o is a text editor limited to the VT100 standard.

It might be a good fit for:

• Editing git commit messages (using EDITOR=o git commit).
• Editing README.md and TODO.md files.
• Write Markdown files and then export to PDF.
• Learning "up and coming" programming languages, like Zig or Rust.
• Editing files deep within larger Go or C++ projects.
• Solving Advent of Code tasks.
• Writing and maintaining to-do lists and project documentation in Markdown.

For a more feature complete editor that is also written in Go, check out micro.

Packaging status

Quick start

You can install o with Go 1.10 or later:

go get -u github.com/xyproto/o

Setting o as the default editor for git

To set:

git config --global core.editor o

To unset:

git config --global --unset core.editor

Unique features

These features are unique to o, as far as I am aware:

• Smart cursor movement, trying to maintain the X position when moving up and down, across short and long lines.
• Press ctrl-v once to paste one line, press ctrl-v again to paste the rest.
• Press ctrl-c once to copy one line, press ctrl-c again to copy the rest (until a blank line).
• Open or close a portal with ctrl-r. When a portal is open, copy lines across files (or within the same file) with ctrl-v.
• Build code with ctrl-space and format code with ctrl-w, for a wide range of programming languages.
• Press ctrl-w to toggle the checkmark in - [ ] TODO item boxes in Markdown.
• Cycle git rebase keywords with ctrl-r, when in an interactive git rebase session.
• Jump to a line with ctrl-l. Either enter a number to jump to a line or just press return to jump to the top. Press ctrl-l and return again to jump to the bottom.
• All text will be red if the loaded file is read-only.
• If tab completion in the terminal went wrong and you are trying to open a main. file that does not exist, but main.cpp and main.o does exists, then main.cpp will be opened.

Other features and limitations

• Loads up instantly.
• Configuration-free, for better and for worse.
• Can render text to PDF.
• Compile "Hello, World" in many popular programming languages simply by pressing ctrl-space.
• ctrl-t can jump between a C++ header and source file.
• Provides syntax highlighting for Go, C++, Markdown, Bash and several other languages. There is generic syntax highlighting.
• The syntax highlighting is instant.
• Will jump to the last visited line when opening a recent file.
• Is provided as a single self-contained executable.
• Tested with alacritty, st, urxvt, konsole and xfce4-terminal.
• Tested on Arch Linux, Debian and FreeBSD.
• Loads faster than both vim and emacs.
• Never asks before saving or quitting. Be careful!
• The NO_COLOR environment variable can be set to disable all colors.
• Rainbow parentheses makes lines with many parentheses easier to read.
• Limited to the VT100 standard, so hotkeys like ctrl-a and ctrl-e must be used instead of Home and End.
• Compiles with either go or gccgo.
• Will strip trailing whitespace whenever it can.
• Must be given a filename at start.
• May provide smart indentation.
• Requires that /dev/tty is available.
• xclip (for X) or wl-clipboard (for Wayland) must be installed if the system clipboard should be used.
• May take a line number as the second argument, with an optional + prefix.
• If the filename is COMMIT_EDITMSG, the look and feel will be adjusted for git commit messages.
• Supports UTF-8, but some runes may be displayed incorrectly.
• Only UNIX-style line endings are supported (\n).
• Will convert DOS/Windows line endings (\r\n) to UNIX line endings (just \n), whenever possible.
• Will replace non-breaking space (0xc2 0xa0) with a regular space (0x20) whenever possible.
• If interactive rebase is launched with git rebase -i, then either ctrl-w or ctrl-r will cycle the keywords for the current line (fixup, drop, edit etc).
• When editing Markdown, checkboxes can be toggled with ctrl-w.
• If the editor executable renamed to red (or have a symlink with that name), the default theme will be red/white/gray.
• If the editor executable renamed to light (or have a symlink with that name), the default theme will be suitable for light backgrounds.
• Want to quickly convert Markdown to PDF and have pandoc installed? Try o filename.md, press ctrl-space twice and quit with ctrl-q.
• o is written mostly in o, with some use of NeoViM at the beginning.

