How Expect works in Linux?

The Linux expect command takes script writing to an entirely new level. Instead of automating processes, it automates running and responding to other scripts. In other words, you can write a script that asks how you are and then create an expect script that both runs it and tells it that you’re ok.

What is expect package in Linux?

Expect is a program that “talks” to other interactive programs according to a script. Following the script, Expect knows what can be expected from a program and what the correct response should be. … It behaves just like Expect and Tk’s wish. Expect can also be used directly in C or C++ (that is, without Tcl).

What is expect in Unix?

Expect is a UNIX scripting and testing utility which can be used with SSH-based applications, like the Oracle VM CLI. Expect scripts can have any file name suffix you like, though they generally have an .exp extension.

How do you run an expect script?

1. Execute expect script from the command line using -c option. expect also also allows you to execute it directly in the command line using -c option as shown below. Once you run the above script, it waits for the newline(n) and upon pressing the enter key, it will print the message “pressed enter” and exits.

What does expect EOF do?

The final command ” expect eof ” causes the script to wait for the end-of-file in the output of passwd . Similar to timeout , eof is another keyword pattern. This final expect effectively waits for passwd to complete execution before returning control to the script.

How do you install expect in Linux?

$ yum install expect

The first line defines the expect command path which is #!/usr/bin/expect . On the second line of code, we disable the timeout. Then start our script using spawn command. We can use spawn to run any program we want or any other interactive script.

What is expect Tool?

Expect is a tool for automating interactive applications such as telnet, ftp, passwd, fsck, rlogin, tip, etc. … You will find that Expect is an absolutely invaluable tool – using it, you will be able to automate tasks that you’ve never even thought of before – and you’ll be able to do this automation quickly and easily.

How do I manually install an expect?


  1. Download the ecpect package from the below link.
  2. Install the required dependecy packages “Tcl/Tk” language toolkit. # yum install tcl.
  3. Install the “expect” package using the below commands.

What is send — in Expect?

send – The send command is used to send a response to a script or program. expect – The expect command waits for entry. In other words is waiting for the program output. spawn – The spawn command is used to launch a script or program such as shell, SSH, FTP, Telnet, SCP and so on.

How do I expect a bash script?

How to Use Expect In Bash Script

  1. Step 1 : Create a new file. vi expectcmd.
  2. Step 2 : Copy and paste below given content in file. …
  3. Step 3: Make your file executable by owner of file , run the given below command. …
  4. Step 4: Give commands as argument along with expectcmd script.

What type of terminal does CLI expect?

Expect is used to automate control of interactive applications such as Telnet, FTP, passwd, fsck, rlogin, tip, SSH, and others. Expect uses pseudo terminals (Unix) or emulates a console (Windows), starts the target program, and then communicates with it, just as a human would, via the terminal or console interface.

How do you check if expect is installed in Linux?

Today, we will see how to find if a package is installed or not in Linux and Unix operating systems. Finding installed packages in GUI mode is easy. All we have to do is to Just open the Menu or Dash, and enter the package name in search box. If the package is installed, you will see the menu entry.

How do I get EOF?

EOF is a symbolic constant that stands for End Of File, and it corresponds to the Ctrl-d sequence: when you press Ctrl-d while inputting data, you signal the end of input.

What is the use of << in Linux?

A command with the << operator will do the following things : Launch the program specified in the left of the operator, cat for instance. Send all that have been read except the EOF value to the standard input of the program on the left.

What is EOF character in Linux?

The EOF operator is used in many programming languages. This operator stands for the end of the file. The “cat” command, followed by the file name, allows you to view the contents of any file in the Linux terminal.

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