How to Use "Script" Command To Record Linux Terminal Session

This script command is very helpful for system admin. If any problem occurs to the system, it is very difficult to find what command was executed previously. Hence, system admin knows the importance of this script command. Sometimes you are on the server and you think to yourself that your team or somebody you know is actually missing a documentation on how to do a specific configuration. It is possible for you to do the configuration, record all actions of your shell session and show the record to the person who will see exactly what you had (the same output) on your shell at the moment of the configuration.

How does script command work?

script command records a shell session for you so that you can look at the output that you saw at the time and you can even record with timing so that you can have a real-time playback. It is really useful and comes in handy in the strangest kind of times and places.

The script command keeps action log for various tasks. The script records everything in a session such as things you type, things you see. To do this you just type script command on the terminal and type exit when finished. Everything between the script and the exit command is logged to the file. This includes the confirmation messages from script itself.

1. Record your terminal session

script makes a typescript of everything printed on your terminal. If the argument file is given, script saves all dialogue in the indicated file in the current directory. If no file name is given, the typescript is saved in default file typescript. To record your shell session so what you are doing in the current shell, just use the command below

# script shell_record1
Script started, file is shell_record1

It indicates that a file shell_record1 is created. Let's check the file

# ls -l shell_*
-rw-r--r-- 1 root root 0 Jun 9 17:50 shell_record1

After completion of your task, you can enter exit or Ctrl-d to close down the script session and save the file.

# exit
exit
Script done, file is shell_record1

You can see that script indicates the filename.

2. Check the content of a recorded terminal session

When you use script command, it records everything in a session such as things you type so all your output. As the output is saved into a file, it is possible after to check its content after existing a recorded session. You can simply use a text editor command or a text file command viewer.

# cat shell_record1 
Script started on Fri 09 Jun 2017 06:23:41 PM UTC
[root@centos-01 ~]# date
Fri Jun 9 18:23:46 UTC 2017
[root@centos-01 ~]# uname -a
Linux centos-01 3.10.0-514.16.1.el7.x86_64 #1 SMP Wed Apr 12 15:04:24 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
[root@centos-01 ~]# whoami
root
[root@centos-01 ~]# pwd
/root
[root@centos-01 ~]# exit
exit

Script done on Fri 09 Jun 2017 06:25:11 PM UTC

While you view the file you realize that the script also stores line feeds and backspaces. It also indicates the time of the recording to the top and the end of the file.

3. Record several terminal session

You can record several terminal session as you want. When you finish a record, just begin another new session record. It can be helpful if you want to record several configurations that you are doing to show it to your team or students for example. You just need to name each recording file.

For example, let us assume that you have to do OpenLDAP, DNS, Machma configurations. You will need to record each configuration. To do this, just create recording file corresponding to each configuration when finished.

# script openldap_record
   ...............
    configuration step
   ..............
# exit

When you have finished with the first configuration, begin to record the next configuration

# script machma_record
    ............
     configuration steps
    .............
# exit

And so on for the other. Note that if you script command followed by existing filename, the file will be replaced. So you will lost everything.

Now, let us imagine that you have begun Machma configuration but you have to abort its configuration in order to finish DNS configuration because of some emergency case. Now you want to continue the machma configuration where you left. It means you want to record the next steps into the existing file machma_record without deleting its previous content; to do this you will use script -a command to append the new output to the file.

This is the content of our recorded file

Now if we want to continue our recording in this file without deleting the content already present, we will do

# script -a machma_record
Script started, file is machma_record

Now continue the configuration, then exit when finished and let's check the content of the recorded file.

Note the new time of the new record which appears. You can see that the file has the previous and actual records.

4. Replay a linux terminal session

We have seen that it is possible to see the content of the recorded file with commands to display a text file content. The script command also gives the possibility to see the recorded session as a video. It means that you will review exactly what you have done step by step at the moment you were entering the commands as if you were looking a video. So you will playback/replay the recorded terminal session.

To do it, you have to use --timing option of script command when you will start the record.

# script --timing=file_time shell_record1
Script started, file is shell_record1

See that the file into which to record is shell_record1. When the record is finished, exit normally

# exit
exit
Script done, file is shell_record1

Let's see check the content of file_time 

# cat file_time 
0.807440 49
0.030061 1
116.131648 1
0.226914 1
0.033997 1
0.116936 1
0.104201 1
0.392766 1
0.301079 1
0.112105 2
0.363375 152

The --timing option outputs timing data to the file indicated. This data contains two fields, separated by a space which indicates how much time elapsed since the previous output how many characters were output this time. This information can be used to replay typescripts with realistic typing and output delays.

Now to replay the terminal session, we use scriptreplay command instead of script command with the same syntax when recording the session. Look below

# scriptreplay --timing=file_time shell_record1

You will that the recorded session with be played as if you were looking a video which was recording all that you were doing. You can just insert the timing file without indicating all the --timing=file_time. Look below

# scriptreplay file_time shell_record1

So you understand that the first parameter is the timing file and the second is the recorded file.

Conclusion

The script command can be your to-go tool for documenting your work and showing others what you did in a session. It can be used as a way to log what you are doing in a shell session. When you run script, a new shell is forked. It reads standard input and output for your terminal tty and stores the data in a file.

About Pungki Arianto

Pungki , currently working as a Linux / Unix administrator for a banking company. He love to work in Linux / Unix since it's fun for him. He is also interested in information technology, information security and writing.

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2 Comments

  1. I have written a couple of useful functions in a ~/.functions file which is sourced on login. The functions work fine when used in regular shell but when i do "script record.text" and then try to run the same functions, weirdly, "bash: myfunc: command not found".

    As soon as i exit the "script" state, my functions are available as usual.

    Any idea why is that?