codex-lv2-may-2025

1 | 2 | 3 | Current Level: 4 | 5

Understanding the Structure of a Shell Command

Look at this example:
```
ls -F /
```
This has three parts:
- ls — the command (what to do)
- -F — the option (how to do it)
- / — the argument (what to do it to)
What do each of these mean?
- The command is the name of the tool you want to run.
- The option (sometimes called a flag or switch) changes how the command behaves. Options start with a - (short) or -- (long).
- The argument is what the command should act on — usually a file or folder.
Spaces matter Each part of the command must be separated by a space. This is wrong:
```
ls-F
```
The shell will look for a command named ls-F, which doesn’t exist.
Case matters too Options are case-sensitive. For example:
```
ls -s
```
shows file sizes (in blocks), while:
```
ls -S
```
sorts files by size.
Try it out Navigate to the lesson folder:
```
cd ~/Desktop/shell-lesson-data
```
Then run:
```
ls -s exercise-data
```
This shows the sizes of the files in the exercise-data folder.

Try:
```
ls -S exercise-data
```
This shows the same files, but sorted by size.
Use options and arguments together Try this example using both:
```
ls -F /
```
This lists the contents of the root directory /, and uses -F to show which entries are folders.

Example output:
```
Applications/  Library/  Network/  System/  Users/  Volumes/
```

A shell command can have just a command, or include options, arguments, or both.
The order usually goes:
```
command [options] [arguments]
```
Use clear spaces and correct case to avoid errors.
Some commands work without arguments. Others require them.