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Linux Commands

Linux terminal commands

• Pipes
• Navigation
  • Files types
• Changing Permissions
  • usermod
• Miscellaneous
• Installation
• Package Manager
  • Advanced package toolapt
• File and Directory Manipulation
• Find
• Computer commands
  • ps, kill
  • job, bg, fg
  • Mount and Unmount drive
  • Recursive size of folders in a directory
• Compression
  • gzip
  • tar
    • tar and gzip combined
  • zip files
• sed
• awk
• Networking
  • ping
  • httprobe
  • curl
• grep
• sort and uniq
• head and tail
• Redirection operations
• alias

Pipes

Pipes allow you to input the output of one command into another.

command1 | command2

The outputs of command1 go into the inputs of command2

Navigation

-rwxrwxrw- 1 root ryan 9999 May 22 00:01 FileName
^[^][^][^] ^ [ ^] [^ ] [^ ] Date of creation
| |  |  |  |   |   |    |
| |  |  |  |   |   |   Size in bytes
| |  |  |  |   |   group
| |  |  |  |   user
| |  |  |  Number of links to this file
| |  |  public
| |  group
| user
File types

Files types

Changing Permissions

usermod

usermod is used to change account properties.

Miscellaneous

Installation

Package Manager

• apt
  • debian based package manager
  • Installs .deb files which share dependencies
• Flatpak
  • A package manager for .flatpakref files
  • Packages applications and dependencies in the same place
  • Used for gui apps
• AppImage
  • A format for distributing portable software.
  • The application and the dependencies are combined.
  • The application is just 1 file
• Pacman
  • Arches package manager
• Snap
  • Umbutu’s competitor to Flatpaks

Dependency hell is when one application needs an older version of a library than another application. You might have to install both the older version and the newer one.

Advanced package tool(apt)

File and Directory Manipulation

Folders and directories are the same thing.

Find

Used for finding files or directories

Examples:

• find . -type f -exec chown user:group {} \; Recursively changes the owner of each file in a directory.
• find . -type f -maxdepth 1 -name "*.jpg" -exec rm {} \; Removes all .jpg files from a directory.

Computer commands

ps, kill

ps is used to show different process running.

job, bg, fg

Mount and Unmount drive

With some linux distros this happens automatically

1. Plug in drive
2. sudo fdisk -l find where drive is
3. sudo mount filePathFromFdisk filePathMountFolder mounts the drive
4. sudo umount filePathMountFolder unmounts the drive

Recursive size of folders in a directory

du --max-depth=1 -h ./

Compression

gzip

gzip is used to compress only 1 file at a time.

tar

tar is used to create an archive, a grouping of multiple files into a single file.

tar and gzip combined

zip files

unzip is used to decompress .zip files

Examples:

• unzip -qd FolderName compressed.zip
  • Decompresses a .zip file
• zip -r compressionName.zip dirPath
  • Compresses files as a .zip file

sed

Stream editor which is used to find and replace things inside files using regex.

sed {options} {script} {optional file}

• #s can also be used instead of the /s

sed -i.backup 's/foo/bar/g' file.txt
    Creates a backup called file.txt.backup and then replaces all occurrences of foo in file.txt to bar.

cat file.txt | sed 's/apple/orange/g'
    Replaces all occurrences of apple with orange and outputs it to the terminal. Doesn't change file.txt at all.

sed 's/o/O/g' <file1.txt >file2.txt
    Reads in file1.txt, replaces o for O, and outputs that into file2.txt. Doesn't change file1.txt

man sed | sed '/replace/s/the/The/g'
    The lines that have "replace" on them have the "the"s changed to "The"s.

awk

Awk is used to run a command on inputs that are separated by some pattern. The default field separator is a space. It can also be used to run commands on each line of a file.

Columns are defined with teh field separator. Rows are defined by new lines.

$# is used to choose which column. $NF is used to get the last column.

Examples:

• awk '{print $2}' /inputFile.txt
  • Prints the the 2nd column from inputFile
• awk '{print $1,$NF}' /inputFile.txt
  • Prints the the 1st column and the last column from inputFile
• echo "[" && awk '{print "\""$1"\""","}' ./text.txt && echo "]" > text.json
  • Converts a text file of lines of data into an array in a json file

Networking

ping

Ping is used to message a server and see if you are getting a response.

• You can use ip 8.8.8.8 which is google’s dns server to check if you have an internet connection.
• Ping uses ICMP network requests and some servers maybe configured to block this traffic.

httprobe

httprobe is used to take a list of domains and probe for working HTTP and HTTPS servers.

cat domains.txt | httprobe > results.txt

curl

Used to get the return information from websites/apis. Makes a get request form a URL.

curl https://api.github.com/users

grep

Grep is used for searching text in a file. Grep returns the lines that match a pattern, or the files that contain the pattern.

grep -Flags pattern fileName

If you don’t want to recursively search through a directory you can do grep pattern dirPath/*

Examples:

• grep -wirn "grep" . Searches for lines with the word “grep” recursively in the current directory
• grep -wirl "grep" . Searches for files that contain the word “grep”
• grep -wirc "grep" . | grep -v :0$ Search for files that contain the word “grep” and how many matches they have to the word “grep”

sort and uniq

sort is used to sort an input by alphabetical order or numerical order.

uniq omits repeated lines. By default uniq removes adjacent duplicated values.

uniq is often used with sort. Sort groups the same lines together and uniq removes duplicated lines.

Example: sort favFlavors.txt | uniq -c | sort -nr Gets the favorite flavors from most popular to least

head and tail

head and tail are used to output on the first or last lines of a file.

Redirection operations

• << is used to input blocks of text into a command
  • The delimiter is any sequence of characters which marks the end of the input block

    # This will input the lines "Input line 1." and "Input line 2." into the command and the command will treat it as an input file.
    command << delimiter
    Input line 1.
    Input line 2.
    delimiter
    

• You can run this to append to the beginning of a file

  echo "Append to beginning" | cat - file.txt > temp && mv temp file.txt
  

alias

alias is used to create shortcuts to commands so you don’t have to always type them out.