How to run commands in Linux?
How to run commands in linux? A complete technical guide
Linux is a operating system Widely known for its power and flexibility. One of its most notable features is its use of commands on the command line, which allow you to perform various tasks efficiently and fast. For those who are new to the world of Linux, or simply want to deepen their knowledge, it is essential to understand how to execute commands in this environment. In this complete technical guide, we will explore the basics and advanced concepts so that you can use commands in Linux effectively and make the most of this powerful tool. Get ready to enter the world of the terminal and discover everything that Linux has to offer you!
1. Introduction to command execution in Linux
Running commands in Linux is an essential skill for any system administrator or advanced user. In this post, I will introduce you to the basics of executing commands in and operating system Linux.
On Linux, you can execute commands using the terminal, also known as the command line. The terminal allows you to interact directly with the operating system and execute commands to perform different tasks, such as managing files and directories, installing software, or configuring the system.
Some of the most common commands used in Linux include cd (to change directories), ls (to list files and directories in a directory), mkdir (to create a new directory), and rm (to delete files and directories). . In this post, we will explore several fundamental commands, learn their syntax, and how to use them to solve common tasks in Linux.
2. Basic commands to run on Linux
In Linux, there are a series of basic commands that are essential to manage the operating system efficiently. These commands allow you to execute various actions, such as accessing directories, managing files, managing processes, among others. Below are the most important basic commands:
1. cd: This command is used to change directories. For example, if we want to access the "Documents" directory, we simply have to run "cd Documents". Also, to go back to the previous directory, you can use "cd .."
2.ls: With the "ls" command we can list the contents of a directory. If we want to show all files, including hidden ones, we can execute "ls -a". It is also possible to use different options to customize the output of the results, such as "ls -l" to display detailed file information.
3. cp: The "cp" command allows us to copy files or directories. To copy a file to another directory, we must execute “cp file source directory destination”. For example, if we want to copy the file “documento.txt” from the “Documents” directory to the “Backup” directory, the command would be “cp document.txt Documents Backup”. Additionally, it is possible to use different options to specify the behavior of the command, such as "cp -r" to copy directories recursively.
3. How to run commands on the Linux command line
On the Linux command line, you can run commands to perform various tasks on your operating system. Below is detailed .
1. Open a terminal: First, you need to open a terminal on your system. You can do this by searching for “terminal” in the start menu or by using the shortcut Ctrl keyboard + Alt + T.
2. Know the basic commands: There are numerous commands available on the Linux command line, but it is helpful to start with some basic commands. Some examples are:
- ls- Lists the files and directories in the current directory.
- cd: Change the current directory.
- mkdir: Create a new directory.
- rm: delete files or directories.
- cp: Copy files and directories.
3. Use commands with options: Many commands have options that allow you to modify their default behavior. To use an option, you usually add a hyphen followed by a letter or word to the command. For example, the "ls -l" command displays files and directories in a long list format, providing additional information such as permissions and owners.
Remember that it is important to be careful when executing commands on the Linux command line, as some commands can have irreversible effects. Always review the specific documentation for each command before using it and make sure you understand how it works. Additionally, you can find online tutorials and detailed documentation for each command, helping you learn more and take full advantage of the power of the Linux command line.
4. Executing commands using the Linux terminal
One of the advantages of using the Linux terminal is the ability to execute commands efficiently and fast. In this section, you will learn how to perform this task Step by Step y an effective form. By using the terminal, you can perform a variety of functions, such as managing files and directories, installing and uninstalling programs, and configuring different aspects. of the operating system.
The first step to execute commands in the Linux terminal is to open it. You can do this by clicking on the terminal icon in the taskbar or by using the keyboard shortcut Ctrl + Alt + T. Once opened, you will see a blank command line where you can enter your commands. It is important to note that commands in Linux are case sensitive, so you need to make sure you type them correctly.
Below I will provide you with some examples of common commands and how to use them in the Linux terminal. To list the files and directories in the current directory, you can use the command ls. To change the directory, use the command cd followed by the name of the directory you want to access. If you want to create a new folder, you can use the command mkdir followed by the name you want to give the folder.
5. Using keyboard shortcuts to execute commands in Linux
Using keyboard shortcuts to execute commands in Linux can save time and increase efficiency in completing tasks. Keyboard shortcuts are key combinations that allow you to execute commands without having to type them completely. Here we will show you some of the most useful keyboard shortcuts in Linux.
1. Ctrl+C: This shortcut allows you to interrupt the execution of a command in the terminal. It is especially useful when a command is in an infinite loop or is taking too long to execute.
2. Ctrl+Z: With this key combination, you can suspend the execution of a command and put it in the background. You can resume running the command in the background by using the “bg” command followed by the suspended job number.
