A log file highlighter

• 🪵 View (or tail) any log file of any format
• 🍰 No setup or config required
• 🌈 Highlights numbers, dates, IP-addresses, UUIDs, URLs and more
• ⚙️ All highlight groups are customizable
• 🧬 Easy to integrate with other commands
• 🔍 Uses less under the hood for scrollback, search and filtering

• Overview
• Installing
• Highlight Groups
• Watching folders
• Customizing Highlight Groups
• Working with stdin and stdout
• Using the pager less
• Settings

tailspin works by reading through a log file line by line, running a series of regexes against each line. The regexes recognize patterns like dates, numbers, severity keywords and more.

tailspin does not make any assumptions on the format or position of the items it wants to highlight. For this reason, it requires no configuration or setup and will work predictably regardless of the format the log file is in.

The binary name for tailspin is spin.

# Cargo
cargo install tailspin

# Debian
apt install tailspin

# AUR
paru -S tailspin

# Nix
nix-shell -p tailspin

tailspin can listen for newline entries in a given folder. Watching folders is useful for monitoring log files that are rotated.

When watching folders, tailspin will start in follow mode (abort with Ctrl + C) and will only print newline entries which arrive after the initial start.

tailspin uses a single config.toml file to configure all highlight groups. When customizing highlights, it is advised to start with the --create-default-config flag to place a config.toml with default options in ~/.config/tailspin.

To disable a highlight group, either comment it out or delete it.

Highlights have the following shape:

style = { fg = "color", bg = "color", italic = false, bold = false, underline = false }

To add custom keywords, either include them in the list of keywords or add new entries:

[[groups.keywords]]
words = ['MyCustomKeyword']
style = { fg = "green" }

[[groups.keywords]]
words = ['null', 'true', 'false']
style = { fg = "red", italic = true }

By default, tailspin will open a file in the pager less. However, if you pipe something into tailspin, it will print the highlighted output directly to stdout. This is similar to running spin [file] --print.

To let tailspin highlight the logs of different commands, you can pipe the output of those commands into tailspin like so:

journalctl -f | spin
cat /var/log/syslog | spin
kubectl logs -f pod_name | spin

tailspin uses less as its pager to view the highlighted log files. You can get more info on less via the man command (man less) or by hitting the h button to access the help screen.

Navigating within less uses a set of keybindings that may be familiar to users of vim or other vi-like editors. Here's a brief overview of the most useful navigation commands:

• j/k: Scroll one line up / down
• d/u: Scroll one half-page up / down
• g/G: Go to the top / bottom of the file

When you run tailspin with the -f or --follow flag, it will scroll to the bottom and print new lines to the screen as they're added to the file.

To stop following the file, interrupt with Ctrl + C. This will stop the tailing, but keep the file open, allowing you to review the existing content.

To resume following the file from within less, press Shift + F.

Use / followed by your search query. For example, /ERROR finds the first occurrence of ERROR.

After the search, n finds the next instance, and N finds the previous instance.

less allows filtering lines by a keyword, using & followed by the pattern. For instance, &ERROR shows only lines with ERROR.

To only show lines containing either ERROR or WARN, use a regular expression: &\(ERROR\|WARN\).

To clear the filter, use & with no pattern.

-f, --follow                 Follow the contents of the file
-t, --tail                   Start at the end of the file
-p, --print                  Print the output to stdout
-c, --config-path PATH       Path to a custom configuration file
-t, --follow-command 'CMD'   Follows the output of the provided command
    --create-default-config  Generate a new configuration file
    --show-default-config    Print the default configuration