ne

ne manipulates "node expressions", which are commonly used in clustered systems to represent groups of nodes. For example, nodes 1 through 5 and 8 in the "foo" cluster would be written "foo[1-5,8]". Single node names can be written either as "foo123" or "foo[123]". Note that the values within [] are not character sequences like in regular expressions, they are comma-separated ranges of decimal numbers.

Installation

Install Crystal per these instructions: https://crystal-lang.org/docs/installation/

$ crystal build src/ne.cr --release

Usage

By default ne accepts node expressions as arguments separated by operators and outputs the result as an optimal node expression:

$ ne foo[1,2,4,5,6,8]
foo[1-2,4-6,8]

"+" means set union, overlapping ranges will be merged:

$ ne foo[1-5] + foo[4-8]
foo[1-8]

"+" is implied so foo[1-5]+foo[4-8] and foo[1-5] foo[4-8] are equivalent.

Spaces are only significant when the operator is implied. foo[1-4]+foo[4-8] and foo[1-4] + foo[4-8] are equivalent but foo[1-4]foo[4-8] is illegal.

"-" means set difference (it's legal to subtract something that's not in the first expression):

$ ne foo[1-8] - foo[6-12]
foo[1-5]

"^" means the intersection of two expressions: nodes that are in both:

$ ne foo[1-12] ^ foo[8-20]
foo[8-12]

Expressions can be chained, and are evaluated strictly left-to-right without precedence:

$ ne foo[1-12] + foo[8-20] - foo[6-14]
foo[1-5,15-20]

Change the group separator:

$ ne -g, foo[1-5] bar[1-5]
foo[1-5],bar[1-5]

(Or use environment variable NE_GROUP_SEPARATOR.)

You can output results as individual node names ("expanded"). For newline separated:

$ ne -e foo[50-54]
foo50
foo51
foo52
foo53
foo54

(Or set environment variable NE_EXPANDED_OUTPUT=something.)

Or use a specific separator:

$ ne -e -s, foo[50-54]
foo50,foo51,foo52,foo53,foo54

(Or use environment variable NE_NODE_SEPARATOR.)

Multiple node name prefixes are supported:

$ ne foo[1-5] + foo[4-8] + bar[6-10]
foo[1-8] bar[6-10]

You can output an arbitrary prefix before each group (useful with pdsh):

$ ne -p"-w " foo[1-5] + bar[6-10]
-w foo[1-5] -w bar[6-10]

(Or use environment variable NE_GROUP_PREFIX.)

Pad up to a minimum number of digits:

$ ne -d4 foo[1-5]
foo[0001-0005]

(Or use environment variable NE_PAD_DIGITS.)

"@" reads a file or standard input, scanning arbitrary text looking for words that look like node names (this can obviously be unreliable) and returns the union:

$ echo "this is a line that contains the node names foo12 and foo13" | ne @
foo[12-13]

Development

TODO: Write development instructions here

Contributing

1. Fork it ( https://github.com/joatca/ne/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• [joatca] Fraser McCrossan - creator, maintainer