HSH.ShellEquivs

Copyright (c) 2006-2009 John Goerzen, [e-mail]

This module provides shell-like commands. Most, but not all, are designed to be used directly as part of a HSH pipeline. All may be used outside HSH entirely as well.

Documentation

abspath :: FilePath -> IO FilePath

Return the absolute path of the arg. Raises an error if the computation is impossible.

appendTo :: FilePath -> String -> IO String

Like catTo, but appends to the file.

basename :: FilePath -> FilePath

The filename part of a path

bracketCD :: FilePath -> IO a -> IO a

Changes the current working directory to the given path, executes the given I/O action, then changes back to the original directory, even if the I/O action raised an exception.

This is an alias for the MissingH function System.Path.bracketCWD.

catFrom :: [FilePath] -> Channel -> IO Channel

Load the specified files and display them, one at a time.

The special file - means to display the input. If it is not given, no input is processed at all.

- may be given a maximum of one time.

See also catBytes .

catBytes

Arguments

:: Maybe Integer

Maximum amount of data to transfer

-> Channel

Handle for input

-> IO Channel

Copy data from input to output, optionally with a fixed maximum size, in bytes. Processes data using ByteStrings internally, so be aware of any possible UTF-8 conversions.

You may wish to use hSetBuffering h (BlockBuffering Nothing) prior to calling this function for optimal performance.

See also catFrom, catBytesFrom

catBytesFrom

Arguments

:: Channel

Handle to read from

-> Maybe Integer

Maximum amount of data to transfer

-> Channel

Handle for input (ignored)

-> IO Channel

Generic version of catBytes; reads data from specified Channel, and ignores stdin.

catTo :: FilePath -> Channel -> IO Channel

Takes input, writes it to the specified file, and does not pass it on. The return value is the empty string. See also catToBS, catToFIFO

catToFIFO :: FilePath -> Channel -> IO Channel

Like catTo, but opens the destination in ReadWriteMode instead of ReadOnlyMode. Due to an oddity of the Haskell IO system, this is required when writing to a named pipe (FIFO) even if you will never read from it.

This call will BLOCK all threads on open until a reader connects.

This is provided in addition to catTo because you may want to cat to something that you do not have permission to read from.

This function is only available on POSIX platforms.

See also catTo

cd :: FilePath -> IO ()

An alias for System.Directory.setCurrentDirectory.

Want to change to a user's home directory? Try this:

 glob "~jgoerzen" >>= cd . head

See also bracketCD.

cut :: Integer -> Char -> String -> String

Split a list by a given character and select the nth list.

 cut ' ' 2 "foo bar baz quux" -> "bar"

cutR :: [Integer] -> Char -> String -> String

Split a list by a given character and select ranges of the resultant lists.

 cutR [2..4] ' ' "foo bar baz quux foobar" -> "baz quux foobar"
 cutR [1..1000] ' ' "foo bar baz quux foobar" -> "bar baz quux foobar"
 cutR [-1000..1000] ' ' "foo bar baz quux foobar" -> "foo bar baz quux foobar"

Note that too large and too small indices are essentially ignored.

dirname :: FilePath -> FilePath

The directory part of a path

discard :: Channel -> IO Channel

Read all input and produce no output. Discards input completely.

echo :: Channelizable a => a -> Channel -> IO Channel

Takes a string and sends it on as standard output.

The input to this function is never read.

You can pass this thing a String, a ByteString, or even a Handle.

See also echoBS.

exit :: Int -> IO a

Exits with the specified error code. 0 indicates no error.

glob :: FilePath -> IO [FilePath]

Takes a pattern. Returns a list of names that match that pattern. Handles:

~username at beginning of file to expand to user's home dir
? matches exactly one character
* matches zero or more characters
[list] matches any character in list
[!list] matches any character not in list

The result of a tilde expansion on a nonexistant username is to do no tilde expansion.

The tilde with no username equates to the current user.

