# snang

                             version: 0.2.7

                             tacit JS ⨉ CLI

    Manipulate things in the command-line with tacit JS in a sandbox

                               ## Globals

1. The literal "x" refers to the current e.g. echo "snang" | snang buffer contents "x.toUpperCase() + '!'"

2. Both "ramda and "entrust" have been e.g. echo "snang" | snang "tail(x)" injected into the sandbox, so any methodecho "snang" | snang "e1('split')('',x)" of theirs will work.

3. "fluture" has also been injected into e.g. echo "snang" | snang "keys(F)" -o the sandbox, but it is aliased to the literal "F".

4. The literal "exec" allows you to run e.g. echo "package.json" | snang child_process.execSync on the given "exec('cat ' + x)" string. This effectively allows you to construct meta commands.

                                   ## Flags

--debug, -d Pass integers in to get specific debug information

--help, -h See this help text

--color, -C Display output with color. Use --no-color to turn color off.

--shell, -P Specify pipe commands with "|" delimiters, like in *nix

--pipe, -p Wrap passed expression in pipe

--compose, -c Wrap passed expression in compose

--json, -i Read JSON values in

--jsonOut, -o Pass JSON values out

--prettyPrint, -L Print the commands you've passed into snang, but pretty

--print, -l Print the commands you've passed into snang

--exportFile, -x Print the commands you've passed into snang, but as a file

--exportES6, -X Print the commands you've passed into snang, but as an ES6 file

--readStdinOnExport, -t Used in concert with -X / -x, this makes the resulting file deal with stdin as an input

--readFileOnExport, -u Used in concert with -X / -x, this makes the resulting file deal with a file as an input

--readDirOnExport, -v Used in concert with -X / -x, this makes the resulting file deal with a directory as an input

--read, -r Read from a file. If this is not passed, snang reads from stdin.

--write, -w Write from a file. If this is not passed, snang writes to stdout.

--require, -q Add a commonjs file to be used within snang's vm.

--import, -Q Add an ES6 style file to be used within snang's vm. Impacts performance, as this transpiles sources on the fly.

--future, -f If the resulting output of the expression is a Future, fork it to (stderr, stdout).

--trim, -m Trim the trailing \n of the input. Default: false

--source, -s Add a source file which takes the form --source ref:path/to/file.js. Adds a source object to the VM which has sources as Futures.

--config, -k Pass a config file to snang. Uses cosmiconfig, so any of the following is valid: '.snangrc' '.snangrc.json' '.snangrc.js' '.snangrc.yaml' '.snangrc.config.js' or a "snang" property in package.json.

--commands, -z Ignore all inputs and list all valid commands.

                              ## Examples

• read name from package.json

  snang --read package.json --json snang --read package.json --json --pipe "x.name" "prop('name')"

  cat package.json | snang -i "x.name" cat package.json | snang -ip "prop('name')"

• list devDependencies in package.json which have eslint in the key, return as string

snang --read package.json --json --shell "prop('devDependencies') | keys | filter(matches('eslint')) | join(' ')"

cat package.json | snang -iP "prop('devDependencies') | keys | filter(matches('eslint')) | join(' ')"

• read package.json, filter devDependencies and then pass to yarn and execute

cat package.json | snang --json "exec( 'yarn add ' + Object.keys(x.devDependencies).filter(z => z.includes('eslint')).join(' ') + ' -D' )"

cat package.json | snang -iP "prop('devDependencies') | keys | filter(includes('eslint')) | join(' ') | z => 'yarn add ' + z + ' -D') | exec"

cat package.json | snang -iP "prop('devDependencies') | keys | filter(includes('eslint')) | join(' ')" | xargs yarn add -D

• read package.json, require local node-module (with optional alias)

snang --read package.json --json --require camel-case -P "prop('devDependencies') | keys | map(camelCase)" -o

snang --read package.json --json --require kool:camel-case -P "prop('devDependencies') | keys | map(kool))" -o

• read package.json, import es6 module (with optional alias)

snang --read package.json --json --import ./require-test-simple.mjs -P "prop('devDependencies') | keys | map(requireTestSimple)" -o

snang --read package.json --json --import kool:./require-test-simple.mjs-P "prop('devDependencies') | keys | map(kool))" -o

API

Table of Contents

• colorize
  • Parameters
• yargsParserOptions
  • Properties
• errors
  • Properties
• handleErrors
  • Parameters
  • Examples
• onError
  • Parameters
• getExpression
  • Parameters
• createComposedExpression
  • Parameters
• runInContext
  • Parameters
• runner
  • Parameters
• makeSandboxWithRequireHook
  • Parameters
  • Examples
• makeSandbox
  • Parameters
  • Examples
• createStreamFromSource
  • Parameters
• toString
• concatConditionally
  • Parameters
• tackOn
  • Parameters

colorize

colorize a string conditionally

Parameters

• fn Function color function
• c Object config
• x string the string to colorize

Returns string

yargsParserOptions

Options hash to be passed to yargs-parser.

Type: Object

Properties

• boolean Array<string> Boolean argv flags.
• alias Object Aliases.

errors

Errors object, used both for filtering and constant definition.

Type: Object

Properties

• chunkArgument string A chunk argument error.
• useObjectFlag string A replacement error for the chunk argument error.

handleErrors

Pure error handler which attempts to address known common errors.

Parameters

• warn Function Function to receive errors.

Examples

handleErrors(console.warn)

Returns Function onError handler.

onError

The inner error handler.

Parameters

• e Error Error.

getExpression

Convert a list of expressions into a string to be evaluated in a virtual machine context.

Parameters

• config Object Config from yargs-parser.
• expressions Array<string> Input expressions.
• sandbox Object Sandbox object for evaluating the eventual expression against.

Returns string The expression to evaluate.

createComposedExpression

Parameters

• pretty boolean Pretty print the expression?
• expressions Array<string> An array of expressions.
• name string Name of the function to compose.

Returns string Composed / piped string.

runInContext

Given an array of [sandbox, expression] Objects, process commands.

Parameters

• config Object Configuration from yargs-parser.
• context Array An array of context Objects.

Returns string Out string or json.

runner

Core chunk => evaluated expression function.

Parameters

• config Object Config from yargs.
• expressions Array<string> List of expression strings.
• chunk (Buffer | string) Chunk from stream.

Returns (Object | string) Converted chunk.

makeSandboxWithRequireHook

A closured form of makeSandbox designed for 100% coverage.

Parameters

• hook Function babel require hook
• r Function require or similar

Examples

const makeSandbox = makeSandboxWithRequireHook(es6hook, require)

Returns Function makeSandbox - a function

makeSandbox

Create a sandbox object to be used within the vm container.

Parameters

• nodeModulesPath string path to node_modules
• source Object from cosmiconfig
• requirements Array<string> imports
• x string String which represents stdin | file stream.

Examples

makeSandbox('cool')

Returns Object Sandbox

createStreamFromSource

createStreamFromSource allows you to read or write from any string source or if not provided, stdin / stdout

Parameters

• readOrWrite boolean read or write to / from source
• source string? potential source

Returns Object a stream

toString

Returns string

concatConditionally

Binary concat method which is used to define both prepend and append methods.

Parameters

• order boolean Prepend or append?
• circumstance boolean Condition?
• str string The string to append or prepend.
• x string The string to be appended or prepended to.

Returns string

tackOn

tackOn(y => y * 5, 10) === [10, 50].

Parameters

• fn Function A function to effect change.
• x any Something else.

Returns Array X followed by a transformed x.