diff --git a/doc.go b/doc.go
index 13c64af..672fd6b 100644
--- a/doc.go
+++ b/doc.go
@@ -12,74 +12,74 @@ Reference
 
 The following commands are provided by lf with default keybindings:
 
-	up                (default "k" and "<up>")
-	half-up           (default "<c-u>")
-	page-up           (default "<c-b>")
-	down              (default "j" and "<down>")
-	half-down         (default "<c-d>")
-	page-down         (default "<c-f>")
-	updir             (default "h" and "<left>")
-	open              (default "l" and "<right>")
-	quit              (default "q")
-	bot               (default "G")
-	top               (default "gg")
-	read              (default ":")
-	read-shell        (default "$")
-	read-shell-wait   (default "!")
-	read-shell-async  (default "&")
-	search            (default "/")
-	search-back       (default "?")
-	search-next       (default "n")
-	search-prev       (default "N")
-	toggle            (default "<space>")
-	invert            (default "v")
-	yank              (default "y")
-	clear             (default "c")
-	delete            (default "d")
-	put               (default "p")
-	renew             (default "<c-l>")
+    up                (default "k" and "<up>")
+    half-up           (default "<c-u>")
+    page-up           (default "<c-b>")
+    down              (default "j" and "<down>")
+    half-down         (default "<c-d>")
+    page-down         (default "<c-f>")
+    updir             (default "h" and "<left>")
+    open              (default "l" and "<right>")
+    quit              (default "q")
+    bot               (default "G")
+    top               (default "gg")
+    read              (default ":")
+    read-shell        (default "$")
+    read-shell-wait   (default "!")
+    read-shell-async  (default "&")
+    search            (default "/")
+    search-back       (default "?")
+    search-next       (default "n")
+    search-prev       (default "N")
+    toggle            (default "<space>")
+    invert            (default "v")
+    yank              (default "y")
+    clear             (default "c")
+    delete            (default "d")
+    put               (default "p")
+    renew             (default "<c-l>")
 
 The following commands are provided by lf without default keybindings:
 
-	sync  synchronizes yanked/deleted files with server
-	echo  prints its arguments to the message line
-	cd    changes working directory to its argument
-	push  simulate key pushes given in its argument
+    sync  synchronizes yanked/deleted files with server
+    echo  prints its arguments to the message line
+    cd    changes working directory to its argument
+    push  simulate key pushes given in its argument
 
 The following options can be used to customize the behavior of lf:
 
-	dirfirst   bool    (default on)
-	hidden     bool    (default off)
-	preview    bool    (default on)
-	reverse    bool    (default off)
-	scrolloff  int     (default 0)
-	tabstop    int     (default 8)
-	filesep    string  (default ":")
-	ifs        string  (default "") (not exported if empty)
-	previewer  string  (default "") (not filtered if empty)
-	shell      string  (default "/bin/sh")
-	sortby     string  (default "natural")
-	timefmt    string  (default "Mon Jan _2 15:04:05 2006")
-	ratios     string  (default "1:2:3")
-	info       string  (default "")
+    dirfirst   boolean (default on)
+    hidden     boolean (default off)
+    preview    boolean (default on)
+    reverse    boolean (default off)
+    scrolloff  integer (default 0)
+    tabstop    integer (default 8)
+    filesep    string  (default ":")
+    ifs        string  (default "") (not exported if empty)
+    previewer  string  (default "") (not filtered if empty)
+    shell      string  (default "/bin/sh")
+    sortby     string  (default "natural")
+    timefmt    string  (default "Mon Jan _2 15:04:05 2006")
+    ratios     string  (default "1:2:3")
+    info       string  (default "")
 
 The following variables are exported for shell commands:
 
-	$f   current file
-	$fs  marked file(s) separated with ':'
-	$fx  current file or marked file(s) if any
-	$id  id number of the client
+    $f   current file
+    $fs  marked file(s) separated with ':'
+    $fx  current file or marked file(s) if any
+    $id  id number of the client
 
 Configuration
 
 The configuration file should be located at:
 
-	$XDG_CONFIG_HOME/lf/lfrc"
+    $XDG_CONFIG_HOME/lf/lfrc"
 
 If "$XDG_CONFIG_HOME" is not set, it defaults to "$HOME/.config" so the
 location should be:
 
-	~/.config/lf/lfrc
+    ~/.config/lf/lfrc
 
 A sample configuration file can be found at
 https://github.com/gokcehan/lf/blob/master/etc/lfrc.example.
@@ -88,12 +88,12 @@ Prefixes
 
