How to capture terminal sessions and output with the Linux script command
script command creates a typescript file from your terminal session. This means that if you invoke the
script command, you are dropped to a "watched and recorded" terminal session subshell that's saved to an ASCII text file. When created with a timing file, you can replay the session, including output. The purpose of
script is that you can easily grab sample output from any command through an interactive session exactly as it's displayed in your terminal. You can use backspace, edit files, create files, and run simple or complex commands.
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The value of the
script command is in its capability to capture output during your terminal session for any terminal command without redirects, which don't always work. I was frustrated so many times when attempting to capture output from a command that somehow is going awry until I discovered
script. With standard redirect operators, some output can be redirected to a file, while other commands will only show output in stdout or the screen. Most sysadmins use the
script command to show output during software installation, when troubleshooting, or for development and programming purposes.
script command does not help you create shell scripts.
As with most commands that I use, I only use a subset of available options for them. The
script command has several options that I've never found useful in my own work. The only ones I use are:
-afor appending new commands and output to a previously-used file.
-qfor removing the initial starting and ending statements when using
--tfor saving timing information for playback.
When I use
script, I always use
--t to create a timing file and
-q for quiet mode. I only use
-a when I need to append more info into an existing script file, which is rare.
The following are two standard examples of the way I use
$ script --t=<logfile> -q <script file>
And, to append to
$ script --t=<logfile> -q -a <script file>
script file can be names that you choose. When you want to end and save the file, use Ctrl-D on your keyboard. You can look at, edit, or remove the script file and the log file at will. They are simple ASCII text files.
Here is an example:
$ script --t=script_log -q scriptfile
I ran the
ls command, the
who command, and then I ended the script with Ctrl-D.
$ ls blah.txt test1 test2 doc.txt $ who root tty1 2021-01-18 09:31 khess pts/0 2021-01-20 14:42 (192.168.0.5) khess pts/1 2021-01-20 14:47 $ exit
When you press Ctrl-D, the script exits and displays exit.
cat command to display the contents of
$ ls blah.txt file_time scriptfile script.rec shell_record1 shell_record3 time_log file_log record.scr script_log scriptrecord shell_record2 snap typescript $ who root tty1 2021-01-18 09:31 khess pts/0 2021-01-20 14:42 (192.168.0.5) khess pts/1 2021-01-20 14:47 $ exit Script done on 2021-01-20 14:47:28-06:00
If you want, you can also
$ cat script_log 0.088699 31 3.393729 1 0.246070 1 0.540094 2 0.003060 196 0.000195 31 2.136900 1 0.177266 1 0.179336 1 0.540818 2 0.003883 134 0.000210 31 4.676286 6
This is the timing log file that behaves similar to a transaction log for your
script commands and responses. It is important when you play back the file, which I demonstrate in the follow-up article, How to replay terminal sessions recorded with the Linux script command.
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For me, the best application of the
script command is for training new Linux users on how to use commands and to show them expected output in real-time, as if they were interacting with the terminal session themselves. For more experienced users, you could create a training session that teaches a new software installation or configuration. Training is the application I think of because of my history with training new sysadmins and writing how-to articles for various venues. And since the output is in ASCII text files, you can change the output for your own needs and audiences.