3. Ctrl+D: This shortcut allows you to close the terminal or end data entry in a command that waits for user input. You can also use "exit" to close the terminal.
6. How to run commands with superuser privileges in Linux
To run commands with superuser privileges on Linux, there are several options available. Here are three common methods:
1. Using the sudo command: The command sudo allows users to execute commands with superuser privileges. To use it, simply type sudo followed by the command you want to run. For example, to install a package with root privileges, you can type: sudo apt-get install nombre-paquete. The password of the current user will be requested before executing the command.
2. Using the su command: The command su It also allows you to change the user to superuser or root. To use it, type su in the terminal and then the root password. Once authenticated, you will be able to execute commands with superuser privileges without typing sudo before each command.
3. Using the sudoers permissions policy: On Linux, it is possible to configure the sudoers permissions policy sudoers to allow users to execute specific commands without prompting for the superuser password each time. This is done by editing the file /etc/sudoers with the command sudo visudo. Within this file, you can specify the commands and users allowed without requiring authentication.
7. Run commands in Linux using scripts and batch files
In Linux, it is possible to execute commands automatically using scripts and batch files. These scripts are text files that contain a sequence of commands that are executed in a specific order. This functionality is especially useful when working with repetitive tasks or multiple actions that must be performed in a certain order.
To run a script on Linux, we must first create the text file with the commands we want to execute. We can use any text editor, such as vi or nano, to create and edit the file. Make sure the file has execute permissions enabled with the command chmod +x nombre_del_script.sh. Once the file is ready, we can run it using the command ./nombre_del_script.sh.
It is important to note that scripts in Linux can include simple commands or combinations of more complex commands. Additionally, it is possible to include comments in the script using the symbol #. This makes the code easier to understand and maintain. It can also be useful to add arguments to scripts to make them more flexible and reusable. To pass arguments to a script, we simply add them after the script name when running it, separated by spaces.
8. Using variables and arguments when executing commands in Linux
It is a fundamental skill to optimize and automate tasks in the operating system. By using variables, we can store information that can be reused in different commands, which is very useful to avoid repeating values and simplify our workflow.
To define a variable in Linux, we use the following format: variable=value. For example, if we want to store the current directory in a variable called "current_dir", we would write current_addr=$(pwd). To access the value of a variable, we use the dollar symbol followed by the variable name, such as $current_dir.
Arguments, on the other hand, are values that are passed to a command when it is executed. They are typically used to provide additional information or modify the behavior of the command. The arguments are passed after the command name, separated by spaces. For example, to list the files in a directory in detail, we use the command Ls -lWhere -l is an argument that indicates that we want to see the information in detailed format.
In short, it allows us to simplify and automate tasks, avoiding the repetition of values and giving us greater flexibility. Through the definition of variables and the use of arguments, we can optimize our workflow and achieve more efficient results. Remember that variables are defined with the format variable=value and are accessed using the dollar symbol followed by the variable name ($variable). Arguments are passed when executing a command and are separated by spaces.
9. Executing remote commands on Linux via SSH
To execute remote commands on Linux via SSH, we first need to ensure that the SSH server is configured and running on the remote system. If not, we will have to install the OpenSSH package and enable the service. Once this is done, we can access the remote system using the SSH command line tool.
To execute a remote command on the Linux system, we simply open a terminal and use the following command:
ssh usuario@direccion_ip_computadora comandoremoto
In this command, user is the username on the remote system and computer_ip_address is the IP address or hostname Computer remote. remote command is the command that we want to execute on the remote system.
When the SSH connection is established, we will be prompted to enter the remote user's password. After entering the password correctly, the remote command will be executed on the remote system and we will see the output in our local terminal.
10. How to run commands in the background on Linux
In Linux, we often need to execute commands in the background to perform tasks without interruption. This can be useful when we want to run long programs or perform continuous tasks. Here we will show you step by step.
1. Run the command you want to run in the background. For example, if you want to run a script called "my_script.sh", simply type:./mi_script.sh
2. To run the command in the background, use the “&” symbol at the end of the command. For example:./mi_script.sh &
3. Now the command will run in the background, which means you can continue using the terminal for other tasks while the command runs in the background. If you want to check the status of the command in the background, you can use the following command:jobs
11. Working with input and output redirection when executing commands in Linux
In Linux, working with input and output redirection when executing commands can be extremely useful for automating tasks and improving efficiency in information management. Input and output redirection allows you to redirect the flow of data to and from different sources, such as files, devices, or even another command. Below are the steps necessary to use this functionality:
1. Output Redirection: To redirect the output of a command to a file>>, the "" symbol is used followed by the name of the file where you want to save the output. For example, the command “ls files.txt” will generate a file called “files.txt” containing the list of files in the current directory. It is important to note that if the file already exists, its contents will be replaced by the new output.
