ov - feature rich terminal pager

ov is a terminal pager.

• ov can be used instead of less, more, tail -f/-F and watch.
• ov also has an effective function for tabular text.

• 1. Feature
  • 1.1. Not supported
• 2. Install
  • 2.1. deb package
  • 2.2. rpm package
  • 2.3. MacPorts (macOS)
  • 2.4. Homebrew(macOS or Linux)
  • 2.5. pkg (FreeBSD)
  • 2.6. Arch Linux
  • 2.7. nix (nixOS, Linux, or macOS)
  • 2.8. Binary
  • 2.9. go install
  • 2.10. go get(details or developer version)
• 3. Usage
  • 3.1. Basic usage
  • 3.2. Config
  • 3.3. Header
    • 3.3.1. Skip
  • 3.4. Column mode
  • 3.5. Column rainbow mode
  • 3.6. column-width
  • 3.7. Wrap/NoWrap
  • 3.8. Alternate-Rows
  • 3.9. Section
  • 3.10. Follow mode
  • 3.11. Follow name
  • 3.12. Follow all mode
  • 3.13. Follow section mode
  • 3.14. Exec mode
  • 3.15. Search
  • 3.16. Mark
  • 3.17. Watch
  • 3.18. Mouse support
  • 3.19. Multi color highlight
  • 3.20. Plain
  • 3.21. Jump target
  • 3.22. View mode
  • 3.23. Output on exit
• 4. How to reduce memory usage
  • 4.1. Regular file (seekable)
  • 4.2. Other files, pipes(Non-seekable)
• 5. Command option
• 6. Key bindings
• 7. Customize
  • 7.1. Style customization
  • 7.2. Customizing the bottom status line
  • 7.3. Key binding customization
• 8. VS
• 9. Work together

1. Feature

• Supports files larger than memory (v0.30.0 or later).
• Regular files can be opened quickly even if they are large (v0.30.0 or later).
• Supports fixed header line display (both wrap/nowrap).
• Supports column mode, which recognizes columns by delimiter.
• Also, in column mode, there is a column-rainbow mode that colors each column.
• Support columns with fixed widths instead of delimiters (v0.30.0 or later).
• Supports section-by-section movement, splitting sections by delimiter.
• Dynamic wrap/nowrap switchable.
• Supports alternating row styling.
• Shortcut keys are customizable.
• The style of the effect is customizable.
• Supports follow-mode (like tail -f).
• Support follow mode by file name (like tail -F) (v0.30.0 or later).
• Supports follow-section, which is displayed when the section is updated.
• Supports following multiple files and switching when updated(follow-all).
• Supports the execution of commands that toggle both stdout and stderr for display.
• Supports watch mode, which reads files on a regular basis.
• Support watch in exec mode (equivalent to watch command) (v0.30.0 or later).
• Supports incremental search and regular expression search.
• Supports multi-color to highlight multiple words individually.
• Better support for Unicode and East Asian Width.
• Supports compressed files (gzip, bzip2, zstd, lz4, xz).
• Suitable for tabular text. psql, mysql, csv, etc...

1.1. Not supported

• Does not support syntax highlighting for file types (source code, markdown, etc.)
• Does not support Filter function (&pattern equivalent of less)

2. Install

2.1. deb package

You can download the package from releases.

curl -L -O https://github.com/noborus/ov/releases/download/vx.x.x/ov_x.x.x-1_amd64.deb
sudo dpkg -i ov_x.x.x-1_amd64.deb

2.2. rpm package

You can download the package from releases.

sudo rpm -ivh https://github.com/noborus/ov/releases/download/vx.x.x/ov_x.x.x-1_amd64.rpm

2.3. MacPorts (macOS)

sudo port install ov

2.4. Homebrew(macOS or Linux)

brew install noborus/tap/ov

2.5. pkg (FreeBSD)

pkg install ov

2.6. Arch Linux

You can install ov using an AUR helper.

