Q. I’m new to Linux and how do I examine filesystem and identify regular files or directories?

A. Both Linux and UNIX comes with ls command for examining the filesystem. You can use ls command to look at the filesystem. ls command can display:
=> Character devices
=> Regular files
=> Sym links (symbolic links)
=> Directories
=> Pipes
=> Sockets
=> Block devices

ls command examples

Display /etc directory files, enter:
$ ls /etc
When invoked without any arguments, ls lists the files in the current working directory:
$ ls
Use -l (long option) to lists filenames, sizes, permissions, type and all other information:
$ ls /etc/passwd
Output:

-rw-r--r-- 1 root root 2453 Jul 17 16:25 /etc/passwd

See Linux / UNIX file permissions for more information

Directory

A directory is marked with a d as the first letter of the permissions field:
ls -ld /etc
Output:

drwxr-xr-x 88 root root 12288 Aug  5 23:46 /etc

Symbolic link

A symbolic link is marked with an l (lower case L) as the first letter of the permissions string:
ls -l /bin/nisdomainname
Output:

lrwxrwxrwx 1 root root 8 Jul 10 08:50 /bin/nisdomainname -> hostname

Similarly,

• A named pipe is marked with a p as the first letter of the permissions string.
• A socket is marked with a s as the first letter of the permissions string.
• A character device is marked with a c as the first letter of the permissions strings. (ls -l /dev/console)
• A block device is marked with a b (ls -l /dev/sdb1).