2. Input Redirection: To redirect the input of a command from a file, the symbol «<" followed by the file name is used. For example, the command "sort < data.txt" will sort the lines in the file "data. txt". This is useful when you need to process information stored in a file instead of entering it manually. 3. Pipelines: Pipelines allow you to combine multiple commands and redirect the output of one to the input of another. The symbols "|" are used. to connect the commands. For example, the command "cat file.txt | grep word" will display on the screen the lines of the file "file.txt" that contain the word "word". With pipelines you can perform complex operations and achieve more precise results. Input and output redirection is an advanced functionality in Linux that It can be very useful in various situations. With its understanding and correct use, you can automate tasks, process large volumes of information and improve efficiency in system administration. It is advisable to explore more examples and tutorials to understand this powerful functionality in greater detail. .
12. Using wildcards and regular expressions when executing commands in Linux
In the Linux environment, wildcards and regular expressions are powerful tools for searching and manipulating text in command execution. Wildcards are special characters that represent one or more characters, while regular expressions are patterns that allow you to search and match text in sophisticated ways.
To use wildcards in a command, two main wildcards are usually used:
- * (asterisk): Represents any number of characters, including no characters.
- ? (question mark): Represents exactly one character.
For example, if we want to search for all files ending in ".txt" in a directory, we can use the command ls *.txt. This would list all files whose names have any set of characters followed by ".txt."
13. How to execute commands within graphical applications in Linux
If you need to execute commands within graphical applications in Linux, there are several options you can use. One of them is through the terminal. To do this, you must first open the terminal by typing Ctrl+Alt+T on your keyboard. Then you can use the command xdotool to send keystrokes or click elements of the application interface. This can be useful if you want to automate repetitive tasks or perform specific actions within a graphical application.
Another option is to use tools like xte o xdotool to simulate keyboard and mouse interaction in graphical applications. These tools allow you to send keystrokes, click buttons, and drag elements within an application's interface. To use these tools, you must first install them on your system and then learn their syntax and specific commands.
Finally, it is also possible to use automation interfaces such as Sikuli, which allow you to interact with graphical applications using images instead of commands or scripts. With Sikuli, you can capture images of an application's interface elements and write scripts that interact with them automatically. This is a pretty powerful option if you need to perform complex interactions within a graphical application on Linux.
14. Solving common problems when executing commands in Linux
When using commands in Linux, you may run into some common problems. Here we present some step-by-step solutions to solve these problems:
1. Command not found: If you receive a "command not found" message when running a command at the command line, first check that you entered the command correctly. If the command is spelled correctly and still displays the error message, it is possible that the command is not installed on your system. In this case, you can use your Linux distribution's package manager to install the package containing the command. For example, if you are using the APT package manager, you can run the command sudo apt-get install nombre_del_paquete to install it.
2. Permission denied: If you receive a "permission denied" message when trying to execute a command, it is likely that you do not have sufficient permissions to execute it. On Linux, some commands require superuser privileges. To fix this problem, you can use the command sudo before the command in question. This will allow you to run it with superuser privileges. For example, if you need to restart the network service, you can run sudo systemctl restart network.
3. Syntax error: If you receive a syntax error message when you run a command, carefully check the command syntax. Make sure all arguments and options are written correctly and in the proper order. If you are not sure how to use a specific command, you can use the option -h o --help to obtain information about its use. For example, if you want to know the syntax of the command grep, you can execute grep --help for details on how to use it correctly.
In conclusion, we have explored various ways to execute commands in Linux and learned how to make the most of the power of the command line. From simply running a program to automating complex tasks, Linux offers a wide range of tools and commands to meet the needs of any user.
Here we have discussed some of the fundamental commands like `cd` to navigate between directories, `ls` to list files and directories, and `mkdir` to create new directories. We've also explored how to use pipes to combine the output of one command with the input of another, and we've learned how to run programs in the background using `&`.
Additionally, we've seen how to use wildcards to specify file patterns, how to search for text within files with `grep`, and how to redirect both the input and standard output of commands. We have also briefly introduced the use of environment variables to customize system settings.
We hope this article has given you a basic but solid understanding of how to execute commands in Linux. As you become more familiar with the command line, you will realize that it is an extremely powerful and efficient tool for managing your operating system.
Remember to practice regularly and explore more commands and options available on your Linux distribution. As you experiment and gain experience, you will discover new ways to maximize your productivity and efficiency in your Linux environment. Don't hesitate to immerse yourself in the world of the command line and take full advantage of the advantages it offers!