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HackIT

UNIX filesystem

Unix filesystem commands allow one to access, view and edit files and directories present on one's device through a command line interface. The following commands are found useful in Unix file systems

  • 'cd' command for entering a directory named 'xyz'

     abhinavg21@DESKTOP-QULR5HS:~$ cd experiments/

 abhinavg21@DESKTOP-QULR5HS:~/experiments$ cd experiments1/

 abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ |

  • 'cd -' or 'cd ..' command for going to the previous directory

    abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ cd ..

abhinavg21@DESKTOP-QULR5HS:~/experiments$ cd experiments1/

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ cd -
/home/abhinavg21/experiments

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'cd /' for entering the root directory

    abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ cd /

abhinavg21@DESKTOP-QULR5HS:/$ |

  • 'cd ~' to return to the home directory

    abhinavg21@DESKTOP-QULR5HS:/$ cd ~

abhinavg21@DESKTOP-QULR5HS:~$ pwd
/home/abhinavg21

abhinavg21@DESKTOP-QULR5HS:/$ |

  • 'pwd' to print the name of the directory you are currently working in

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ pwd
/home/abhinavg21/experiments

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'ls' to view the list of files and directories present in the current directory

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls
experiments1  new.txt  new1.txt  new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'Along with 'ls', the following arguments could be used:

    • '-l' for using a long listing format.

    • '-a' to include the filenames starting with '.'(yes, the ls command ignores them by default)

    • '-h' to make files human readable, i.e, print the size of files(wherever applicalbe along with units)

    • '-R' to also see the list of files in the directories inside the directory on which 'ls' is applied

      abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls -a
.  ..  experiments1  new.txt  new1.txt  new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls -l
total 16
drwxr-xr-x 2 abhinavg21 abhinavg21 4096 May 29 14:22 experiments1
-rwxrwx--- 1 abhinavg21 abhinavg21   17 May 29 15:07 new.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new1.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls -lah
total 24K
drwxr-xr-x 3 abhinavg21 abhinavg21 4.0K May 29 14:58 .
drwxr-xr-x 4 abhinavg21 abhinavg21 4.0K May 29 14:58 ..
drwxr-xr-x 2 abhinavg21 abhinavg21 4.0K May 29 14:22 experiments1
-rwxrwx--- 1 abhinavg21 abhinavg21   17 May 29 15:07 new.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new1.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls -la
total 24
drwxr-xr-x 3 abhinavg21 abhinavg21 4096 May 29 14:58 .
drwxr-xr-x 4 abhinavg21 abhinavg21 4096 May 29 14:58 ..
drwxr-xr-x 2 abhinavg21 abhinavg21 4096 May 29 14:22 experiments1
-rwxrwx--- 1 abhinavg21 abhinavg21   17 May 29 15:07 new.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new1.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls -R
.:
experiments1  new.txt  new1.txt  new2.txt

./experiments1:
new3.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'll' is an alias for the command 'ls -la' (see '-la' in the codeblock above)

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ ll
total 24
drwxr-xr-x 3 abhinavg21 abhinavg21 4096 May 29 14:58 ./
drwxr-xr-x 4 abhinavg21 abhinavg21 4096 May 29 14:58 ../
drwxr-xr-x 2 abhinavg21 abhinavg21 4096 May 29 14:22 experiments1/
-rwxrwx--- 1 abhinavg21 abhinavg21   17 May 29 15:07 new.txt*
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new1.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'cat [file]' is used to print the contents of 'file' on the standard output

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat new1.txt
aaaaaa
bbbbbb
cccccc
ddddd
vvvvvvvv
ddd
nnnnnn
akhdftcb
hhhhhhhh

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'cat > abc.txt' is used to create a new file abc.txt(or rewrite if already existing) and add into the input that follows

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat > new.txt
aaaaaaaa
bbtttt
sfdsghhr
afwgenngfb
^C

abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat new.txt
aaaaaaaa
bbtttt
sfdsghhr
afwgenngfb

