10 Tools To Add Some Spice To Your UNIX/Linux Shell Scripts

There are some misconceptions that shell scripts are only for a CLI environment. You can efficiently use various tools to write GUI and network (socket) scripts under KDE or Gnome desktops. Shell scripts can make use of some of the GUI widget (menus, warning boxes, progress bars, etc.). You can always control the final output, cursor position on the screen, various output effects, and more. With the following tools, you can build powerful, interactive, user-friendly UNIX / Linux bash shell scripts.



Creating GUI application is not an expensive task but a task that takes time and patience. Luckily, both UNIX and Linux ships with plenty of tools to write beautiful GUI scripts. The following tools are tested on FreeBSD and Linux operating systems but should work under other UNIX like operating systems.

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1. notify-send Command

The notify-send command allows you to send desktop notifications to the user via a notification daemon from the command line. This is useful to inform the desktop user about an event or display some form of information without getting in the user’s way. You need to install the following package on a Debian/Ubuntu Linux using apt command/apt-get command:

$ sudo apt-get install libnotify-bin

CentOS/RHEL user try the following yum command:

$ sudo yum install libnotify

Fedora Linux user type the following dnf command:

$ sudo dnf install libnotify

In this example, send simple desktop notification from the command line, enter:

## send some notification ## notify-send "rsnapshot done :)" ## send some notification ## notify-send "rsnapshot done :)"

Sample outputs:



.... alert = 18000 live =$ ( lynx --dump http: // money.rediff.com / | grep 'BSE LIVE' | awk '{ print $5}' | sed 's/,//g;s/\.[0-9]*//g' ) [ $notify_counter -eq 0 ] && [ $live -ge $alert ] && { notify-send -t 5000 -u low -i "BSE Sensex touched 18k" ; notify_counter = 1 ; } ... .... alert=18000 live=$(lynx --dump http://money.rediff.com/ | grep 'BSE LIVE' | awk '{ print $5}' | sed 's/,//g;s/\.[0-9]*//g') [ $notify_counter -eq 0 ] && [ $live -ge $alert ] && { notify-send -t 5000 -u low -i "BSE Sensex touched 18k"; notify_counter=1; } ...

Here is another code with additional options:

Sample outputs:



-t 5000: Specifies the timeout in milliseconds ( 5000 milliseconds = 5 seconds)

-u low : Set the urgency level (i.e. low, normal, or critical).

-i gtk-dialog-info : Set an icon filename or stock icon to display (you can set path as -i /path/to/your-icon.png).

Where,

For more information on use of the notify-send utility, please refer to the notify-send man page, viewable by typing man notify-send from the command line:

man notify-send

#2: tput Command

The tput command is used to set terminal features. With tput you can set:

Move the cursor around the screen.

Get information about terminal.

Set colors (background and foreground).

Set bold mode.

Set reverse mode and much more.

Here is a sample code:

#!/bin/bash # clear the screen tput clear # Move cursor to screen location X,Y (top left is 0,0) tput cup 3 15 # Set a foreground colour using ANSI escape tput setaf 3 echo "XYX Corp LTD." tput sgr0 tput cup 5 17 # Set reverse video mode tput rev echo "M A I N - M E N U" tput sgr0 tput cup 7 15 echo "1. User Management" tput cup 8 15 echo "2. Service Management" tput cup 9 15 echo "3. Process Management" tput cup 10 15 echo "4. Backup" # Set bold mode tput bold tput cup 12 15 read -p "Enter your choice [1-4] " choice tput clear tput sgr0 tput rc #!/bin/bash # clear the screen tput clear # Move cursor to screen location X,Y (top left is 0,0) tput cup 3 15 # Set a foreground colour using ANSI escape tput setaf 3 echo "XYX Corp LTD." tput sgr0 tput cup 5 17 # Set reverse video mode tput rev echo "M A I N - M E N U" tput sgr0 tput cup 7 15 echo "1. User Management" tput cup 8 15 echo "2. Service Management" tput cup 9 15 echo "3. Process Management" tput cup 10 15 echo "4. Backup" # Set bold mode tput bold tput cup 12 15 read -p "Enter your choice [1-4] " choice tput clear tput sgr0 tput rc

Sample outputs:



man 5 terminfo

man tput

#3: setleds Command

For more detail concerning the tput command, see the following man page:

The setleds command allows you to set the keyboard leds. In this example, set NumLock on:

setleds -D +num setleds -D +num

To turn it off NumLock, enter:

setleds -D -num setleds -D -num

-caps : Clear CapsLock.

