How to Find a File in Linux

Managing multiple Java versions on Ubuntu is essential for developers working on diverse projects. Different applications often require different versions of the Java Development Kit (JDK) or Java Runtime Environment (JRE), making it crucial to switch between these versions efficiently. Ubuntu provides powerful tools to handle this, and one of the most effective methods is using the update-java-alternatives command. Switching Between Java Versions In this article, the process of switching between Java versions using updata-java-alternatives will be shown. This specialized tool simplifies the management of Java environments by updating all associated commands (such as java, javac, javaws, etc.) in one go.  Overview of Java version management A crucial component of development is Java version control, especially when working on many projects with different Java Runtime Environment (JRE) or Java Development Kit (JDK) needs. In order to prevent compatibility problems and ensure efficient development workflows, proper management ensures that the right Java version is utilized for every project. Importance of using specific Java versions You must check that the Java version to be used is compatible with the application, program, or software running on the system. Using the appropriate Java version ensures that the product runs smoothly and without any compatibility issues. Newer versions of Java usually come with updates and security fixes, which helps protect the system from vulnerabilities. Using an out-of-date Java version may expose the system to security vulnerabilities. Performance enhancements and optimizations are introduced with every Java version. For maximum performance, use a Java version that is specific to the application. Checking the current Java version It is important to know which versions are installed on the system before switching to other Java versions.  To check the current Java version, the java-common package has to be installed. This package contains common tools for the Java runtimes including the update-java-alternatives method. This method allows you to list the installed Java versions and facilitates switching between them. Use the following command to install the java-common package: sudo apt-get install java-common Upon completing the installation, verify all installed Java versions on the system using the command provided below: sudo update-java-alternatives --list The report above shows that Java versions 8 and 11 are installed on the system. Use the command below to determine which version is being used at the moment. java -version The displayed output indicates that the currently active version is Java version 11. Installing multiple Java versions Technically speaking, as long as there is sufficient disk space and the package repositories support it, the administrator of Ubuntu is free to install as many Java versions as they choose. Follow the instructions below for installing multiple Java versions. Begin by updating the system using the following command:   sudo apt-get update -y && sudo apt-get upgrade -y To add another version of Java, run the command below. sudo apt-get install <java version package name> In this example, installing Java version 17 can be done by running:  sudo apt-get install openjdk-17-jdk openjdk-17-jre Upon completing the installation, use the following command to confirm the correct and successful installation of the Java version: sudo update-java-alternatives --list Switching and setting the default Java version To switch between Java versions and set a default version on Ubuntu Linux, you can use the update-java-alternatives command.  sudo update-java-alternatives --set <java_version> In this case, the Java version 17 will be set as default: sudo update-java-alternatives --set java-1.17.0-openjdk-amd64 To check if Java version 17 is the default version, run the command:  java -version The output shows that the default version of Java is version 17. Managing and Switching Java Versions in Ubuntu Conclusion In conclusion, managing multiple Java versions on Ubuntu Linux using update-java-alternatives is a simple yet effective process. By following the steps outlined in this article, users can seamlessly switch between different Java environments, ensuring compatibility with various projects and taking advantage of the latest features and optimizations offered by different Java versions. Because Java version management is flexible, developers may design reliable and effective Java apps without sacrificing system performance or stability.

Linux has an unlimited set of commands to perform assigned tasks. The Linux cp command is the primary tool and the basis for copying and managing files and directories in this operating system. This function is designed to duplicate files or directories in the same or different location. Armed with this functionality, users have advanced capabilities: from creating backup copies to moving files between directories. Linux cp command is simple to learn You can find all the necessary information covered in this tutorial. You will discover how the Linux cp command and cp directory work, as well as its grammatical structures, crucial hints, parameters, settings, and recommended practices. Readers will learn the tricks of the cp command, which will help them become more proficient. You can try our Linux VPS hosting for your projects. The core of the cp command in Linux The functionality of the command allows users to control the creation of copies. One feature offers overwriting existing files, another is responsible for recursively copying a directory with its entire entities, and the third protects the first data for repeating backups. This command demonstrates more features for specific purposes and user experience during the process. A key benefit of the cp command is its exceptional accuracy in duplicating files and directories. You can be absolutely sure that the duplicated files are identical to the original ones