Heads up! To view this whole video, sign in with your Courses account or enroll in your free 7-day trial. Sign In Enroll
Start a free Courses trial
to watch this video
Command Arguments are all the same to the shell, but there's a type of argument that many commands treat specially: options. Options generally make some small change to the way a command works.
Command Arguments are all the same to the shell, but there's a type of argument that many commands treat specially: options. options generally make some small change to the way a command works.
- Options usually consist of a dash followed by a single letter.
- For example, we can get the
ls
command to display all files, even files that are hidden, by passing it the-a
option as an argument:ls -a
- On Unix-like systems, a file is treated as "hidden" if its file name begins with a dot.
- Now that we've told the
ls
command to list all files, we can see .ninja and .spy files that were hidden previously.
- For example, we can get the
- Here's another option for the
ls
command:-t
, which causes files to be sorted by the time they were created:ls -t
- This shows us that
bird.txt
is the newest file, andstatue.txt
is the oldest. - Most options for a command can be combined. If we pass both the
-a
and-t
options tols
, it will show us all files sorted by time of creation:ls -a -t
- This shows us that the
.ninja
and.spy
files are even newer thanbird.txt
.
- This shows us that
treehouse:~/workspace$ ls -a
. .. bird.txt cart.txt library mall .ninja offices .spy statue.txt
treehouse:~/workspace$ ls -t
mall offices library bird.txt cart.txt statue.txt
treehouse:~/workspace$ ls -a -t
. .ninja .spy mall offices library bird.txt cart.txt statue.txt ..
- Most commands accept options, but the set of options and their meaning varies with each command. The
cat
command, for example, accepts a-n
option that numbers each line of output:cat -n bird.txt cart.txt statue.txt
- Notice that the option is followed by regular arguments giving the file names to print. With most commands, options are given before the command's regular arguments.
treehouse:~/workspace$ cat -n bird.txt cart.txt statue.txt
1 There is a bird here, looking up at the statue with interest.
2 A stand selling hot dogs and bottles of diet cola.
3 A statue of a hunter standing over a dead bear. Creepy.
- It can be hard to remember what those single-letter options stand for, so many commands also support longer option names.
- These begin with a double-dash followed by one or more words.
- For example, the
ls
command lets you use a--all
option instead of-a
to list all files:ls --all
- Not all single-letter options have a longer equivalent, though. For example there is no longer version of
ls
's-t
option, so you'll have to use the abbreviation:ls --all -t
treehouse:~/workspace$ ls --all
. .. bird.txt cart.txt library mall .ninja offices .spy statue.txt
treehouse:~/workspace$ ls --all -t
. .ninja .spy mall offices library bird.txt cart.txt statue.txt ..
Related Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign upRelated Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign up
You need to sign up for Treehouse in order to download course files.
Sign upYou need to sign up for Treehouse in order to set up Workspace
Sign up