Documentation

Shell script monad.

Generates a shell script, including hashbang, suitable to be written to a file.

Generates a single line of shell code.

A shell variable.

Expand a shell variable to its value.

A value that is safely quoted.

Quotes the Text to allow it to be safely exposed to the shell.

The method used is to replace ' with '"'"' and wrap the value inside single quotes. This works for POSIX shells, as well as other shells like csh.

Treats the Text as a glob, which expands to one parameter per matching file.

The input is assumed to be a well-formed glob. Characters in it that are not alphanumeric and are not wildcard characters will be escaped before it is exposed to the shell. This allows eg, spaces in globs.

Adds a shell command to the script.

Variadic and polymorphic version of run

A command can be passed any number of Params.

demo = script $ do
  cmd "echo" "hello, world"
  name <- newVar "name"
  readVar name
  cmd "echo" "hello" name

For the most efficient use of cmd, add the following boilerplate, which will make string literals in your program default to being Text:

{-# LANGUAGE OverloadedStrings, ExtendedDefaultRules #-}
{-# OPTIONS_GHC -fno-warn-type-defaults #-}
import Control.Monad.Shell
import qualified Data.Text.Lazy as L
default (L.Text)

Note that the command to run is itself a Param, so it can be a Text, or a String, or even a Var or Output. For example, this echos "hi":

demo = script $ do
   echovar <- newVarContaining "echo" ()
   cmd echovar "hi"

A Param is anything that can be used as the parameter of a command.

Allows a function to take any number of Params.

The output of a command, or even a more complicated Script can be passed as a parameter to cmd

Examples:

cmd "echo" "hello there," (Output (cmd "whoami"))
cmd "echo" "root's pwent" (Output (cmd "cat" "/etc/passwd" -|- cmd "grep" "root"))

An arbitrary value.

Adds a comment that is embedded in the generated shell script.

Suggests that a shell variable or function have its name contain the specified Text.

Class of values that provide a hint for the name to use for a shell variable or function.

To skip providing a hint, use '()'. To provide a hint, use '(NamedLike "name")'.

Defines a new shell variable.

Each call to newVar will generate a new, unique variable name.

The namehint can influence this name, but is modified to ensure uniqueness.

Creates a new shell variable, with an initial value.

Gets a Var that refers to a global variable, such as PATH

This special Var expands to whatever parameters were passed to the shell script.

Inside a func, it expands to whatever parameters were passed to the func.

(This is $@ in shell)

Takes the first positional parameter, removing it from positionalParameters and returning a new Var that holds the value of the parameter.

If there are no more positional parameters, the script will crash with an error.

For example:

removefirstfile = script $ do
  cmd "rm" =<< takeParameter
  cmd "echo" "remaining parameters:" positionalParameters

Defines a shell function, and returns an action that can be run to call the function.

The action is variadic; it can be passed any number of CmdParams. Typically, it will make sense to specify a more concrete type when defining the shell function.

The shell function will be given a unique name, that is not used by any other shell function. The namehint can be used to influence the contents of the function name, which makes for more readable generated shell code.

For example:

demo = script $ do
   hohoho <- mkHohoho
   hohoho (Val 1)
   echo "And I heard him exclaim, ere he rode out of sight ..."
   hohoho (Val 3)

mkHohoho :: Script (Val Int -> Script ())
mkHohoho = func (NamedLike "hohoho") $ do
   num <- takeParameter
   forCmd (cmd "seq" "1" num) $ \_n ->
      cmd "echo" "Ho, ho, ho!" "Merry xmas!"

Runs the command, and separates its output into parts (using the IFS)

The action is run for each part, passed a Var containing the part.

As long as the first Script exits nonzero, runs the second script.

if with a monadic conditional

If the conditional exits 0, the first action is run, else the second.

when with a monadic conditional

unless with a monadic conditional

Generates shell code to fill a variable with a line read from stdin.

By default, shell scripts continue running past commands that exit nonzero. Use "stopOnFailure True" to make the script stop on the first such command.

Makes a nonzero exit status be ignored.

Pipes together two Scripts.

ANDs two Scripts.

ORs two Scripts.

Any function that takes a RedirFile can be passed a a FilePath, in which case the default file descriptor will be redirected to/from the FilePath.

Or, it can be passed a tuple of (Fd, FilePath), in which case the specified Fd will be redirected to/from the FilePath.

Redirects to a file, overwriting any existing file.

For example, to shut up a noisy command:

cmd "find" "/" |> "/dev/null"

Appends to a file. (If file doesn't exist, it will be created.)

Redirects standard input from a file.

Redirects a script's output to stderr.

Redirects the first file descriptor to output to the second.

For example, to redirect a command's stderr to stdout:

cmd "foo" ->- stdError) |>& stdOutput

Redirects the first file descriptor to input from the second.

Helper for |>& and |<&

Provides the Text as input to the Script, using a here-document.