with all its interior. Therefore, the user can replicate the original file without any changes. The cp command in Linux inherently tells the user a destination directory for storing copies in a specific repository. The command's precision makes it indispensable for both novice and advanced users. Linux cp syntax This command consists of the following parameters: source file or directory and destination directory. The basic syntax of the Linux cp command is as follows: cp [...file/directory-sources] [destination] Here [file/directory-sources] specifies the files or directories sources to copy, while the [destination] specifies the location to copy the file to. There are the letter flags to specify the way of creation a replica of files and directories: -a leaves the first file attributes the same; -r recursively replicates directories and their interior entities; -v shows copied files in detail; -i requires consent to overwrite the file; -u rewrites new or missing files in the destination directory; -f forcibly copies without user consent; -s makes a symbolic link instead of a file replica; -ra recreates an exact duplicate of a file or directory without changing attributes; -rf updates or changes a file or directory with the original name in the same place; -pv (if installed) monitors and shows the time required to complete copying large folders. How to copy files with the cp command To make a file copy, apply the cp command in Linux as follows: cp ./DirectoryA_1/README.txt ./DirectoryA_2 where ./DirectoryA_1/README.txt is the source file, and ./DirectoryA_2 is the destination. The cp command was originally designed to interact with files. To replicate directories, you must use the -r flag to command that the directory with all its interior entities to be copied recursively. Therefore, you should write cp -r before the directory sources in Linux as follows: cp -r ./DirectoryA_1/Folder/ ./DirectoryA_2 The cp -r command in Linux will recursively duplicate the Folder directory in ./DirectoryA_1/ as well as all contents in the Folder directory. For instance, if you need to replicate the whole file contents in DirectoryA_1 with the .txt extension, try following command: cp ./DirectoryA_1/*.txt ./DirectoryA_2 where ./DirectoryA_1/*.txt matches files with the .txt extension in their names, and the cp command duplicates all those data to the destination. Best practices of the cp Linux command To duplicate one unit of information via the Linux cp command, write down the file name and destination directory. For instance, to replicate a file named example.txt to the 'Documents' directory, try the following command: cp example.txt Documents/ The action leads to creating a file duplicate in the 'Documents' directory with the original name. To copy multiple files at once, utilize the cp command in Linux, specifying the file names separated by a space. For instance, to duplicate three files named 'file1.txt', 'file2.txt', and 'file3.txt' to the 'Documents' directory, try the following command: cp file1.txt file2.txt file3.txt Documents/ To replicate a directory with all its interior entities, apply the -r that means cp recursive feature in Linux. For instance, to duplicate a directory named 'Pictures' to the 'Documents' directory, try the following command: cp -r Pictures Documents/ The action leads to creating a copy of the 'Pictures' directory with all its interior contents in the 'Documents' directory. To replicate a folder in Linux, you should utilize the -r flag. For instance, to duplicate a folder named 'Pictures' from the existing directory to a folder named 'Photos' in the home directory, try the following command: cp -r Pictures/ ~/Photos/ The destination folder will be created automatically if none exists. The files in the destination folder will be combined with the core of the source folder if one already exists. The cp -a feature in Linux leaves unchanged the initial file attributes while copying. Therefore, the duplicates will have the same parameters as their originals. For instance, to replicate a file named 'example.txt' to the 'Documents' directory while leaving unchanged its attributes, try the following command: cp -a example.txt Documents/ The Linux cp -v function showcases the progress of the duplication. At the same time the user can copy large files while monitoring the process. For instance, to replicate a file named 'largefile.zip' to the 'Downloads' directory while watching the progress, try the following command: cp -v largefile.zip Downloads/ The -i option requires the consent before overwriting an initial file. to protect against an accidental file rewriting. For instance, to duplicate a file named 'example.txt' to the 'Documents' directory, if a file with the identical name already exists, the cp command will require the consent before rewriting the original file. Initially, the Linux cp command copies a file or a directory to a default location. The system allows the user to specify any other location for the duplicate file or directory. For instance, to replicate a file named 'example.txt' from the 'Documents' directory to the 'Downloads' directory, try the following command: cp Documents/example.txt Downloads/ The cp -ra function in Linux is designed to carry out the copying process of directories with all their contents inside. The -r flag gives an order to repeat all the files and directories within an existing location, while the -a flag keeps the initial attributes preserved. Therefore, it is possible to make an exact duplicate of a directory without changing attributes. For instance, if you apply the command cp -ra /home/user1/documents /home/user2, it will replicate the 'documents' directory with all its entities inside in the 'user2' directory. The new folder will show the identical attributes as the initial item. The cp -rf feature in Linux is similar to the previous -ra option. The difference between these two functions is that the -f flag rewrites the given files or directories in the destination without