ls command

ls - List

Shows or lists the contents i.e., files and directories of the current working directory.

Usage: ls [OPTION]... [FILE]...

List information about the FILEs (the current directory by default). Sorts entries alphabetically if none of -cftuvSUX nor --sort is specified.

To get help related to the ls command use --help option

$ ls --help
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.

Mandatory arguments to long options are mandatory for short options too.
  -a, --all                  do not ignore entries starting with .
  -A, --almost-all           do not list implied . and ..
      --author               with -l, print the author of each file
  -b, --escape               print C-style escapes for nongraphic characters
      --block-size=SIZE      with -l, scale sizes by SIZE when printing them;
                               e.g., '--block-size=M'; see SIZE format below
  -B, --ignore-backups       do not list implied entries ending with ~
  -c                         with -lt: sort by, and show, ctime (time of last
                               modification of file status information);
                               with -l: show ctime and sort by name;
                               otherwise: sort by ctime, newest first
  -C                         list entries by columns
      --color[=WHEN]         colorize the output; WHEN can be 'always' (default
                               if omitted), 'auto', or 'never'; more info below
  -d, --directory            list directories themselves, not their contents
  ...
  ...
  ... contd..

To read the complete documentation about how to use ls use man pages

$ man ls

Some of the most used ls command options are listed below

• ls - Just using without any options lists the files and directories in the current working directory, often color-coded to distinguish between file types (directories, executables, etc.).

  $ ls
  file1.txt  file2.pdf  folder1  folder2

• ls -r or ls --reverse - Lists content in reverse order while sorting, best used in a scenario where there are huge results for ls to avoid scrolling for the last

  $ ls -r
  folder2  folder1  file2.pdf  file1.txt

• ls -l - Long listing format with file type and permissions, number of hard links, owner name, group name, file size(bytes), last modification time, file/directory name.

  $ ls -l
  total 8
  -rw-r--r-- 1 ubuntu ubuntu    0 Feb 18 17:00 file1.txt
  -rw-r--r-- 1 ubuntu ubuntu    0 Feb 18 17:00 file2.pdf
  drwxr-xr-x 2 ubuntu ubuntu 4096 Feb 18 17:00 folder1
  drwxr-xr-x 2 ubuntu ubuntu 4096 Feb 18 17:00 folder2

  The first part of the long listing (-rw-r--r--) represents file permissions. It's broken down into three sets of three characters:

  • First character: File type (- for file, d for directory, l for symbolic link, etc.)
  • Next three (owner permissions): r (read), w (write), x (execute). - means permission is denied.
  • Next three (group permissions): r (read), w (write), x (execute). - means permission is denied.
  • Last three (others permissions): r (read), w (write), x (execute). - means permission is denied.

• ls -lh - -h or --human-readable - Print the file and directory sizes as kilobytes (kB), Megabytes (MB) or Gigabytes (GB) like 1K 234M 2G etc.

  $ ls -lh
  total 8.0K
  -rw-r--r-- 1 ubuntu ubuntu    0 Feb 18 17:00 file1.txt
  -rw-r--r-- 1 ubuntu ubuntu    0 Feb 18 17:00 file2.pdf
  drwxr-xr-x 2 ubuntu ubuntu 4.0K Feb 18 17:00 folder1
  drwxr-xr-x 2 ubuntu ubuntu 4.0K Feb 18 17:00 folder2

• ls -a - Lists all hidden files, directories without ignoring entries starting with .. Hidden files are usually system files that begin with a full stop or a period

  $ ls -la
  total 20
  drwxr-xr-x  5 ubuntu ubuntu 4096 Feb 18 17:44 .
  drwxr-x--- 24 ubuntu ubuntu 4096 Feb 18 17:00 ..
  drwxr-xr-x  2 ubuntu ubuntu 4096 Feb 18 17:44 .git
  -rw-r--r--  1 ubuntu ubuntu    0 Feb 18 17:00 file1.txt
  -rw-r--r--  1 ubuntu ubuntu    0 Feb 18 17:00 file2.pdf
  drwxr-xr-x  2 ubuntu ubuntu 4096 Feb 18 17:00 folder1
  drwxr-xr-x  2 ubuntu ubuntu 4096 Feb 18 17:00 folder2

• ls -R - List subdirectories recursively

  $ ls -R
  .:
  file1.txt  file2.pdf  folder1  folder2
  
  ./folder1:
  docs
  
  ./folder1/docs:
  node
  
  ./folder1/docs/node:
  
  ./folder2:
  

• ls -n - -n or --numeric-uid-gid like -l, but lists numeric user and group IDs

  $ ls -n
  total 8
  -rw-r--r-- 1 1000 1000    0 Feb 18 17:00 file1.txt
  -rw-r--r-- 1 1000 1000    0 Feb 18 17:00 file2.pdf
  drwxr-xr-x 3 1000 1000 4096 Feb 18 18:14 folder1
  drwxr-xr-x 2 1000 1000 4096 Feb 18 17:00 folder2