diff --git a/update_version.nim b/update_version.nim
index 2f824a5..d49076b 100644
--- a/update_version.nim
+++ b/update_version.nim
@@ -11,6 +11,9 @@ const USAGE = """Usage:
 
 Options:
 
+  -d, --dir <dir>         Use the given directory as the project root (defaults
+                          to the current working directory).
+
   -l, --lang <language>   Choose the language/ecosystem to consider. Valid
                           values are: 'nim' or 'node'. If not provided, this
                           is auto-detected by the presence of either a *.nimble
@@ -64,13 +67,14 @@ type
   SemVerParts = enum major, minor, patch, prerelease, buildmetadata
 
 type PackageVersion = object
-  packageFile: Path
+  file: Path
   version: string
   name: string
 
   case lang: LangType
   of lNim:
-    discard
+    lines: seq[string]
+    versionLine: int
   of lNode:
     nodePackage: JsonNode
 
@@ -85,27 +89,29 @@ let SemVerPattern =
   re"^(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$"
 
 proc parseNimblePackage(dir: Path): PackageVersion =
+  result = PackageVersion(lang: lNim)
+
   for fe in walkDir(dir):
     if fe.kind == pcFile and
        fe.path.splitFile.ext == ".nimble":
 
-      let content = readFile($fe.path)
-      for v in content.splitLines:
-        if v.startsWith("version"):
-          return PackageVersion(
-            lang: lNim,
-            packageFile: fe.path,
-            version: v.split("=")[^1].strip(chars = {' ', '"'}),
-            name: $fe.path.splitFile.name)
-
+      result.lines = readFile($fe.path).splitLines
+      for idx, l in result.lines:
+        if l.startsWith("version"):
+          result.versionLine = idx
+          result.version = l.split("=")[^1].strip(chars = {' ', '"'})
+          result.name = $fe.path.splitFile.name
+          result.file = fe.path
+          return result
 
   raise newException(IOError, "No valid .nimble file found in $#" % [$dir])
 
 
 proc parseNodePackage(dir: Path): PackageVersion =
-  result.packageFile = dir / Path("package.json")
-  result.lang = lNode
-  result.nodePackage = parseFile($result.packageFile)
+  result = PackageVersion(
+    file: dir / Path("package.json"),
+    lang: lNode,
+    nodePackage: parseFile($result.file))
 
   if not result.nodePackage.hasKey("name") or
      not result.nodePackage.hasKey("version") or
@@ -118,6 +124,28 @@ proc parseNodePackage(dir: Path): PackageVersion =
   result.version = result.nodePackage{"version"}.getStr
 
 
+proc detectAndParsePackage(dir: Path): PackageVersion =
+  try: result = parseNimblePackage(dir)
+  except:
+    let nimEx = getCurrentException()
+    try: result = parseNodePackage(dir)
+    except:
+      let nodeEx = getCurrentException()
+      stderr.writeLine(
+        "Unable to find a package definitions file.  Errors:\n\t$#\n\t$#" %
+        [nimEx.msg, nodeEx.msg])
+
+
+proc writePackage(pkg: PackageVersion) =
+  if pkg.lang == lNim:
+    var lines = pkg.lines
+    lines[pkg.versionLine] = "version       = \"$#\"" % pkg.version
+    writeFile($pkg.file, lines.join("\p"))
+  elif pkg.lang == lNode:
+    pkg.nodePackage["version"] = %pkg.version
+    writeFile($pkg.file, pkg.nodePackage.pretty)
+
+
 proc incrementLastVersionPart(version: string): string =
   let versionParts = toSeq(findIter(version, re"([^\d.]+)?\.?(\d+)"))
   let lastVersionPartMatch = versionParts[^1]
@@ -178,15 +206,7 @@ proc incrementSemverPart(
 when isMainModule:
   let args = docopt(USAGE, version = UV_VERSION)
 
-  if args["bump"]:
-    discard
-  elif args["set"]:
-    discard
-  elif args["get"]:
-    discard
-  elif args["interactive"]:
-    discard
-  elif args["test"]:
+  if args["test"]:
 
     # incrementLastVersionPart
     assert incrementLastVersionPart("1.0.0") == "1.0.1"
@@ -206,3 +226,55 @@ when isMainModule:
     assert incrementSemverPart("1.5.10", buildmetadata) == "1.5.10+build.0"
 
     echo "All tests passed."
+    quit(QuitSuccess)
+
+
+  let dir =
+    if args["--dir"]: Path($args["--dir"])
+    else: Path(".")
+
+  var pkg =
+    if args["--lang"] and $args["--lang"] == "nim":
+      parseNimblePackage(dir)
+    elif args["--lang"] and $args["--lang"] == "node":
+      parseNodePackage(dir)
+    else:
+      detectAndParsePackage(dir)
+
+  if args["bump"]:
+    if $args["<part>"] == "last":
+      pkg.version = incrementLastVersionPart(pkg.version)
+    else:
+      let part = parseEnum[SemVerParts]($args["<part>"])
+      pkg.version = incrementSemverPart(pkg.version, part)
+
+    writePackage(pkg)
+    echo pkg.version
+
+  elif args["set"]:
+    pkg.version = $args["<new-version>"]
+    writePackage(pkg)
+    echo pkg.version
+
+  elif args["get"]: echo pkg.version
+
+  elif args["interactive"]:
+    var acceptNewVersion = false
+    var newVersion = pkg.version
+    while not acceptNewVersion:
+      stdout.writeLine "Current version is " & pkg.version
+      stdout.write "New version? "
+      newVersion  = stdin.readLine
+
+      stdout.write "New version will be set to '" & pkg.version & "'. Is this correct (yes/no)? "
+      let isCorrect = stdin.readLine
+      let acceptNewVersion = "yes".startsWith(isCorrect.toLower)
+
+    pkg.version = newVersion
+    echo "Updating version definition in " & $pkg.file
+    writePackage(pkg)
+
+    # TODO:
+    # for f in filesToUpdate:
+    #   echo "Updating version definition in " & $f
+    #   updateVersionInFile(f)
diff --git a/update_version.nimble b/update_version.nimble
index 3796f44..132d34b 100644
--- a/update_version.nimble
+++ b/update_version.nimble
@@ -1,6 +1,6 @@
 # Package
 
-version       = "1.0.0"
+version       = "1.0.1"
 author        = "Jonathan Bernard"
 description   = "Small util to update version consistently for nim and node packages."
 license       = "MIT"