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'cat >> abc.txt' is used to concatenate the input that follows into the already existing abc.txt

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat >> new.txt
this line was added later
^C

abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat new.txt
aaaaaaaa
bbtttt
sfdsghhr
afwgenngfb
this line was added later

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • Along with 'cat' the following arguments could be used:

    • '-e' to print a '$' at the end of every line to be able identify every different line in lengthy/clumpsy documents
    • '-n' or '-b' to number the lines in the document. Apart from these extensions, the command 'nl txt_file' does the same jab.
    abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat -e new.txt
  aaaaaaaa$
  bbtttt$
  sfdsghhr$
  afwgenngfb$
  this line was added later$

  abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat -n new.txt
      1  aaaaaaaa
      2  bbtttt
      3  sfdsghhr
      4  afwgenngfb
      5  this line was added later

  abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat -b new.txt
      1  aaaaaaaa
      2  bbtttt
      3  sfdsghhr
      4  afwgenngfb
      5  this line was added later

  abhinavg21@DESKTOP-QULR5HS:~/experiments$ nl new.txt
      1  aaaaaaaa
      2  bbtttt
      3  sfdsghhr
      4  afwgenngfb
      5  this line was added later

  abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'Ctrl' + 'C' is used to interupt an ongoing command or exit it. The "^C" seen on the standard output is actually 'Crtl' + 'C'.

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat >> new.txt
this line was added later
^C

abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat new.txt
aaaaaaaa
bbtttt
sfdsghhr
afwgenngfb
this line was added later

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'rm file_name' is used to remove files.

    abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ ls
new3.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ cat new3.txt
aaaaaa
bbbbbb
cccccc
ddddd
vvvvvvvv
ddd
nnnnnn
akhdftcb
hhhhhhhh

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ rm new3.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ ls

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ |

  • 'rmdir dir_name' is used to remove empty directories.

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls
experiments1  new.txt  new1.txt  new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ rmdir experiments1/

abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls
new.txt  new1.txt  new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'mkdir new_dir_name' is used to make directory inside the directory one is present in.

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls
new.txt  new1.txt  new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ mkdir experiments1

abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls
experiments1  new.txt  new1.txt  new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'touch new_file_name' is used to create new files in the directory one is present in.

    abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ ls

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ touch new3.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ ls
new3.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ |

  • 'file file_name' gives the type of the file

    abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ file new3.txt
new3.txt: empty

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ cd ..

abhinavg21@DESKTOP-QULR5HS:~/experiments$ file experiments1/
experiments1/: directory

abhinavg21@DESKTOP-QULR5HS:~/experiments$ file new.txt
new.txt: ASCII text

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'mv existing_file_name new_file_name' is used to rename a file or even change its extension

    abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ ls
new3.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ mv new3.txt renamed.exe