Known bugs

• In some terminal emulators, scrolling quickly up or down with the arrow keys can make the text jump around (it works fine in alacritty). Scroll up and down with ctrl-n and ctrl-p instead to avoid this. Press esc to repaint the text, if needed.
• Some unicode runes may disrupt the text flow. This is generally not a problem for editing code and configuration files, but may be an issue when editing files that contains text in many languages.
• For some terminal emulators, if o is busy performing an operation, pressing ctrl-s may lock the terminal. Some terminal emulators, like konsole, can be configured to turn off this behavior. Press ctrl-q to unlock the terminal again (together with the unfortunate risk of quitting o). You can also use the ctrl-o menu for saving and quitting.
• o may have issues with large files (of several MB+). For normal text files or source code files, this is a non-issue.
• Middle-click pasting (instead of pasting with ctrl-v) may have issues with only pasting the first character.
• The smart indentation is not always smart.

Hotkeys

• ctrl-s - Save.
• ctrl-q - Quit.
• ctrl-r - Open or close a portal. Text can be pasted from the portal into another file with ctrl-v. For "git interactive rebase" mode (git rebase -i), this will cycle the rebase keywords.
• ctrl-w - Format the current file (see the table below).
• ctrl-a - Go to start of text, then start of line and then to the previous line.
• ctrl-e - Go to end of line and then to the next line.
• ctrl-p - Scroll up 10 lines, or go to the previous match if a search is active.
• ctrl-n - Scroll down 10 lines, or go to the next match if a search is active.
• ctrl-k - Delete characters to the end of the line, then delete the line.
• ctrl-g - Toggle a status line at the bottom for displaying: filename, line, column, Unicode number and word count.
• ctrl-d - Delete a single character.
• ctrl-t - Render the current document to a PDF file. For C++, toggle between header and implementation files.
• ctrl-o - Open a command menu with actions that can be performed. The first menu item is always Save and quit.
• ctrl-x - Cut the current line. Press twice to cut a block of text (to the next blank line).
• ctrl-c - Copy one line. Press twice to copy a block of text.
• ctrl-v - Paste one trimmed line. Press twice to paste multiple untrimmed lines.
• ctrl-space - Build (see table below)
• ctrl-j - Join lines (or jump to the bookmark, if set).
• ctrl-u - Undo (ctrl-z is also possible, but may background the application).
• ctrl-l - Jump to a specific line number. Follows by return to jump to the top. If at the top, press return to jump to the bottom.
• ctrl-f - Search for a string. The search wraps around and is case sensitive.
• esc - Redraw the screen and clear the last search.
• ctrl-b - Toggle a bookmark for the current line, or if set: jump to a bookmark on a different line.
• ctrl-\ - Comment in or out a block of code.
• ctrl-~ - Jump to a matching parenthesis.

Updating PKGBUILD files

When editing PKGBUILD files, it is possible to press ctrl-o and select Call Guessica to update the pkgver= and source= fields, by a combination of guesswork and online searching.

guessica must be installed for this feature to work.

Build and format

• At the press of ctrl-space, o will try to build or export the current file.
• At the press of ctrl-w, o will try to format the current file, in an opinionated way.

Programming language	File extensions	Jump to error	Build command	Format command ($filename is a temporary file)
Go	.go	yes	go build	goimports -w -- $filename
C++	.cpp, .cc, .cxx, .h, .hpp, .c++, .h++, .c	yes	cxx	clang-format -fallback-style=WebKit -style=file -i -- $filename
Rust	.rs	yes	rustc $filename	rustfmt $filename
Rust, if Cargo.toml or ../Cargo.toml exists	.rs	yes	cargo build	rustfmt $filename
Zig	.zig	yes	zig build-exe -lc $filename	zig fmt $filename
V	.v	yes	v build	v fmt $filename
Haskell	.hs	yes	ghc -dynamic $filename	brittany --write-mode=inplace $filename
Python	.py	yes	python -m py_compile $filename	autopep8 -i --maxline-length 120 $filename
Crystal	.cr	yes	crystal build --no-color $filename	crystal tool format $filename
Kotlin	.kt	yes	kotlinc $filename -include-runtime -d	ktlint
Kotlin, if kotlinc-native is installed	.kt	yes	kotlinc-native -nowarn -opt -Xallocator=mimalloc -produce program -linker-option '--as-needed' $filename	ktlint
Java	.java	yes	javac + jar, see details below	google-java-format -i $filename
Scala	.scala	yes	scalac + jar, see details below	WIP
Lua	.lua	yes	luac	lua-format -i --no-keep-simple-function-one-line --column-limit=120 --indent-width=2 --no-use-tab $filename
Object Pascal	.pas, .pp, .lpr	yes	fpc	WIP
Nim	.nim	WIP	nim c	WIP
Odin	.odin	yes	odin build	N/A