requiring consent. Therefore, it is possible to update or replace an item with the identical name in the place of destination. For instance, if you apply the command cp -rf /home/user1/documents /home/user2, and there is already a 'documents' directory in the 'user2' directory, it will be overwritten with the contents of the 'documents' directory from the 'user1' directory. Be careful while utilizing the -rf function. Incorrect use of it leads to data loss. Check up twice the destination folder to avoid unwanted rewriting items. It is simpler to work with files and directories when you use Linux's cp -r capability with the -a and -f settings. Whereas the -rf particle modifies or replaces files and directories, the -ra particle precisely copies a directory and everything within it. You can learn how to handle stuff in this operating system by properly applying these differences. If you want to monitor and control the process of item duplication, which is not possible with other parameters of the cp command, use the -pv utility. To install the pv utility on Debian/Ubuntu you need to open the terminal and run the following command:  apt-get install pv After the installation is complete, verify it by running the following command in the terminal pv --version To install the pv utility on CentOS/Fedora, you need to connect the EPEL repository, which contains additional software packages unavailable in the default repositories. Run in the terminal: yum install epel-release Then run the following command in the terminal:  yum install pv  After the installation is complete, verify it by running the following command in the terminal:  pv --version To use this particle with the cp command, you should utilize | symbol. You can use the ~ symbol to indicate the root directory if the full path needs to be specified. For instance, to replicate a folder named 'Documents' from the root directory to a folder named 'Backup' in the home directory, try the following action: cp -r Documents/ ~/Backup/ | pv Example of executed Linux cp command Conclusion The cp command, although not an inherently difficult tool to learn, nevertheless provides basic knowledge of using the Linux operating system in terms of managing files and directories. In this tutorial, we tried to show the capabilities of the cp command in Linux from all sides, demonstrating best practices and useful tips of its various parameters. With new knowledge, you will be able to improve your skills in interacting with files and directories in Linux. The extreme accuracy of the copying process and additional options allow you to solve a wide range of problems. Multifunctionality helps users choose the file management mode and complete tasks efficiently. The command is a prime example of the many capabilities of this operating system, including the cp with progress feature in Linux. Altogether they unlock a potential of the system for novice and advanced users.

The ls command is essential for navigating the Linux or UNIX file system. To understand how to use it effectively, you need to be familiar with basic navigation in the Linux OS and the additional options available. Now knowing what is ls command in Linux can be frustrating Navigation in Linux Linux distributions have a tree-like file system structure. The root directory, indicated by a slash (/), is at the base and houses all of the OS's data. "Branches" or other directories proliferate from the root directory. You can specify a path to a folder using either a full (absolute) or relative path. A full (absolute) path specifies the location of files and directories starting from the root directory. This path always starts with a slash. Example of a full path: /home/hostman/file1/ A relative path specifies the location of objects relative to the current position (current directory). In the beginning of the address line, you might see: ~ — home directory; . — indicates the current directory; .. — indicates the parent directory. Description of the ls Command The Linux ls command displays information about directories and files located in folders. The command name comes from the word "list." By specifying additional options, you can customize the output format as needed. Syntax of the command: ls [OPTIONS][FILE|FOLDER] In place of [OPTIONS], you specify the desired option and then refer to a file [FILE] or directory [FOLDER]. If you do not specify a directory name, you will get a list of the contents of the directory you are currently working in by default. In some cases, there is no need to enter the folder itself. You can use a simplified version by specifying the path in the context of the ls command: ls /PATH/TO/FILE Methods for specifying the path are described above. Options -a – display all contents of the directory, including hidden files (their names start with a dot). -A – display all files except hidden ones. --author – display the author information. -b – output the file name, even if it contains special characters that are not visible when printed. -B – do not display backup copies. Backup copies are recognized by the tilde ~ at the end of the name. -c – display files sorted by the time of the last modification. By default, new files are listed first. -C – display files in columns. -d – display information about the directory without showing its contents. -f – disable sorting. -F – enable visibility of the object type. The object type can be identified by the assigned symbol at the file name's end. --full-time – display complete information, including time in ISO format. -i – display the inode where the file is located. -l – display a long list with detailed information. -g – similar to the -l option, but without displaying the owner's name. -m – separate list elements with a comma. -1 (one) – display information about only one object per line. -n – output objects' names without quotes. -h – convert file size values to the required format. By default, file sizes are displayed in bytes without specifying the unit of measurement. --color – use