Some basic unix commands
- uname: Shows device and kernel information.
# Shows architecture of the current server
uname -m
# Shows kernel
uname -r
# Shows all the options of the OS
uname -a
- man: Manual of any command
# Syntax: man [command]
man uname
- ls: List the files of the current directory:
# Normal
ls
# Include hidden files and details
ls -lsa
- mkdir: Make a new directory in the current path or another path:
# Make a directory named mydir
mkdir mydir
# Make a new directory inside mydir called as mydir2
mkdir mydir/mydir2
- cd: Go to the given directory:
# Enter to a simple directory
cd mydir
# Out of the current directory
cd ../
# Enter to a nested directory
cd mydir/mydir2
- tree or lstree: Shows the structure of the current directory
tree
- touch: Creates a new file
# creates a empty file
touch example.txt
- vi: Opens the text editor.
Tips.
VI works with Mnemonic commands for example:
- Press "i" key in order to switch to "Insert" mode.
- Press "v" key in order to switch to "Visual" mode.
- Press "ESC" key to exit any mode.
- Press : key in normal mode in order to input commands like save with the "w" key and "q" key to exit VI.
# First press I, then enter a random text then press ESC and finally press :wq and ENTER key in order to exit and save
vi example.txt
Some random text 1
Some random text 2
Some random text 3
Some random text 4
Some random text 5
Some random text 6
----INSERT----
:wq!
- cp: Copy a file or a directory
# Syntax: cp original_file destiny_file
cp example.txt example2.txt
# Copying your file to one directory up
cp example.txt ../example3.txt
- mv: Move or rename any file or directory
# Syntax: mv original_file destiny_file
mv example2.txt another_example.txt
# Moving your file to one directory up
mv another_example.txt ../
- rm: Remove any file or directory
# Removing a simple file
touch deleteme.txt && rm deleteme.txt
# Removing a directory
mkdir dir1 && rm -R dir1
- cat: Shows the content of a file
cat example.txt
- chmod: Change who can execute, write and read any file or directory
# Syntax: chmod [permissions] [file]
# Permissions with Mnemonic. u: user, g: group, o: others, r: read, w: write, x: execute
chmod ugo+rwx example.txt
# Permissions with Octal. 1st position user, 2nd position group, 3rd position others, 4: read, 2: write, 1: execute, 0: no permission.
# You can add any numbers in order for obtain different combination of permissions, for example 7 represents all the permissions.
chmod 740 example.txt
- chown: Change the owner of a file or directory
# Syntax: chown [user]:[group] file
# If you only want to change the user you don't have to specify the group
chown anotheruser example.txt
# Or specify the group also
chown anotheruser:anothergroup example.txt
In Unix process we have different types of descriptors: 0. stdin: It is used to input data or files into a command.
- stdout: It is used to redirect the output of a command to another command or file.
- stderr: It is used to indicate the errors of the command.
First lets try to list a directory that doesn't exists and also the home directory. In this case will be "tests" directory:
ls -l /home /tests
It will display something like this:
ls: /tests: No such file or directory
lrwxr-xr-x 1 root wheel 25 Mar 18 08:16 /home -> /System/Volumes/Data/home
The first output it's stderr output because it doesn't exists. Then it shows the stdout output result of listing the /home directory, now we can try to output this result to a random file, using the > operator:
ls -l /home /tests 1> success.txt
The above command will create a new file call success.txt which contains the correct output of stdout because we specify to redirect to the 1 output, which belongs to sdtout. Now we will try using the stderr:
ls -l /home /tests 2> errors.txt
The above command will create a new file call errors which contains the errors of the command, it's important to specify the 2 output because it belongs to stderr. Now we will try to use both at the same time:
ls -l /home /tests > both.txt 2>&1
In the above command first we have to specify the normal redirection symbol in order to indicate the file that will be writted, then we have to specify the outputs, the stderr and stdout will be attached using the "&" operator.
Also we can append text to another file instead of overwrite it with the following operator:
echo "Whatever" >> success.txt
Also if we need to use the output of the command as input of another command we can use the operator pipe or '|':
ls -l | cat
- grep: It is used to search patterns inside the content of a file
# Syntax: grep [pattern] [file]
grep text example.txt
- find: It is used to find files or directories with the given pattern
# Syntax: find [directory] --name [pattern]
find ./ --name '*.txt'
Also we can use both together:
# Regular find
find ./ –type f –name '*txt*'
# Pipeing with grep
find ./ –type f | grep 'txt'
# Using grep with exec option
find ./ -name '*.txt' -exec grep '4' {} \;
- Create the following directories structure:
- node1
|
------node11
|
------------node111
|
------node12
|
------node13
|
------------node131
|
------------node132
|
------------------node1321
|
|
- node2
|
------node21
|
------node22
|
------------node221
|
------------node222
|
------------------node2221
|
------------node223
|
------------------node2231
|
|
- node3
|
------node31
|
------------node311
|
------------------node3111
|
------------------node3112
|
------------------node3113
|
------------node312
|
------------node313
|
------------------node3131
|
------------------node3132
|
------------------node3133
- Download the Great Gatsby inside node111, Alice in Wonderlands inside node12, Sherlock Holmes inside node1321, Adventures of Huckleberry Finn inside node2221, Metamorphosis inside node3133 and Les Misérables inside node3132. You must download in txt format and you can do it from this website. Use the wget command in order to download the book:
# Example
wget https://www.gutenberg.org/files/84/84-0.txt
- Change the default name, give a proper name to each book.
- Copy the Great Gatsby to node11, Alice in Wonderlands to node131, Sherlock Holmes to node1, Adventures of Huckleberry Finn to node2231, Metamorphosis to node2 and Les Misérables to node1321.
- Delete all the original files.
- Change the permissions of all the files and directories of node1 to execute, write and read for the user and read to others with Mnemonic command. Then node2 change only read for the user with octal command and finally node3 write and read for the user, read for the group and also read for others usign Mnemonic.
- Search in all previously downloaded files the sentences that contain the words "money", "strawberry", "fields", "black", "dog", "smooth", "criminal". Print those sentences in different files, each named after the word that was searched, for example: money.txt, dog.txt, etc... Also at the end of each file write the number of occurrences found of each word.
- Tip: You can use more than one command to do it.
- 2nd Tip: If there is some file that can not be readed by your command you can change the permissions to 700 again.
- Zip all the books and the results of each word in one file tar.gz. Tip: It doesn't matter if you move the file to another directory, but if you do it without move the current directories structure you will be The one and only H A C K E R M A N 3 0 0 0.
(VI commands)[https://www.guru99.com/the-vi-editor.html]