Black Belt Text-Fu
19 May 2022 | OSCPThis is the Advanced Text-Fu section from Linux Journey
Regex (Regular expression)
Regular expression is a tool that uses special notations as an universal language with almost any programming language. I would guess that it is a stone age retrocomputer’s early language. Ok this part wants to create a file with a string.
# remove sample.txt if you already have it
# actually don't need to, '>' will overwrite, I am just paranoid
$ rm sample.txt
# create a file with two lines string like this
$ echo "sally sells shells\nby the seashore" > sample.txt
$ cat sample.txt
# result:
sally sells shells
by the seashore
# ^ looks for beginning of a matching line
$ grep ^by sample.txt
# result:
by the seashore
# $ looks for ending of a matchining line
grep seashore$
# result:
by the seashore
# . looks for any matching single character
grep b. sample.txt
# result:
by the seashore
# [ ] specify characters found within bracket
# there are many tricks inside bracket notations
# [iou] looks for anything that has iou in between
$grep d[iou]g sample.txt
# [^i] excludes anything that has i in between
$grep d[^i]g sample.txt
# [a-c] looks for anything from a to c in between
# bracket notations are case sensitive, so might need to use [A-C]
$grep d[a-c]g sample.txt
Text Editors
I am still sort of new with linux to be honest. I am unfamilar with Vim and Emacs, however these two are recommended by Linux Journey. I have seen professional programmers/hackers in youtube using either vim or emacs or nano. Some like to use GUI text editors like Sublime Text, or Geany. Okay emacs looks like a GUI!
| vim | emacs |
|---|---|
 |
 |
Vim, short for vi + IMproved
I didn’t know there’s a text editor vi, but apparently Vim is the improved version. Gonna play with vim for awhile and using the same sample.txt from previous exercise.
# type colon key --> : literally in the vim to start something
# :e is what opens a file, I am guessing e for execute
:e sample.txt
# you will see
sally sells shells
by the seashore
# Try navigate by using
# h, j, k, l == left, up, down, right
# not a clockwise ¯\_(ツ)_/¯
# can feel like stuck inside vim, no clue of how to exit or whatever
# type ":" and you will see it on the bottom, type h
# it calls vim's very own "help.txt", and navigate with h, j, k ,l.
:h
# too much, and it has its own tutorial for beginner, I will do that!
# let's exit by doing this
:qa!
After looking into help, I realize vim has its own tutorial. I think I am going to do a post on vim alone and same with emacs. It is too much to cover in this post. Linux Journey did great by recommending these text editors and highlights.
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