Distribution.Simple.Program.Find

Cabal-1.22.5.0: A framework for packaging Haskell software

Copyright | Duncan Coutts 2013
Maintainer | cabal-devel@haskell.org
Portability | portable
Safe Haskell | None
Language | Haskell98

Distribution.Simple.Program.Find

Contents

- Program search path

Description

A somewhat extended notion of the normal program search path concept.

Usually when finding executables we just want to look in the usual places using the OS's usual method for doing so. In Haskell the normal OS-specific method is captured by `findExecutable`. On all common OSs that makes use of a `PATH` environment variable, (though on Windows it is not just the `PATH`).

However it is sometimes useful to be able to look in additional locations without having to change the process-global `PATH` environment variable. So we need an extension of the usual `findExecutable` that can look in additional locations, either before, after or instead of the normal OS locations.

Synopsis

- type ProgramSearchPath = [ProgramSearchPathEntry]
- data ProgramSearchPathEntry
  - = ProgramSearchPathDir FilePath
  - | ProgramSearchPathDefault
- defaultProgramSearchPath :: ProgramSearchPath
- findProgramOnSearchPath :: Verbosity -> ProgramSearchPath -> FilePath -> IO (Maybe FilePath)
- programSearchPathAsPATHVar :: ProgramSearchPath -> IO String

# Program search path

type ProgramSearchPath = [ProgramSearchPathEntry]

A search path to use when locating executables. This is analogous to the unix `$PATH` or win32 `%PATH%` but with the ability to use the system default method for finding executables (`findExecutable` which on unix is simply looking on the `$PATH` but on win32 is a bit more complicated).

The default to use is `[ProgSearchPathDefault]` but you can add extra dirs either before, after or instead of the default, e.g. here we add an extra dir to search after the usual ones.

    ['ProgramSearchPathDefault', 'ProgramSearchPathDir' dir]

data ProgramSearchPathEntry

Constructors

ProgramSearchPathDir FilePath | A specific dir
ProgramSearchPathDefault | The system default

defaultProgramSearchPath :: ProgramSearchPath

findProgramOnSearchPath :: Verbosity -> ProgramSearchPath -> FilePath -> IO (Maybe FilePath)

programSearchPathAsPATHVar :: ProgramSearchPath -> IO String

Interpret a `ProgramSearchPath` to construct a new `$PATH` env var. Note that this is close but not perfect because on Windows the search algorithm looks at more than just the `%PATH%`.