awkrepl

A REPL of sorts for AWK.

Syntax-checks and pretty-prints your AWK code in the lower right-hand pane when you save it, and shows the results of your program's execution in the lower-left. The top pane is your text editor (whatever you have $EDITOR set to, or defaults to nano), with the file ~/.repl.awk open for editing.

Any lines after #DATA at the end of the program are supplied as input to your program, for quick testing on sample inputs. If you have a line in your source file that starts with #ARGS, anything on the line after that is provided as command-line arguments to your script (which you can read from ARGV[1]…). Whitespace within individual arguments is probably not preserved, though; see #4.

awkrepl automatically wraps simple programs like print $1 in END{…} for you, so it's a piece of cake to try out little snippets of AWK code.

Some reasonable heuristics are applied when deciding whether to automatically apply an outer set of curly braces for you, so that if your script contains something like

/^r/

# or
NF>1

where the {print} is implicit, this should work as expected.

Requirements

• Docker
• —or— tmux, entr, GNU Awk (as gawk), and Perl
  • also bat, if you want your pretty-printed AWK source to also be syntax-highlighted

Usage

If you have all the prereqs and want to run it without Docker, simply make the awkrepl script executable with chmod a+x (if it's not already) and put it somewhere in your search path, like $HOME/bin. Run awkrepl.

Otherwise, for Docker:

make build
# or, if you don't have 'make'
docker build -t awkrepl .

make run
# or
docker run -it --rm awkrepl

Or, pull the image straight from Docker Hub, without even cloning this repo:

docker run -it --rm ernstki/awkrepl

The image is about ~65 MB compressed, and based on debian:stable-slim.

The examples.awk from this repository is copied to ~/.repl.awk in the Docker container, to provide you with some working examples to play with. Just clear out the entire contents of this file and replace with your own code when you get bored with those examples.

Using a different editor with the Docker container

The make run target shown above will respect the EDITOR environment variable from your current login session, defaulting to nano if it's not set. You can specify a different editor like this:

make run EDITOR=vim

# or
docker run -it -e EDITOR=vim --rm

There's no GNU Emacs in the Docker image to keep the size down, but there's jove, which installs itself as emacs, and that'll do in a pinch. You could always modify the Dockerfile and make build!

It's also possible to run straight from Docker Hub, if that's your thing:

docker run -it -e EDITOR=emacs --rm ernstki/awkrepl

Bugs

The whole script probably should've just been written in Perl.

Please report any issues you find, though.

See also

• https://en.wikipedia.org/wiki/AWK
• https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop
• https://www.grymoire.com/Unix/Awk.html

Author

Kevin Ernst (ernstki -at- mail.uc.edu)

License

MIT.