Non-tilde expansion is done by the MissingH module System.Path.Glob.

grep :: String -> [String] -> [String]

Search for the string in the lines. Return those that match. Same as:

 grep needle = filter (isInfixOf needle)

grepV :: String -> [String] -> [String]

Search for the string in the lines. Return those that do NOT match.

egrep :: String -> [String] -> [String]

Search for the regexp in the lines. Return those that match.

egrepV :: String -> [String] -> [String]

Search for the regexp in the lines. Return those that do NOT match.

joinLines :: [String] -> [String]

Join lines of a file

lower :: String -> String

Convert a string to all lower case

upper :: String -> String

Convert a string to all upper case

mkdir :: FilePath -> FileMode -> IO ()

Creates the given directory. A value of 0o755 for mode would be typical.

An alias for System.Posix.Directory.createDirectory.

The second argument will be ignored on non-POSIX systems.

numberLines :: [String] -> [String]

Number each line of a file

pwd :: IO FilePath

An alias for System.Directory.getCurrentDirectory.

readlink :: FilePath -> IO FilePath

Return the destination that the given symlink points to.

An alias for System.Posix.Files.readSymbolicLink

This function is only available on POSIX platforms.

readlinkabs :: FilePath -> IO FilePath

As readlink, but turns the result into an absolute path.

This function is only available on POSIX platforms.

rev, revW :: [String] -> [String]

Reverse characters on each line (rev)

setenv :: ShellCommand cmd => [(String, String)] -> cmd -> EnvironCommand cmd

Sets an environment variable, replacing an existing one if it exists.

Here's a sample ghci session to illustrate. First, let's see the defaults for some variables:

 Prelude HSH> runIO $ "echo $TERM, $LANG"
 xterm, en_US.UTF-8

Now, let's set one:

 Prelude HSH> runIO $ setenv [("TERM", "foo")] $ "echo $TERM, $LANG"
 foo, en_US.UTF-8

Or two:

 Prelude HSH> runIO $ setenv [("TERM", "foo")] $ setenv [("LANG", "de_DE.UTF-8")] $ "echo $TERM, $LANG"
 foo, de_DE.UTF-8

We could also do it easier, like this:

 Prelude HSH> runIO $ setenv [("TERM", "foo"), ("LANG", "de_DE.UTF-8")] $ "echo $TERM, $LANG"
 foo, de_DE.UTF-8

It can be combined with unsetenv:

 Prelude HSH> runIO $ setenv [("TERM", "foo")] $ unsetenv ["LANG"] $ "echo $TERM, $LANG"
 foo,

And used with pipes:

 Prelude HSH> runIO $ setenv [("TERM", "foo")] $ "echo $TERM, $LANG" -|- "tr a-z A-Z"
 FOO, EN_US.UTF-8

See also unsetenv.

space :: [String] -> [String]

Double space a file; add an empty line between each line.

unspace :: [String] -> [String]

Inverse of double space; drop all empty lines.

tac :: [String] -> [String]

Reverse lines in a String (like Unix tac).

Implemented as:

 tac = reverse

See uniq.

tee :: [FilePath] -> Channel -> IO Channel

Takes input, writes it to all the specified files, and passes it on. This function does NOT buffer input.

See also catFrom.

teeFIFO :: [FilePath] -> Channel -> IO Channel

FIFO-safe version of tee.

This call will BLOCK all threads on open until a reader connects.

This function is only available on POSIX platforms.

tr :: Char -> Char -> String -> String

Translate a character x to y, like:

tr 'e' 'f'

Or, in sed,

y//

trd :: Char -> String -> String

Delete specified character in a string.

wcW :: [String] -> [String]

Count number of words in a file (like wc -w)

wcL :: [String] -> [String]

Count number of lines. Like wc -l

unsetenv :: ShellCommand cmd => [String] -> cmd -> EnvironCommand cmd

Removes an environment variable if it exists; does nothing otherwise.

See also setenv, which has a more extensive example.

uniq :: String -> String

Remove duplicate lines from a file (like Unix uniq).

Takes a String representing a file or output and plugs it through lines and then nub to uniqify on a line basis.