AUR package: https://aur.archlinux.org/packages/ov-bin

2.7. nix (nixOS, Linux, or macOS)

ov is available as a nix package. You can install it with

nix profile install nixpkgs#ov

if you use flakes, or using nix-env otherwise:

nix-env -iA nixpkgs.ov

2.8. Binary

You can download the binary from releases.

curl -L -O https://github.com/noborus/ov/releases/download/vx.x.x/ov_x.x.x_linux_amd64.zip
unzip ov_x.x.x_linux_amd64.zip
sudo install ov /usr/local/bin

2.9. go install

It will be installed in $GOPATH/bin by the following command.

go install github.com/noborus/ov@latest

2.10. go get(details or developer version)

First of all, download only with the following command without installing it.

go get -d github.com/noborus/ov
cd $GOPATH/src/github.com/noborus/ov

Next, to install to $GOPATH/bin, run the make install command.

make install

Or, install it in a PATH location for other users to use (For example, in /usr/local/bin).

make
sudo install ov /usr/local/bin

3. Usage

(default key key) indicates the key that can be specified even after starting the same function as the command line option.

3.1. Basic usage

ov supports open file name or standard input.

ov filename

cat filename|ov

Used by other commands by setting the environment variable PAGER.

export PAGER=ov

See the ov site for more use cases.

3.2. Config

You can set style and key bindings in the configuration file.

ov will look for a configuration file in the following paths in descending order:

$XDG_CONFIG_HOME/ov/config.yaml
$HOME/.config/ov/config.yaml
$HOME/.ov.yaml

On Windows:

%USERPROFILE%/.config/ov/config.yaml
%USERPROFILE%/.ov.yaml

Create a config.yaml file in one of the above directories. If the file is in the user home directory, it should be named .ov.yaml.

Please refer to the sample ov.yaml configuration file.

3.3. Header

The --header (-H) (default key H) option fixedly displays the specified number of lines.

ov --header 1 README.md

3.3.1. Skip

When used with the --skip-lines (default key ctrl+s) option, it hides the number of lines specified by skip and then displays the header.

ov --skip-lines 1 --header 1 README.md

3.4. Column mode

Specify the delimiter with --column-delimiter(default key is d) and set it to --column-mode(default key is c) to highlight the column.

ov --column-delimiter "," --column-mode test.csv

Regular expressions can be used for the --column-delimiter. Enclose in '/' when using regular expressions.

ps aux | ov -H1 --column-delimiter "/\s+/" --column-rainbow --column-mode

3.5. Column rainbow mode

You can also color each column individually in column mode. Specify --column-rainbow(default key is ctrl+r) in addition to the --column-mode option.

Color customization is possible. Please specify 7 or more colors in config.yaml.

StyleColumnRainbow:
  - Foreground: "white"
  - Foreground: "aqua"
  - Foreground: "lightsalmon"
  - Foreground: "lime"
  - Foreground: "blue"
  - Foreground: "yellowgreen"
  - Foreground: "red"

3.6. column-width

For output like ps, using --column-width is a better way to separate columns than using spaces as delimiters.

You can specify the column width with --column-width (default key alt+o).

ps aux|ov -H1 --column-width --column-rainbow

This column-width feature is implemented using guesswidth.

3.7. Wrap/NoWrap

Supports switching between wrapping and not wrapping lines.

The option is --wrap, specify --wrap=false (default key w, W) if you do not want to wrap.

3.8. Alternate-Rows

Alternate row styles with the --alternate-rows(-C) (default key C) option The style can be set with Style customization.

ov --alternate-rows test.csv

3.9. Section

You specify --section-delimiter(default key alt+d), you can move up and down in section units. The start of the section can be adjusted with --section-start(default key ctrl+F3, alt+s).

The section-delimiter is written in a regular expression (for example: "^#"). (Line breaks are not included in matching lines).

For example, if you specify "^diff" for a diff that contains multiple files, you can move the diff for each file.

