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Overview

hline is designed to work with minimal configuration. It reads your bash history file directly and doesn’t require a separate configuration file.

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History file location

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Default path

When you run hline without arguments, it automatically locates your bash history:
  1. Checks the HOME environment variable
  2. Constructs the path as $HOME/.bash_history
  3. Falls back to ./.bash_history if HOME is not set
The default path logic is defined in history.rs:11-16.

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Custom path

You can specify a different history file using the --file flag: 
hline --file /path/to/custom_history
This is useful for:
  • Browsing history from different shells (zsh, fish, etc.)
  • Reviewing history from other users
  • Reading command logs from custom locations

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Environment variables

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HOME
string
Standard environment variable pointing to your home directory.hline uses this to construct the default history path: $HOME/.bash_historyIf HOME is not set, hline falls back to ./.bash_history in the current directory.

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History file format

hline expects a plain text file with one command per line, matching the standard bash history format.

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Supported format

ls -la
git status
cd ~/projects
make build

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Timestamp entries

Bash can optionally store timestamps in the history file when HISTTIMEFORMAT is set. These appear as lines starting with # followed by a Unix timestamp: 
#1700000000
ls -la
#1700000123
git status
hline automatically ignores these timestamp lines when loading history (implemented in history.rs:41-47).

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Line processing

When loading your history file, hline:
  • Strips carriage returns (\r) from line endings for cross-platform compatibility
  • Skips timestamp lines (lines matching #<digits>)
  • Filters out empty lines
  • Reverses the order so the most recent commands appear first
The parsing logic is in history.rs:18-39.

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Shell integration

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Bash configuration

To get the most out of hline, configure bash to maintain a comprehensive history: 
# ~/.bashrc or ~/.bash_profile

# Increase history size
export HISTSIZE=10000
export HISTFILESIZE=20000

# Append to history file instead of overwriting
shopt -s histappend

# Save multi-line commands as single entries
shopt -s cmdhist

# Avoid duplicate entries
export HISTCONTROL=ignoredups:erasedups

# Optional: Add timestamps to history
export HISTTIMEFORMAT="%F %T "

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Other shells

While hline is optimized for bash history, you can browse history from other shells by pointing to their history files: 
# Zsh
hline --file ~/.zsh_history

# Fish (requires conversion, as fish uses a different format)
# First export: history --export > /tmp/fish_history.txt
hline --file /tmp/fish_history.txt
Zsh and Fish use different history formats with metadata. You may see extra formatting characters when browsing their history files with hline.

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No configuration file

hline does not use a configuration file. All options are specified via command-line flags. This keeps the tool simple and predictable. If you frequently use custom options, create a shell alias: 
# ~/.bashrc
alias hl='hline --file ~/.zsh_history'

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Permissions

hline needs read access to the history file. If you encounter permission errors: 
# Check file permissions
ls -l ~/.bash_history

# Ensure the file is readable
chmod 600 ~/.bash_history
For browsing another user’s history, you’ll need appropriate permissions (typically root access).

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