Commands on Aamnah - Frontend Web Developer

Copy contents to clipboard form command line (Ubuntu, macOS)

Mon, 26 Jul 2021 12:07:12 +0500

macOS

macOS comes with pbcopy

1pbcopy < ~/.ssh/id_rsa.pub
2
3# or 
4
5cat ~/.ssh/id_rsa.pub | pbcopy

Ubuntu

On Ubuntu you can use xclip

1sudo apt install xclip
2xclip -selection clipboard -i < inputFile
3
4# xclip -sel c < inputFile

clipboard is a parameter for -selection
-i means inoput (standard input or file). Since file is default, you can omit the -i in most cases

-i, -in
      read text into X selection from standard input or files (default)

-o, -out
      print the selection to standard out (generally for piping to a file or program)

-selection
      specify which X selection to use, options are "primary" to use XA_PRIMARY (default), "secondary" for XA_SECONDARY or "clipboard" for XA_CLIPBOARD

NOTE: xclip and xsel are X11 utilities, they manipulate the X11 selections, so can only be used in a X11 environment where $DISPLAY is set. Running in a terminal only context (e.g. WSL or headless) will give you this error:

[gcp --parents] Copy selected files and recreate folder structure

Fri, 23 Jun 2017 00:00:00 +0500

Why?

Makes it easier to copy a default OpenCart extension. Find the files by name and copy them while also creating the required folder structure.

How

Use the cp command with --parents flag.

1cp --parents admin/controller/extension/payment/bank_transfer.php easypaisa/

Won’t work on macOS by default, so brew install coreutils first and then use gcp instead of cp

1gcp --parents admin/controller/extension/payment/bank_transfer.php easypaisa/

easypaisa
└── admin
    └── controller
        └── extension
            └── payment
                └── bank_transfer.php

Examples

Extract/Clone an OpenCart Extension with one command

1find . -iname 'bank_transfer.*' -exec gcp --parents {} foo/ \;

{} will be replaced with the path name of the file. The last token, \; is there only to mark the end of the exec expression. foo is the directory you’re assumed to have created before running the command

[grep, sed] Find and Replace string in multiple files

Wed, 06 Jan 2016 00:00:00 +0500

1# replace all htttp://link to https://link in all files
2grep -rl 'http://' ./ | xargs sed -i 's|http://|https://|g'

1# if filenames have spaces, blanks or new lines
2grep -rl --null mangoes/ . | xargs -0 sed -i '' 's/mangoes/oranges/g'

why?

Here’s the scenario, i exported some files for this blog from a software that used a different image folder structure. Lots of new files with different links. So i needed a way to

find all the files spanning multiple directories containing a specific string
edit (in place) all them files found in multiple directories and replace it with new string

Basically, what i needed to do was change the path for images directory from resources/file.png to /assets/img/file.png. But i didn’t know which files had the new link structure and which files had the old one. We’re talking about 500+ files, in 25+ directories, so i can’t just go open them one by one and find stuff..

[grep] Find and Delete files based on string

Tue, 08 Dec 2015 00:00:00 +0500

1grep -lZrw xxx-hacker /home/theitali/ | xargs -0 rm -f --

where xxx-hacker is your string and /home/theitali/ is your location.

l lists the file name
Z is required for the xargs -0 part
r is for recursive, try -R if small r doesnt work.
w is for searching the whole word

[du] Disk Space Usage

Sat, 21 Nov 2015 00:00:01 +0500

Examples

check how much space is taken by files of a certain type

Say you want to find out how much space in total the .tar.gz backup files are taking, you can do so with the following command. (note that it will not check subdirectories)

-h, --human-readable prints sizes in human readable format (e.g. 261M instead of 266692)
The -c or --total size produces a grand total

1# find out space taken by tarballs in current dir
2du -h *.tar.gz

23M     aamnah.tar.gz
54M     clients.aamnah.tar.gz
261M    clients.hostmarkaz.tar.gz
113M	clients.ravihost.tar.gz
2.9M	ravihost.tar.gz
36K 	tldrdevnotes.tar.gz

1# find out TOTAL space taken by all tarballs in current dir
2du -ch *.tar.gz

23M     aamnah.tar.gz
54M     clients.aamnah.tar.gz
261M    clients.hostmarkaz.tar.gz
113M	clients.ravihost.tar.gz
2.9M	ravihost.tar.gz
36K 	tldrdevnotes.tar.gz
453M	total

check space consumed and sort by size

explainshell

[df] Disk Free

Sat, 21 Nov 2015 00:00:00 +0500

1df -h

The -h flag is for human readable output, show 30G instead of 30830588.

Summing numbers in the output of `df`

We can do that by pip the output of the df command to something like awk and have awk sum up the numbers, like so:

1df -lP | awk '{}'
2df -lP | awk '{do math} END {print result}'

If the device names are long, df splits the output on multiple line to fit it in the normal 80 character long terminal. -P is for portability, use the POSIX output format (and not try to fit everything in by breaking lines) Get the foramt data in a consistent format, every device on one line.