3.10. Follow mode

--follow(-f)(default key ctrl+f) prints appended data and moves to the bottom line (like tail -f).

ov --follow-mode /var/log/syslog

(while :; do echo random-$RANDOM; sleep 0.1; done;)|./ov  --follow-mode

3.11. Follow name

You can specify the file name to follow with --follow-name(like tail -F). Monitor file names instead of file descriptors.

ov --follow-name /var/log/nginx/access.log

3.12. Follow all mode

--follow-all(-A)(default key ctrl+a) is the same as follow mode, it switches to the last updated file if there are multiple files.

ov --follow-all /var/log/nginx/access.log /var/log/nginx/error.log

3.13. Follow section mode

Use the --follow-section(default key F2) option to follow by section. Follow mode is line-by-line, while follow section mode is section-by-section. Follow section mode displays the bottom section. The following example is displayed from the header (#) at the bottom.

ov --section-delimiter "^#" --follow-section README.md

3.14. Exec mode

Use the --exec (-e) option to run the command and display stdout/stderr separately. Arguments after (--) are interpreted as command arguments.

Shows the stderr screen as soon as an error occurs, when used with --follow-all.

ov --follow-all --exec -- make

3.15. Search

Search by forward search / key(default) or the backward search ? key(default). Search can be toggled between incremental search, regular expression search, and case sensitivity. Displayed when the following are enabled in the search input prompt:

Specify true/false in config file.

CaseSensitive: false
RegexpSearch: false
Incsearch: true
SmartCaseSensitive: true

3.16. Mark

Mark the display position with the m key(default). The mark is decorated with StyleMarkLine and MarkStyleWidth.

Marks can be erased individually with the M key(default). It is also possible to delete all marks with the ctrl + delete key(default).

Use the >next and <previous (default) key to move to the marked position.

3.17. Watch

ov has a watch mode that reads the file every N seconds and adds it to the end. When you reach EOF, add '\f' instead. Use the --watch(-T) option. Go further to the last section. The default is'section-delimiter', so the last loaded content is displayed.

for example.

ov --watch 1 /proc/meminfo

3.18. Mouse support

The ov makes the mouse support its control. This can be disabled with the option --disable-mouse(default key ctrl+F3, ctrl+alt+r).

If mouse support is enabled, tabs and line breaks will be interpreted correctly when copying.

Copying to the clipboard uses atotto/clipboard. For this reason, the 'xclip' or 'xsel' command is required in Linux/Unix environments.

Selecting the range with the mouse and then left-clicking will copy it to the clipboard.

Pasting in ov is done with the middle button. In other applications, it is pasted from the clipboard (often by pressing the right-click).

Also, if mouse support is enabled, horizontal scrolling is possible with shift+wheel.

3.19. Multi color highlight

This feature styles multiple words individually. .key(default) enters multi-word input mode. Enter multiple words (regular expressions) separated by spaces.

For example, error info warn debug will color errors red, info cyan, warn yellow, and debug magenta.

It can also be specified with the command line option --multi-color(-M)(default key .). For command line options, pass them separated by ,(comma).

For example:

ov --multi-color "ERROR,WARN,INFO,DEBUG,not,^.{24}" access.log

Color customization is possible. Please specify 7 or more colors in config.yaml.

StyleMultiColorHighlight:
  - Foreground: "red"
    Reverse: true
  - Foreground: "aqua"
  - Foreground: "yellow"
  - Foreground: "fuchsia"
  - Foreground: "lime"
  - Foreground: "blue"
  - Foreground: "grey"

3.20. Plain

Supports disable decoration ANSI escape sequences. The option is --plain (or -p) (default key ctrl+e).

3.21. Jump target

You can specify the lines to be displayed in the search results. This function is similar to --jump-target of less. Positive numbers are displayed downwards by the number of lines from the top(1). Negative numbers are displayed up by the number of lines from the bottom(-1). . (dot) can be used to specify a percentage. .5 is the middle of the screen(.5). You can also specify a percentage, such as (50%).

This option can be specified with --jump-target(or -j) (default key j).

If section is specified as the --jump-target, the display will start from the beginning of the section as much as possible and the jump-target will be changed.

ov --section-delimiter "^#" --jump-target section README.md

3.22. View mode

You can also use a combination of modes using the --view-mode(default key p) option. In that case, you can set it in advance and specify the combined mode at once.

