.433 ms
64 bytes from 74.125.228.212: icmp_seq=4 ttl=52 time=42.401 ms
64 bytes from 74.125.228.212: icmp_seq=5 ttl=52 time=42.837 ms
64 bytes from 74.125.228.212: icmp_seq=6 ttl=52 time=44.203 ms
^C
--- www.google.com ping statistics ---
7 packets transmitted, 7 packets received, 0.0% packet loss

Start Postgres.app from the Command Line

Wed, 21 Apr 2021 16:50:27 -0400

Today I was trying to restore a production Postgres dump on a remote machine, to test some migrations. I haven’t granted myself Heroku production database access, hence the SSH into a machine with a Heroku user that has access.

I quickly hit a problem— this remote machine runs Postgres using Postgres.app. Without that program, I’m out of luck. No local Postgres server, no production database restore, no testing.

It turns out you can start Postgres.app from the command line. Find the executable and call it.

Watch That Program

Wed, 21 Apr 2021 16:50:27 -0400

Have you ever been working in the terminal and found yourself repeating the same command many times? Delegate that work to the computer.

watch comes with Linux and can be installed on OSX via homebrew. It executes a program periodically, defaulting to every two seconds.

We used it today while writing a database backup script. Instead of checking our dump directory every time a cron job executed, we ran watch ls, and watched the script succeed or fail with live updates.