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ ls
renamed.exe

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ |
~~~

  • 'cp file_name dir_name' is used to copy a file another directory

    abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ ls
new3.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ cd ..

abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls
experiments1  new.txt  new1.txt  new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ cp new.txt experiments1/

abhinavg21@DESKTOP-QULR5HS:~/experiments$ cd experiments1/

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ ls
new.txt  new3.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments/experiments1$ |

Note that until now I was introducing newlines inside the codeblocks representing the standard output above for the sake of better understanding. From hereon(for echo command), I will be copy pasting the standard output as it is.

  • 'echo text' is used to print text on the standard output and then take the cursor on the next line

    abhinavg21@DESKTOP-QULR5HS:~$ echo hello world
hello world
abhinavg21@DESKTOP-QULR5HS:~$ |

  • Echo also supports the following arguments:

    • '-n' is used to print the text on the standard output while keeping cursor on the same line

    • '-e'allows bash to interpret backslashes, i.e., \n as newline, \b as back-space, etc.

      abhinavg21@DESKTOP-QULR5HS:~$ echo -n hello world
hello worldabhinavg21@DESKTOP-QULR5HS:~$ echo

abhinavg21@DESKTOP-QULR5HS:~/experiments$ echo "hello\nworld"
hello\nworld
abhinavg21@DESKTOP-QULR5HS:~/experiments$ echo -e "hello\nworld"
hello
world
abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'echo *' is used to print the list of directories and files inside the directory this command is used in.(similar to 'ls')

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls
experiments1  new.txt  new1.txt  new2.txt
abhinavg21@DESKTOP-QULR5HS:~/experiments$ echo *
experiments1 new.txt new1.txt new2.txt
abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'echo text > file_name' is used to create a new file and add text to it.

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls
experiments1  new.txt  new1.txt  new2.txt
abhinavg21@DESKTOP-QULR5HS:~/experiments$ echo experimenting with ubuntu > f
ile
abhinavg21@DESKTOP-QULR5HS:~/experiments$ ls
experiments1  file  new.txt  new1.txt  new2.txt
abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat file
experimenting with ubuntu
abhinavg21@DESKTOP-QULR5HS:~/experiments$ file file
file: ASCII text
abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'echo text >> file_name' is used to add text at the end of an existing file

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ echo lets add more to it >> file
abhinavg21@DESKTOP-QULR5HS:~/experiments$ cat file
experimenting with ubuntu
lets add more to it
abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'cksum file_name' gives a hash value for the file and also the no. of bits the file is occupying.

    abhinavg21@DESKTOP-QULR5HS:~/experiments$ cksum new.txt
3146570867 62 new.txt
abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'sudo' is a command that supposedly stands for 'Super User DO' and implements commands requiring admin rights.

    • 'sudo su' and 'exit' are used to enter and exit root.
    abhinavg21@DESKTOP-QULR5HS:~/experiments$ sudo su
[sudo] password for abhinavg21:
root@DESKTOP-QULR5HS:/home/abhinavg21/experiments# echo success
success
root@DESKTOP-QULR5HS:/home/abhinavg21/experiments# exit
exit
abhinavg21@DESKTOP-QULR5HS:~/experiments$ |
    • 'sudo chmod XYZ file_name' is used to change file mode/permissions. When we use the 'll' command, the first column tells the mode of the correspundinf file, the first alphabet tells if it is a directory, the next three tells the readability, writability and executability of the file for the you, the next three tell the same for friends and the last three tell the same for the other public.
    abhinavg21@DESKTOP-QULR5HS:~/experiments$ ll
total 28
drwxr-xr-x 3 abhinavg21 abhinavg21 4096 May 29 18:50 ./
drwxr-xr-x 4 abhinavg21 abhinavg21 4096 May 29 18:50 ../
drwxr-xr-x 2 abhinavg21 abhinavg21 4096 May 29 17:02 experiments1/
-rw-r--r-- 1 abhinavg21 abhinavg21   46 May 29 18:48 file
-rwxrwx--- 1 abhinavg21 abhinavg21   62 May 29 18:50 new.txt*
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new1.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ sudo chmod 644 new.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ ll