+caps : Set CapsLock.

-scroll : Clear ScrollLock.

+scroll : Set ScrollLock.

See setleds command man page for more information and options:

man setleds

#4: zenity Command

The zenity commadn will display GTK+ dialogs box, and return the users input. This allows you to present information, and ask for information from the user, from all manner of shell scripts. Here is a sample GUI client for the whois directory service for given domain name:

#!/bin/bash # Get domain name _zenity = "/usr/bin/zenity" _out = "/tmp/whois.output.$$" domain =$ ( ${_zenity} --title "Enter domain" \ --entry --text "Enter the domain you would like to see whois info" ) if [ $? -eq 0 ] then # Display a progress dialog while searching whois database whois $domain | tee > ( ${_zenity} --width = 200 --height = 100 \ --title = "whois" --progress \ --pulsate --text = "Searching domain info..." \ --auto-kill --auto-close \ --percentage = 10 ) > ${_out} # Display back output ${_zenity} --width = 800 --height = 600 \ --title "Whois info for $domain " \ --text-info --filename = " ${_out} " else ${_zenity} --error \ --text = "No input provided" fi #!/bin/bash # Get domain name _zenity="/usr/bin/zenity" _out="/tmp/whois.output.$$" domain=$(${_zenity} --title "Enter domain" \ --entry --text "Enter the domain you would like to see whois info" ) if [ $? -eq 0 ] then # Display a progress dialog while searching whois database whois $domain | tee >(${_zenity} --width=200 --height=100 \ --title="whois" --progress \ --pulsate --text="Searching domain info..." \ --auto-kill --auto-close \ --percentage=10) >${_out} # Display back output ${_zenity} --width=800 --height=600 \ --title "Whois info for $domain" \ --text-info --filename="${_out}" else ${_zenity} --error \ --text="No input provided" fi

Sample outputs:



zenity --help

man zenity

#5: kdialog Command

See the zenity man page for more information and all other supports GTK+ widgets:

kdialog is just like zenity but it is designed for KDE desktop / qt apps. You can display dialogs using kdialog. The following will display message on screen:

kdialog --dontagain myscript:nofilemsg --msgbox "File: '~/.backup/config' not found." kdialog --dontagain myscript:nofilemsg --msgbox "File: '~/.backup/config' not found."

Sample outputs:



See shell scripting with KDE Dialogs tutorial for more information.

#6: Dialog

Dialog is an application used in shell scripts which displays text user interface widgets. It uses the curses or ncurses library. Here is a sample code:

#!/bin/bash dialog --title "Delete file" \ --backtitle "Linux Shell Script Tutorial Example" \ --yesno "Are you sure you want to permanently delete \" /tmp/foo.txt \" ?" 7 60 # Get exit status # 0 means user hit [yes] button. # 1 means user hit [no] button. # 255 means user hit [Esc] key. response = $? case $response in 0 ) echo "File deleted." ;; 1 ) echo "File not deleted." ;; 255 ) echo "[ESC] key pressed." ;; esac #!/bin/bash dialog --title "Delete file" \ --backtitle "Linux Shell Script Tutorial Example" \ --yesno "Are you sure you want to permanently delete \"/tmp/foo.txt\"?" 7 60 # Get exit status # 0 means user hit [yes] button. # 1 means user hit [no] button. # 255 means user hit [Esc] key. response=$? case $response in 0) echo "File deleted.";; 1) echo "File not deleted.";; 255) echo "[ESC] key pressed.";; esac

See the dialog man page for details:

man dialog

A Note About Other User Interface Widgets Tools

UNIX and Linux comes with lots of other tools to display and control apps from the command line, and shell scripts can make use of some of the KDE / Gnome / X widget set:

gmessage – a GTK-based xmessage clone.

– a GTK-based xmessage clone. xmessage – display a message or query in a window (X-based /bin/echo)

– display a message or query in a window (X-based /bin/echo) whiptail – display dialog boxes from shell scripts

– display dialog boxes from shell scripts python-dialog – Python module for making simple Text/Console-mode user interfaces

#7: logger command

The logger command writes entries in the system log file such as /var/log/messages. It provides a shell command interface to the syslog system log module:

logger "MySQL database backup failed." tail -f / var / log / messages logger -t mysqld -p daemon.error "Database Server failed" tail -f / var / log / syslog logger "MySQL database backup failed." tail -f /var/log/messages logger -t mysqld -p daemon.error "Database Server failed" tail -f /var/log/syslog

Sample outputs:

