Page Comparison

About File Systems 

So far all the files we've been dealing with have been in your Home directory, which is your personal directory. All Unix systems will provide you with a Home directory of your own.

...

Note that in Unix, and on Macs, directories are separated by forward slash ( / ) characters, unlike Windows where the backslash ( \ ) is used. And the root of all the file systems is that 1st forward slash ( / ).

Finding file systems

So if you're on a new system, how do you know what file systems are available to you? The df (disk free) command will list all the available file systems. As its name suggests, it also shows file system sizes, so it's always good to use df -h (human readable) to see sizes in more readable form. Also, there can be many many file systems available on any given system, so always pipe the output to more.

...

Here the big important file systems are /home1 (7.0T), /scratch (8.1P) and /work (6.8P). There's also /admin (3.5T) but its name suggests that normal users won't be able to access it.

Navigating the file system

Now that we know there are other places, how do we get there? Enter the cd (change directory) command:

...

• On our system, we've arranged that the command prompt "follows you" around the file system.
• On other systems you can use the pwd (present working directory) command to see the full pathname of the directory you're in

Exercise 4-1

What is the full pathname of your Home directory?

...

cd /stor/work/CBRS_unix
cd                          # Back home
cd -                        # Last directory (here /stor/work/CBRS_unix)
cd ~                        # And home again

Relative pathname syntax

Rather than always typing a full pathname (that is, a pathname starting with the / root directory) of where you want to go, you can specify a directory relative to where you are. This is where the special directory names . (single period =  current directory) and .. (double period =  parent of current directory) come in handy.

...

cd                      # make sure you're in your Home directory
pwd                     # where am I now, really? /stor/home/student01
cd ..                   # up one level - now I'm in /stor/home
cd ../work/CBRS_unix/   # change into /stor/work/CBRS_unix using relative syntax
cd ./unix/docs/         # change into the unix/docs sub-directory relative to /stor/work/CBRS_unix
cd ../../fastq/         # go up two levels, then into fastq directory
cd ../../../home/       # change to the /stor/home directory using relative syntax
cd                      # go Home

Pathname wildcards ("globbing")

Since we've seen that a goal of Unix is to type as little as possible, there are several metacharacters that serve as wildcards to represent sets of characters when typing file names. Using these metacharacters is called globbing (don't ask me why ) and the pattern is called a glob.

...

ls *.txt        # lists all files with names ending in ".txt"
ls [a-z]*.txt   # does the same but only lists files starting with a lowercase letter
ls [ABhi]*      # lists all filenames whose 1st letter is A, B, h, or i
ls *.{txt,tsv}  # lists filenames ending in either .txt or .tsv

Exercise 4-2

Design a wildcard that will match the files haiku.txt and mobydick.txt but not jabberwocky.txt in your Home directory.

ls [hm]*.txt
ls {haiku,jabberwocky}.txt 

File attributes

Let's revisit a listing of our Home directory contents. Before we created any files, an ls -l listing looked something like this:

...

Notice I call everything a file, even directories. That's because directories are just a special kind of file – one that contains information about the directory's contents.

Owner and Group

A file's owner is the Unix account that created the file (here student01, me). That account belongs to one or more Unix groups, and the group associated with a file is listed in field 4.

The owner will always be a member of the group associated with a file, and other accounts may also be members of the same group. The Unix group for our class is CCBB_Workshops_1. (To see the Unix groups you belong to, just type the groups command.)

Permissions

File permissions (and some information about the file type) are encoded in that 1st 10-character field. Permissions govern who can access a file, and what actions they are allowed.

...

Exercise 4-3

What are the directory permissions and ownership of /stor/work/CBRS_unix/test? Can you list its contents? Why or why not?

...

Basic file manipulation commands

The basic file manipulation commands are:

...