 The following command prefixes are used by lf:
 
-	:  read (default)    built-in command
-	$  read-shell        shell command
-	!  read-shell-wait   shell command waiting for key press
-	&  read-shell-async  asynchronous shell command
-	/  search            search file in current directory
-	?  search-back       search file in the reverse order
+    :  read (default)    built-in command
+    $  read-shell        shell command
+    !  read-shell-wait   shell command waiting for key press
+    &  read-shell-async  asynchronous shell command
+    /  search            search file in current directory
+    ?  search-back       search file in the reverse order
 
 The same evaluator is used for the command line and the configuration file. The
 difference is that prefixes are not necessary in the command line. Instead
@@ -104,54 +104,55 @@ Syntax
 
 Characters from "#" to "\n" are comments and ignored:
 
-	# comments start with '#'
+    # comments start with '#'
 
 There are three special commands for configuration.
 
 "set" is used to set an option which could be boolean, integer, or string:
 
-	set hidden        # boolean on
-	set nohidden      # boolean off
-	set hidden!       # boolean toggle
-	set scrolloff 10  # integer value
-	set sortby time   # string value w/o quotes
+    set hidden        # boolean on
+    set nohidden      # boolean off
+    set hidden!       # boolean toggle
+    set scrolloff 10  # integer value
+    set sortby time   # string value w/o quotes
+    set sortby 'time' # string value with quotes
 
 "map" is used to bind a key to a command which could be built-in command,
 custom command, or shell command:
 
-	map gh cd ~       # built-in command
-	map D trash       # custom command
-	map i $less "$f"  # shell command
-	map u !du -h .    # waiting shell command
+    map gh cd ~       # built-in command
+    map D trash       # custom command
+    map i $less "$f"  # shell command
+    map u !du -h .    # waiting shell command
 
 You can delete an existing binding by leaving the expression empty:
 
-	map gh            # deletes 'gh' mapping
+    map gh            # deletes 'gh' mapping
 
 "cmd" is used to define a custom command
 
-	cmd usage $du -h . | less
+    cmd usage $du -h . | less
 
 You can delete an existing command by leaving the expression empty:
 
-	cmd trash         # deletes trash command
+    cmd trash         # deletes trash command
 
 If there is no prefix then ":" is assumed:
 
-	map zt set info time
+    map zt set info time
 
 An explicit ":" could be provided to group statements until a "\n" occurs which
 is especially useful for "map" and "cmd" commands:
 
-	map st :set sortby time; set info time
+    map st :set sortby time; set info time
 
 If you need multiline you can wrap statements in "{{" and "}}" after the proper
 prefix.
 
-	map st :{{
-		set sortby time
-		set info time
-	}}
+    map st :{{
+        set sortby time
+        set info time
+    }}
 
 Mappings
 
@@ -165,16 +166,16 @@ various keybindings.
 This is mainly useful for two purposes. First, it can be used to map a command
 with a command count:
 
-	map <c-j> push 10j
+    map <c-j> push 10j
 
 Second, it can be used to avoid typing the name when a command takes arguments:
 
-	map r push :rename<space>
+    map r push :rename<space>
 
 One thing to be careful is that since "push" command works with keys instead of
 commands it is possible to accidentally create recursive bindings:
 
-	map j push 2j
+    map j push 2j
 
 These types of bindings create a deadlock when executed.
 
@@ -185,36 +186,36 @@ trash.
 
 A first attempt to write such a command may look like this:
 
-	cmd trash ${{
-		mkdir -p ~/.trash
-		if [ -z $fs ]; then
-			mv --backup=numbered "$f" $HOME/.trash
-		else
-			IFS=':'; mv --backup=numbered $fs $HOME/.trash
-		fi
-	}}
+    cmd trash ${{
+        mkdir -p ~/.trash
+        if [ -z $fs ]; then
+            mv --backup=numbered "$f" $HOME/.trash
+        else
+            IFS=':'; mv --backup=numbered $fs $HOME/.trash
+        fi
+    }}
 
 We check "$fs" to see if there are any marked files. Otherwise we just delete
 the current file. Since this is such a common pattern, a separate "$fx"
 variable is provided. We can use this variable to get rid of the conditional:
 
-	cmd trash ${{
-		mkdir -p ~/.trash
-		IFS=':'; mv --backup=numbered $fx $HOME/.trash
-	}}
+    cmd trash ${{
+        mkdir -p ~/.trash
+        IFS=':'; mv --backup=numbered $fx $HOME/.trash
+    }}
 
