Category Archives: MacOS/*BSD

macOS/OS X, FreeBSD/OpenBSD/NetBSD

Automatically Conceal Sender’s IP Address in Email Clients via SSH Tunneling

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Last updated on May 5, 2021

Desktop email clients, such as Thunderbird and Claws Mail, are preferred over their web counterparts by many professionals and power users due to their additional convenience and security. However, one big downside is that they often expose the sender's IP address to the receivers, since many SMTP servers record the sender's IP address and put it in the header, something similar to Received: from [xxx.xxx.xxx.xxx] (my.example.com. [xxx.xxx.xxx.xxx]). This, unfortunately, puts the sender's privacy in great jeopardy, as an IP address can reveal so much information including location, ISP, and institution names.

To address this issue, one simple solution is to let the email client connect via a proxy. While a system-widely available proxy works for many users, some of us just want our email clients, but not other programs, to go through a specific proxy. In this post, I'll demonstrate how to use an email client automatically via SSH tunneling. The instructions are specifically tailored for GNU/Linux and MacOS users, as it involves some uses of UNIX commands and bash scripts; if you are on Windows, you can still follow the instructions with the help of Cygwin.

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Enable Auto Completion for pip in Zsh

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Last updated on August 8, 2017

Pip is a package management system for installing and managing Python software packages. To enable auto completion for pip in zsh, the documentation of pip suggests adding the following line to ~/.zshrc:

eval "`pip completion --zsh`"

However, merely having this line would not enable auto completion for pip3. To enable auto completion for pip3 as well, add the following line after the line above:

compctl -K _pip_completion pip3

Enable Natural Scrolling for Trackpads Using libinput

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Last updated on October 28, 2018

Libinput is a library to handle input devices in Wayland and X.Org. It can be used as a drop-in replacement for evdev and synaptics in X.Org, and it is supported by a wide range of desktop environments, including GNOME and Xfce. In this post, we will see how to enable natural scrolling for trackpads using libinput. We will also leave mouses alone, i.e., no natural scrolling for mouses.

First, we need to know the name of the trackpad to enable natural scrolling for. This can be easily known by executing xinput --list. My output includes the following:

⎡ Virtual core pointer                          id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
⎜   ↳ bcm5974                                   id=13   [slave  pointer  (2)]

It is easy to see that my trackpad is bcm5974.

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Parallelize make by Default

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Last updated on December 13, 2016

The make utility is an standard utility on POSIX systems (GNU/Linux, macOS, etc.) that update files derived from other files, such as compiling source files to their binary forms. It is widely supported and used across different fields such as organizing and building C/C++/Fortran projects, building Sphinx documentation, etc.

The most popular implementation of the make utility is probably GNU make, which is usually the default make program on various GNU/Linux distributions. (On macOS, the version of the default GNU make is pretty old. Please consult Install and Use GNU Command Line Tools on macOS/OS X for a newer version.) It adds one very important feature besides the standard make specification: parallelization. The command line option -j can be used to specify the maximum number of jobs that it is allowed to run simultaneously. However, it is quite annoying to type up this option every time when using it—we want a setting such that the CPU can be fully utilized by default. To achieve this goal, add the following lines to your ~/.bashrc if you use bash or ~/.zshrc if you use zsh:

# set MAKEFLAGS
if type nproc &>/dev/null; then   # GNU/Linux
  export MAKEFLAGS="$MAKEFLAGS -j$(($(nproc)-1))"
elif type sysctl -n hw.ncpu &>/dev/null; then   # macOS, FreeBSD
  export MAKEFLAGS="$MAKEFLAGS -j$(($(sysctl -n hw.ncpu)-1))"
fi

The code above sets the envrionmental variable MAKEFLAGS, which specifies the command line arguments of any invoked make subprocesses. It is set such that the maximum number of jobs that is allowed to be run simultaneously is equal to the number of available CPU cores minus 1. In this way, the hardware is more or less fully utilized when using make, with one CPU core left for other potential tasks on the system.

