HSH-2.0.1: Library to mix shell scripting with Haskell programs

Portabilityportable
Stabilityprovisional
MaintainerJohn Goerzen <jgoerzen@complete.org>

HSH.ShellEquivs

Description

Copyright (c) 2006-2009 John Goerzen, jgoerzen@complete.org

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.

Synopsis

Documentation

abspath :: FilePath -> IO FilePathSource

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

appendTo :: FilePath -> String -> IO StringSource

Like catTo, but appends to the file.

basename :: FilePath -> FilePathSource

The filename part of a path

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

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 ChannelSource

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 .

catBytesSource

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

catBytesFromSource

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 ChannelSource

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 ChannelSource

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 ()Source

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 -> StringSource

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

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

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

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 -> FilePathSource

The directory part of a path

discard :: Channel -> IO ChannelSource

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

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

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 aSource

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

glob :: FilePath -> IO [FilePath]Source

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]Source

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

 grep needle = filter (isInfixOf needle)

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

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

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

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

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

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

joinLines :: [String] -> [String]Source

Join lines of a file

lower :: String -> StringSource

Convert a string to all lower case

upper :: String -> StringSource

Convert a string to all upper case

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

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]Source

Number each line of a file

pwd :: IO FilePathSource

An alias for System.Directory.getCurrentDirectory.

readlink :: FilePath -> IO FilePathSource

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 FilePathSource

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

This function is only available on POSIX platforms.

revW :: [String] -> [String]Source

Reverse characters on each line (rev)

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

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]Source

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

unspace :: [String] -> [String]Source

Inverse of double space; drop all empty lines.

tac :: [String] -> [String]Source

Reverse words on each line

Reverse lines in a String (like Unix tac).

Implemented as:

 tac = reverse

See uniq.

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

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 ChannelSource

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 -> StringSource

Translate a character x to y, like:

tr 'e' 'f'

Or, in sed,

y//

trd :: Char -> String -> StringSource

Delete specified character in a string.

wcW :: [String] -> [String]Source

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

wcL :: [String] -> [String]Source

Count number of lines. Like wc -l

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

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

See also setenv, which has a more extensive example.

uniq :: String -> StringSource

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.