 The trash directory is checked each time the command is executed. We can move
 it outside of the command so it would only run once at startup:
 
-	${{ mkdir -p ~/.trash }}
+    ${{ mkdir -p ~/.trash }}
 
-	cmd trash ${{ IFS=':'; mv --backup=numbered $fx $HOME/.trash }}
+    cmd trash ${{ IFS=':'; mv --backup=numbered $fx $HOME/.trash }}
 
 Since these are one liners, we can drop "{{" and "}}":
 
-	$mkdir -p ~/.trash
+    $mkdir -p ~/.trash
 
-	cmd trash $IFS=':'; mv --backup=numbered $fx $HOME/.trash
+    cmd trash $IFS=':'; mv --backup=numbered $fx $HOME/.trash
 
 Finally note that we set "IFS" variable accordingly in the command. Instead we
 could use the "ifs" option to set it for all commands (e.g. "set ifs ':'").
@@ -233,20 +234,20 @@ To use this feature, you need to use a client which supports communicating with
 a UNIX-domain socket. OpenBSD implementation of netcat (nc) is one such
 example. You can use it to send a command to the socket file:
 
-	echo 'send echo hello world' | nc -U /tmp/lf.${USER}.sock
+    echo 'send echo hello world' | nc -U /tmp/lf.${USER}.sock
 
 Since such a client may not be available everywhere, lf comes bundled with a
 command line flag to be used as such. When using lf, you do not need to specify
 the address of the socket file. This is the recommended way of using remote
 commands since it is shorter and immune to socket file address changes:
 
-	lf -remote 'send echo hello world'
+    lf -remote 'send echo hello world'
 
 In this command "send" is used to send the rest of the string as a command to
 all connected clients. You can optionally give it an id number to send a
 command to a single client:
 
-	lf -remote 'send 1000 echo hello world'
+    lf -remote 'send 1000 echo hello world'
 
 All clients have a unique id number but you may not be aware of the id number
 when you are writing a command. For this purpose, an "$id" variable is exported
@@ -255,53 +256,53 @@ from a client to the server which in return sends a command back to itself. So
 now you can display a message in the current client by calling the following in
 a shell command:
 
-	lf -remote "send $id echo hello world"
+    lf -remote "send $id echo hello world"
 
 A common use for this feature is to display an error message back in the
 client. You can implement a safe rename command which does not overwrite an
 existing file or directory as such:
 
-	cmd rename ${{
-		if [ -e "$1" ]; then
-			lf -remote "send $id echo file exists"
-		else
-			mv "$f" "$1"
-		fi
-	}}
+    cmd rename ${{
+        if [ -e "$1" ]; then
+            lf -remote "send $id echo file exists"
+        else
+            mv "$f" "$1"
+        fi
+    }}
 
 Since lf does not have control flow syntax, remote commands are used for such
 needs. Following example can be used to dynamically set the number of columns
 on startup based on terminal width:
 
-	${{
-		w=$(tput cols)
-		if [ $w -le 80 ]; then
-			lf -remote "send $id set ratios 1:2"
-		elif [ $w -le 160 ]; then
-			lf -remote "send $id set ratios 1:2:3"
-		else
-			lf -remote "send $id set ratios 1:2:3:4"
-		fi
-	}}
+    ${{
+        w=$(tput cols)
+        if [ $w -le 80 ]; then
+            lf -remote "send $id set ratios 1:2"
+        elif [ $w -le 160 ]; then
+            lf -remote "send $id set ratios 1:2:3"
+        else
+            lf -remote "send $id set ratios 1:2:3:4"
+        fi
+    }}
 
 Besides "send" command, there are also two commands to get or set the current
 file selection. Two possible modes "copy" and "move" specify whether selected
 files are to be copied or moved. File names are separated ":" character.
 Setting the file selection is done with "save" command:
 
-	lf -remote 'save copy foo.txt:bar.txt:baz.txt'
+    lf -remote 'save copy foo.txt:bar.txt:baz.txt'
 
 Getting the file selection is similarly done with "load" command. You may need
 to parse the response as such to achieve what you need:
 
-	resp=$(echo 'load' | nc -U /tmp/lf.${USER}.sock)
-	mode=$(echo $resp | cut -d' ' -f1)
-	list=$(echo $resp | cut -d' ' -f2-)
-	if [ $mode = 'copy' ]; then
-		# do something with the $list
-	elif [ $mode = 'move' ]; then
-		# do something else with the $list
-	fi
+    resp=$(echo 'load' | nc -U /tmp/lf.${USER}.sock)
+    mode=$(echo $resp | cut -d' ' -f1)
+    list=$(echo $resp | cut -d' ' -f2-)
+    if [ $mode = 'copy' ]; then
+        # do something with the $list
+    elif [ $mode = 'move' ]; then
+        # do something else with the $list
+    fi
 
