-a lists all files including .[hidden]
-l follows symbolic links

storage drives

parsed into cylinders, heads, sectors (CHS).

broken into 'partitions' for better management.

newer, smarter drives use logical block addressing (LBA) to simplify access.

partitions

each partition numbers its own sectors starting from LBA 0.

each partition contains its own file-system.

different partitions may contain different types of file-systems.

Unix type partitions - one primary feature is the inode table

inode

member of a type of database, the inode table.

each Unix-style partition on a drive has its own inode table

each created file is assigned to a single inode entry

inode contains info about ownership, permissions, file type, size,
and location of storage sectors (LBAs) on storage device.

does NOT contain a file's name.

directory

is a special purpose file

contain filenames and inode numbers of files being listed.

multiple filenames may reference a specific inode on a particular partition.

directory must be readable to list filenames stored.

directory must be executable to retrieve the inode info of a file.

current working directory

default directory used when using a relative path to specify a target file.

or when referencing a file with out any additional path information.

pwd

command that prints the current working directory

echo $PWD prints the current working directory

pwd is both a built-in bash command and a separate program - /bin/pwd.

$PWD is built-in bash variable.

Special file names

Two filenames that always exist in all directory listings.

. - dot, refers to current directory.

.. - double dot, refers to parent directory.

. and .. are relative filenames

. and .. act as links in a doubly linked list

. and .. in root, /, link to root itself.

$HOME - bash variable set on login to your home directory.

~ (tilde_) - bash symbolic reference to $HOME.

~ - quoting the tilde will denature it. (stops working)

   $ echo ~

   /home/hopper/berezin

relative

location of file determined starting from current directory.

filename by itself

commands look in current directory only.




./filename1

look only in current directory

usually same as just filename

may be required by some commands when used as an argument

may be required if file being invoked as a command




./dirA/filename1

look for directory "dirA" in current directory, then look in that directory for target file.




../filename

look in parent of current directory for target file.




../dir2/filename1

goes up 1 level then down into dir2 to look for filename1



• Note directory permissions can block path access.

absolute

filename preceded by full path starting from / (root)

command interpreter can always find the root directory.

/home/hopper/berezin/bin/pingit

cd directory

change-directory - changes the current working directory to one specified in command line argument.

shell built-in

directory has to be a valid directory name for which user has permission to access.

cd, by itself, resets current directory to home directory.

Note : Unix is case sensitive so Dir and dir are 2 different files.

Filename used must not already exist in current directory
User must have write and execute permissions to parent directory, directory new directory will be listed in.

• -m mode - sets permissions, overrides defaults.
  • mkdir -m 700 newdir
  • mkdir -m u=rwx,g=,o= newdir
  
  
• -p - makes parent directories as needed and don't exist.
  • mkdir -p Assns/Assn1

Directory file must be empty
User must have write and execute permissions to parent directory

• -p - remove directory and it's listed parent. All directories in path must be empty.
  • rmdir -p Temp/Bob
  • rmdir Temp/Bob Temp # without option, two steps.