P2-7.2 Terminal, Shell, and Working Directory¶

Section ID: P2-7.2 Version: v2026.09.15

Running python example.py involves a shell that interprets the command and a base folder used to locate the file. The same command run from a different folder can fail even when the file exists.

Origins of Terminals and Shells¶

Terminal and shell are not names of recently created apps. Both keep traces of the era when many people used computers through text.

The early terminal was not an app inside a laptop like today. It was an input-output device connected to a central computer. Text-Terminal-HOWTO explains that real text terminals looked like a monitor and keyboard but displayed not pictures but a text-based command-line interface, and that they were widely used for connecting to mainframe computers in the late 1970s and 1980s. Later, real hardware terminals decreased, but today's terminal apps are closer to terminal emulators that imitate that behavior in software.

Shell is also an old concept. The GNU Bash manual explains that Bash is the shell, or command language interpreter, for the GNU operating system. It also explains that a Unix shell is both a command interpreter and a programming language.

Historical terminal devices connect to modern apps as follows.

• past: people entered commands to a central computer through a separate terminal device
• present: terminal apps provide that text-based way of working through software
• shell: the program that interprets and executes the command entered by the user

That is why expressions such as open the terminal, run it in the shell, and type it on the command line remain even in modern development environments. All of these are connected to the flow instead of pressing graphical buttons, enter commands as text and execute them.

Terminal Apps and Shells¶

The terminal is the screen where commands are entered and results are viewed. Terminal on macOS, Windows Terminal, and the Terminal panel in VS Code belong here.

The shell is the program that reads, interprets, and executes the commands entered by the user. Through the shell, the user can run and combine many utilities of the operating system.

Here we distinguish them like this.

• terminal: the window where commands are entered and results are viewed
• shell: the program inside the terminal that reads and executes commands
• command: the thing we ask the shell to do

So even inside the single phrase I opened the terminal, there are several cases.

Current Location, Navigation, and File Lists¶

The sentence entered in the terminal is not a natural-language sentence. It is an execution request that the shell reads according to fixed rules.

For example, the following is a command that checks the current location.

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pwd

The next command moves to a folder.

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cd docs

The next command looks at the file list of the current folder.

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ls

In Windows PowerShell, use Get-Location to check the current location and Set-Location to change it. Aliases such as pwd and cd are also common in PowerShell. Microsoft documentation describes these commands as displaying and setting the current working location.

The same command can target different files when the current folder is different.

Working Directories and Running Files¶

The working directory is the folder currently used as the base by a command. It is also called the current working directory (CWD).

For example, suppose the following command is executed in the terminal.

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python example.py

This command can usually be read as, find the file called example.py in the current working directory and run it with Python. But if there is no example.py in the current working directory, the command fails.

Did it fail because the file does not exist? Not necessarily.

In a common case, the file is not absent. The file exists, but I am in the wrong folder.

A common error begins not from code syntax, but from a location problem. The file may be in downloads/, but the terminal may be in home/. The project folder may be in project-name/, but the terminal may be in its parent folder.

So before practice, we check the current location.

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pwd

Then we move to the needed folder.

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cd /Users/someone/ws/project-name

In Windows PowerShell, you can check it like this.

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Get-Location

And move like this.

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Set-Location C:\Users\someone\ws\project-name

Even if the command names differ, the core is the same.

So first check these two questions.

• In what folder am I now?
• On what folder does this command execute as its base?

Relative and Absolute Paths¶

A path is the string that indicates the location of a file or folder. Here we distinguish relative path and absolute path.

The two terms are distinguished as follows.

• relative path: a location found based on the current working directory
• absolute path: the full location written starting from the beginning of the file system

If the current working directory is /Users/someone/ws/project-name, the relative path docs/parts refers to the docs/parts folder beneath it.

By contrast, an absolute path writes everything from the starting point.

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/Users/someone/ws/project-name/docs/parts

Relative paths are short and convenient. But if the current working directory changes, their meaning changes too.

docs/parts has meaning when executed inside the project-name folder. But if it is executed from another project folder, it points to a completely different location or to a path that does not exist.