 Lastly, there is a "conn" command to connect the server as a client. This
 should not be needed for users.
@@ -329,20 +330,24 @@ called by "open" when the current file is not a directory. Normally a user maps
 the "open" command to a key (default "l") and customize "open-file" command as
 desired. You can define it just as you would define any other command:
 
-	cmd open-file $IFS=':'; vim $fx
+    cmd open-file $IFS=':'; vim $fx
 
 It is possible to use different command types:
 
-	cmd open-file &xdg-open "$f"
+    cmd open-file &xdg-open "$f"
 
 You may want to use either file extensions or mime types from "file" command:
 
-	cmd open-file ${{
-		case $(file --mime-type "$f" -b) in
-			text/*) IFS=':'; vim $fx;;
-			*) IFS=':'; for f in $fx; do xdg-open "$f" > /dev/null 2> /dev/null & done;;
-		esac
-	}}
+    cmd open-file ${{
+        case $(file --mime-type "$f" -b) in
+            text/*)
+                IFS=':'; vim $fx;;
+            *)
+                IFS=':'; for f in $fx; do
+                    xdg-open "$f" > /dev/null 2> /dev/null &
+                done;;
+        esac
+    }}
 
 lf does not come bundled with a file opener. You can use any of the existing
 file openers as you like. Possible options are "open" (for Mac OS X only),
@@ -364,8 +369,8 @@ argument and the height of the preview pane as the second argument when running
 this file. Output of the execution is printed in the preview pane. You may want
 to use the same script in your pager mapping as well if any:
 
-	set previewer ~/.config/lf/pv.sh
-	map i $~/.config/lf/pv.sh "$f" | less -R
+    set previewer ~/.config/lf/pv.sh
+    map i $~/.config/lf/pv.sh "$f" | less -R
 
 Since this script is called for each file selection change it needs to be as
 efficient as possible and this responsibility is left to the user. You may use
@@ -373,16 +378,16 @@ file extensions to determine the type of file more efficiently compared to
 obtaining mime types from "file" command. Extensions can then be used to match
 cleanly within a conditional:
 
-	#!/bin/sh
+    #!/bin/sh
 
-	case "$1" in
-		*.tar*) tar tf "$1";;
-		*.zip) unzip -l "$1";;
-		*.rar) unrar l "$1";;
-		*.7z) 7z l "$1";;
-		*.pdf) pdftotext "$1" -;;
-		*) highlight -O ansi "$1" || cat "$1";;
-	esac
+    case "$1" in
+        *.tar*) tar tf "$1";;
+        *.zip) unzip -l "$1";;
+        *.rar) unrar l "$1";;
+        *.7z) 7z l "$1";;
+        *.pdf) pdftotext "$1" -;;
+        *) highlight -O ansi "$1" || cat "$1";;
+    esac
 
 Another important consideration for efficiency is the use of programs with
 short startup times for preview. For this reason, "highlight" is recommended
diff --git a/docstring.go b/docstring.go
index d6cf7f6..e5678b8 100644
--- a/docstring.go
+++ b/docstring.go
@@ -52,12 +52,12 @@ The following commands are provided by lf without default keybindings:
 
 The following options can be used to customize the behavior of lf:
 
-    dirfirst   bool    (default on)
-    hidden     bool    (default off)
-    preview    bool    (default on)
-    reverse    bool    (default off)
-    scrolloff  int     (default 0)
-    tabstop    int     (default 8)
+    dirfirst   boolean (default on)
+    hidden     boolean (default off)
+    preview    boolean (default on)
+    reverse    boolean (default off)
+    scrolloff  integer (default 0)
+    tabstop    integer (default 8)
     filesep    string  (default ":")
     ifs        string  (default "") (not exported if empty)
     previewer  string  (default "") (not filtered if empty)
@@ -122,6 +122,7 @@ There are three special commands for configuration.
     set hidden!       # boolean toggle
     set scrolloff 10  # integer value
     set sortby time   # string value w/o quotes
+    set sortby 'time' # string value with quotes
 
 "map" is used to bind a key to a command which could be built-in command,
 custom command, or shell command:
@@ -156,8 +157,8 @@ If you need multiline you can wrap statements in "{{" and "}}" after the
 proper prefix.
 
     map st :{{
-    	set sortby time
-    	set info time
+        set sortby time
+        set info time
     }}
 
