diff --git a/lib/command-error.coffee b/lib/command-error.coffee
new file mode 100644
index 0000000..c9861e9
--- /dev/null
+++ b/lib/command-error.coffee
@@ -0,0 +1,5 @@
+class CommandError
+  constructor: (@message) ->
+    @name = 'Command Error'
+
+module.exports = CommandError
diff --git a/lib/command.coffee b/lib/command.coffee
index 851f859..0b5849b 100644
--- a/lib/command.coffee
+++ b/lib/command.coffee
@@ -1,22 +1,164 @@
 ExViewModel = require './ex-view-model'
 Ex = require './ex'
-
-class CommandError
-  constructor: (@message) ->
-    @name = 'Command Error'
+Find = require './find'
+CommandError = require './command-error'
 
 class Command
   constructor: (@editor, @exState) ->
     @viewModel = new ExViewModel(@)
 
-  execute: (input) ->
-    return unless input.characters.length > 0
-    [command, args...] = input.characters.split(" ")
+  parseAddr: (str, curPos) ->
+    if str is '.'
+      addr = curPos.row
+    else if str is '$'
+      # Lines are 0-indexed in Atom, but 1-indexed in vim.
+      addr = @editor.getBuffer().lines.length - 1
+    else if str[0] in ["+", "-"]
+      addr = curPos.row + @parseOffset(str)
+    else if not isNaN(str)
+      addr = parseInt(str) - 1
+    else if str[0] is "'" # Parse Mark...
+      unless @vimState?
+        throw new CommandError("Couldn't get access to vim-mode.")
+      mark = @vimState.marks[str[1]]
+      unless mark?
+        throw new CommandError("Mark #{str} not set.")
+      addr = mark.bufferMarker.range.end.row
+    else if str[0] is "/"
+      addr = Find.findNextInBuffer(@editor.buffer, curPos, str[1...-1])
+      unless addr?
+        throw new CommandError("Pattern not found: #{str[1...-1]}")
+    else if str[0] is "?"
+      addr = Find.findPreviousInBuffer(@editor.buffer, curPos, str[1...-1])
+      unless addr?
+        throw new CommandError("Pattern not found: #{str[1...-1]}")
 
-    func = Ex.singleton()[command]
-    if func?
-      func(args...)
+    return addr
+
+  parseOffset: (str) ->
+    if str.length is 0
+      return 0
+    if str.length is 1
+      o = 1
     else
-      throw new CommandError("#{input.characters}")
+      o = parseInt(str[1..])
+    if str[0] is '+'
+      return o
+    else
+      return -o
 
