How to Write a Shell Script: Linux Terminal 201 - HakTip 175

Hak5 -- Cyber Security Education, Inspiration, News & Community since 2005:
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In today's HakTip, Shannon covers writing and executing shell scripts in the terminal.

This HakTip is sponsored by Moogsoft.

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Editor: Perrin M
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Founded in 2005, Hak5's mission is to advance the InfoSec industry. We do this through our award winning educational podcasts, leading pentest gear, and inclusive community – where all hackers belong.

[KSMcLeod]

Want to thank you Shannon and Hak5 for producing these Haktips. I have been following along and with other books I have been getting more and more comfortable using the terminal. Each episod builds on the last and you make it clear and easy to follow.

[banas]

Old guy time. (a) "#!" didn't exist before around 1980. It actually has to be baked into the kernel itself, and finding a way to do that securely was difficult. The kernel actually checks the first two characters of a file it's asked to execute. (b) "#" is used because it's a comment character in most shell languages, so that the script interpreter (bash or whatever) ignores the shebang line. (c) Any fully-pathed executable can follow the shebang: /usr/bin/perl, /usr/bin/python, etc. Very popular is "env", as in "#!/usr/bin/env python": this will execute the script with whatever version of "python" is first in the user's PATH environment variable. Use with caution. (d) Google "perlrun" or "running_under_some_shell" for a stupid Perl trick to make "#!" work (at least for Perl) on the few Unix-like systems that don't implement it. (e) Until you really know what you're doing, do NOT set the set-UID or set-GID flags on shell scripts!

[ahmedhlilioune]

Nice video and I hope to do advanced things in next haktip episodes

[DJMontePGH]

Thank you Shannon! You are a beautiful human.

[farahmohumad]

your videos make me love terminal more

[mica]

im to busy looking at her microphone..

[infobahnpirate]

I'm taking a Cisco Linux class at NSCC, I have gotten more information from these linux videos than the class that I'm paying for. Thank you all so much for the information. I will be getting my Linux certification because of your videos not that class....

[JNET_Reloaded]

Also remember its in unix type filetype and not windows as it wont work, but on linux unit / linux is default anyways so just letting you all know in case it dont work that might be why! Also i really prefer using .sh extension so i can use wildcards like chmod +x *.sh that does it on all .sh files only! why would you have a .sh that isnt executable is my thinking!

[cunninghamb]

Thanks can you do more advanced stuff. Would love to see a how to make a Linux kiosk

[toaster]

What is the extension for .elf? She is wrong to assume that's it bash. Also, is it not common to use .sh for bash?

[purushothamsharma]

Can you please teach complete shell scripting. I really like the way you teach.

[teslafreak]

Minor gripe, but the '#' is not a hash tag.

[MsHojat]

I don't have anything against white backgrounds (heck I use them myself) but it's pretty silly to be using such a layout when the OS is using a dark theme.

[AndersJackson]

Nice introduction. But please use symbols and not octal numbers to change file rights. So instead of that octal number you used, use this.


chmod +x heyworld # Set the file to a program.

[trufulnuffsaid]

What do u think about linux new code of conduct and how u gonna code with shell when all the devs taking heat from social politics pull there code off the kernel.

[TheElijahMinistries]

iEYE heard the Ocean . . . tips. . . . and saw the Pearl of GrEat PRiCE Hidden DEEP iNsidE!

[DAVIDGREGORYKERR]

sudo apt-get update && apt-get upgrade -y

[fixerdeyz]

Wahahahahahahahaha!
Am very proud of u

[charlesbrasil]

I think I am in love with that woman :):)