Helpful command-line tips for Linux users part 3: working with directories - ls

list of all commands

explanation of the convention:

[] : values in square brackets are optional

... : means more elements of that type can be used

ls BASIC USAGE 
ls [option] ... [file] ... - list information about normal [file]s, by default if no options given, you are looking for the file in current directory and sort alphabetically.
for example this will display all files in directory /home/ishtar:

ls /home/ishtar

will show:

bin

Which means that in my home directory I only have one normal (not hidden) directory and no normal files. But really there's more there. For the rest of this entry I am assuming I am in directory /home/isthar so I don't need to specify it next time.

Usually you would like to use several basic options for ls command. And there are more, but the most useful I find are those:

list all files but . and .. (these are in all directories and are used by the system, not much use to normal user).

ls -A

and now suddenly my home directory shows:

.bash_history  bin     .fonts    .mozilla  .vimrc
.bashrc        .emacs  .inputrc  .profile

bold=directory
.name_of_the_file=hidden file

List files in long format

ls -l

will display:

total 4
drwxr-xr-x 2 ishtar users 4096 Feb 17  2014 bin

you see here 7 columns, these are:
drwxr-xr-x file type (here d for directory) and permissions for group (3 letters following d) user (next three letters) and everyone else (last three letters) (w=write, x=execute, r=read, -=no rights)
2 number of hard links
ishtar owner name
users group name
4096 size in bytes
Feb 17 2014 timestamp
bin file/directory/link name
The first line that command produces is total 4 and it is showing you the number of 1kB blocks used by the files in the directory, non-recursively.

List files in long format, but do not list owner

ls -g

When listing files in long format, do not list group

ls -G

Sort by file size

ls -S

Sort by modification time

ls -t

Reverse sort order

ls -r

List one file per line

ls -1

Print sizes in human readable format (e.g., 1K 234M 2G), only makes sense if sizes are displayed, so for long formats only -l, -g and -G

ls -h

Do not sort; list entries in directory order. In combination with one_per_line format '-1', it will show files immediately and it has no memory limitations. Very useful if you're listing very large directories!

ls -U

You can use several options at the same time by combining them into a list starting with -, just like this:

ls -GgAh

This will show you long format list of files with no group and no ., .. directories and with sizes in human readable format:

-rw------- 1   53 Nov  7 13:13 .bash_history
-rw-r--r-- 1 1.2K Feb 17  2014 .bashrc
drwxr-xr-x 2 4.0K Feb 17  2014 bin
-rw-r--r-- 1 1.6K Feb 17  2014 .emacs
drwxr-xr-x 2 4.0K Feb 17  2014 .fonts
-rw-r--r-- 1  861 Feb 17  2014 .inputrc
drwxr-xr-x 2 4.0K Feb 17  2014 .mozilla
-rw-r--r-- 1 1.1K Feb 17  2014 .profile
-rw-r--r-- 1  849 Feb 17  2014 .vimrc

I usually create several aliases in my .bashrc file to speed up traversing through files using the following:

alias la='ls -A'
alias ll='ls -lA'
alias lbig='ll -Sh'
alias lnew='ll -th'

to create lbig command to find the biggest files, and lnew to find the newest ones. As you can see it is simple to combine aliases and options too, so in my system this:

lnew -rG

will display files ordered from the oldest to the newest and will not show me file owner group.