The ls command

• Looking around in the filesystem can be done by the ls command.

  $ ls
  assignments  README.md
  

• The command comes with many options.

  split=8

  $ ls -F
  assignments/  README.md
  

  Command line options are very typical for UNIX commands. The -F option instructs ls to show directories with the / indicator.

• Command line options can be combined.

  split=8

  \$ ls -a -F
  ./  ../  assignments/  README.md
  
  \$ ls -aF
  ./  ../  assignments/  README.md
  

  The -a option shows all files, including hidden files (which have names starting with .).

  Multiple options can be provided to the command.

• We can show specific files.

  split=8

  \$ ls
  K.png  main  main.c  main.o  Makefile
  

  Here is the list of files in some directory.

  split=8

  \$ ls main*
  main  main.c  main.o
  

  We can use wildcards to selectively show certain files.

  split=8

  $ ls assignments/assignment_1 assignments/assignment_2
  assignments/assignment_1:
  K.png
  
  assignments/assignment_2:
  main  main.c  main.o  Makefile
  

  We can also list the contents of one or more specific directories.

• Each file has many metadata. We can use the -l to indicate we want the long format.

  split=8

  $ ls -l
  total 32
  -rwxrwxr-x 1 kenpu kenpu 16688 Aug 13 13:28 main
  -rw-rw-r-- 1 kenpu kenpu    64 Aug 13 13:12 main.c
  -rw-rw-r-- 1 kenpu kenpu  1672 Aug 13 13:28 main.o
  -rw-rw-r-- 1 kenpu kenpu    66 Aug 13 13:13 Makefile
  

  • total 32 shows that there are 32 blocks consumed.
  • -rw-rw-r-- is the read-write-execute permissions of the file with respect to the user, the group, and everyone.
  • kenpu kenpu is the owner and the owner group.
  • 16688 is the file size in bytes.
  • Aug 13 13:28 is the last modification time.

• We can show the entire subtree of a directory using the recursive option.

  $ ls -R
  .:
  assignments  README.md  reports
  
  ./assignments:
  assignment_1  assignment_2
  
  ./assignments/assignment_1:
  K.png
  
  ./assignments/assignment_2:
  main  main.c  main.o  Makefile
  
  ./reports:
  

• Other useful options:

  1. -1: display in single column.
  2. -h: display in more human friendly format.
  3. -S: sort files from largest to smallest.
  4. ...

More on ls

You can refer to the documentation:

box

https://man7.org/linux/man-pages/man1/ls.1.html