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neferbar

A dead simple status bar for Wayland: one line of terminal text, nothing else.

Each part of the bar is a script. A script prints text, and neferbar shows it. If you can write echo, you can write a module.

[neferbar showing a workspace number, an app name, a clock and system stats, with Nerd Font icons]

Text only. ASCII, Unicode and Nerd Font icons. No images, no widgets, no clicks.
Exactly one character high. The bar is as tall as a terminal row, and it follows your monitor's scale.
Scripts do the work. Any language, anything that prints to stdout.
Fast when you ask. Print 60 times a second and the bar redraws 60 times a second. Print nothing and it uses no CPU or GPU.

It needs a compositor with wlr-layer-shell, such as Sway, Hyprland, Niri, River or NeferWL. GNOME is not supported.

Install

You need Go 1.27, a Vulkan 1.3 GPU driver, and a Nerd Font.

go build -o neferbar ./cmd/neferbar
./neferbar

Start it from your compositor's autostart. For NeferWL:

startup = /full/path/to/neferbar

Configure

Create ~/.config/neferbar/config.toml:

[bar]
font = "JetBrainsMono Nerd Font Mono"   # use a "Mono" Nerd Font so icons fit one cell
size = 14                                # text size
theme = "auto"                           # colors of your terminal, or the path of a theme file

[[module]]
name = "clock"          # a unique name
zone = "center"         # left, center or right
exec = "~/.config/neferbar/clock.sh"

Add one [[module]] block per script. Save the file and the bar updates immediately. If you make a typo, the bar keeps the old config and prints the error.

The bar also watches the folder of each script. Edit a script, or a helper it sources from the same folder, and the modules in that folder restart by themselves. Hidden files (.name) and backups (name~) are ignored, so an editor's swap file does nothing.

Setting	Default	Meaning
`bar.font`	`JetBrainsMono Nerd Font Mono`	A font family known to fontconfig (`fc-list`).
`bar.size`	`14`	Text size in logical pixels.
`bar.scale`	`1.0`	Extra zoom on top of the monitor scale.
`bar.position`	`top`	`top` or `bottom`: the screen edge the bar sits on. Applies live.
`bar.output`	any	A monitor name such as `HDMI-A-1`. Needs a restart.
`bar.theme`	`auto`	`auto` reads the colors of the terminal you use. Or the path of a theme file (see Colors).
`bar.accent`	`4`	Which of the theme's 16 colors (0-15) the highlights use. 4 is the ANSI blue; try 2 (green), 6 (cyan) or 5 (magenta) to match your theme.
`bar.background`, `bar.foreground`	from the theme	`#rrggbb`. Set them to override the theme.

If the font is not installed, neferbar warns and falls back to another font, and icons may be missing.

Colors

The bar takes its colors from your terminal, so it matches the rest of your desktop.

theme = "auto"                                  # the terminal you use
theme = "~/.config/kitty/themes/mytheme.conf"   # or one file

auto reads the theme of the terminal named by the $TERMINAL environment variable, and nothing else. It knows kitty, ghostty, foot and alacritty (TERMINAL=kitty, or a path such as /usr/bin/foot). A theme file can be any of those formats, and the bar recognizes it by its content. Includes and ghostty theme = names are followed. Colors the file does not set come from a built-in dark theme.

Set $TERMINAL for your whole session, not only in a shell. A variable you set -x in an open terminal is not seen by programs your compositor starts. The simplest place is a systemd user environment file, read when a session starts, whatever your shell is:

# ~/.config/environment.d/10-terminal.conf
TERMINAL=kitty

Then start a new session. If $TERMINAL is missing, the bar says so in its log and uses the built-in colors.

The bar watches every file it read: change your terminal's theme and the bar changes with it. If the theme cannot be read, the bar uses the built-in colors and says why in its log.

Scripts get the colors as environment variables, each #rrggbb, so a script never hard-codes one:

Variable	Color
`NEFERBAR_BACKGROUND`, `NEFERBAR_FOREGROUND`	the bar's own background and text
`NEFERBAR_ACCENT`	the highlight color, the theme color that `bar.accent` picks
`NEFERBAR_COLOR0` .. `NEFERBAR_COLOR15`	the theme's 16 ANSI colors

The 16 ANSI codes a script prints (\033[31m red, \033[44m blue background and so on) use the theme as well.

