The command is most used command (there is not a definite answer out there in the wild and wide expanses of the internet). It stands for ‘ (of course), and is fundamental and indispensable to everyone who at least knows how to open a terminal window. So, I’ve decided to kinda do the basics on the command in this article, what it does, how it works and how can you do some nice hacky stuff with it. cd probably the Linux ‘change directory cd What is the cd command? The command is a built-in shell command that allows users to change their current working directory. A shell command is a function called from the shell which is also executed in the shell itself, instead of an external executable. A shell is… a Unix-based interpreter that provides the command line interface for us to use. An interpreter is… well, this is too low-level to know for the topic at hand, so we’ll ignore it. We need in Linux systems because we are interacting with the computer that runs a Linux or Unix-like system primarily through the command line interface (CLI). We can use cd to traverse the directory tree, move between different directories, and access files. cd cd The following is the syntax: cd cd [option] <directory> On a deeper level works as follows. Unix-like operating systems have a current working directory for every running process. The directory serves as the reference point for any relative file system operations that the process may perform. When we run a command, it starts in the context of the current working directory, which then can be changed using the command. By running we trigger a state change in the running process. The kernel will execute this state change by running the system call (change directory) and set the new working directory for the process. The command takes one or more arguments, which are actually directory paths. We could use absolute paths from the working directory ( ) or relative paths from our current directory ( ). If we don’t provide the argument will default to the home directory. It will check and validate the provided directory path, by checking whether the directory exists, whether the process has permission to access and, and if there are any errors in the process. If errors are found reports an error and doesn’t change the working directory. cd cd cd chdir cd /var/ftp/pub .../music cd cd Some of the most common uses of are following: cd Navigating the File System The most basic and fundamental use of the command. We can utilize it to navigate the file system by moving to a specific directory. The following command changes your working directory to : cd /documents/Invoices cd /documents/Invoices Returning to the Home Directory Also, a common use, with this command we return to our home directory. Simply typing without any arguments is enough. An alternative way to achieve the same thing is typing with Tilda ( ). cd cd ~ cd cd ~ Keep in mind that you can change the base directory by using the command . When the variable is set, you create a search path of directories that will look through to find the directory you specified. This can make navigation more convenient, especially in complex directory structures. export CDPATH=.:~:/etc:/var CDPATH cd Moving to the Parent Directory We also need a way to move up one level in the directory hierarchy, for this we’ll use .. as the argument. cd cd .. Using Relative Paths You can use relative paths to navigate the file system. For example, to move to a subdirectory of your current location. cd documents/my_folder Using Absolute Paths The difference between absolute and relative paths is that absolute paths begin with the root directory -> . The absolute pathname is the path from the root directory to the directory we want to navigate to. When is a good use case for absolute paths? Let us say we are deep into a directory searching for something and we realize, oh we should go to a completely different directory. Instead of repeating to go to the parent directory, we could just write something like this: / .. cd /var/ftp/pub Auto-Completion A helpful feature, autocompletion can save time, and reduce the chance of making typos. We can trigger it by typing just a part of the directory name and pressing the ‘ ‘ key. Tab Using Environment Variables You can use environment variables in the cd command, making it more versatile. The following snippet would navigate us to our home directory (if the home directory variable exists, hint: it should). cd $HOME Tips and tricks Credit where credit is due. Some of these tricks were inspired by the hacks from website. If you haven’t please visit the site for amazing Linux tips. thegeekstuff Using an alias You may find yourself frequently moving up the directory hierarchy to access parent directories. While the trusty command does the job, there’s a more efficient way to achieve this – by creating aliases for commands. cd .. cd In the context of a command-line interface, an alias is a custom-made shortcut or abbreviation for a longer command. We create aliases to make our workload more efficient and faster. When it comes to commands, you can create custom aliases that allow you to move up the directory tree with a single, easy-to-remember shortcut. cd Generally in Bash, you can add aliases to your file. Open it with a text editor and add the following lines to create an alias for moving up one directory level: ~/.bashrc alias ..="cd .."
alias ...="cd ../.."
alias ....="cd ../../.."

cd ..
cd ...
cd .... The first line sets up an alias to move up one directory, the second for moving up two directories, and so on. You can add as many aliases as you want. To reiterate takes you up one directory, takes you up two directories, takes you up three directories, and you can go to infinity. .. ... .... There are alternatives to the method above. For example, using the numbering methodology. alias ..="cd .."
alias ..2="cd ../.."
alias ..3="cd ../../.."

cd ..
cd ..2
cd ..3 alias cd1="cd .."
alias cd2="cd ../.."
alias cd3="cd ../../.."

cd cd1
cd cd2
cd cd3 Create a new directory and cd using a single command In Linux, you can use a combination of commands and operators to perform both (make directory) and (change directory) in a single command. This can be achieved using command chaining with the operator. Here’s an example: mkdir cd && mkdir new_directory && cd new_directory The alternative to combining both and into one command by changing the , and adding the following function mkdir cd .bash_profile code .bash_profile

function mcd() {
    mkdir "$1" && cd "$1"
} Toggling between the last two directories Toggling between the last two directories in Linux using the command is a simple and convenient way to switch back and forth between two locations in the file system. Here’s a step-by-step guide on how to achieve this: cd - # Navigate to the first directory
cd /path/to/first_directory

# Navigate to the second directory
cd /path/to/second_directory

# Toggle between the last two directories
cd -  # Toggles to /path/to/first_directory
cd -  # Toggles back to /path/to/second_directory Now, you can use the command to toggle between the last two directories you visited. This command automatically switches to the previous directory. cd - and together Using find cd We initiate a search starting from the directory, and we look for files based on the option. We search for a file named filename in the directory, and its subdirectories. Next, we come to the option that will extract the directory part of the file’s path for every file found by . Then, when we have found a path the command will change the current working directory to the path found. /path/to/search -type f /path/to/search -exec dirname {} \; find cd cd "$(find /path/to/search -type f -name "filename" -exec dirname {} \;)" Navigate to the Newest Subdirectory Below we have the command that will change the directory to the latest modified subdirectory. With we list all directories, sorting them by modification time, with the newest first. The output is then taken to the pipe, which prints only the first line of the output (in our case it will print the most recently modified directory). Then with we substitute the output and change the working directory to the captured path. ls -td -- */ head -n 1 cd "$( ... )" cd "$(ls -td -- */ | head -n 1)" Conclusion In essence, with we can explore the file system, access files, and in combination with other commands we can even manipulate data and control environments. In the end, it is not a simple/basic command; it is an important system call that handles processes and their interaction with the file system. cd Also published here.

This story contains new, firsthand information uncovered by the writer.

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Mastering the Linux CD Command

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