`tail -f | grep | bat` fails (on Linux)

[nekr0z]

When working with logs, it's common to tail -f a log to view it in realtime, and then pipe it to grep for interesting data.

bat fails to produce output when feed such a pipe.

Steps to reproduce the bug

1. Have a long enough log with a common pattern appearing from time to time. /var/log/apt/history.log of a Debian system is used in this example, but any log will do.
2. Find a pattern and allow enough lines for tail to have it: tail -n 1000 -f /var/log/apt/history.log | grep Date should give several lines of output.
3. Pipe the above output to bat, i.e.: tail -n 1000 -f /var/log/apt/history.log | grep Date | bat --paging=never.

Result The output is empty.

Expected result The output contains the lines observed on step 2.

More investigation

• If no -f option is given to tail, bat works as expected. (tail -n 1000 /var/log/apt/history.log | grep Date | bat --paging=never produces the expected output)
• If no grep is done, bat works as expected. (tail -n 1000 -f /var/log/apt/history.log | bat --paging=never produces the expected output)

How did you install bat? Official deb repo.

---

bat version and environment

Software version

bat 0.21.0 (405e5f7)

Operating system

Linux 5.10.0-14-amd64

Command-line

bat --diagnostic 

Environment variables

SHELL=/bin/bash
PAGER=<not set>
LESS=<not set>
LANG=ru_RU.UTF-8
LC_ALL=<not set>
BAT_PAGER=<not set>
BAT_CACHE_PATH=<not set>
BAT_CONFIG_PATH=<not set>
BAT_OPTS=<not set>
BAT_STYLE=<not set>
BAT_TABS=<not set>
BAT_THEME=<not set>
XDG_CONFIG_HOME=<not set>
XDG_CACHE_HOME=<not set>
COLORTERM=truecolor
NO_COLOR=<not set>
MANPAGER=<not set>

Config file

Could not read contents of '/home/evgeny/.config/bat/config': No such file or directory (os error 2).

Custom assets metadata

Could not read contents of '/home/evgeny/.cache/bat/metadata.yaml': No such file or directory (os error 2).

Custom assets

'/home/evgeny/.cache/bat' not found

Compile time information

• Profile: release
• Target triple: x86_64-unknown-linux-gnu
• Family: unix
• OS: linux
• Architecture: x86_64
• Pointer width: 64
• Endian: little
• CPU features: fxsr,sse,sse2
• Host: x86_64-unknown-linux-gnu

Less version

> less --version 
less 551 (GNU regular expressions)
Copyright (C) 1984-2019  Mark Nudelman

less comes with NO WARRANTY, to the extent permitted by law.
For information about the terms of redistribution,
see the file named README in the less distribution.
Home page: http://www.greenwoodsoftware.com/less