Unix3
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The document provides an overview of essential Linux commands and concepts, organized into sections on essential commands, command structure, help, moving around directories, reading and writing files, directories, moving and renaming files, copying and removing files, links, searching, ownership and permissions, switching users, and useful commands. Key commands covered include ls, cd, pwd, touch, mkdir, mv, cp, rm, chmod, and sudo. File permissions are explained using rwx notation and octal representation.
![Wildcards:
* = 0 or more characters can be represented
? = any one characters
[] = any of the characters within the brackets
you can do more complex searches for size, read the man pages.
find ~ -name *.txt -and -not -path *Quicktime*
Searches in the user folder anything with .txt in their name and not
within a path that contains Quicktime in the route.
FILE OWNERSHIP AND PRIVILEGES
whoami = tells you which user you are
cd ~ = will send you to the folder of whoever you are logged in as
echo $HOME = that's where your home directory is (for your user)
GROUPS
Each user can belong to a group. File permissions can be assigned to users
or groups of users. By adding a user to a group they can gain access to files.
Groups = shows you the groups you belong to
FILE AND DIRECTORY OWNERSHIP
The owner is the third column, the group is the fourth column.
We can set permissions based on the owner or the group.
Any file you create is yours to own
chown kevin:staff ownership.txt
chown kevin ownsership.txt
chown :staff ownership.txt
chown kevin:staff directory1
changes ownership of ownership.txt to kevin owner and staff group
chown R kevin:staff testdirectory�
changes ownership of testdirectory and all its contents to kevin and the
group staff
sudo chown lynda:staff ownership.txt
changes ownership as superuser
FILE AND DIRECTORY PERMISSIONS
in ls -la first colum:
first character: d directory, - file, l for symbolic link
following characters: user, group, other
r read the file, w write the file, x execute the file or directory
example:
drwxrw-r--
a directory where the user can read, write, and execute, a group that can
read and write but not execute, and others who can only read the file
chmod
change mode or change permissions
structure:
chmod mode filename](https://image.slidesharecdn.com/unix3-170217035504/85/Unix3-4-320.jpg)
Unix3
- 1. ESSENTIALS Ctrl + plus key or minus = increese or decrease font size in terminal window echo Hello World = types Hello World� � Up and down arrows = move to previous next commands (command history) exit = closes the window Ctrl + a = move the cursor to the beginning Ctrl + e = move the cursor to the end Tab = Will try to guess what you want to type Tab + Tab = Will show you a list of all possible matches for autocomplete Ctrl + l = clear the screen COMMAND STRUCTURE command options (arguments of options) arguments echo $SHELL = what shell will you be launched as (login shell) echo $0 = what is the current shell in use sh = move to the sh shell HELP man echo = shows you the manual page for the echo commands man man = shows you the manual page for the man commands apropos ban = searches for possible matches for commands containing ban whatis banner MOVING AROUND DIRECTORIES pwd = present working directory, where i am located right now ls = list the contents of pwd ls -l = list vertical format ls -a = list dot files which are invisible config files ls -h = returns the size of the files listed cd nameofdirectory = changes pwd to nameofdirectory directory cd .. = changes directory to parent directory cd Library/Preferences = moves two directories at once cd ../.. = go to the parent of the parent of this directory cd / = go to root of our hard drive cd /Library/Preferences = move to absolute path cd ~ = moves you to the user directory cd - = toggles you between current directory and last dir you were in cd Application Support or cd Application Support� � will move into the Application Support directory. As a general rule, try not to use spaces or symbols except the _ on file names. Use numbers and letters. Most unix systems are case sensitive so MyFile and myfile are two different files. CREATE FILES touch newfile.txt = create a file touch existingfile.txt = update the file's access time nano = enter the nano editor nano newfile.txt = it will enter the editor and will have that name waiting for you. Within nano you can move forwards and backwards, cut and uncut (paste)
- 2. text, help menu, search for, etc.. at www.nano-editor.org is a resource to learn more READ FILES you can read files using nano filetoread.txt to read the file 1. cat = reads and output the first file and read and concatenate second file if you pass only one file, you just use it to read that filetoread.txt example cat short_file.txt newfile.txt outputs the two files concatenated 2. more = output one page of text and you can move forward pressing spacebar 3. less = same as more but loads one page into memory and you can scroll backwards. Even if you type more, less will execute, because less is an improvement on more. f = go forwards b = go backwards q = quit shift+g = go to the end of the doc g = takes you to the top of the doc less -M = get info on scrolling less -N = get line numbers head somefile.txt = shows you the first lines of a file tail somefile.txt = shows you the last lines of a file tail -f = it will watch for changes in the file.txt on a different terminal window. ctrl+c = exit DIRECTORIES mkdir directoryname = creates directory mkdir directoryname/test1 = creates directory inside another to create all parent directories at once mkdir -p directory1/test1/test2/test3 ls -la testdir/ shows you what is in there MOVING AND RENAMING FILES AND DIRECTORIES mv newfile.txt testdir/newfile.txt or mv newfile.txt testdir moves the file into the testdir directory mv newfile.txt ../newfile.txt or mv newfile.txt .. moves the newfile.txt file into the parent folder mv test1/test3 test1/test2 moves test3 directory inside the test1 directory into the test1/test2 directory1 TO RENAME A FILE
