38 stable releases

2.19.0 Nov 13, 2023
2.18.0 Nov 9, 2023
2.13.0 Oct 28, 2023
2.11.1 Jul 6, 2023
1.0.1 Feb 21, 2023

#34 in Template engine

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MIT license

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Kapow is a template processor that provides the following directives to support injecting file contents, command output, current date/time, elapsed time, etc in generated output.

It can be used in some different ways:

  • Standard: Create a (Markdown) file with kapow directives then run kapow [OPTIONS] path/to/file.ext; optionally save the output via redirection: kapow [OPTIONS] path/to/file.ext >output.ext
  • Shebang: Place #!/usr/bin/env kapow as the first line of a (Markdown) file, make it "executable" via chmod +x file.ext, then run via ./file.ext (see note #3 under block directives). Use env's -S option if passing options to kapow, for example: #!/usr/bin/env -S kapow -w 60. See build.md for an example.

While kapow is designed around Markdown syntax, it can be used with any text format that works with its directives.

Block directives

Directive Description
!inc:path Include file contents; path is relative to its containing file
!run:command Run command and insert stdout
!start:name - !stop:name Optional content included only if name is provided in -f value


  1. Block directives must be placed at the beginning of a line.
  2. Long commands can be backslash-wrapped.
  3. Included file paths and commands are processed from the directory where the source file is located when it is passed as an argument. However, if the source file is read on stdin or run via shebang, included file paths and commands are processed relative to the current directory. So, if any included files use relative paths or commands that depend on the current directory, it will be necessary to manually change to the source file's directory and then run via ./file.ext.
  4. Block directives are entirely replaced by their contents/output, so you are free to embed them inside or as Markdown syntax... for example, as listing contents, prepend a prompt showing the command, etc.
  5. If a !run directive fails, kapow prints the error and stops processing, unless the user specifies the -k option.

Span directives

Directive Example Description
`!elapsed` 0s Processing time
`!now` 2023-11-13T21:52:50Z Current date/time in UTC / RFC 3339
`!now:local` Mon 13 Nov 2023 16:52:50 EST Current date/time in local timezone
`!now:local:%A %H:%M` Monday 16:52 Current date/time in local timezone and custom format
`!now:MST7MDT` Mon 13 Nov 2023 14:52:50 MST Current date/time in custom timezone
`!now:MST7MDT:%A %H:%M` Monday 14:52 Current date/time in custom timezone and format
`!now:US/Hawaii` Mon 13 Nov 2023 11:52:50 HST Current date/time in custom locale
`!now:US/Hawaii:%A %H:%M` Monday 11:52 Current date/time in custom locale and format
`!now:UTC:%A %H:%M` Monday 21:52 Current date/time in UTC and custom format
`!now:x` XhACLqo Current date/time in "x" format
`!today` 2023-11-13 Current date in UTC / RFC 3339
`!today:local` 2023-11-13 Current date in local timezone
`!today:MST7MDT` 2023-11-13 Current date in custom timezone
`!today:MST7MDT:%v` 13-Nov-2023 Current date in custom timezone and format
`!today:US/Hawaii` 2023-11-13 Current date in custom locale
`!today:US/Hawaii:%x` 11/13/23 Current date in custom locale and format
`!today:UTC:%A` Monday Current date in UTC and custom format
  • Span directives must be placed inside a code span and may appear zero or more times in any line.
  • Disable processing a span directive by escaping ! with a backslash: \!.

Other features

  • Escaped wrap: End a line with a single backslash \ and it will be unwrapped in the output; this enables an author to wrap long lines in the source but have them be unwrapped by kapow. If trailing backslash(es) need to be maintained, add an additional backslash and the line will not be unwrapped and the extra backslash will be removed.
  • Relative image paths: Markdown images (![alt](path "title")) with a local path are processed relative to the containing file, unless the -R option is used to disable this feature.
  • Eliminate multiple empty lines.


cargo install kapow bat

NOTE: Installing bat is optional, but if installed, kapow uses it for syntax highlighting and paging (if on a Linux, macOS, or UNIX system; see the -p, -P, -H, -l, and -r options); also it's a nice utility to have around.


$ kapow -V
kapow 2.19.0
$ kapow -h

Usage: kapow [OPTIONS] [PATH]...

  [PATH]...  Source file(s) [default: -]

  -f <FLAGS>       Flags (comma-separated list of flags to enable)
  -p               Page output
  -P               Do not page output
  -H               Disable syntax highlighting
  -L               Display all syntax highlight languages
  -l <LANG>        Syntax higlight language [default: md]
  -w <WRAP>        Wrap !run directive columns [default: 0]
  -c <STRING>      Wrap !run directive continuation [default: \]
  -k               Ignore !run directive failures
  -R               Disable relative image paths
  -r, --readme     Print readme
  -h, --help       Print help
  -V, --version    Print version


Code Description
101 Could not read input file
102 Could not read included file
103 Could not change directory
104 !run directive command failed

NOTE: The kapow process may not appear to have exited with these error codes in "normal usage" because output is piped to bat as a pager if it is installed and output is a TTY and unfortunately bat masks the error code.


See the readme task in Makefile.toml:

  • Generates t/VERSION.md from t/VERSION.t.md
    • !run:../target/release/kapow -V
  • Generates t/USAGE.md from t/USAGE.t.md
    • !run:../target/release/kapow -h
  • Generates README.md from t/README.md
    • !inc:VERSION.md
    • !inc:USAGE.md
    • `!now` (all variants)
    • Escaped wraps
    • Relative image path


Please find the CHANGELOG.md in the repository.


cargo install b3sum bat cargo-audit cargo-edit cargo-make \
cargo-outdated dtg kapow miniserve


~252K SLoC