For example, if you write the following settings in ov.yaml, the csv mode will be set with --view-mode csv.

ov --view-mode csv test.csv

Mode:
  p:
    Header: 2
    AlternateRows: true
    ColumnMode: true
    LineNumMode: false
    WrapMode: true
    ColumnDelimiter: "|"
    ColumnRainbow: true
  m:
    Header: 3
    AlternateRows: true
    ColumnMode: true
    LineNumMode: false
    WrapMode: true
    ColumnDelimiter: "|"
  csv:
    Header: 1
    AlternateRows: true
    ColumnMode: true
    LineNumMode: false
    WrapMode: true
    ColumnDelimiter: ","
    ColumnRainbow: true

3.23. Output on exit

--exit-write -X(default key Q) option prints the current screen on exit. This looks like the display remains on the console after the ov is over.

By default, it outputs the amount of the displayed screen and exits.

ov -X README.md

You can change how much is written using --exit-write-before and --exit-write-after(default key ctrl+q). --exit-write-before

--exit-write-before specifies the number of lines before the current position(top of screen). --exit-write-before 3 will output from 3 lines before.

--exit-write-after specifies the number of lines after the current position (top of screen).

--exit-write-before 3 --exit-write-after 3 outputs 6 lines.

4. How to reduce memory usage

Since v0.30.0 it no longer loads everything into memory. The first chunk from the beginning to the 10,000th line is loaded into memory and never freed. Therefore, files with less than 10,000 lines do not change behavior.

The --memory-limit option can be used to limit the chunks loaded into memory. Memory limits vary by file type.

Also, go may use a lot of memory until the memory is freed by GC. Also consider setting the environment variable GOMEMLIMIT.

export GOMEMLIMIT=100MiB

4.1. Regular file (seekable)

Normally large (10,000+ lines) files are loaded in chunks when needed. It also frees chunks that are no longer needed. If --memory-limit is not specified, it will be limited to 100.

ov --memory-limit-file 3 /var/log/syslog

Specify MemoryLimit in the configuration file.

MemoryLimitFile: 3

You can also use the --memory-limit-file option and the MemoryLimitFile setting for those who think regular files are good memory saving.

4.2. Other files, pipes(Non-seekable)

Non-seekable files and pipes cannot be read again, so they must exist in memory.

If you specify the upper limit of chunks with --memory-limit or MemoryLimit, it will read up to the upper limit first, but after that, when the displayed position advances, the old chunks will be released. Unlimited if --memory-limit is not specified.

cat /var/log/syslog | ov --memory-limit 10

It is recommended to put a limit in the config file as you may receive output larger than memory.

MemoryLimit: 1000

5. Command option

It can also be changed after startup.

6. Key bindings

7. Customize

7.1. Style customization

You can customize the following items.

• StyleAlternate
• StyleHeader
• StyleOverStrike
• StyleOverLine
• StyleLineNumber
• StyleSearchHighlight
• StyleColumnHighlight
• StyleMarkLine
• StyleSectionLine
• StyleMultiColorHighlight
• StyleColumnRainbow
• StyleJumpTargetLine

Specifies the color name for the foreground and background colors. Specify bool values for Reverse, Bold, Blink, Dim, Italic, and Underline.

[Example]

StyleAlternate:
  Background: "gray"
  Bold: true
  Underline: true

7.2. Customizing the bottom status line

You can customize the bottom status line.

Whether to display file names. Whether to invert the color of the file name.

[Example]

Prompt
  Normal:
    ShowFilename: false
    InvertColor: false

7.3. Key binding customization

You can customize key bindings.

[Example]

    down:
        - "Enter"
        - "Down"
        - "ctrl+N"
    up:
        - "Up"
        - "ctrl+p"

See ov.yaml for more information.

8. VS

The following software can be used instead. If you are not satisfied with ov, you should try it.

• less
  • less is versatile, feature-rich, and the de facto standard for pagers.
• most
  • most is a general-purpose pager with split-window capabilities.
• pspg
  • pspg is a pager suitable for output of psql etc.
• moar
  • moar is a pager with code highlighting.
• slit
  • slit is a pager suitable for viewing logs.
• lnav
  • lnav analyzes logs and can be used as a viewer.
• peep
  • peep is a pager that can work in a small pane.

9. Work together

The following are not actually pagers and do not conflict. can work together.

• bat
  • bat is an alternative to cat. It supports a lot of highlighting and automatically calls the pager.
• delta
  • delta processes the diff for easy viewing and displays it. Call the pager automatically.