- 3. mv newfile.txt new_file.txt renames newfile as new_file mv newfile.txt testdir/new_file.txt renames new file and moves it inside testdir mv -n = no overwriting dont accidentally overwrite a file.txt� mv -f = force overwriting mv -i = ask me if i want to overwrite mv -v = gives you reporting information by default mv is mv -f COPY FILES cp filetobecopied.txt destinationofcopy.txt cp -n = no overwriting cp -f = force overwriting cp -i = ask me if i want to overwrite cp -v = get information cp -R = copy a directory and all of its contents cp -R directorytocopy copyofdirectory REMOVING FILES AND DIRECTORIES rm filetoremove.txt completely deletes a file rmdir directorytodelete completely deletes an empty directory1 rm -R directorytodelete completely deletes a directory and all its contents LINKS IN UNIX ln filetolink hardlink creates a link(shortcut) to a file.txt like in windows except hardlinks don't break if original file is deleted ln -s filetolink symlink creates a symbolic link Symbolic links reference the path to the file, not the file itself. Hardlinks keep track of the file, symbolic links just of the path. They break if the file is moved or deleted. SEARCHING FILES AND DIRECTORIES find path expression find ~/Documents -name someimage.jpg� � where -name and someimage.jpg are arguments not options.� � That will return searching in the User/Documents folder anything with the name someimage.jpg
- 4. Wildcards: * = 0 or more characters can be represented ? = any one characters [] = any of the characters within the brackets you can do more complex searches for size, read the man pages. find ~ -name *.txt -and -not -path *Quicktime* Searches in the user folder anything with .txt in their name and not within a path that contains Quicktime in the route. FILE OWNERSHIP AND PRIVILEGES whoami = tells you which user you are cd ~ = will send you to the folder of whoever you are logged in as echo $HOME = that's where your home directory is (for your user) GROUPS Each user can belong to a group. File permissions can be assigned to users or groups of users. By adding a user to a group they can gain access to files. Groups = shows you the groups you belong to FILE AND DIRECTORY OWNERSHIP The owner is the third column, the group is the fourth column. We can set permissions based on the owner or the group. Any file you create is yours to own chown kevin:staff ownership.txt chown kevin ownsership.txt chown :staff ownership.txt chown kevin:staff directory1 changes ownership of ownership.txt to kevin owner and staff group chown R kevin:staff testdirectory� changes ownership of testdirectory and all its contents to kevin and the group staff sudo chown lynda:staff ownership.txt changes ownership as superuser FILE AND DIRECTORY PERMISSIONS in ls -la first colum: first character: d directory, - file, l for symbolic link following characters: user, group, other r read the file, w write the file, x execute the file or directory example: drwxrw-r-- a directory where the user can read, write, and execute, a group that can read and write but not execute, and others who can only read the file chmod change mode or change permissions structure: chmod mode filename
- 5. user: u, group: g, other: o chmod ugo=rwx filename give read write and execute permissions to user group and other chmod u=rwx, g=rw, o=r filename chmod ug+w filename for user and group add the write permissions chmod o-w filename for other remove write permissions chmod a+rw add read write permission to all (a) (user, group, other) chmod -R g+w test1 will changes write permissions for groups on the test1 directory and everything inside of it OCTAL NOTATION TO CHANGE FILE PERMISSIONS r = 4, w =2, x= 1 rwx = 7, rw=6, rx=5, w=2 and so on chmod 777 filename give all the permissions to everyone chmod 764 filename user has all privileges, group read and write, and others only read chmod 000 filename take all privileges from everyone SWITCH TO A DIFFERENT USER IDENTITY The root user can do absolutely anything on the unix system. Not bound by normal user permissions sudo = substitute the user and do sudo ls -la won't require a password for five minutes after entering the password the first time. sudo -k to ask it to ask you a password sudo whoami (it will show current user as sudo) sudo -u lynda whoami (it will say lynda) sudo without any options will make you into the root user.
- 6. Only admins can do sudo. UNIX COMMANDS AND PROGRAMS commands are executable files, they are shorthands of files and you pass arguments the file executes. Whereis echo which echo whatis banner get information about commands it's common you can pass -v, –version, or –help after the command to learn more about commands To exit programs, most common: q, x, ctrl + x, ctrl + q, or ESC you can force quite Ctrl + c. you can put semicolons between commands to execute two commands in sequence MANAGE COMMANDS echo $PATH outputs a colon separated list of directories where to look for the command echo it will look from left to write PATH=directory/subfolder:directory2/subfolder to set the path, it only lasts for the current session which ruby it will tell us the path we'll get if we type the command ruby USEFUL COMMANDS date tells you the current date the computer has been set to uptime tells us the time the computer has been turned on who shows us a list of all users and what they are doing (each new terminal open adds an instance of the same user)
- 7. Only admins can do sudo. UNIX COMMANDS AND PROGRAMS commands are executable files, they are shorthands of files and you pass arguments the file executes. Whereis echo which echo whatis banner get information about commands it's common you can pass -v, –version, or –help after the command to learn more about commands To exit programs, most common: q, x, ctrl + x, ctrl + q, or ESC you can force quite Ctrl + c. you can put semicolons between commands to execute two commands in sequence MANAGE COMMANDS echo $PATH outputs a colon separated list of directories where to look for the command echo it will look from left to write PATH=directory/subfolder:directory2/subfolder to set the path, it only lasts for the current session which ruby it will tell us the path we'll get if we type the command ruby USEFUL COMMANDS date tells you the current date the computer has been set to uptime tells us the time the computer has been turned on who shows us a list of all users and what they are doing (each new terminal open adds an instance of the same user)