-module.exports = {Command, CommandError}
+  execute: (input) ->
+    @vimState = @exState.globalExState.vim?.getEditorState(@editor)
+    # Command line parsing (mostly) following the rules at
+    # http://pubs.opengroup.org/onlinepubs/9699919799/utilities
+    # /ex.html#tag_20_40_13_03
+    # Steps 1/2: Leading blanks and colons are ignored.
+    cl = input.characters
+    cl = cl.replace(/^(:|\s)*/, '')
+    return unless cl.length > 0
+    # Step 3: If the first character is a ", ignore the rest of the line
+    if cl[0] is '"'
+      return
+    # Step 4: Address parsing
+    lastLine = @editor.getBuffer().lines.length - 1
+    if cl[0] is '%'
+      range = [0, lastLine]
+      cl = cl[1..]
+    else
+      addrPattern = ///^
+        (?:                               # First address
+        (
+        \.|                               # Current line
+        \$|                               # Last line
+        \d+|                              # n-th line
+        '[\[\]<>'`"^.(){}a-zA-Z]|         # Marks
+        /.*?[^\\]/|                       # Regex
+        \?.*?[^\\]\?|                     # Backwards search
+        [+-]\d*                           # Current line +/- a number of lines
+        )((?:\s*[+-]\d*)*)                # Line offset
+        )?
+        (?:,                              # Second address
+        (                                 # Same as first address
+        \.|
+        \$|
+        \d+|
+        '[\[\]<>'`"^.(){}a-zA-Z]|
+        /.*?[^\\]/|
+        \?.*?[^\\]\?|
+        [+-]\d*
+        )((?:\s*[+-]\d*)*)
+        )?
+      ///
+
+      [match, addr1, off1, addr2, off2] = cl.match(addrPattern)
+
+      curPos = @editor.getCursorBufferPosition()
+
+      if addr1?
+        address1 = @parseAddr(addr1, curPos)
+      else
+        # If no addr1 is given (,+3), assume it is '.'
+        address1 = curPos.row
+      if off1?
+        address1 += @parseOffset(off1)
+
+      if address1 < 0 or address1 > lastLine
+        throw new CommandError('Invalid range')
+
+      if addr2?
+        address2 = @parseAddr(addr2, curPos)
+      if off2?
+        address2 += @parseOffset(off2)
+
+      if address2 < 0 or address2 > lastLine
+        throw new CommandError('Invalid range')
+
+      if address2 < address1
+        throw new CommandError('Backwards range given')
+
+      range = [address1, if address2? then address2 else address1]
+      cl = cl[match?.length..]
+
+    # Step 5: Leading blanks are ignored
+    cl = cl.trimLeft()
+
+    # Step 6a: If no command is specified, go to the last specified address
+    if cl.length is 0
+      @editor.setCursorBufferPosition([range[1], 0])
+      return
+
+    # Ignore steps 6b and 6c since they only make sense for print commands and
+    # print doesn't make sense
+
+    # Ignore step 7a since flags are only useful for print
+
+    # Step 7b: :k<valid mark> is equal to :mark <valid mark> - only a-zA-Z is
+    # in vim-mode for now
+    if cl.length is 2 and cl[0] is 'k' and /[a-z]/i.test(cl[1])
+      command = 'mark'
+      args = cl[1]
+    else if not /[a-z]/i.test(cl[0])
+      command = cl[0]
+      args = cl[1..]
+    else
+      [m, command, args] = cl.match(/^(\w+)(.*)/)
+
+    # If the command matches an existing one exactly, execute that one
+    if (func = Ex.singleton()[command])?
+      func(range, args)
+    else
+      # Step 8: Match command against existing commands
+      matching = (name for name, val of Ex.singleton() when \
+        name.indexOf(command) is 0)
+
+      matching.sort()
+
+      command = matching[0]
+
+      func = Ex.singleton()[command]
+      if func?
+        func(range, args)
+      else
+        throw new CommandError("Not an editor command: #{input.characters}")
+
+module.exports = Command
diff --git a/lib/ex-mode.coffee b/lib/ex-mode.coffee
index 243477a..1a4979d 100644
--- a/lib/ex-mode.coffee
+++ b/lib/ex-mode.coffee
@@ -33,3 +33,4 @@ module.exports = ExMode =
 
   consumeVim: (vim) ->
     @vim = vim
+    @globalExState.setVim(vim)
diff --git a/lib/ex-state.coffee b/lib/ex-state.coffee
index 7aff344..e52ea1c 100644
--- a/lib/ex-state.coffee
+++ b/lib/ex-state.coffee
@@ -1,6 +1,7 @@
 {Emitter, Disposable, CompositeDisposable} = require 'event-kit'
 
-{Command, CommandError} = require './command'
+Command = require './command'
+CommandError = require './command-error'
 
 class ExState
   constructor: (@editorElement, @globalExState) ->
diff --git a/lib/ex.coffee b/lib/ex.coffee
index 024f04c..874c9f7 100644
--- a/lib/ex.coffee
+++ b/lib/ex.coffee
@@ -1,4 +1,5 @@
 path = require 'path'
+CommandError = require './command-error'
 
 trySave = (func) ->
   deferred = Promise.defer()
@@ -9,20 +10,47 @@ trySave = (func) ->
   catch error
     if error.message.endsWith('is a directory')
       atom.notifications.addWarning("Unable to save file: #{error.message}")
-    else if error.code is 'EACCES' and error.path?
-      atom.notifications.addWarning("Unable to save file: Permission denied '#{error.path}'")
-    else if error.code in ['EPERM', 'EBUSY', 'UNKNOWN', 'EEXIST'] and error.path?
-      atom.notifications.addWarning("Unable to save file '#{error.path}'", detail: error.message)
-    else if error.code is 'EROFS' and error.path?
-      atom.notifications.addWarning("Unable to save file: Read-only file system '#{error.path}'")
-    else if errorMatch = /ENOTDIR, not a directory '([^']+)'/.exec(error.message)
+    else if error.path?
+      if error.code is 'EACCES'
+        atom.notifications
+          .addWarning("Unable to save file: Permission denied '#{error.path}'")
+      else if error.code in ['EPERM', 'EBUSY', 'UNKNOWN', 'EEXIST']
+        atom.notifications.addWarning("Unable to save file '#{error.path}'",
+          detail: error.message)
+      else if error.code is 'EROFS'
+        atom.notifications.addWarning(
+          "Unable to save file: Read-only file system '#{error.path}'")
+    else if (errorMatch =
+        /ENOTDIR, not a directory '([^']+)'/.exec(error.message))
       fileName = errorMatch[1]
-      atom.notifications.addWarning("Unable to save file: A directory in the path '#{fileName}' could not be written to")
+      atom.notifications.addWarning("Unable to save file: A directory in the "+
+        "path '#{fileName}' could not be written to")
     else
       throw error
 
