bash cd or make dir if not exists with code examples

Bash is a popular shell used in Unix and Unix-like systems. It is a powerful tool that allows users to execute commands and automate tasks on their systems. Working with directories is a common task in Bash, and the cd and mkdir commands are frequently used for this purpose. In this article, we will explore how to automatically create directories if they do not already exist using Bash.

Bash cd Command

The cd command is used to change the current working directory. It is one of the most frequently used commands in Bash, as it allows users to navigate through the filesystem. To use the cd command, simply type cd followed by the directory path that you want to change to. For example, to change to the Documents directory, you would type:

cd Documents

However, sometimes you might want to change to a directory that does not exist yet. In this case, you can use the mkdir command to create the directory and then change to it.

Bash mkdir Command

The mkdir command is used to create directories in Bash. To use the mkdir command, type mkdir followed by the name of the directory that you want to create. For example, to create a directory called my_dir, you would type:

mkdir my_dir

If the directory already exists, the mkdir command will not do anything. However, if you want to make sure that the directory is created even if it already exists, you can use the -p flag. For example, to create a directory called my_dir even if it already exists, you would type:

mkdir -p my_dir

Checking if a Directory Exists

Before we can write a Bash script that automatically creates directories if they do not exist, we need to be able to check whether a directory already exists or not. The easiest way to do this is to use the test command with the -d flag. The -d flag checks whether the given file path is a directory. For example, to check whether the directory my_dir exists, you would type:

if test -d my_dir; then
    echo "my_dir exists"
else
    echo "my_dir does not exist"
fi

This will print my_dir exists if the directory exists and my_dir does not exist if it does not.

Creating a Directory if it Does Not Exist

Now that we know how to check whether a directory exists, we can write a Bash script that automatically creates directories if they do not exist. Here is an example Bash script that creates a directory called my_dir and then changes to it:

#!/bin/bash

if test -d my_dir; then
    echo "my_dir exists"
else
    mkdir -p my_dir
    echo "my_dir created"
fi

cd my_dir

This script first checks whether the directory my_dir exists. If it does, it prints a message saying that the directory exists. If it does not exist, it creates the directory using the mkdir command with the -p flag and then prints a message saying that the directory was created. Finally, it changes to the my_dir directory using the cd command.

Conclusion

In this article, we learned how to automatically create directories in Bash using the mkdir command and how to check whether a directory already exists using the test command with the -d flag. We also wrote a Bash script that creates a directory if it does not already exist and changes to it using the cd command. These techniques can be useful for automating directory creation tasks in Bash scripts.

let's dive deeper into the topics we covered in the previous article.

Bash cd Command

The cd command is a fundamental command in the Bash shell and is used to change the current working directory. When you enter the cd command without any argument, it changes the current directory to the home directory of the user.

You can specify a directory path to change to a specific directory by using the cd command. For example, if you want to change to a directory called Documents, you can use the following command:

cd Documents

If your current directory is /home/user/ and you execute the above command, it will change your current directory to /home/user/Documents/.

You can also use a relative path or an absolute path with the cd command. The following command will change the current directory to the parent directory:

cd ..

The following command will change the directory to an absolute path:

cd /var/www/html

Bash mkdir Command

The mkdir command is used to create directories in Bash. You can create a directory using the mkdir command followed by the directory name. For example, the following command creates a directory called testdir in the current directory:

mkdir testdir

You can also create a directory with a specific permission using the mkdir command. The following command creates a directory with 755 permissions:

mkdir -m 755 testdir

If you want to create a directory with a parent directory that does not exist, you can use the -p flag. The following command creates a directory and all of its parent directories:

mkdir -p /path/to/directory

Checking if a Directory Exists

Before creating a directory, it's important to check if the directory already exists. To check if a directory exists, you can use the test command with the -d option followed by the directory name. The following command will check if the directory Documents exists in the current directory:

if test -d Documents; then
    echo "Directory exists.";
else
    echo "Directory does not exist.";
fi

If the directory exists, the script will print "Directory exists.", otherwise, it will print "Directory does not exist."

Creating a Directory if it Does Not Exist

You may want to create a directory only if it does not exist. To do this, you can combine the mkdir and test commands into a Bash script. The following script creates a directory called testdir if it doesn't already exist:

#!/bin/bash

if [ ! -d "testdir" ]; then
    mkdir testdir
fi

This Bash script checks if the testdir directory exists using the test command. If it doesn't exist, it creates the directory using the mkdir command.

Conclusion

In this article, we learned more about the Bash cd and mkdir commands, as well as how to check if a directory exists using the test command. These Bash commands can be used together to automate tasks like creating directories and changing to them. Understanding these fundamental Bash commands is essential for anyone working with a Unix-like system.

Popular questions

1. What is the cd command used for in Bash?
   Answer: The cd command is used to change the current working directory in Bash.

2. How do you create a directory in Bash?
   Answer: You can create a directory in Bash using the mkdir command followed by the directory name.

3. How do you check if a directory exists in Bash?
   Answer: You can check if a directory exists in Bash using the test command with the -d option followed by the directory name.

4. How can you create a directory only if it does not already exist in Bash?
   Answer: You can create a directory only if it does not already exist in Bash by using a Bash script that checks if the directory exists using the test command, and creates it using the mkdir command if it does not exist.

5. What is the -p flag used for with the mkdir command in Bash?
   Answer: The -p flag is used with the mkdir command in Bash to create a directory and all of its parent directories if they do not already exist.

Tag

DirectoryOps