Write a script

A module is any program that prints lines. Each line replaces what the module showed before.

The smallest module:

#!/bin/sh
echo "hello"
sleep 100000

A clock, updated every second:

#!/bin/sh
while true; do
    date +%H:%M:%S
    sleep 1
done

Make it executable (chmod +x clock.sh) and put its path in exec. That's all.

Rules:

Print one line, then print another line later. The new line replaces the old one.
A frame ends at a newline (\n) or a form feed (\f). They mean the same thing. Text after the last one, with no ending yet, is not shown until its frame is finished.
Keep the script running. A script that exits is restarted after a short delay, and the bar shows [name!] in the meantime.
Print errors to stderr. They go to the bar's log and not to the screen.
Frames are cut to 16 KiB, and text wider than the bar is clipped.

Colors and styles

Use ordinary terminal escape codes. If it works in a terminal, it works here.

printf '\033[32mOK\033[0m  \033[1;31mFAIL\033[0m\n'

Code	Effect
`\033[1m`	bold
`\033[2m`	dim
`\033[3m`	italic
`\033[4m`	underline
`\033[7m`	inverse
`\033[9m`	~~strikethrough~~
`\033[30m`..`\033[37m`	foreground colors
`\033[40m`..`\033[47m`	background colors
`\033[38;5;Nm` / `\033[48;5;Nm`	256-color palette
`\033[38;2;R;G;Bm` / `\033[48;2;R;G;Bm`	true color
`\033[0m`	reset

Italic, bold and bold italic use the font's own files when it has them.

Icons

Nerd Font icons are ordinary characters, but GitHub cannot draw them in a code block, so the examples here write them as escape sequences. Give printf the icon's code point:

printf '\Uf017 %s\n' "$(date +%H:%M)"      # clock icon (U+F017)

\U works in bash. Some minimal shells do not support it; the UTF-8 bytes work everywhere: printf '\357\200\227 %s\n' "$(date +%H:%M)".

Find icon names and code points at https://www.nerdfonts.com/cheat-sheet. In an editor with a Nerd Font you can also paste the icon itself into the script.

Animation

Print faster. Each frame ends with \f:

#!/bin/sh
# a spinner at 20 fps
while true; do
    for c in '|' '/' '-' '\'; do
        printf '%s\f' "$c"
        sleep 0.05
    done
done

neferbar draws at most as often as your monitor refreshes. If a script prints faster than that, only the latest frame is drawn. A script that prints nothing costs nothing.

The bundled bar

examples/bundle is a ready-made bar: workspaces on the left, the focused app in the middle, the clock on the right, in your terminal's colors.

[The bundled bar] Copy it to ~/.config/neferbar/ (the install steps are at the top of examples/bundle/config.toml).

Its helper lib.sh has what a themed script needs: fg/bg to set a color from #rrggbb, mix to blend two, fade for the soft edge, and state_changed_loop to react to NeferWL. Read the three scripts: each is about thirty lines.

On NeferWL the workspaces show one dot per window and the stash. On other compositors the workspace and focus modules show nothing yet, and the clock still works.

Reacting to your compositor (workspace effects)

A module can watch anything, including the compositor's own state. NeferWL keeps a JSON file up to date and passes its path to every program it starts as $NEFERWL_STATE. It replaces the file on each change, so a module only has to check the file's modification time:

stamp=$(mktemp)
touch -r "$NEFERWL_STATE" "$stamp"
while sleep 0.1; do
    if [[ $NEFERWL_STATE -nt $stamp ]]; then       # the file changed
        touch -r "$NEFERWL_STATE" "$stamp"
        jq -r '.outputs[] | "\(.name) is on workspace \(.active)"' "$NEFERWL_STATE"
    fi
done

That is all it takes to draw an effect when you switch workspace. examples/bundle/left.sh redraws the workspaces that way.

Example modules

The examples/modules directory has these:

static.sh: one line, then idle.
clock.sh: a clock with an icon.
rainbow.sh [fps] [width]: a 60 fps scrolling rainbow.

Layout

The bar has three zones. Modules in the same zone appear side by side, in the order of the config file.

left starts at the left edge.
right ends at the right edge.
center sits in the middle of the space that is left. If the bar is too narrow, the center is cut first.

