# ter - Text Expression Runner

`ter` is a cli to run text expressions and perform basic text operations such as filtering, ignoring
and replacing on the command line. There are many great tools that do this job. But most other tools
have one in common: They are hard to memorize if you dont use them regularly. `ter` tries to solve
this issue by providing a super simple cli & expression language which can be easily memorized and
is well documented.

## Quickstart

```
$ ter filter 'equals "foobar"' -m word				# matches all occurences `foobar` in the text
$ ter filter 'length 20'							# matches all lines with 20 chars
$ ter ignore 'numeric or special'					# ignores all lines which contain only numbers and special chars
$ ter replace 'numeric and length 5' 12345 -m word	# replaces all 5 digit numbers with `12345`
```

## Common tasks where `ter` excels `grep` in readability

| Task                                                    | `ter`                                                                   | `grep`                                                                                         |
|---------------------------------------------------------|-------------------------------------------------------------------------|------------------------------------------------------------------------------------------------|
| Find all words containing a string                      | `ter filter 'contains "substr"' -m word`                                | `grep -oh "\w*substr\w*"`                                                                      |
| Find all lines in a file with a specific length         | `ter filter 'length 10'`                                                | `grep -x '.\{10\}'`                                                                            |                        |                              | `grep -oh "\w*substr\w*"` |
| Ignore all lines containing a string                    | `ter ignore 'contains "hide me"'`                                       | `grep -v "hide me"`                                                                            |
| Replacing all words following a specific pattern        | `ter replace 'numeric and length 5' 12345 -m word`                      | `grep` itself cant replace, you need to use `sed` for that (which gets even more complicated). |
| Replacing all email addresses in a file with your email | `ter replace 'contains "@" and contains ".com"' your@email.com -m word` | Same as above.                                                                                 |


## When to use other tools

As said earlier: `ter` is no direct competitor to `grep`, `awk`, etc.! If you find yourself reaching the limits of the text expression language, you probably want to use more advanced tools.

# Installing

At the moment `ter` can be installed only via `cargo` using:

```
$ cargo install ter
```

# Documentation

There are the following global options:

- `-m` / `--mode`, sets the operation mode, can be either `line` or `word`, defaults to `line`

And there are the following global flags:

- `-f` / --first`, print only the first match if available
- `-l` / --last`, print only the last match if available
- `--skip n`, skip the first n matches
- `--limit n`, show at most n matches

```
ter filter [FLAGS] [OPTIONS] <EXPRESSION> [FILE]
ter ignore [FLAGS] [OPTIONS] <EXPRESSION> [FILE]
ter replace [FLAGS] [OPTIONS] <EXPRESSION> <REPLACEMENT> [FILE]
```

If no file is provided `ter` tries to read from stdin.

## Examples

```
$ docker ps | ter filter 'alphanumeric and length 12' -m word # prints all docker container ids
```

# The Text Expression Language

This is a super simple format of writing readable and easy to memorize text processing expressions - there are many great and far more advanced languages and tools to process text on the commandline out there but all of them have one problem in common - they're unreadable and hard to memorize if not used often.

The Text Expression Languages provides only 9 Attributes to query by. These attributes indicate the format of a string which gets tested against it.

| Attribute        | Resolve to true if the tested string           |
|------------------|------------------------------------------------|
| `starts <str>`   | starts with the given string                   |
| `ends <str>`     | ends with the given string                     |
| `contains <str>` | contains a substring equal to the given string |
| `equals <str>`   | exactly equals the given string                |
| `length <int>`   | has the given length                           |
| `numeric`        | contains only numeric chars                    |
| `alpha`          | contains only alphabetic chars                 |
| `alphanumeric`   | contains only alphanumeric chars               |
| `special`        | contains only special chars                    |

Currently there are only two binary logical operations: `and` and `or`

| Operator | Boolean Algebra |
|----------|-----------------|
| `and`    | Conjunction     |
| `or`     | Disjunction     |

Attributes can be concattenated by logical operators.

## Examples

```
starts "FOO" and ends "BAR"
contains "@" and contains ".com"
length 5 and length 10
numeric and length 8
```

## Limitations

This Syntax might not cover all use cases. It's not meant to do that. If you find yourself reaching the limits of this language you might want to use more advanced tools (such as awk, grep, sed..)

---

The code for the language itself lives in a seperate [repository](https://github.com/schulke-214/te).