   deferred.promise
 
+getFullPath = (filePath) ->
+  return filePath if path.isAbsolute(filePath)
+  return path.join(atom.project.getPath(), filePath)
+
+replaceGroups = (groups, replString) ->
+  arr = replString.split('')
+  offset = 0
+  cdiff = 0
+
+  while (m = replString.match(/(?:[^\\]|^)\\(\d)/))?
+    group = groups[m[1]] or ''
+    i = replString.indexOf(m[0])
+    l = m[0].length
+    replString = replString.slice(i + l)
+    arr[i + offset...i + offset + l] = (if l is 2 then '' else m[0][0]) +
+      group
+    arr = arr.join('').split ''
+    offset += i + l - group.length
+
+  return arr.join('').replace(/\\\\(\d)/, '\\$1')
+
 class Ex
   @singleton: =>
     @ex ||= new Ex
@@ -35,7 +63,9 @@ class Ex
 
   q: => @quit()
 
-  tabedit: (filePaths...) ->
+  tabedit: (range, args) ->
+    args = args.trim()
+    filePaths = args.split(' ')
     pane = atom.workspace.getActivePane()
     if filePaths? and filePaths.length > 0
       for file in filePaths
@@ -43,9 +73,9 @@ class Ex
     else
       atom.workspace.openURIInPane('', pane)
 
-  tabe: (filePaths...) => @tabedit(filePaths...)
+  tabe: (args...) => @tabedit(args...)
 
-  tabnew: (filePaths...) => @tabedit(filePaths...)
+  tabnew: (args...) => @tabedit(args...)
 
   tabclose: => @quit()
 
@@ -63,25 +93,32 @@ class Ex
 
   tabp: => @tabprevious()
 
-  edit: (filePath) => @tabedit(filePath) if filePath?
+  edit: (range, filePath) ->
+    filePath = filePath.trim()
+    if filePath.indexOf(' ') isnt -1
+      throw new CommandError('Only one file name allowed')
+    buffer = atom.workspace.getActiveEditor().buffer
+    filePath = buffer.getPath() if filePath is ''
+    buffer.setPath(getFullPath(filePath))
+    buffer.load()
 
-  e: (filePath) => @edit(filePath)
+  e: (args...) => @edit(args...)
 
-  enew: => @edit()
+  enew: ->
+    buffer = atom.workspace.getActiveEditor().buffer
+    buffer.setPath(undefined)
+    buffer.load()
 
-  write: (filePath) ->
+  write: (range, filePath) ->
+    filePath = filePath.trim()
     deferred = Promise.defer()
 
-    projectPath = atom.project.getPath()
     pane = atom.workspace.getActivePane()
     editor = atom.workspace.getActiveEditor()
     if atom.workspace.getActiveTextEditor().getPath() isnt undefined
-      if filePath?
+      if filePath.length > 0
         editorPath = editor.getPath()
-        fullPath = if path.isAbsolute(filePath)
-          filePath
-        else
-          path.join(projectPath, filePath)
+        fullPath = getFullPath(filePath)
         trySave(-> editor.saveAs(fullPath))
           .then ->
             deferred.resolve()
@@ -90,11 +127,8 @@ class Ex
         trySave(-> editor.save())
           .then deferred.resolve
     else
-      if filePath?
-        fullPath = if path.isAbsolute(filePath)
-          filePath
-        else
-          path.join(projectPath, filePath)
+      if filePath.length > 0
+        fullPath = getFullPath(filePath)
         trySave(-> editor.saveAs(fullPath))
           .then deferred.resolve
       else
@@ -105,18 +139,22 @@ class Ex
 
     deferred.promise
 
-  w: (filePath) =>
-    @write(filePath)
+  w: (args...) =>
+    @write(args...)
+
+  wq: (args...) =>
+    @write(args...).then => @quit()
 
-  wq: (filePath) =>
-    @write(filePath).then => @quit()
-  
   x: => @wq()
 
   wa: ->
     atom.workspace.saveAll()
 
-  split: (filePaths...) ->
+  split: (range, args) ->
+    args = args.trim()
+    filePaths = args.split(' ')
+    filePaths = undefined if filePaths.length is 1 and filePaths[0] is ''
+    console.log filePaths, filePaths is ['']
     pane = atom.workspace.getActivePane()
     if filePaths? and filePaths.length > 0
       newPane = pane.splitUp()
@@ -126,9 +164,56 @@ class Ex
     else
       pane.splitUp(copyActiveItem: true)
 
-  sp: (filePaths...) => @split(filePaths...)
+  sp: (args...) => @split(args...)
 