[chmod] Permissions

Thu, 19 Nov 2015 00:00:00 +0500

change permissions on all dirs

1find . -type d -exec chmod 700 {} \;

change permissions on all files

1find . -type f -exec chmod 600 {} \;

change permissions recursively

use the -R flag

1chmod 755 -R var/

make executable

1chmod +x file

copy permissions from another file

On GNU/Linux chown and chmod have a --reference option

1chown --reference=otherfile thisfile
2chmod --reference=otherfile thisfile

Example from Magento

Enter the following commands to set sensible permission defaults:

1find . -type f -exec chmod 400 {} \;
2find . -type d -exec chmod 500 {} \; 
3find var/ -type f -exec chmod 600 {} \; 
4find media/ -type f -exec chmod 600 {} \;
5find var/ -type d -exec chmod 700 {} \; 
6find media/ -type d -exec chmod 700 {} \;

Devil's Commands

Sat, 31 Oct 2015 00:00:00 +0500

List of dangerous shell commands

It is not uncommon to see trolls tricking new Linux/Unix users run commands as a joke. These commands can destroy users data. Here are a few:

rm -rf /
:(){ :|: & };:
mkfs /dev/sda1
cat /dev/zero > /dev/sda1
wget url -O - | sh –
curl url | sh
dd if=/dev/zero of=/dev/sda2
echo 726d202d7266202a | xxd -r -p
dd if=/dev/random of=/dev/port
echo 1 > /proc/sys/kernel/panic
cat /dev/port or cat /dev/mem
cat /dev/zero > /dev/mem
sudo chmod -r 444 / or sudo chown -r nobody:nobody /
last | reboot

Explanations

rm -rf / Doesn’t work anymore. Don’t bother. Used to remove all files in the directory tree.
:(){ :|: & };: Fork bomb. Job control has partially mitigated this by now. It won’t fully bork up the system anymore.
mkfs /dev/sda1 Formats first partition on sda disk.
cat /dev/zero > /dev/sda1 Zeroes out the first partition (many systems host either / or /boot there). Using sda might’ve been better.
wget url -O - | sh – Grab arbitrary shell script from online and execute it.
curl url | sh Deviation of 5.
dd if=/dev/zero of=/dev/sda2 Zeroes out sda2. Just like 4 it kinda sucks. It assumes the existence of that partition.
echo 726d202d7266202a | xxd -r -p Doesn’t do jack shit unless put inside $( ). It just echoes rm -rf *
dd if=/dev/random of=/dev/port Write random stuff to memory. Better use urandom instead.
echo 1 > /proc/sys/kernel/panic Induce kernel panic.
cat /dev/port or cat /dev/mem View system memory.
cat /dev/zero > /dev/mem Write zero bits into system memory.
sudo chmod -r 444 / or sudo chown -r nobody:nobody / Make all files on system read-only and pass their ownership to nobody user.
last | reboot View last logged in users and send its output to reboot? What kinda bullshit is that?

So, newb commands mostly. Learn from any source but not these shitty commands please _/\_

[wget] How to store an entire website offline

Tue, 26 Aug 2014 00:00:01 +0500

1wget --random-wait -r -p -e robots=off -U mozilla http://yoursite.com

OR, as a bash function added to ~/.bash_profile (MacOS) or ~/.bashrc (Linux)

 1# Download an entire website
 2# -p --page-requisites: get all the elements that compose the page (images, CSS and so on)
 3# -e robots=off you don't want wget to obey by the robots.txt file
 4# -U mozilla as your browsers identity.
 5# --random-wait to let wget chose a random number of seconds to wait, avoid get into black list.
 6# Other Useful wget Parameters:
 7# -k --convert-links: convert links so that they work locally, off-line.
 8# --limit-rate=20k limits the rate at which it downloads files.
 9# -b continues wget after logging out.
10# -o $HOME/wget_log.txt logs the output
11
12getwebsite() {
13    wget --random-wait -r -p -e robots=off -U mozilla $1
14}

To use the bash function

Commands on Aamnah - Frontend Web Developer

Copy contents to clipboard form command line (Ubuntu, macOS)

macOS

Ubuntu

[gcp --parents] Copy selected files and recreate folder structure

Why?

How

Examples

Extract/Clone an OpenCart Extension with one command

[grep, sed] Find and Replace string in multiple files

why?

[grep] Find and Delete files based on string

[du] Disk Space Usage

Examples

check how much space is taken by files of a certain type

check space consumed and sort by size

[df] Disk Free

Summing numbers in the output of df

[chmod] Permissions

change permissions on all dirs

change permissions on all files

change permissions recursively

make executable

copy permissions from another file

Example from Magento

Links

Devil's Commands

List of dangerous shell commands

Explanations

[wget] How to store an entire website offline

Summing numbers in the output of `df`