total 28
drwxr-xr-x 3 abhinavg21 abhinavg21 4096 May 29 18:50 ./
drwxr-xr-x 4 abhinavg21 abhinavg21 4096 May 29 18:50 ../
drwxr-xr-x 2 abhinavg21 abhinavg21 4096 May 29 17:02 experiments1/
-rw-r--r-- 1 abhinavg21 abhinavg21   46 May 29 18:48 file
-rw-r--r-- 1 abhinavg21 abhinavg21   62 May 29 18:50 new.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new1.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |
    • 'sudo chown new_owner_name file_name' is used to change the owner of the file which is given by third column of output of 'll'.
    abhinavg21@DESKTOP-QULR5HS:~/experiments$ ll
total 28
drwxr-xr-x 3 abhinavg21 abhinavg21 4096 May 29 18:50 ./
drwxr-xr-x 4 abhinavg21 abhinavg21 4096 May 29 18:50 ../
drwxr-xr-x 2 abhinavg21 abhinavg21 4096 May 29 17:02 experiments1/
-rw-r--r-- 1 abhinavg21 abhinavg21   46 May 29 18:48 file
-rw-r--r-- 1 abhinavg21 abhinavg21   62 May 29 18:50 new.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new1.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ sudo chown root new.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ ll
total 28
drwxr-xr-x 3 abhinavg21 abhinavg21 4096 May 29 18:50 ./
drwxr-xr-x 4 abhinavg21 abhinavg21 4096 May 29 18:50 ../
drwxr-xr-x 2 abhinavg21 abhinavg21 4096 May 29 17:02 experiments1/
-rw-r--r-- 1 abhinavg21 abhinavg21   46 May 29 18:48 file
-rw-r--r-- 1 root       abhinavg21   62 May 29 18:50 new.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new1.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |
    • 'sudo chgrp new_owner_name file_name' is used to change the owner of the file which is given by fourth column of output of 'll'.
    abhinavg21@DESKTOP-QULR5HS:~/experiments$ ll
total 28
drwxr-xr-x 3 abhinavg21 abhinavg21 4096 May 29 18:50 ./
drwxr-xr-x 4 abhinavg21 abhinavg21 4096 May 29 18:50 ../
drwxr-xr-x 2 abhinavg21 abhinavg21 4096 May 29 17:02 experiments1/
-rw-r--r-- 1 abhinavg21 abhinavg21   46 May 29 18:48 file
-rw-r--r-- 1 root       abhinavg21   62 May 29 18:50 new.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new1.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ sudo chgrp root new.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ ll
total 28
drwxr-xr-x 3 abhinavg21 abhinavg21 4096 May 29 18:50 ./
drwxr-xr-x 4 abhinavg21 abhinavg21 4096 May 29 18:50 ../
drwxr-xr-x 2 abhinavg21 abhinavg21 4096 May 29 17:02 experiments1/
-rw-r--r-- 1 abhinavg21 abhinavg21   46 May 29 18:48 file
-rw-r--r-- 1 root       root         62 May 29 18:50 new.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new1.txt
-rw-r--r-- 1 abhinavg21 abhinavg21   65 May 29 14:56 new2.txt

abhinavg21@DESKTOP-QULR5HS:~/experiments$ |

  • 'vi txt_file_name' is used edit the text in vim. More on that in the next section.

VIM

Since it is difficult to show the command do its magic(as shown for bash via code-blocks) in Vim, this section will only conatain a list of command and their usage. VIM allows the following functions:

  • h => to move left
  • j => to move down
  • k => to move up
  • l => to move right
  • i => to enter insertion mode, where it funtions somewhat similar to a normal text editor. It starts editing from the place where cursor was placed
  • a => to enter appending mode. Similar to insertion mode but the editing is started from an alphabet/space/character forward off where the cursor is initially placed.
  • :wq => Save the changes and exit
  • dw => to delete the word before which cursor is placed
  • d$ => to delete the entire line to the right of the cursor
  • 2w => to move cursor 2 words forward (from present position)
  • 3e => to move cursor at the end of the 3rd word (from present position)
  • 0 => to move to the start of the line in which cursor is present
  • ndd => where n is a natural no. To delete the next n lines including the one in which's starting the cursor is placed
  • u => Undo
  • Ctrl+R => Restore
  • rx => where 'x' is any alphabet/character replace the alphabet/character in front of the cursor with 'x'.
  • ce => deleted the entire word in which's front the cursor was placed
  • gg => to move to the start of the file
  • G => to move to the end of the file
  • Ctrl+G => to see your position in the file
  • xG => where x is the line no. you want to go to, hence it takes you there.
  • /abc => where abc is the word uou want to search for, hence it searches for it from top to bottom
  • ?abc => where abc is the word uou want to search for, hence it searches for it from bottom to top