Command line

neferbar [-config file] [-display socket] [-pprof addr] [-memstats interval]

Flag	Meaning
`-config`	Config file. Default: `$XDG_CONFIG_HOME/neferbar/config.toml`.
`-display`	Wayland socket name or path. Default: `$NEFERBAR_DISPLAY`, then `$WAYLAND_DISPLAY`.
`-pprof`	Serve Go profiling on a loopback address, such as `localhost:6060`.
`-memstats`	Log allocation counters at this interval.

Reading the focused window

neferbar app prints fields of the window that has the focus: one line now, then a new one each time the focus or a title changes. It works on compositors that offer zwlr_foreign_toplevel_manager_v1 (NeferWL, Sway, Hyprland, River, Niri).

neferbar app title            # Dumber - docs
neferbar app id               # com.github.bnema.dumber
neferbar app name             # dumber (the part of the id after the last dot)
neferbar app name title       # several fields, separated by a tab
neferbar app -once title      # print once and exit

A line is empty when no window has the focus. Control characters are removed from every field, so a title cannot move a terminal's cursor. Scripts started by the bar find the binary in $NEFERBAR_BIN.

Test without touching your desktop

go test ./...
scripts/headless.sh examples/config.toml 5        # runs in a nested headless NeferWL
SCALE=1.5 SIZE=1200x200 scripts/headless.sh examples/config.toml 5

Screenshots land in /tmp/neferbar-shots.

License

MIT.