/etc/fstab files are also supported, and can be formatted with ctrl-w if fstabfmt is installed.

| Markup language | File extensions | Jump to error | Format command ($filename is a temporary file) | | HTML | .htm, .html | no | tidy -w 120 -q -i -utf8 --show-errors 0 --show-warnings no --tidy-mark no --force-output yes -ashtml -omit no -xml no -m -c |

• o will try to jump to the location where the error is and otherwise display Success.
• For regular text files, ctrl-w will word wrap the lines to a length of 99.
• If kotlinc-native is not available, this build command will be used instead: kotlinc $filename -include-runtime -d $name.jar

CXX can be downloaded here: GitHub project page for CXX.

File type	File extensions	Build or export command
AsciiDoc	.adoc	asciidoctor -b manpage (writes to out.1)
scdoc	.scd, .scdoc	scdoc (writes to out.1)
Markdown	.md	pandoc -N --toc -V geometry:a4paper (writes to $filename.pdf)

If guessica is installed, PKGBUILD files will be updated at the press of ctrl-w. The guessica utility tries to guess the latest project version, tag and git commit hash for a PKGBUILD file and may or may not succeed.

Manual installation

On Linux:

git clone https://github.com/xyproto/o
cd o
go build -mod=vendor
sudo install -Dm755 o /usr/bin/o
gzip o.1
sudo install -Dm644 o.1.gz /usr/share/man/man1/o.1.gz

Dependencies

C++

• For building code with ctrl-space, cxx must be installed.
• For formatting code with ctrl-w, clang-format must be installed.

Go

• For building code with ctrl-space, The go compiler must be installed.
• For formatting code with ctrl-w, goimports must be installed.

Zig

• For building and formatting Zig code, only the zig command is needed.

V

• For building and formatting V code, only the v command is needed.

Rust

• For building code with ctrl-space, Cargo.toml must exist and cargo must be installed.
• For formatting code with ctrl-w, rustfmt must be installed.

Haskell

• For building the current file with ctrl-space, the ghc compiler must be installed.
• For formatting code with ctrl-w, brittany must be installed.

Python

• ctrl-space only checks the syntax, without executing. This only requires python to be available.
• For formatting the code with ctrl-w, autopep8 must be installed.

Crystal

• For building and formatting Crystal code, only the crystal command is needed.

Kotlin

• For building code with ctrl-space, kotlinc must be installed. A .jar file is created if the compilation succeeded.
• For formatting code with ctrl-w, ktlint must be installed.

Java

• For building code with ctrl-space, javac and jar must be installed. A .jar file is created if the compilation succeeded.
• For formatting code with ctrl-w, google-java-format must be installed.

Scala

• For building code with ctrl-space, scalac and jar must be installed. A .jar file is created if the compilation succeeded.
• The jar file can be executed with java -jar main.jar. Use scalac -d main.jar MyFile.scala if you want to produce a jar that can be executed with scala main.jar.
• For formatting code with ctrl-w, scalafmt must be installed.

JSON

• The JSON formatter is built-in.

fstab

• For formatting fstab files (usually /etc/fstab) with ctrl-w, fstabfmt must be installed.

A note on Java and Scala

Since kotlinc $filename -include-runtime -d builds to a .jar, I though I should do the same for Java. The idea is to easily build a single or a small collection of .java files, where one of the file has a main function.