 
@@ -196,12 +197,12 @@ trash.
 A first attempt to write such a command may look like this:
 
     cmd trash ${{
-    	mkdir -p ~/.trash
-    	if [ -z $fs ]; then
-    		mv --backup=numbered "$f" $HOME/.trash
-    	else
-    		IFS=':'; mv --backup=numbered $fs $HOME/.trash
-    	fi
+        mkdir -p ~/.trash
+        if [ -z $fs ]; then
+            mv --backup=numbered "$f" $HOME/.trash
+        else
+            IFS=':'; mv --backup=numbered $fs $HOME/.trash
+        fi
     }}
 
 We check "$fs" to see if there are any marked files. Otherwise we just
@@ -210,8 +211,8 @@ delete the current file. Since this is such a common pattern, a separate
 conditional:
 
     cmd trash ${{
-    	mkdir -p ~/.trash
-    	IFS=':'; mv --backup=numbered $fx $HOME/.trash
+        mkdir -p ~/.trash
+        IFS=':'; mv --backup=numbered $fx $HOME/.trash
     }}
 
 The trash directory is checked each time the command is executed. We can
@@ -275,11 +276,11 @@ client. You can implement a safe rename command which does not overwrite an
 existing file or directory as such:
 
     cmd rename ${{
-    	if [ -e "$1" ]; then
-    		lf -remote "send $id echo file exists"
-    	else
-    		mv "$f" "$1"
-    	fi
+        if [ -e "$1" ]; then
+            lf -remote "send $id echo file exists"
+        else
+            mv "$f" "$1"
+        fi
     }}
 
 Since lf does not have control flow syntax, remote commands are used for
@@ -287,14 +288,14 @@ such needs. Following example can be used to dynamically set the number of
 columns on startup based on terminal width:
 
     ${{
-    	w=$(tput cols)
-    	if [ $w -le 80 ]; then
-    		lf -remote "send $id set ratios 1:2"
-    	elif [ $w -le 160 ]; then
-    		lf -remote "send $id set ratios 1:2:3"
-    	else
-    		lf -remote "send $id set ratios 1:2:3:4"
-    	fi
+        w=$(tput cols)
+        if [ $w -le 80 ]; then
+            lf -remote "send $id set ratios 1:2"
+        elif [ $w -le 160 ]; then
+            lf -remote "send $id set ratios 1:2:3"
+        else
+            lf -remote "send $id set ratios 1:2:3:4"
+        fi
     }}
 
 Besides "send" command, there are also two commands to get or set the
@@ -311,9 +312,9 @@ need to parse the response as such to achieve what you need:
     mode=$(echo $resp | cut -d' ' -f1)
     list=$(echo $resp | cut -d' ' -f2-)
     if [ $mode = 'copy' ]; then
-    	# do something with the $list
+        # do something with the $list
     elif [ $mode = 'move' ]; then
-    	# do something else with the $list
+        # do something else with the $list
     fi
 
 Lastly, there is a "conn" command to connect the server as a client. This
@@ -355,10 +356,14 @@ You may want to use either file extensions or mime types from "file"
 command:
 
     cmd open-file ${{
-    	case $(file --mime-type "$f" -b) in
-    		text/*) IFS=':'; vim $fx;;
-    		*) IFS=':'; for f in $fx; do xdg-open "$f" > /dev/null 2> /dev/null & done;;
-    	esac
+        case $(file --mime-type "$f" -b) in
+            text/*)
+                IFS=':'; vim $fx;;
+            *)
+                IFS=':'; for f in $fx; do
+                    xdg-open "$f" > /dev/null 2> /dev/null &
+                done;;
+        esac
     }}
 
 lf does not come bundled with a file opener. You can use any of the existing
@@ -395,12 +400,12 @@ match cleanly within a conditional:
     #!/bin/sh
 
     case "$1" in
-    	*.tar*) tar tf "$1";;
-    	*.zip) unzip -l "$1";;
-    	*.rar) unrar l "$1";;
-    	*.7z) 7z l "$1";;
-    	*.pdf) pdftotext "$1" -;;
-    	*) highlight -O ansi "$1" || cat "$1";;
+        *.tar*) tar tf "$1";;
+        *.zip) unzip -l "$1";;
+        *.rar) unrar l "$1";;
+        *.7z) 7z l "$1";;
+        *.pdf) pdftotext "$1" -;;
+        *) highlight -O ansi "$1" || cat "$1";;
     esac
 
 Another important consideration for efficiency is the use of programs with