Kommand ~ Kotlin Command Line DSL

Kommand is essentially Java’s Process class and its associated libs wrapped up in a nicer package.

Commands can be easily piped into each other, by calling another command on top of the other. And no process is created until out() is called. out() returns a Flow of output from the pipeline of commands, which can then be operated on with any method that extends a Kotlin Flow<String> or whatever type you decide to transform it into.

It has all of the Unix command line hits, but may be missing something you’re looking for. In that case, feel free to extend it and submit a pull request.

Examples:

check the number of gradle files in the current directory

fun main() = runBlocking {

    shell { }
        .ls { -"a" }
        .grep { -"e" of "gradle" }
        .wc { -"w" }
        .out()
        .collect { println(it) }
}

Print the output from pinging google.com to check our network connection:

    shell { }
        .ping(host = "google.com") { }
        .out()
        .collect { println(it) }

Run a custom script and observe the output:

    shell { }
        .cd(dir = "some/path/to/bash-scripts") { }
        .kommand { +"./some_bash_script.sh" } 
        .out()
        .collect { println(it) }

Go up one directory and run ls:

    shell { }
        .cd(dir = "..") { }
        .ls { }
        .out()
        .collect { println(it) }

Execute a command without a special extension method using the generic `kommmand()` method:

    shell { }
        .ls { }
        .kommand("wc") { -"w" }
        .out()
        .collect { println(it) }

Add/update variables in environment and print out for sanity check:

    shell { 
        env {
            "LD_LIBRARY_PATH" to "LD_LIBRARY_PATH:/some/other/dynamic/lib"
            "JAVA_HOME" to "path/to/java/we/want/to/use" 
        } 
    }
        .env
        .entries
        .forEach { println(it) }

# Output: 
# LD_LIBRARY_PATH=LD_LIBRARY_PATH:/some/other/dynamic/lib
# JAVA_HOME=path/to/java/we/want/to/use

Add/update variables on the fly with the `export()` method:

    shell {
        env {
            "LD_LIBRARY_PATH" to "LD_LIBRARY_PATH:/some/other/dynamic/lib"
            "JAVA_HOME" to "path/to/java/we/want/to/use"
        }
    }
        .export { "KRB5CC" to "/dev/null" }
        .env
        .entries
        .forEach { println(it) }

# Output: 
# LD_LIBRARY_PATH=LD_LIBRARY_PATH:/some/other/dynamic/lib
# JAVA_HOME=path/to/java/we/want/to/use
# KRB5CC=/dev/null 

Take a certain number of outputs and then automatically destroy all the processes that were used to get them:

    shell { }
        .cd(dir = "../log") { }
        .ls { }
        .sort { }
        .out()
        .take(10)
        .toList()
        .collect { 
            println("top ten log files: $it")
        }

Argument Syntax

There are currently three main styles to using arguments with a given command:

using a dash, as in -"l", which is equivalent to typing -l at the command line
- note that a - is inserted before the argument string with this method
using a plus, as in +"--some-flag" or +"file.txt", which is equivalent to typing --some-flag or file.txt at the command line
- note that no - is inserted before the argument string here
using a dashed-string with infix of followed by another string, as in -"e" of "*", which is equivalent to typing -e * at the command line when using grep -e * for example and * is a pattern provided in conjunction with the -e arg (but this can be used any place that requires the same format)
- the actual method signature for this is infix fun String.of(value: String): KommandArg

Given the above, we can assume that a command such as

    shell { }
        .grep {   
            -"i" 
            +"mr_tube" 
            +"users.txt"
        }

would be equivalent to entering grep -i mr_tube users.txt at the command line.

Some Kommand methods have explicit parameters, such as cd(dir: String)–this is mostly only currently in the spots where it (usually) doesn’t make sense to use the command without that argument.

kommand

$ Kotlin command line DSL