diff --git a/plugins/bundler/bundler.plugin.zsh b/plugins/bundler/bundler.plugin.zsh
index 382a1a47..c5284dbb 100644
--- a/plugins/bundler/bundler.plugin.zsh
+++ b/plugins/bundler/bundler.plugin.zsh
@@ -58,7 +58,7 @@ bundle_install() {
     if [[ $bundler_version > '1.4.0' || $bundler_version = '1.4.0' ]]; then
       if [[ "$OSTYPE" = darwin* ]]
       then
-        local cores_num="$(sysctl hw.ncpu | awk '{print $2}')"
+        local cores_num="$(sysctl -n hw.ncpu)"
       else
         local cores_num="$(nproc)"
       fi
diff --git a/plugins/emacs/emacsclient.sh b/plugins/emacs/emacsclient.sh
index d61ebb15..41682512 100755
--- a/plugins/emacs/emacsclient.sh
+++ b/plugins/emacs/emacsclient.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-function _emacsfun
+_emacsfun()
 {
     # get list of available X windows.
     x=`emacsclient --alternate-editor '' --eval '(x-display-list)' 2>/dev/null`
@@ -18,7 +18,8 @@ function _emacsfun
 # adopted from https://github.com/davidshepherd7/emacs-read-stdin/blob/master/emacs-read-stdin.sh
 # If the second argument is - then write stdin to a tempfile and open the
 # tempfile. (first argument will be `--no-wait` passed in by the plugin.zsh)
-if [[ $# -ge 2 ]] && [[ "$2" == - ]]; then
+if [ "$#" -ge "2" -a "$2" = "-" ]
+then
     tempfile="$(mktemp emacs-stdin-$USER.XXXXXXX --tmpdir)"
     cat - > "$tempfile"
     _emacsfun --no-wait $tempfile
diff --git a/plugins/gb/README.md b/plugins/gb/README.md
new file mode 100644
index 00000000..822c29aa
--- /dev/null
+++ b/plugins/gb/README.md
@@ -0,0 +1,21 @@
+# `gb` plugin
+
+> A project based build tool for the Go programming language.
+
+See https://getgb.io for the full `gb` documentation
+
+* * * *
+
+- Adds completion support for all `gb` commands.
+- Also supports completion for the [`gb-vendor` plugin](https://godoc.org/github.com/constabulary/gb/cmd/gb-vendor).
+
+To use it, add `gb` to your plugins array:
+```sh
+plugins=(... gb)
+```
+
+## Caveats
+
+The `git` plugin defines an alias `gb` that usually conflicts with the `gb` program.
+If you're having trouble with it, remove it by adding `unalias gb` at the end of your
+zshrc file.
diff --git a/plugins/gb/_gb b/plugins/gb/_gb
new file mode 100644
index 00000000..8148adf1
--- /dev/null
+++ b/plugins/gb/_gb
@@ -0,0 +1,111 @@
+#compdef gb
+#autoload
+
+_gb () {
+	local ret=1 state
+	_arguments -C ':command:->command' '*::options:->options' && ret=0
+
+	case $state in
+	(command)
+		local -a subcommands
+		subcommands=(
+			"build:build a package"
+			"doc:show documentation for a package or symbol"
+			"env:print project environment variables"
+			"generate:generate Go files by processing source"
+			"help:displays the help"
+			"info:info returns information about this project"
+			"list:list the packages named by the importpaths"
+			"test:test packages"
+			"vendor:manage your vendored dependencies"
+		)
+		_describe -t subcommands 'gb subcommands' subcommands && ret=0
+		;;
+	(options)
+		case $line[1] in
+		(build)
+			_arguments \
+				-f'[ignore cached packages]' \
+				-F'[do not cache packages]' \
+				-q'[decreases verbosity]' \
+				-P'[the number of build jobs to run in parallel]' \
+				-R'[sets the base of the project root search path]' \
+				-dotfile'[output a dot formatted file of the build steps]' \
+				-ldflags'["flag list" arguments to pass to the linker]' \
+				-gcflags'["arg list" arguments to pass to the compiler]' \
+				-race'[enable data race detection]' \
+				-tags'["tag list" additional build tags]'
+			;;
+		(list)
+			_arguments \
+				-f'[alternate format for the list, using the syntax of package template]' \
+				-s'[read format template from STDIN]' \
+				-json'[prints output in structured JSON format]'
+			;;
+		(test)
+			_arguments \
+				-v'[print output from test subprocess]' \
+				-ldflags'["flag list" arguments to pass to the linker]' \
+				-gcflags'["arg list" arguments to pass to the compiler]' \
+				-race'[enable data race detection]' \
+				-tags'["tag list" additional build tags]'
+			;;
+		(vendor)
+			_gb-vendor
+		esac
+		;;
+	esac
+
+	return ret
+}
+
+_gb-vendor () {
+	local curcontext="$curcontext" state line
+	_arguments -C ':command:->command' '*::options:->options'
+
+	case $state in
+	(command)
+		local -a subcommands
+		subcommands=(
+			'delete:deletes a local dependency'
+			'fetch:fetch a remote dependency'
+			'list:lists dependencies, one per line'
+			'purge:remove all unreferenced dependencies'
+			'restore:restore dependencies from the manifest'
+			'update:update a local dependency'
+		)
+		_describe -t subcommands 'gb vendor subcommands' subcommands && ret=0
+		;;
+	(options)
+		case $line[1] in
+			(delete)
+				_arguments \
+					-all'[remove all dependencies]'
+				;;
+			(fetch)
+				_arguments \
+					-branch'[fetch from a particular branch]' \
+					-no-recurse'[do not fetch recursively]' \
+					-tag'[fetch the specified tag]' \
+					-revision'[fetch the specific revision from the branch (if supplied)]' \
+					-precaire'[allow the use of insecure protocols]' \
+				;;
+			(list)
+				_arguments \
+					-f'[controls the template used for printing each manifest entry]'
+				;;
+			(restore)
+				_arguments \
+					-precaire'[allow the use of insecure protocols]'
+				;;
+			(update)
+				_arguments \
+					-all'[update all dependencies in the manifest or supply a given dependency]' \
+					-precaire'[allow the use of insecure protocols]'
+				;;
+		esac
+		;;
+	esac
+}
+
+_gb
diff --git a/plugins/git/git.plugin.zsh b/plugins/git/git.plugin.zsh
index eb7bc803..c186a6e1 100644
--- a/plugins/git/git.plugin.zsh
+++ b/plugins/git/git.plugin.zsh
@@ -88,7 +88,7 @@ alias gdw='git diff --word-diff'
 alias gf='git fetch'
 alias gfa='git fetch --all --prune'
 function gfg() { git ls-files | grep $@ }
-compdef gfg=grep
+compdef _grep gfg
 alias gfo='git fetch origin'
 
 alias gg='git gui citool'
diff --git a/plugins/osx/osx.plugin.zsh b/plugins/osx/osx.plugin.zsh
index c66325cd..4dbc7578 100644
--- a/plugins/osx/osx.plugin.zsh
+++ b/plugins/osx/osx.plugin.zsh
@@ -175,7 +175,7 @@ function quick-look() {
 function man-preview() {
   man -t "$@" | open -f -a Preview
 }
-compdef man-preview=man
+compdef _man man-preview
 
 function vncviewer() {
   open vnc://$@