10 Tools to Spice Up Linux Shell Scripting

English: Vivek Gite, translation: Linux China/pygmalion666

linux.cn/article-9510-1.html

There is some misconception that shell scripts are only used in the CLI environment. In fact, under the KDE or Gnome desktop, you can effectively use various tools to write GUI or network (socket) scripts. Shell scripts can use some GUI components (menus, alert boxes, progress bars, etc.), you can control terminal output, cursor position, and various output effects, etc. With the tools below, you can build robust, interactive, user-friendly UNIX/Linux bash scripts.

Making a GUI application is not a difficult task, but it takes time and patience. Fortunately, both UNIX and Linux come with plenty of tools for writing nice GUI scripts. The following tools are tested on FreeBSD and Linux operating systems, but are also applicable to other UNIX-like operating systems.

1. notify-send command

The notify-send command allows you to send desktop notifications to users via the notification daemon. This way of avoiding disturbing the user is useful for notifying the desktop user of an event or displaying some information. On Debian or Ubuntu, you need the packages installed using the apt command or the apt-get command:

sudo apt-get install libnotify-bin

CentOS/RHEL users use the following yum command:

sudo yum install libnotify

Fedora Linux users use the following dnf command:

`$ sudo dnf install libnotify`

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

### Send some notifications ###

notify-send "rsnapshot done :)"

Sample output:

notify-send: Shell Script Get Or Send Desktop Notifications

Here is the code for another additional option:

...

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; }

...

Sample output:

Linux / UNIX: Display Notifications From Your Shell Scripts With notify-send

here:

• -t 5000: Specify timeout in milliseconds (5000 milliseconds = 5 seconds)

• -u low: Set the emergency level (eg: low, normal, urgent)

• -i gtk-dialog-info: Set the icon name to be displayed or the specified icon (you can set the path to: -i /path/to/your-icon.png)

For more information on using the notify-send function, please refer to the man page. Enter man notify-send at the command line to see:

man notify-send

2. tput command

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

• Move the cursor on the screen.

• Get terminal information.

• Set colors (background and foreground).

• Set bold mode.

• Set inversion mode and more.

Here's 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

示例输出：

Linux / UNIX Script Colours and Cursor Movement With tput

关于 tput 命令的详细信息，参见手册：

man 5 terminfo

man tput

3、setleds 命令

setleds 命令允许你设置键盘灯。下面是打开数字键灯的示例：

setleds -D +num

关闭数字键灯，输入：

setleds -D -num

• -caps：关闭大小写锁定灯

• +caps：打开大小写锁定灯

• -scroll：关闭滚动锁定灯

• +scroll：打开滚动锁定灯

查看 setleds 手册可看见更多信息和选项 man setleds。

4、zenity 命令

zenity 命令显示 GTK+ 对话框，并且返回用户输入。它允许你使用各种 Shell 脚本向用户展示或请求信息。下面是一个 whois 指定域名目录服务的 GUI 客户端示例。

#!/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

示例输出：

zenity: Linux / UNIX display Dialogs Boxes From The Shell Scripts

参见手册获取更多 zenity 信息以及其他支持 GTK+ 的组件：

zenity --help

man zenity

5、kdialog 命令

kdialog 命令与 zenity 类似，但它是为 KDE 桌面和 QT 应用设计。你可以使用 kdialog 展示对话框。下面示例将在屏幕上显示信息：

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

示例输出：

Kdialog: Suppressing the display of a dialog

6、Dialog

Dialog 是一个使用 Shell 脚本的应用，显示用户界面组件的文本。它使用 curses 或者 ncurses 库。下面是一个示例代码：

#!/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

参见 dialog 手册获取详细信息：man dialog。

关于其他用户界面工具的注意事项

UNIX、Linux 提供了大量其他工具来显示和控制命令行中的应用程序，shell 脚本可以使用一些 KDE、Gnome、X 组件集：

• gmessage - 基于 GTK xmessage 的克隆

• xmessage - 在窗口中显示或询问消息（基于 X 的 /bin/echo）

• whiptail - 显示来自 shell 脚本的对话框

• python-dialog - 用于制作简单文本或控制台模式用户界面的 Python 模块

7、logger 命令

logger 命令将信息写到系统日志文件，如：/var/log/messages。它为系统日志模块 syslog 提供了一个 shell 命令行接口：

logger "MySQL database backup failed."

tail -f /var/log/messages

logger -t mysqld -p daemon.error "Database Server failed"

tail -f /var/log/syslog

示例输出：

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

可以查看 logger 手册获取详细信息：man logger

8、setterm 命令

setterm 命令可设置不同的终端属性。下面的示例代码会强制屏幕在 15 分钟后变黑，监视器则 60 分钟后待机。

setterm -blank 15 -powersave powerdown -powerdown 60

下面的例子将 xterm 窗口中的文本以下划线展示：

setterm -underline on;

echo "Add Your Important Message Here"

setterm -underline off

另一个有用的选项是打开或关闭光标显示：

setterm -cursor off

打开光标：

setterm -cursor on

参见 setterm 命令手册获取详细信息：man setterm

9、smbclient：给 MS-Windows 工作站发送消息

smbclient 命令可以与 SMB/CIFS 服务器通讯。它可以向 MS-Windows 系统上选定或全部用户发送消息。

smbclient -M WinXPPro <<eof

Message 1

Message 2

...

..

EOF

或

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

参见 smbclient 手册：man smbclient

10、Bash 套接字编程

在 bash 下，你可以打开一个套接字并通过它发送数据。你不必使用 curl 或者 lynx 命令抓取远程服务器的数据。bash 和两个特殊的设备文件可用于打开网络套接字。以下选自 bash 手册：

1. /dev/tcp/host/port - 如果 host 是一个有效的主机名或者网络地址，而且端口是一个整数或者服务名，bash 会尝试打开一个相应的 TCP 连接套接字。

2. /dev/udp/host/port - 如果 host 是一个有效的主机名或者网络地址，而且端口是一个整数或者服务名，bash 会尝试打开一个相应的 UDP 连接套接字。

你可以使用这项技术来确定本地或远程服务器端口是打开或者关闭状态，而无需使用 nmap 或者其它的端口扫描器。

# 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"

下面的代码片段，你可以利用 bash 循环找出已打开的端口：

echo "Scanning TCP ports..."

for p in {1..1023}

do

  (echo >/dev/tcp/localhost/$p) >/dev/null 2>&1 && echo "$p open"

done

示例输出：

Scanning TCP ports...

22 open

53 open

80 open

139 open

445 open

631 open

下面的示例中，你的 bash 脚本将像 HTTP 客户端一样工作：

#!/bin/bash

exec 3<> /dev/tcp/${1:-www.cyberciti.biz}/80

printf "GET / HTTP/1.0\r\n" >&3

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

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

printf "User-Agent: nixCraft_BashScript v.%s\r\n" "${BASH_VERSION}"   >&3

printf "\r\n" >&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 manual for more information: man bash

Notes on GUI tools and cron tasks

If you use crontab to start your script, you need to request a local display or output service with the command export DISPLAY=[user machine]:0. For example, calling /home/vivek/scripts/monitor.stock.sh using the zenity tool:

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

Do you have a favorite UNIX tool to spice up shell scripting? Please share it in the comments section below.

About the author

The author of this article is the founder of nixCraft, a seasoned system administrator, and a Linux operating system and UNIX shell programming trainer. He serves clients from around the world and a variety of industries, including IT, education, defense and space exploration, and non-profit organizations. You can follow him on Twitter, Facebook, Google+.