A Better ls Command

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Last updated on April 14, 2024

The ls command is a command to list files on a UNIX-like system. It is probably one of the most used command. However, a plain ls command without any polishing may look really “plain”. Here, we will slightly configure this command to make it more usable:

  • More colorful output
  • Automatic pagination for long file lists
  • File type indication
  • Human readable sizes
  • Natural ordering of files

Screenshots:

Output of ls before configuration

Output of ls before configuration

Output of ls after configuration

Output of ls after configuration

ls pagination

Pagination for ls

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Speed Test: Check the Existence of a Command in Bash and Zsh

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Last updated on December 10, 2016

In both bash and zsh, there are multiple methods to check whether a command exists. In this post, a set of speed tests will be performed on them to find the fastest way in each of the two shells (NOT to compare the two shells). We will test 5 different methods (foobar is the command to test for existence in the list):

  • type foobar &> /dev/null
  • hash foobar &> /dev/null
  • command -v foobar &> /dev/null
  • which foobar &> /dev/null
  • (( $+commands[foobar] )) (zsh only)

All the methods listed above will have a return status of zero if the command foobar exists, otherwise non-zero. That is, after replacing testing-command by any of the commands listed above, you can test the existence of the command foobar by executing testing-command && echo exist || echo non-exist.

Throughout this post, ls will be the command that is used for testing existence, which does exist on the system which runs the tests. The test environment is Debian Jessie with bash 4.3.30 and zsh 5.0.7 on Intel Xeon processor E3-1240 v3 (8 MB Cache, 3.4 GHz). The test scripts are also available at the end of the post.

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Restore the Previously Canceled Command in Zsh

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Last updated on December 10, 2016

In zsh, it is often annoying that we can't easily restore the command we just canceled by Ctrl-C: canceled commands are not recorded into the history file and thus cannot be restored by searching previous commands. To make the restoration possible, zsh provides a variable ZLE_LINE_ABORTED which keeps a record of the last command that was canceled—everything looks so simple. However, for some reasons, such as canceling stuck tab completion, we often push Ctrl-C for more than once—but ZLE_LINE_ABORTED would become empty if Ctrl-C is used on an empty line! Thanks to the great extensibility of zsh, we can solve this issue by tweaking zle-line-init (add the following to your ~/.zshrc):

function zle-line-init {
  # Your other zle-line-init configuration ...

  # Store the last non-empty aborted line in MY_LINE_ABORTED
  if [[ -n $ZLE_LINE_ABORTED ]]; then
    MY_LINE_ABORTED="$ZLE_LINE_ABORTED"
  fi

  # Restore aborted line on the first undo.
  if [[ -n $MY_LINE_ABORTED ]]; then
    local savebuf="$BUFFER" savecur="$CURSOR"
    BUFFER="$MY_LINE_ABORTED"
    CURSOR="$#BUFFER"
    zle split-undo
    BUFFER="$savebuf" CURSOR="$savecur"
  fi
}
zle -N zle-line-init
  • Line 1: Define the zle-line-init widget which will be executed every time when the a new command line is ready to take input.
  • Line 5-7: If ZLE_LINE_ABORTED is non-empty, save it to MY_LINE_ABORTED.
  • Line 10-16: If MY_LINE_ABORTED is non-empty, the initial undo will restore the contents in MY_LINE_ABORTED. Also see man zshzle for an explanation of split-undo.
  • Line 18: Install the widget zle-line-init.

Now type any command and push Ctrl-C twice and undo (bound to Ctrl-/ by default): your canceled command is back!

Note that if you use zsh-autosuggestions this code snippet somehow breaks it. Adding _zsh_autosuggest_widget_clear before the end of zle-line-init would fix it.

References

Make the less Command More Powerful

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Last updated on April 14, 2024

Due to its speed and simplicity, GNU less is probably the most common default terminal pager on various GNU/Linux distributions—you may have probably used it explicitly via the less command, or implicitly when you execute the man command or git diff. Although the default configuration of less does not really offer much except for a basic text viewer, it is actually much more powerful than most people think. Here a few improvements over the default configuration are offered.

For macOS/OS X users: consider installing a newer version of less and other GNU command line utilities. To do so, you can follow the instructions here.

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Back up (Migrate) Homebrew Packages

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Last updated on October 9, 2016

As one of the most popular package manager on OS X, Homebrew is indeed a very nice tool to manage packages. However, when you want to back up your packages, or migrate the packages onto another machine, Homebrew didn’t invent such a tool. If you are moving to an OS X of the same version, you can simply copy the Homebrew directory (default is /usr/local) to your new machine. Otherwise, we need to find a way to install the exactly same packages on your new machine. In order to accomplish the goal, I wrote a small piece of bash script to generate a restore script to install the packages.

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