or disable coloring of objects when displayed on the screen. You can set variables to three values, one of which is automatic color output: --color=auto/always/never -R – display a list of subdirectories recursively. -S – display sorted files by size, from largest to smallest. -Sr – opposite of the previous command: files are displayed from smallest to largest. -u – sort objects by the time of the last access. -p – if the object is a directory, a slash is displayed at the end of the name. -q – a question mark if NPC control characters are in the file name. -T – set the tab width. By default, it is 8. -w – set the column width. -v – sort by file version number. Using Multiple Options Simultaneously The ls -l command in Linux allows you to display a long list of all folders. It is often combined with other options to show only selective information. ls -lr – display a list of all elements sorted in reverse order; ls -lt – display information according to the last modification date; ls -l --author – display the document's creator. In this way, you can combine most options. In addition to basic files, the ls- la command displays hidden documents starting with a dot in the name. Sorting Files There is a sorting switch that allows you to quickly sort the output by the desired parameter, such as size, time, or version. The syntax of the command is as follows: ls -l --sort=WORD/-x The parameters—size, time, version, and extension—are entered after the equals sign. Alternatively, you can type just the initial letter rather than the entire term. Setting the Output Format for Files When using the ls on Linux, files are arranged in columns by default. To display them vertically, horizontally, or list them with a comma, use the command: --format=WORD/-x (The function is set as a whole word or symbol) Across/-x – arrange files alphabetically by column. Horizontal/-x – sort output horizontally. Vertical/-C – sort output vertically. Commas/-m – list directory contents separated by a comma. Long/-l – output detailed information about files in a long list. Single-column/-1 – arrange all files in one column. Output Format for File Sizes To view file sizes in a specific unit of measurement, use the option: --block-size=SIZE After the equals sign, specify the first letter of the unit of measurement (K, M, G, etc.). In this case, the multiplier is 1024. If you specify kilobytes or megabytes, the multiplier is 1000. For this, you can use the separate option --si. Examples of Using the ls Command Let's see how the Linux ls command is used in practice. Open a terminal window. Run the ls command and specify the path if needed. To navigate directories, use the cd (change directory) command using the syntax: cd [location] Run the command with arguments; otherwise, it will return to the home directory. Use the pwd (Print Working Directory) command to find out the working directory. This command does not use arguments. You can now begin experimenting with the choices that interest you. Examples of what the inputs and output information should look like are shown below. First, enter the command in the terminal window without using arguments. In this case, you will get a list of directories and files in the usual format. ls Output: Videos   file.html lib    DownloadsFile7   Pictures   DirDocuments   020.Pcap   Public Display files in reverse order: ls -r Output: Public 020.Pcap DocumentsDir Pictures File7Downloads lib file.html Videos Next, to display a long list, use the -l option: ls -l Output: drwxr-xr-x. 3 root root 1785 Jun 29 10:11 Videos -rw-r--r--. 2 root root 989 Aug 10 12:38 file.html -rw-r--r--. 2 root root 989 Aug 10 12:38 lib drwxr-xr-x. 4 root root 1580 Jul 16 01:20 Downloads -rw-r--r--. 1 root root 3948 Aug 09 03:01 File7 drwxr-xr-x. 3 root root 5170 May 28 13:40 Pictures drwxr-xr-x. 4 root root 3580 Jun 14 17:45 Dir drwxr-xr-x. 1 root root 28320 Jul 25 10:11 Documents -rw-r--r--. 2 root root 1444 May 27 17:45 020.Pcap drwxr-xr-x. 1 root root 32150 Jun 10 09:58 Public Now let's interpret what was displayed on the screen using the long list option. Column 1: The type of file. If the line starts with a hyphen, it is a regular file. If the line begins with the letter d, it is a directory. Column 2: The next 9 letters and symbols represent access rights to these elements in the file system. The letter r gives the right to read the file, x the right to write to the file, xr the right to execute the file. Column 3: The number indicates how many hard links point to this file. Column 4: Displays the creator of the object and the file group. Column 5: The file size. Column 6: Time data when the last changes were made. Column 7: The name of the element for which information is displayed. Let's work with this list. Now display hidden files using the following option: ls -a Output: .opera  .gconf   .  Videos  file.html.libreoffice lib Downloads .cshrc File7 ..Pictures  .pki Dir 020.Pcap   Public Sort files by last modification date: ls -lt Output: -rw-r--r--. 2 root root 1444 May 27 17:45 020.Pcap drwxr-xr-x. 3 root root 5170 May 28 13:40 Pictures drwxr-xr-x. 1 root root 32150 Jun 10 09:58 Public drwxr-xr-x. 4 root root 3580 Jun 14 17:45 Dir drwxr-xr-x. 3 root root 1785 Jun 29 10:11 Videos drwxr-xr-x. 4 root root 1580 Jul 16 01:20 Downloads -rw-r--r--. 2 root root 989 Aug 10 12:38 file.html drwxr-xr-x. 1 root root 28320 Jul 25 10:11 Documents -rw-r--r--. 1 root root 3948 Aug 09 03:01 File7 -rw-r--r--. 2 root root 989 Aug 10 12:38 lib Test the -F option to find out which objects are directories: ls -F Output: Videos/   file.html    Downloads/File7     Pictures/    Dir/Documents/020.Pcap    Public/ When you finally understood what ls command in linux is Conclusion We reviewed a basic usage of the ls command in Linux for working with the file system. This tool is available in all operating system distributions and is much more efficient than viewing document properties through a graphical user interface. You can try our reliable Linux VPS hosting for your projects.