Command Line

Manpage Syntax Explained: 5 Baffling Cases Solved 2025

Tired of cryptic manpage syntax? Unlock the command line by learning what `[]`, `|`, and `...` really mean. We solve 5 baffling cases to make you a terminal pro.

Alex Petrov

Senior Linux Systems Engineer with a passion for demystifying the command line.

September 8, 20257 min read17 views

Ever stared at a manpage, trying to decipher a command's options, and felt like you were reading an alien language? You type man grep, and you're met with a SYNOPSIS section that looks something like grep [OPTIONS] PATTERN [FILE...]. All those brackets, pipes, and ellipses can be intimidating. You're not alone.

The truth is, manpages (manual pages) are the definitive, built-in documentation for nearly every command on a Linux or Unix-like system. Learning to read their syntax is a superpower. It's the difference between fumbling with Google searches and confidently constructing complex commands on the fly. In this post, we'll demystify the five most baffling parts of manpage syntax, turning confusion into clarity for 2025 and beyond.

Case #1: The Ubiquitous Square Brackets []

This is the most common symbol you'll encounter, and thankfully, it's the simplest. Anything enclosed in square brackets is optional.

Let's look at the mkdir (make directory) command. Its manpage might show:

mkdir [OPTION]... DIRECTORY...

The [OPTION]... part is in brackets, meaning you don't have to provide any options. You can simply run mkdir my_new_directory, and it works perfectly. The DIRECTORY... part is not in brackets, which tells us you must provide at least one directory name.

The Plot Twist: Nested Brackets

Things get interesting when brackets are nested inside each other. Consider a hypothetical command syntax:

command [-o FILE]

This means the entire group -o FILE is optional. You can't just provide -o. If you use the -o flag, you must also provide its argument, FILE. They are a package deal. If they were written as [-o] [FILE], it would imply that -o is optional, and FILE is also independently optional, which is usually not how flags اقتصادtheir arguments work.

Case #2: The Deceptive Vertical Bar |

If you're used to the command line, you see the pipe symbol | and immediately think of piping the output of one command into another. In a manpage SYNOPSIS, it means something completely different.

Here, the vertical bar means OR. It presents a list of mutually exclusive choices. You can pick one, but not more than one from the group.

A classic example is in the tar command for creating or extracting archives:

tar -c | -x | -t ...

This syntax tells you that you must choose one primary mode of operation: -c (create an archive), -x (extract an archive), or -t (list the contents of an archive). You can't create and extract in the same command. The vertical bar enforces this choice.

When combined with square brackets, it signifies an optional choice. For example:

command [--format=json | --format=xml]

This means you can optionally specify a format, and if you do, it must be either json or xml.

Case #3: The Repeating Ellipsis ...

The ellipsis (...) is your cue for repetition. It means that the preceding item can be specified one or more times.

Let's go back to our mkdir example:

mkdir [OPTION]... DIRECTORY...

The ellipsis after DIRECTORY means you can create multiple directories at once: mkdir dir1 dir2 dir3. The ellipsis after [OPTION] means you can use multiple options, like mkdir -p -v new/nested/dir.

The key distinction is whether the item before the ellipsis is in brackets:

item...: You must provide at least one `item`, and can provide more.
[item]...: You can provide zero or more instances of `item`. It's completely optional, but if you do provide it, you can provide many.

Quick Syntax Summary Table

Before we tackle the last two cases, let's pause and summarize the core symbols in a handy table. This is the Rosetta Stone of manpage syntax.

Symbol	Name	Meaning	Example
`[item]`	Square Brackets	The 'item' is optional.	`ls [FILE]` (The FILE is optional)
`item1 \| item2`	Vertical Bar	Choose exactly one: 'item1' OR 'item2'.	`netstat [-t\|-u]` (Show TCP or UDP)
`item...`	Ellipsis	The 'item' can be repeated.	`rm FILE...` (Remove one or more files)
`{item1\|item2}`	Curly Braces	A required choice: must pick 'item1' OR 'item2'.	`vim {-R \| -v}` (Must be in read-only or vi-mode)

Case #4: The Grouping Curly Braces {}

This one is less common, but powerful. Curly braces {} are used for grouping, and when combined with the vertical bar, they indicate a required choice.

It's like the square bracket and vertical bar combo, but without the option of skipping it. You must choose one of the items.

Imagine a service control script with this syntax:

service-ctl {start|stop|restart}

The curly braces tell you that you cannot just run service-ctl on its own. You are required to supply one of the arguments: start, stop, or restart.

The difference is subtle but crucial:

[a|b]: Optional. You can provide 'a', 'b', or nothing at all.
{a|b}: Required. You must provide 'a' or 'b'.

Case #5: The Meaning of Bold and Underlined Text

Finally, we get to the formatting. This isn't about symbols, but about typographical conventions that are just as important.

Bold text indicates something that should be typed literally, exactly as it appears. This is almost always the command name itself or its flags.

In ls -l --human-readable, the bold parts are the command and the literal flags you type.

Underlined text (or in many modern terminals, italicized text) indicates a placeholder or argument that you, the user, must replace with an actual value.

In cp SOURCE DEST, you don't literally type the word "SOURCE". You replace it with your source file, like cp my_document.txt. DEST is also a placeholder for the destination, like /home/alex/documents/.

So, when you see a synopsis like:

ssh [user@]hostname [command]

You now know:

ssh must be typed literally.
[user@] is an optional group. If you use it, you replace user with a real username.
hostname is a required placeholder. You must replace it with a server's address.
[command] is an optional placeholder. You can optionally provide a command to run on the remote host.

Key Takeaways: Your Manpage Cheat Sheet

Mastering manpages is a journey, but you've just taken a massive leap forward. The next time you're faced with a SYNOPSIS, you'll see a helpful guide, not a cryptic puzzle. Just remember these core rules:

✅ [] (Brackets): It's optional. You can leave it out.
✅ | (Bar): It's a choice. Pick one or the other.
✅ ... (Ellipsis): It's repeatable. Use one or more.
✅ {} (Braces): It's a required choice. You MUST pick one.
✅ Bold Text: Type it exactly as shown.
✅ Underlined/Italic Text: Replace it with your own value.

Now, go forth and man all the things! The command line is your oyster.