log_view

log_viewer is an ncurses text UI for viewing rosout logs.

Motivation

Receive, filter, and navigate through all published rosout log messages from within a terminal to support debugging a robot live.

Problem

Many rosout log messages don’t get printed to the terminal in the normal course when there are lots of nodes/messages. There is also not a convenient way to filter and navigate through them in real time.

swri_console provides most of the desired functionality very well, but is Qt based and requires a graphical interface.

Solution

log_viewer is very similar in concept and design to swri_console, but uses ncurses instead of Qt for the interface.

Log messages can be filtered based on:

• log level
• node
• whitelist text filter
• exclude text filter

log_viewer also supports text searches and jumping from match to match.

Log messages are copied to the clipboard by selecting them.

Like swri_console, log_viewer doesn’t need ROS to be running to start and will automatically connect/reconnect when it becomes available.

Log Persistence

log_viewer can optionally persist log messages to disk and reload them on startup. This is useful for preserving log history across sessions.

Log files are stored under <workspace>/.log_view/ as timestamped text files (log_view_YYYYMMDD_HHMMSS.log), where <workspace> is derived from the COLCON_PREFIX_PATH environment variable set when a ROS 2 workspace is sourced. This keeps logs isolated per workspace. The format is human-readable and can be inspected with standard tools such as cat, grep, and less.

Persistence is automatically disabled if COLCON_PREFIX_PATH is not set or does not point to a valid directory.

Session boundaries are marked in the log with separator lines:

-------- Session Started At 2026-05-04 09:15:00 --------
-------- Recording Ended At 2026-05-04 09:47:23 --------

Log persistence is configured in the preferences panel (CTRL-k):

Clearing the message history (CTRL-r) also deletes all persisted log files.

Keybindings

CTRL-c       Exit log viewer
CTRL-h       Show/hide help screen

Up Arrow     Scroll up
Down Arrow   Scroll down
Left Arrow   Scroll left
Right Arrow  Scroll right
Page Up      Scroll up a screen
Page Down    Scroll down a screen
Home         Scroll to first message
End          Scroll to last message and follow

Tab          Change focus to next input

F1           Show/hide debug level
F2           Show/hide info level
F3           Show/hide warning level
F4           Show/hide error level
F5           Show/hide fatal level
F7           Enable/disable node filter
CTRL-a       Select all log lines and copy to clipboard
CTRL-d       Show/hide message details
CTRL-e       Enable/disable text exclude filter
CTRL-f       Enable/disable text include filter
CTRL-i       Invert node selection
CTRL-k       Show/hide preferences
CTRL-n       Show/hide node selection
CTRL-r       Clear message history
CTRL-s       Search for matching string
CTRL-x       Clear search
Backspace    Prev search match
Enter        Next search match

File truncated at 100 lines see the full file

Changelog for package log_view

Forthcoming

• Added support for UTF8 glyphs in log messages.
• Added support for ANSI color codes in log messages.
• Fixed display for terminals limited to 8 colors.
• Fixed session boundaries to not be treated as normal log entries.
• Fixed details panel to scroll vertically when insufficient space is available.
• Fixed help panel to scroll vertically when insufficient space is available.
• Fixed preference panel to scroll vertically when insufficient space is available.
• Updated node panel scrolling to make it consistent with other panels.

0.3.2 (2026-05-04)

• Scope log and preference storage to the active ROS 2 workspace via COLCON_PREFIX_PATH (stored under <workspace>/.log_view/).
• Show file paths in preferences panel; display a warning when persistence is unavailable.
• Contributors: Marc Alban

0.3.1 (2026-05-04)

• Persist logs to disk in ~/.local/share/log_view/ with configurable rotation and max size.
• Load persisted logs on startup.
• Add preferences panel (CTRL-k) for persistence and filter settings.
• Show filtered log count in status bar (logs: X of Y when a filter is active).
• Contributors: Marc Alban

0.3.0 (2026-03-29)

• Add details panel with per-message metadata display.
• Enable static analysis and linting tests.
• Contributors: Marc Alban

0.2.7 (2026-02-18)

• Replace ament_target_dependencies with target_link_libraries.
• Contributors: Marc Alban

0.2.5 (2024-11-25)

• Fix mvwprintw format-security error
• Contributors: Marc Alban

0.2.4 (2024-07-24)

• Fix build error caused by mvwprintw. (#19)
• Contributors: Marc Alban

0.2.3 (2024-07-08)

• Use default C++ version (#16)
• Disable mouse move events on exit. (#12)
• Contributors: Marc Alban

0.2.2 (2022-07-30)

• Improve message handling so that log messages are not dropped. (#8)
• Contributors: Marc Alban

0.2.1 (2022-07-07)

• Remove unused boost include.
• Contributors: Marc Alban

0.2.0 (2022-07-04)

• Port to ROS2
• Contributors: Marc Alban

0.1.3 (2021-03-01)

• Prevent help screen text from wrapping.
• Make help screen modal.
• Add keybindings for selecting all nodes and inverting the node selection.
• Update README.
• Fix compiler warnings.
• Contributors: Marc Alban

0.1.2 (2020-11-26)

• Install binary log_viewer to package destination instead of global destination.
• Contributors: Marc Alban

0.1.1 (2020-11-24)

• Fixes for build farm.

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