If you know an easier way to build a .jar file from *.java without using something like gradle, please let me know by submitting a pull request. This is pretty verbose...

javaFiles=$(find . -type f -name '*.java')
for f in $javaFiles; do
  grep -q 'static void main' "$f" && mainJavaFile="$f"
done
className=$(grep -oP '(?<=class )[A-Z]+[a-z,A-Z,0-9]*' "$mainJavaFile" | head -1)
packageName=$(grep -oP '(?<=package )[a-z,A-Z,0-9,.]*' "$mainJavaFile" | head -1)
if [[ $packageName != "" ]]; then
  packageName="$packageName."
fi
mkdir -p _o_build/META-INF
javac -d _o_build $javaFiles
cd _o_build
echo "Main-Class: $packageName$className" > META-INF/MANIFEST.MF
classFiles=$(find . -type f -name '*.class')
jar cmf META-INF/MANIFEST.MF ../main.jar $classFiles
cd ..
rm -rf _o_build

For Scala, I'm using this code, to produce a main.jar file that can be run directly with java -jar main.jar:

#!/bin/sh
scalaFiles=$(find . -type f -name '*.scala')
for f in $scalaFiles; do
  grep -q 'def main' "$f" && mainScalaFile="$f"
  grep -q ' extends App ' "$f" && mainScalaFile="$f"
done
objectName=$(grep -oP '(?<=object )[A-Z]+[a-z,A-Z,0-9]*' "$mainScalaFile" | head -1);
packageName=$(grep -oP '(?<=package )[a-z,A-Z,0-9,.]*' "$mainScalaFile" | head -1);
if [[ $packageName != "" ]]; then
  packageName="$packageName."
fi
mkdir -p _o_build/META-INF
scalac -d _o_build $scalaFiles
cd _o_build
echo -e "Main-Class: $packageName$objectName\nClass-Path: /usr/share/scala/lib/scala-library.jar" > META-INF/MANIFEST.MF
classFiles=$(find . -type f -name '*.class')
jar cmf META-INF/MANIFEST.MF ../main.jar $classFiles
cd ..
rm -rf _o_build

If /usr/share/scala/lib/scala-library.jar is not found scalac -d run_with_scala.jar is used instead. This file can only be run with the scala command.

List of optional runtime dependencies

• go / golang
• goimports
• cxx
• g++ / base-devel
• clang-format
• rustc
• rustfmt
• cargo
• zig
• v
• ghc
• brittany
• python
• autopep8
• kotlin
• ktlint
• javac
• jar
• google-java-format
• pandoc

Size

• The o executable is only 508k when built with GCC 9.3 (for 64-bit Linux) and compressed with upx.
• This isn't as small as e3, an editor written in assembly (which is 234k), but it's reasonably lean.

One way of building with gccgo and upx:

go build -mod=vendor -gccgoflags '-Os -s' && upx o

It's 5.2M when built with Go 1.14 and no particular build flags are given.

Jumping to a specific line when opening a file

These four ways of opening file.txt at line 7 are supported:

• o file.txt 7
• o file.txt +7
• o file.txt:7
• o file.txt+7

This also means that filenames containing + or :, and then followed by a number, are not supported.

Spinner

When loading files that are large or from a slow disk, an animated spinner will appear. The loading operation can be interrupted by pressing esc, q or ctrl-q.

Find and open

This shell function works in zsh and bash and may be useful for both searching for and opening a file at the given line number (works best if there is only one matching file, if not it will open several files in succession):

fo() { find . -type f -wholename "*$1" -exec /usr/bin/o {} $2 \;; }

Example use:

fo somefile.cpp 123

Easter eggs

Press ctrl-space twice to render Markdown files to PDF using pandoc (ctrl-t will save the text directly to PDF, without using pandoc).

If the PAPERSIZE environment variable is set to ie. a4 or letter, it will be respected when exporting from Markdown to PDF using pandoc, at the press of ctrl-space.

The --pdf-engine=xelatex and --listings flags are used, so xelatex and the listings package needs to be available. A standard installation of LaTeX and Pandoc should provide both.

Suggested settings

These should work well together with o:

• Try the JetBrains Mono NL font.

Konsole

• Try the Breeze color scheme (but with a black background). It should work well together with o.
• Untick the Flow control option in the profile settings, to ensure that ctrl-s will never freeze the terminal.

General info

• Version: 2.36.0
• License: 3-clause BSD
• Author: Alexander F. Rødseth <xyproto@archlinux.org>