https://github.com/rwaskiewicz/rawk

a toy awk implementation
https://github.com/rwaskiewicz/rawk

Last synced: about 1 month ago
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a toy awk implementation

• Host: GitHub
• URL: https://github.com/rwaskiewicz/rawk
• Owner: rwaskiewicz
• Created: 2020-11-26T16:59:18.000Z (about 4 years ago)
• Default Branch: main
• Last Pushed: 2024-03-11T01:38:09.000Z (11 months ago)
• Last Synced: 2024-12-20T19:26:39.753Z (about 1 month ago)
• Language: Rust
• Homepage:
• Size: 409 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 3
• Metadata Files:
  • Readme: README.md

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README

        
# r-awk

a toy [awk](https://en.wikipedia.org/wiki/AWK) written in [Rust](https://www.rust-lang.org/), feature incomplete.

## Minimum Rust Version

The minimum version required to compile and run r-awk can be found under the `rust-version` key in the project's [`Cargo.toml`](./Cargo.toml) file.

## Compiling

```commandline

cargo build --release

```

## Running

At this time, running a REPL is fully supported and has limited support for awk file reading. 

Like a real awk, this r-awk will take a single program from the STDIN when invoked.

It then will prompt for input to serve as the data that is fed into the program.

The program below demonstrates running a [compiled](#compiling) r-awk and demonstrates the usage of 

[field variables](https://www.gnu.org/software/gawk/manual/gawk.html#Fields) and

[field separators](https://www.gnu.org/software/gawk/manual/html_node/Single-Character-Fields.html).

```commandline

./rawk -F, '{print $2 * $3 + $1;}'

1,2,3

7

4,5,6

34

```

Patterns are supported:

```commandline

./rawk -F, '$1 > $2 {print "First is bigger";} $2 > $1 {print "Second is bigger";}'

1,2

Second is bigger

2,1

First is bigger

```

Multi-line programs are supported in the REPL.

Take 'fizzbuzz' for example:

```

./rawk '{

    for (i=0; i<=100; i=i+1) {

      result = "";

      if (i % 3 == 0) { 

        result = "fizz";

      }

      if (i % 5 == 0) {

        result = result "buzz";

      }

      if (result == "") {

        result = i;

      }

      print result;

    }

}'

```

Reading an awk program from a file:

```commandline

./rawk -f ./awk_examples/field_variables/it_prints_all_line_parts.awk

IN: alice 40 25

OUT: alice 40 25

```

Reading an awk program and data from a file:

```commandline

./rawk -f ./awk_examples/field_variables/it_prints_all_line_parts.awk ./tests/data/hours1.dat

Alice 25.00 10

Bob 20.75 20

Charlie 15.25 40

Dan 21.50 0

Erin 22.00 30

```

## Logging

The `env_logger` crate is used as the implementation behind the `log` facade.

Instructions for configuring log levels can be found in the crate's [documentation](https://docs.rs/env_logger/0.8.2/env_logger/).

By default, the REPL will run with the ['Info' log filter](https://docs.rs/env_logger/0.8.2/env_logger/struct.Builder.html).

Example usage:

```commandline

RUST_LOG=debug cargo run -- '{print $2 * $3 + $1;}'

```

## References

- [IEEE Std 1003.1-2017](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/awk.html) - the POSIX specification for the awk language