Apr 20 00:11:45 vivek-desktop kernel: [38600.515354] CPU0: Temperature/speed normal Apr 20 00:12:20 vivek-desktop mysqld: Database Server failed

See howto write message to a syslog / log file for more information. Alternatively, you can see the logger man page for details:

man logger

#8: setterm Command

The setterm command can set various terminal attributes. In this example, force screen to turn black in 15 minutes. Monitor standby will occur at 60 minutes:

setterm -blank 15 -powersave powerdown -powerdown 60 setterm -blank 15 -powersave powerdown -powerdown 60

In this example show underlined text for xterm window:

setterm -underline on; echo "Add Your Important Message Here" setterm -underline off setterm -underline on; echo "Add Your Important Message Here" setterm -underline off

Another useful option is to turn on or off cursor:

setterm -cursor off setterm -cursor off

Turn it on:

setterm -cursor on setterm -cursor on

See the setterm command man page for details:

man setterm

#9: smbclient: Sending Messages To MS-Windows Workstations

The smbclient command can talk to an SMB/CIFS server. It can send a message to selected users or all users on MS-Windows systems:

smbclient -M WinXPPro <<eof Message 1 Message 2 ... .. EOF smbclient -M WinXPPro <<eof Message 1 Message 2 ... .. EOF

OR

echo " ${Message} " | smbclient -M salesguy2 echo "${Message}" | smbclient -M salesguy2

See smbclient man page or read our previous post about “sending a message to Windows Workstation” with smbclient command:

man smbclient

#10: Bash Socket Programming

Under bash you can open a socket to pass some data through it. You don’t have to use curl or lynx commands to just grab data from remote server. Bash comes with two special device files which can be used to open network sockets. From the bash man page:

/dev/tcp/host/port – If host is a valid hostname or Internet address, and port is an integer port number or service name, bash attempts to open a TCP connection to the corresponding socket. /dev/udp/host/port – If host is a valid hostname or Internet address, and port is an integer port number or service name, bash attempts to open a UDP connection to the corresponding socket.

You can use this technquie to dermine if port is open or closed on local or remote server without using nmap or other port scanner:

# find out if TCP port 25 open or not ( echo >/ dev / tcp / localhost / 25 ) &>/ dev / null && echo "TCP port 25 open" || echo "TCP port 25 close" # find out if TCP port 25 open or not (echo >/dev/tcp/localhost/25) &>/dev/null && echo "TCP port 25 open" || echo "TCP port 25 close"

You can use bash loop and find out open ports with the snippets:

echo "Scanning TCP ports..." for p in { 1 .. 1023 } do ( echo >/ dev / tcp / localhost / $p ) >/ dev / null 2 >& 1 && echo " $p open" done echo "Scanning TCP ports..." for p in {1..1023} do (echo >/dev/tcp/localhost/$p) >/dev/null 2>&1 && echo "$p open" done

Sample outputs:

Scanning TCP ports... 22 open 53 open 80 open 139 open 445 open 631 open

In this example, your bash script act as an HTTP client:

#!/bin/bash exec 3 <> / dev / tcp / ${1:-www.cyberciti.biz} / 80 printf "GET / HTTP/1.0 \r

" >& 3 printf "Accept: text/html, text/plain \r

" >& 3 printf "Accept-Language: en \r

" >& 3 printf "User-Agent: nixCraft_BashScript v.%s \r

" " ${BASH_VERSION} " >& 3 printf " \r

" >& 3 while read LINE <& 3 do # do something on $LINE # or send $LINE to grep or awk for grabbing data # or simply display back data with echo command echo $LINE done #!/bin/bash exec 3<> /dev/tcp/${1:-www.cyberciti.biz}/80 printf "GET / HTTP/1.0\r

" >&3 printf "Accept: text/html, text/plain\r

" >&3 printf "Accept-Language: en\r

" >&3 printf "User-Agent: nixCraft_BashScript v.%s\r

" "${BASH_VERSION}" >&3 printf "\r

" >&3 while read LINE <&3 do # do something on $LINE # or send $LINE to grep or awk for grabbing data # or simply display back data with echo command echo $LINE done

See the bash man page for more information:

man bash

A Note About GUI Tools and Cronjob

You need to request local display/input service using export DISPLAY=[user’s machine]:0 command if you are using cronjob to call your scripts. For example, call /home/vivek/scripts/monitor.stock.sh as follows which uses zenity tool:

@hourly DISPLAY=:0.0 /home/vivek/scripts/monitor.stock.sh

Have a favorite UNIX tool to spice up shell script? Share it in the comments below.