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We'll admit,

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it's a little difficult to remember
how to use some of these commands.

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It gets better as you get
more practice using them.

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But even experienced shell users
have to look up commands or

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options that they don't use as often.

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Fortunately, it's really easy to look
up program documentation on Unix-like

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systems.

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There's a standard command called man,
short for manual.

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You type the man command name, and

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then the name of the program you
want more info on as an argument.

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For example, let's try bringing
up info on the ls command.

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man sends its output
through the less command, so

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you can use the arrow keys to scroll,
and type Q to quit.

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So I'll run man ls again,
to bring it back up.

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The format of the manual or man page for
every program is different.

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But there are some conventions that
program authors try to follow,

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when writing their documentation.

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The purpose of the program is
usually listed near the top.

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It says the ls program is used
the list directory contents,

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which we know to be true.

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Then it usually lists
arguments the command accepts.

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OPTION means command line options,
like -a or -t.

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And then the ls command accepts
the names of one or more files or

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directories you want to list.

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You don't have to provide
any options to ls, and

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you don't have to provide any filenames.

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That's why both OPTION and
FILE are in square brackets,

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to show that those arguments are optional.

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But ls can also accept more than one
option, and more than one filename.

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That's why there's an ellipsis,

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a set of of three periods,
following both OPTION and FILE.

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Next, you'll usually find a description of
the various options the program accepts.

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Here, you can see the -a option,
or its longer synonym, --all.

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It says, this option tells ls,
do not ignore entries starting with dot.

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We also know this to be true.

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If we run ls with the -a option,

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it reveals files whose
names begin with a dot.

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If we scroll down further, we'll see -l,

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which is an option to use
a long listing format.

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Let's try that, I'll quit out
of the man page and run ls -l.

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It looks like it lists additional
information about each file,

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like the user who created it,
and the date it was created.

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If we scroll down still
further in the man page,

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we'll see the -t option
that we used before.

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It sorts files by the time
they were last modified.

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There are many other options listed here,
some you'll understand, and

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some you won't, and that's okay.

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Manual pages tend to be written
in a very technical style.

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They're intended to be more of
a reminder of how to use a command,

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rather than a tutorial in using it.

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Now, let's take a look at man pages for
a couple other commands.

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Let's start with the rm command.

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We can see at the top that its purpose
is to remove files or directories.

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We can see that it takes one or more
options, or you can skip the option, and

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then it takes one or more files to remove.

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And if we scroll down,
we can see it has a variety of options,

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including the --recursive
option that we used before.

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You can see that there's both
a one-letter -r version,

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as well as a double-dash version,
with the word --recursive.

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Now, let's try bringing up the manual for
the make directory command.

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We can see that its purpose
is to make directories.

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We can see that it takes one or more
options, or no options, if you prefer.

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And you can see that it takes the name
of one or more directories to create.

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And if I scroll down,
you can see it takes a variety of options.

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Including the -p option
that we used before,

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to create the parents of
the directory we're creating.

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It looks like the -p option
also has a synonym, --parents.

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Even expert shell users don't
bother trying to memorize

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every aspect of a command.

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They rely on web searches to help them
learn which commands will solve their

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problems.

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And once they've learned to use a command,

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they rely on the man command to
help them remember the details.

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So feel free to forget the command
options you don't often use.

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Instead, just remember the man command.