# excavate
A command line tool to excavate columns from multi-column texts.
`excavate` is a simple program that does one specific job, getting and printing the specified column, line-by-line reading from standard input. This is a job that can be done by some more sophisticated programs, e.g. `awk` or `sed`, but having the memory capacity of a goldfish, I never could recall their syntax when I need to. Personally, I frequently need the fetching of a column, and infrequently need anything that requires the rich feature-set offered by those tools. That's my rationale for creating this highly specialized, simplistic, one-trick-pony program.
## Usage:
```bash
excavate <COLUMNS>
```
`<COLUMNS>` is supplied in the format of comma delimited list. Each item can be a positive integer, or a range in the format of "a-b". At least one column must be specified. The column ID starts from 0 (first column is 0, the second 1, etc.). The range "a-b" includes both end, with "a" being the lower end, and "b" the higher end. If "a" is greater than "b", the range is empty (selects no column).
For example:
| fields | Description |
| :----- | :-------------------------------------------------- |
| 0 | Select the first column |
| 0-2 | Select the first three columns |
| 0,3,5 | Select the first, the fourth, and the sixth column |
| 0-3,5 | Select the first four columns, and the sixth column |
For example:
Printing the all the process IDs matching "bash":
```bash
$ ps aux | grep bash
henry 7308 0.0 0.0 8988 5652 pts/3 S+ 12:03 0:00 bash
henry 7482 0.0 0.0 8988 5500 pts/4 S+ 12:03 0:00 bash
henry 7656 0.0 0.0 8988 5540 pts/5 S+ 12:03 0:00 bash
henry 8776 0.0 0.0 6564 2176 pts/1 S+ 12:08 0:00 grep --color=auto bash
$ ps aux | grep bash | excavate 1
7308
7482
7656
8826
```
The columns, regardless of your input order, will always be printed from low to high, i.e. from left to right in the table, and duplicates are ignored. `excavate 1,2` is equivalent to `excavate 2,1,1`.
If a line has not enough columns, `excavate` ignores any field beyond the limit. For instance, running `excavate 2,10` against the input `bob alice eve` gets you `eve`. Running it against `bob alice` gets you a blank line. The output always has the same number of lines as the input, even if some of them are empty.
## Installation
At the moment, the program can be installed via `cargo`:
```bash
cargo install excavate
```
## Build
`excavate` has only Rust dependencies, `clap` and `nom`. There's no external dependencies. Clone this repository, and run
```bash
cargo build
```