-  vsplit: (filePaths...) ->
+  substitute: (range, args) ->
+    args = args.trimLeft()
+    delim = args[0]
+    if /[a-z]/i.test(delim)
+      throw new CommandError(
+        "Regular expressions can't be delimited by letters")
+    delimRE = new RegExp("[^\\\\]#{delim}")
+    spl = []
+    args_ = args[1..]
+    while (i = args_.search(delimRE)) isnt -1
+      spl.push args_[..i]
+      args_ = args_[i + 2..]
+    if args_.length is 0 and spl.length is 3
+      throw new CommandError('Trailing characters')
+    else if args_.length isnt 0
+      spl.push args_
+    if spl.length > 3
+      throw new CommandError('Trailing characters')
+    spl[1] ?= ''
+    spl[2] ?= ''
+
+    try
+      pattern = new RegExp(spl[0], spl[2])
+    catch e
+      if e.message.indexOf('Invalid flags supplied to RegExp constructor') is 0
+        # vim only says 'Trailing characters', but let's be more descriptive
+        throw new CommandError("Invalid flags: #{e.message[45..]}")
+      else if e.message.indexOf('Invalid regular expression: ') is 0
+        throw new CommandError("Invalid RegEx: #{e.message[27..]}")
+      else
+        throw e
+
+    buffer = atom.workspace.getActiveTextEditor().buffer
+    cp = buffer.history.createCheckpoint()
+    for line in [range[0]..range[1]]
+      buffer.scanInRange(pattern,
+        [[line, 0], [line, buffer.lines[line].length]],
+        ({match, matchText, range, stop, replace}) ->
+          replace(replaceGroups(match[..], spl[1]))
+      )
+    buffer.history.groupChangesSinceCheckpoint(cp)
+
+  s: (args...) => @substitute(args...)
+
+  vsplit: (range, args) ->
+    args = args.trim()
+    filePaths = args.split(' ')
+    filePaths = undefined if filePaths.length is 1 and filePaths[0] is ''
     pane = atom.workspace.getActivePane()
     if filePaths? and filePaths.length > 0
       newPane = pane.splitLeft()
@@ -138,6 +223,6 @@ class Ex
     else
       pane.splitLeft(copyActiveItem: true)
 
-  vsp: (filePaths...) => @vsplit(filePaths...)
+  vsp: (args...) => @vsplit(args...)
 
 module.exports = Ex
diff --git a/lib/find.coffee b/lib/find.coffee
new file mode 100644
index 0000000..2f0c597
--- /dev/null
+++ b/lib/find.coffee
@@ -0,0 +1,27 @@
+module.exports = {
+  findInBuffer : (buffer, pattern) ->
+    found = []
+    buffer.scan(new RegExp(pattern, 'g'), (obj) -> found.push obj.range)
+    return found
+
+  findNextInBuffer : (buffer, curPos, pattern) ->
+    found = @findInBuffer(buffer, pattern)
+    more = (i for i in found when i.compare([curPos, curPos]) is 1)
+    if more.length > 0
+      return more[0].start.row
+    else if found.length > 0
+      return found[0].start.row
+    else
+      return null
+
+  findPreviousInBuffer : (buffer, curPos, pattern) ->
+    found = @findInBuffer(buffer, pattern)
+    console.log found, curPos
+    less = (i for i in found when i.compare([curPos, curPos]) is -1)
+    if less.length > 0
+      return less[less.length - 1].start.row
+    else if found.length > 0
+      return found[found.length - 1].start.row
+    else
+      return null
+}
diff --git a/lib/global-ex-state.coffee b/lib/global-ex-state.coffee
index 5325113..be51b85 100644
--- a/lib/global-ex-state.coffee
+++ b/lib/global-ex-state.coffee
@@ -1,4 +1,5 @@
 class GlobalExState
   commandHistory: []
+  setVim: (@vim) ->
 
 module.exports = GlobalExState