File path handling in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What function in MATLAB is used to join folder names and file names into a full file path?

The fullfile function joins folder names and file names into a full file path that works across different operating systems.

beginner

How do you get the folder path from a full file path in MATLAB?

Use the fileparts function. It splits a full file path into folder path, file name, and extension.

beginner

What is the difference between pwd and cd in MATLAB?

pwd returns the current folder path as a string. cd changes the current folder to a new path.

intermediate

Why should you use fullfile instead of manually concatenating strings with slashes?

fullfile automatically uses the correct file separator for your operating system, avoiding errors and making your code portable.

intermediate

How can you check if a file or folder exists at a given path in MATLAB?

Use the exist function with the path string. It returns different codes for files, folders, or if the path does not exist.

Which MATLAB function combines folder and file names into a full path correctly?

A fullfile

B strcat

C joinpath

D pathjoin

fullfile is the correct function to join parts of a file path in MATLAB.

What does the fileparts function return when given a full file path?

A Only the file extension

B Only the file name

C Only the folder path

D Folder path, file name, and extension

fileparts splits a full path into folder, file name, and extension.

Which function returns the current working directory in MATLAB?

A cd

B pwd

C dir

D ls

pwd returns the current folder path as a string.

Why is it better to use fullfile instead of manually adding slashes?

A It is faster

B It adds extra security

C It automatically uses the correct file separator for your OS

D It compresses the path

fullfile ensures your path works on Windows, Mac, or Linux by using the right separator.

How can you check if a folder exists at a path in MATLAB?

A Using <code>exist</code> with a code for folder

B Using <code>isfolder</code>

C Using <code>dir</code>

D Using <code>fileparts</code>

The exist function returns 7 if the path is a folder.

Explain how to build a full file path from folder and file names in MATLAB and why this method is preferred.

Think about how different computers use different slashes.

Describe how to extract the folder, file name, and extension from a full file path in MATLAB.

This function splits the path into three parts.

Practice

1. What does the MATLAB function fullfile do?

easy

A. Joins folder and file names into a full file path safely

B. Splits a full file path into folder, name, and extension

C. Reads the contents of a file

D. Deletes a file from the disk

Solution

1. Step 1: Understand the purpose of fullfile

   fullfile is used to combine folder and file names into one complete path, handling different operating systems correctly.

2. Step 2: Compare with other functions

   fileparts splits paths, reading or deleting files are unrelated to fullfile.

3. Final Answer:

   Joins folder and file names into a full file path safely -> Option A

4. Quick Check:

   fullfile joins paths [OK]

Hint: Remember: fullfile combines parts into one path [OK]

Common Mistakes:

• Confusing fullfile with fileparts
• Thinking fullfile reads or deletes files
• Assuming fullfile only works on Windows

2. Which of the following is the correct syntax to split a full file path into folder, name, and extension in MATLAB?

easy

A. [folder, name, ext] = fileparts(path);

B. [folder, name, ext] = splitfile(path);

C. split(path, folder, name, ext);

D. fileparts = [folder, name, ext](path);

Solution

1. Step 1: Recall the correct function name and syntax

   The MATLAB function to split a path is fileparts, and it returns folder, name, and extension as outputs.

2. Step 2: Check the syntax format

   The correct syntax uses square brackets for multiple outputs: [folder, name, ext] = fileparts(path);

3. Final Answer:

   [folder, name, ext] = fileparts(path); -> Option A

4. Quick Check:

   fileparts splits path correctly [OK]

Hint: Use square brackets and fileparts to split paths [OK]

Common Mistakes:

• Using wrong function name like splitfile
• Incorrect output assignment syntax
• Trying to call fileparts like a variable

3. What is the output of the following MATLAB code?

fullPath = fullfile('C:', 'Users', 'Documents', 'file.txt');
[folder, name, ext] = fileparts(fullPath);
disp(folder)

medium

A. file.txt

B. C:\Users\Documents

C. C:/Users/Documents/file.txt

D. Documents

Solution

1. Step 1: Understand fullfile output

   fullfile joins parts into a full path: 'C:\Users\Documents\file.txt' (Windows style).

2. Step 2: Use fileparts to split the path

   fileparts splits into folder = 'C:\Users\Documents', name = 'file', ext = '.txt'.

3. Final Answer:

   C:\Users\Documents -> Option B

4. Quick Check:

   fileparts folder output = C:\Users\Documents [OK]

Hint: fileparts(folder) excludes file name and extension [OK]

Common Mistakes:

• Expecting file name or extension as folder output
• Confusing path separators (\ vs /)
• Thinking fullfile returns a list instead of string

4. Identify the error in this MATLAB code snippet:

path = fullfile('folder', 'subfolder', 'file.txt');
[folder, name, ext] = fileparts(path);
disp(name)

medium

A. The fullfile function cannot join more than two parts

B. The function fileparts requires three output variables, not one

C. There is no error; the code runs correctly and displays 'file'

D. Variable path is a reserved word and should not be used

Solution

1. Step 1: Check variable naming

   Although path is a common variable name, it is not reserved in MATLAB and can be used safely.

2. Step 2: Verify function usage

   fileparts can return multiple outputs, but it also works correctly with three outputs as shown. fullfile can join multiple parts, more than two.

3. Final Answer:

   There is no error; the code runs correctly and displays 'file' -> Option C

4. Quick Check:

   Code runs and shows file name [OK]

Hint: Check if code runs before assuming errors [OK]

Common Mistakes:

• Thinking path is a reserved keyword
• Believing fullfile only joins two parts
• Assuming fileparts needs different syntax

5. You want to create a MATLAB script that saves a file named data.csv inside a folder results located in the current working directory. Which code snippet correctly creates the full path to save the file, regardless of the operating system?

hard

A. savePath = ['results' filesep 'data.csv'];

B. savePath = strcat('results\', 'data.csv');

C. savePath = 'results/data.csv';

D. savePath = fullfile(pwd, 'results', 'data.csv');

Solution

1. Step 1: Understand the need for OS-independent path

   Using fullfile with pwd (current folder) ensures the path works on Windows, Mac, or Linux.

2. Step 2: Analyze each option

   savePath = ['results' filesep 'data.csv']; uses filesep but misses pwd so path is relative; savePath = 'results/data.csv'; uses forward slash which may fail on Windows; savePath = strcat('results\', 'data.csv'); uses backslash manually which is error-prone.

3. Final Answer:

   savePath = fullfile(pwd, 'results', 'data.csv'); -> Option D

4. Quick Check:

   fullfile + pwd = OS-independent full path [OK]

Hint: Use fullfile with pwd for safe full paths [OK]

Common Mistakes:

• Hardcoding slashes instead of using fullfile
• Not including current directory with pwd
• Using strcat which ignores path separators