source

1# neferbar
2
3A dead simple status bar for Wayland: **one line of terminal text, nothing else.**
4
5Each part of the bar is a script. A script prints text, and neferbar shows it. If you can write `echo`, you can write a module.
6
7![neferbar showing a workspace number, an app name, a clock and system stats, with Nerd Font icons](docs/img/bar.png)
8
9- **Text only.** ASCII, Unicode and Nerd Font icons. No images, no widgets, no clicks.
10- **Exactly one character high.** The bar is as tall as a terminal row, and it follows your monitor's scale.
11- **Scripts do the work.** Any language, anything that prints to stdout.
12- **Fast when you ask.** Print 60 times a second and the bar redraws 60 times a second. Print nothing and it uses no CPU or GPU.
13
14It needs a compositor with `wlr-layer-shell`, such as Sway, Hyprland, Niri, River or NeferWL. GNOME is not supported.
15
16## Install
17
18You need Go 1.27, a Vulkan 1.3 GPU driver, and a [Nerd Font](https://www.nerdfonts.com/).
19
20```sh
21go build -o neferbar ./cmd/neferbar
22./neferbar
23```
24
25Start it from your compositor's autostart. For NeferWL:
26
27```
28startup = /full/path/to/neferbar
29```
30
31## Configure
32
33Create `~/.config/neferbar/config.toml`:
34
35```toml
36[bar]
37font = "JetBrainsMono Nerd Font Mono"   # use a "Mono" Nerd Font so icons fit one cell
38size = 14                                # text size
39theme = "auto"                           # colors of your terminal, or the path of a theme file
40
41[[module]]
42name = "clock"          # a unique name
43zone = "center"         # left, center or right
44exec = "~/.config/neferbar/clock.sh"
45```
46
47Add one `[[module]]` block per script. Save the file and the bar updates immediately. If you make a typo, the bar keeps the old config and prints the error.
48
49The bar also watches the folder of each script. Edit a script, or a helper it sources from the same folder, and the modules in that folder restart by themselves. Hidden files (`.name`) and backups (`name~`) are ignored, so an editor's swap file does nothing.
50
51| Setting | Default | Meaning |
52|---|---|---|
53| `bar.font` | `JetBrainsMono Nerd Font Mono` | A font family known to fontconfig (`fc-list`). |
54| `bar.size` | `14` | Text size in logical pixels. |
55| `bar.scale` | `1.0` | Extra zoom on top of the monitor scale. |
56| `bar.position` | `top` | `top` or `bottom`: the screen edge the bar sits on. Applies live. |
57| `bar.output` | any | A monitor name such as `HDMI-A-1`. Needs a restart. |
58| `bar.theme` | `auto` | `auto` reads the colors of the terminal you use. Or the path of a theme file (see Colors). |
59| `bar.accent` | `4` | Which of the theme's 16 colors (0-15) the highlights use. 4 is the ANSI blue; try 2 (green), 6 (cyan) or 5 (magenta) to match your theme. |
60| `bar.background`, `bar.foreground` | from the theme | `#rrggbb`. Set them to override the theme. |
61
62If the font is not installed, neferbar warns and falls back to another font, and icons may be missing.
63
64## Colors
65
66The bar takes its colors from your terminal, so it matches the rest of your desktop.
67
68```toml
69theme = "auto"                                  # the terminal you use
70theme = "~/.config/kitty/themes/mytheme.conf"   # or one file
71```
72
73`auto` reads the theme of the terminal named by the **`$TERMINAL`** environment variable, and nothing else. It knows kitty, ghostty, foot and alacritty (`TERMINAL=kitty`, or a path such as `/usr/bin/foot`). A theme file can be any of those formats, and the bar recognizes it by its content. Includes and ghostty `theme =` names are followed. Colors the file does not set come from a built-in dark theme.
74
75**Set `$TERMINAL` for your whole session**, not only in a shell. A variable you `set -x` in an open terminal is not seen by programs your compositor starts. The simplest place is a systemd user environment file, read when a session starts, whatever your shell is:
76
77```
78# ~/.config/environment.d/10-terminal.conf
79TERMINAL=kitty
80```
81
82Then start a new session. If `$TERMINAL` is missing, the bar says so in its log and uses the built-in colors.
83
84The bar watches every file it read: change your terminal's theme and the bar changes with it. If the theme cannot be read, the bar uses the built-in colors and says why in its log.
85
86Scripts get the colors as environment variables, each `#rrggbb`, so a script never hard-codes one:
87
88| Variable | Color |
89|---|---|
90| `NEFERBAR_BACKGROUND`, `NEFERBAR_FOREGROUND` | the bar's own background and text |
91| `NEFERBAR_ACCENT` | the highlight color, the theme color that `bar.accent` picks |
92| `NEFERBAR_COLOR0` .. `NEFERBAR_COLOR15` | the theme's 16 ANSI colors |
93
94The 16 ANSI codes a script prints (`\033[31m` red, `\033[44m` blue background and so on) use the theme as well.
95
96## Write a script
97
98A module is any program that prints lines. **Each line replaces what the module showed before.**
99
100The smallest module:
101
102```sh
103#!/bin/sh
104echo "hello"
105sleep 100000
106```
107
108A clock, updated every second:
109
110```sh
111#!/bin/sh
112while true; do
113    date +%H:%M:%S
114    sleep 1
115done
116```
117
118Make it executable (`chmod +x clock.sh`) and put its path in `exec`. That's all.
119
120Rules:
121
1221. Print one line, then print another line later. The new line replaces the old one.
1232. A frame ends at a newline (`\n`) or a form feed (`\f`). They mean the same thing. Text after the last one, with no ending yet, is not shown until its frame is finished.
1243. Keep the script running. A script that exits is restarted after a short delay, and the bar shows `[name!]` in the meantime.
