mkdir folderName
mkdir [option] folderName

This page shows you how to create new folders and directories on Linux or Unix-like system using the command line option.

How to create a new folder named foo

Open the Terminal app and type the following command:
mkdir foo
To see directory listing use the ls command:
ls
ls -l
You can simultaneously create any number of folders/directories:
mkdir dir1 dir2 dir3 dir_4
Verify it:
ls -l

drwxr-xr-x 2 vivek vivek  4096 Aug  7 20:57 dir_4

1. drwxr-xr-x – The file mode (see below for file mode).
2. 2 – Number of links
3. vivek – The owner name
4. vivek – The group name
5. 4096 – The number of bytes in the file
6. Aug 7 20:57 – The date when the file was last modified
7. dir_4 – File/dir name path

More on file mode

The entry type character describes (the first character drwxr-xr-x) the type of file, as follows:

1. - : Regular file.
2. b : Block special file.
3. c : Character special file.
4. d : Directory.
5. l : Symbolic link.
6. p : FIFO.
7. s : Socket.
8. w : Whiteout.

So basically d character in above entry tell us that it is a directory/folder. The next three fields are three characters ach: owner permissions, group permissions, and other permissions. Each field has three character positions:

	   1.	If r, the file is readable; if -, it is	not readable.
 
	   2.	If w, the file is writable; if -, it is	not writable.
 
	   3.	The first of the following that	applies:
 
		      S	    If in the owner permissions, the file is not exe-
			    cutable and	set-user-ID mode is set.  If in	the
			    group permissions, the file	is not executable and
			    set-group-ID mode is set.
 
		      s	    If in the owner permissions, the file is exe-
			    cutable and	set-user-ID mode is set.  If in	the
			    group permissions, the file	is executable and set-
			    group-ID mode is set.
 
		      x	    The	file is	executable or the directory is search-
			    able.
 
		      -	    The	file is	neither	readable, writable, exe-
			    cutable, nor set-user-ID nor set-group-ID mode,
			    nor	sticky.	 (See below.)
 
		These next two apply only to the third character in the	last
		group (other permissions).
 
		      T	    The	sticky bit is set (mode	1000), but not execute
			    or search permission.  (See	chmod(1) or
			    sticky(7).)
 
		      t	    The	sticky bit is set (mode	1000), and is search-
			    able or executable.	 (See chmod(1) or sticky(7).)

How to create a new directory named bar

Open the Terminal app and type the following command but pass the -v option to get visual confirmation about your folder/directory name:
mkdir -v foo
Sample outputs:

mkdir: created directory 'foo'

How to make parent folder if needed

The syntax is:
mkdir -p dir1/dir2
mkdir -p parent/child
mkdir -p pictures/vacations
ls -l
ls -l pictures

How to make a folder/directory and set permissions on it

New directories are by default created with the read, write and execute permissions. Pass the -m option to directory to set the the permissions of new directories:
mkdir -m {permissions} {dirName}
mkdir -m 777 delta
ls -l
To create a directory named delta for which all three types of permissions were enabled for all users, the sequence 777 would be added after the -m as above. More information about mkdir can be obtained from the mkdir man page:
man mkdir
Or
mkdir --help
Sample outputs:

Usage: mkdir [OPTION]... DIRECTORY...
Create the DIRECTORY(ies), if they do not already exist.
 
Mandatory arguments to long options are mandatory for short options too.
  -m, --mode=MODE   set file mode (as in chmod), not a=rwx - umask
  -p, --parents     no error if existing, make parent directories as needed
  -v, --verbose     print a message for each created directory
  -Z                   set SELinux security context of each created directory
                         to the default type
      --context[=CTX]  like -Z, or if CTX is specified then set the SELinux
                         or SMACK security context to CTX
      --help     display this help and exit
      --version  output version information and exit

To delete the directory, use the rmdir command/rm command.