Checking File Lists¶

When a command fails, before immediately editing the code, check the current folder and the file list.

In Unix-like shells, the following commands are usually used.

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pwd
ls

In Windows PowerShell, the following commands can be used.

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Get-Location
Get-ChildItem

In PowerShell, ls often works as an alias of Get-ChildItem. But it is still helpful to look once at the original name rather than only the alias. Later, when searching documentation, you can search using the official name.

Shell Commands in a Colab Runtime¶

Colab can also execute commands. But misunderstanding appears if it is understood as exactly the same thing as the local PC terminal.

If you put ! like the following inside a Colab code cell, you can execute a shell command.

Running !pwd in a Colab cell connected to a hosted runtime prints that runtime’s current folder path.

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# This shell command checks the current working folder from a Colab code cell.
!pwd

At that time, the command is executed not on my laptop computer, but in the Colab runtime. So the file location, installed packages, and saved files can differ from the local PC.

In summary, it is as follows.

• terminal of my PC: executed on the basis of my computer's files and environment
• ! command in a Colab code cell: executed on the basis of the Colab runtime's files and environment

! runs shell commands in IPython-based notebooks; it is not syntax for a regular Python file.

Common Terminal Errors¶

Even when terminal errors look complicated, they can be divided into a few types.

When an Existing File Cannot Be Run¶

Suppose a workspace folder contains a project folder with example.py inside it.

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workspace/
└── project/
    └── example.py

If the current working directory is workspace, python example.py looks for workspace/example.py. That file is absent, so it cannot run. Check the file with ls project, then use either method below.

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# Change to project, then run the file.
cd project
python example.py

Or remain in workspace and specify the file’s relative path.

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python project/example.py

Both run the same script, but the working directory differs. If the script reads data using a relative path such as data.csv, the first method looks for project/data.csv, while the second looks for workspace/data.csv. Distinguish locating the script from locating data inside the script.

Keeping a Directory Change in a Notebook¶

IPython runs !cd in a separate shell, so it does not change the notebook kernel’s working directory after that shell exits. Use %cd to change the kernel’s directory. Running the following cell from an existing working directory moves to its parent.

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%pwd
%cd ..
%pwd

Compare the two printed paths to confirm the change. Run %cd - to return to the previous directory. Both %cd and !pwd are IPython syntax and cannot be used in an ordinary .py file.

Checklist¶

• You can explain the terminal as the screen for command input and result checking.
• You can explain the shell as the program that interprets and executes commands.
• You can explain that terminal apps inherited in software the role of older text-based terminal devices.
• You can explain the working directory as the current base location of commands.
• You can explain the difference between relative path and absolute path at an introductory level.
• You can explain why pwd, cd, and ls are needed.
• You know that in PowerShell, official command names such as Get-Location, Set-Location, and Get-ChildItem exist.
• You can explain that the ! command in a Colab code cell is executed in the Colab runtime, not on the local PC.
• You can first check what shell am I using, what folder am I in now, and what file or program is this command trying to find.

Sources and References¶

• David S. Lawyer, Text-Terminal-HOWTO, The Linux Documentation Project, checked 2026-07-20. Used as historical support for the relationship between older text terminals and modern command-line interfaces.
• Free Software Foundation, Bash Reference Manual, GNU Bash 5.3 manual, checked 2026-07-20. Used to confirm that a shell is both a command interpreter and a programming language, and to support the Bash command-processing context.
• Microsoft, Get-Location, PowerShell documentation, checked 2026-07-20. Used to confirm the official PowerShell command for checking the current working location and its pwd alias context.
• Microsoft, Set-Location, PowerShell documentation, checked 2026-07-20. Used to confirm the official PowerShell command for changing the current working location and its cd alias context.

• Python Software Foundation, os.getcwd, Python 3 documentation, checked 2026-07-20. Used to support the point that Python code can read the current working directory as a string.

• IPython magic commands: %cd, Accessed: 2026-09-15.