1254. Print errors to stderr. They go to the bar's log and not to the screen.
1265. Frames are cut to 16 KiB, and text wider than the bar is clipped.
127
128### Colors and styles
129
130Use ordinary terminal escape codes. If it works in a terminal, it works here.
131
132```sh
133printf '\033[32mOK\033[0m  \033[1;31mFAIL\033[0m\n'
134```
135
136| Code | Effect |
137|---|---|
138| `\033[1m` | **bold** |
139| `\033[2m` | dim |
140| `\033[3m` | *italic* |
141| `\033[4m` | underline |
142| `\033[7m` | inverse |
143| `\033[9m` | ~~strikethrough~~ |
144| `\033[30m`..`\033[37m` | foreground colors |
145| `\033[40m`..`\033[47m` | background colors |
146| `\033[38;5;Nm` / `\033[48;5;Nm` | 256-color palette |
147| `\033[38;2;R;G;Bm` / `\033[48;2;R;G;Bm` | true color |
148| `\033[0m` | reset |
149
150Italic, bold and bold italic use the font's own files when it has them.
151
152### Icons
153
154Nerd Font icons are ordinary characters, but GitHub cannot draw them in a code block, so the examples here write them as escape sequences. Give `printf` the icon's code point:
155
156```sh
157printf '\Uf017 %s\n' "$(date +%H:%M)"      # clock icon (U+F017)
158```
159
160`\U` works in bash. Some minimal shells do not support it; the UTF-8 bytes work everywhere: `printf '\357\200\227 %s\n' "$(date +%H:%M)"`.
161
162Find icon names and code points at <https://www.nerdfonts.com/cheat-sheet>. In an editor with a Nerd Font you can also paste the icon itself into the script.
163
164### Animation
165
166Print faster. Each frame ends with `\f`:
167
168```sh
169#!/bin/sh
170# a spinner at 20 fps
171while true; do
172    for c in '|' '/' '-' '\'; do
173        printf '%s\f' "$c"
174        sleep 0.05
175    done
176done
177```
178
179neferbar draws at most as often as your monitor refreshes. If a script prints faster than that, only the latest frame is drawn. A script that prints nothing costs nothing.
180
181### The bundled bar
182
183`examples/bundle` is a ready-made bar: workspaces on the left, the focused app in the middle, the clock on the right, in your terminal's colors.
184
185![The bundled bar](docs/img/bundle.png)
186 Copy it to `~/.config/neferbar/` (the install steps are at the top of `examples/bundle/config.toml`).
187
188Its helper `lib.sh` has what a themed script needs: `fg`/`bg` to set a color from `#rrggbb`, `mix` to blend two, `fade` for the soft edge, and `state_changed_loop` to react to NeferWL. Read the three scripts: each is about thirty lines.
189
190On NeferWL the workspaces show one dot per window and the stash. On other compositors the workspace and focus modules show nothing yet, and the clock still works.
191
192### Reacting to your compositor (workspace effects)
193
194A module can watch anything, including the compositor's own state. NeferWL keeps a JSON file up to date and passes its path to every program it starts as `$NEFERWL_STATE`. It replaces the file on each change, so a module only has to check the file's modification time:
195
196```sh
197stamp=$(mktemp)
198touch -r "$NEFERWL_STATE" "$stamp"
199while sleep 0.1; do
200    if [[ $NEFERWL_STATE -nt $stamp ]]; then       # the file changed
201        touch -r "$NEFERWL_STATE" "$stamp"
202        jq -r '.outputs[] | "\(.name) is on workspace \(.active)"' "$NEFERWL_STATE"
203    fi
204done
205```
206
207That is all it takes to draw an effect when you switch workspace. `examples/bundle/left.sh` redraws the workspaces that way.
208
209### Example modules
210
211The `examples/modules` directory has these:
212
213- `static.sh`: one line, then idle.
214- `clock.sh`: a clock with an icon.
215- `rainbow.sh [fps] [width]`: a 60 fps scrolling rainbow.
216
217## Layout
218
219The bar has three zones. Modules in the same zone appear side by side, in the order of the config file.
220
221- **left** starts at the left edge.
222- **right** ends at the right edge.
223- **center** sits in the middle of the space that is left. If the bar is too narrow, the center is cut first.
224
225## Command line
226
227```
228neferbar [-config file] [-display socket] [-pprof addr] [-memstats interval]
229```
230
231| Flag | Meaning |
232|---|---|
233| `-config` | Config file. Default: `$XDG_CONFIG_HOME/neferbar/config.toml`. |
234| `-display` | Wayland socket name or path. Default: `$NEFERBAR_DISPLAY`, then `$WAYLAND_DISPLAY`. |
235| `-pprof` | Serve Go profiling on a loopback address, such as `localhost:6060`. |
236| `-memstats` | Log allocation counters at this interval. |
237
238## Reading the focused window
239
240`neferbar app` prints fields of the window that has the focus: one line now, then a new one each time the focus or a title changes. It works on compositors that offer `zwlr_foreign_toplevel_manager_v1` (NeferWL, Sway, Hyprland, River, Niri).
241
242```
243neferbar app title            # Dumber - docs
244neferbar app id               # com.github.bnema.dumber
245neferbar app name             # dumber (the part of the id after the last dot)
246neferbar app name title       # several fields, separated by a tab
247neferbar app -once title      # print once and exit
248```
249
250A line is empty when no window has the focus. Control characters are removed from every field, so a title cannot move a terminal's cursor. Scripts started by the bar find the binary in `$NEFERBAR_BIN`.
251
252## Test without touching your desktop
253
254```sh
255go test ./...
256scripts/headless.sh examples/config.toml 5        # runs in a nested headless NeferWL
257SCALE=1.5 SIZE=1200x200 scripts/headless.sh examples/config.toml 5
258```
259
260Screenshots land in `/tmp/neferbar-shots`.
261
262## License
263
264MIT.

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