Cmd review detail content in file năm 2024
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We now know how to move around the file system and look at the contents of directories, but how do we look at the contents of files? On your laptop, viewing a file is as simple as finding it in the file explorer window and double clicking to open it. As you will have noticed so far, the point and click of the mouse is not very useful when working on the command-line. Instead we will need to equip ourseleves with some helpful commands. Show
cat commandThe easiest way to examine a file is to just print out all of its contents using the command 0. Enter the command followed by the filename, including the path when necessary: The 2 to the screen. What does this file contain? 4 command
6 modifier to see how big the files are. The In the fourth column you wll see the size of each of these files, and you can see they are quite large, so we probably do not want to use the 4 command. Move into our 2 directory and enter the following command: Rather than printing to screen, the 4 command opens the file in a new buffer allowing you to navigate through it. Does this look familiar? You might remember encountering a similar interface when you used the 4 command. This is because 4 is using the 4 command to open up the documentation files! The keys used to move around the file are identical to the 4 command. Below we have listed some additional shortcut keys for naviagting through your file when using 4. Shortcuts for 4 key action SPACE to go forward b to go backwards g to go to the beginning G to go to the end q to quit Use the shortcut keys to move through your FASTQ file, we will explore these files in more detail later in the workshop. Searching files with4 4 also gives you a way of searching through files. Just type in / to begin a search, you will see that the 2 will show up at the bottom of the 4 buffer. Now, enter the name of the string of characters you would like to search for and hit the enter key. The interface will move to show you the location where that string is found, and highlight the string. If you hit / then ENTER, 4 will just repeat the previous search. 4 searches from the current location and works its way forward. For instance, let’s search for the sequence 6 in our file. You can see that we go right to that sequence and can see what it looks like. If you start a search when you are at the end of the file, 4 will not find it. You need to go to the beginning of the file and search. To exit hit q. There are other more sophisticated commands to search through your file (and we will cover these later), but this shortcut search is useful for a quick scan through. You can think of it as being analagous to using the Ctrl-F keystroke when searching on your laptop. 8 and 9 commands There’s another way that we can look at files, and just look at part of them. In particular, if we just want to see the beginning or end of the file to see how it’s formatted. The commands are 8 and 9 and they just let you look at the beginning and end of a file respectively. By default, the first or last 10 lines will be printed to screen. The 2 option can be used with either of these commands to specify the number 3 lines of a file to display. For example, let’s print the first/last line of the file: Exercise
Writing filesWe’ve been able to do a lot of work with files that already exist, but what if we want to write and/or create our own files? Obviously, we’re not going to type in sequence information for a FASTA file, but you’ll see as we go that there are a lot of situations in which we would need to write/create a file or edit an existing file. In order to create or edit files we will need to use a text editor. When we say, “text editor,” we really do mean “text”: these editors can only work with plain character data, not tables, images, or any other media. The types of text editors available can generally be grouped into two categories: graphical user interface (GUI) text editors and command-line editors. GUI text editorsA GUI is an interface that has buttons and menus that you can click on to issue commands to the computer and you can move about the interface just by pointing and clicking. You might be familar with GUI text editors, such as BBEdit, Sublime, and Notepad++, which allow you to write and edit plain text documents. These editors often have features to easily search text, extract text, and highlight syntax from multiple programming languages. They are great tools, but since they are ‘point-and-click’, we cannot efficiently use them from the command line. Command-line editorsWhen working remotely, we need a text editor that functions from the command line interface. With command-line editors you must navigate the interface using the arrow keys and shortcuts, since you do not have the option to ‘point-and-click’. Some popular editors include Emacs, Vim, or a graphical editor such as Gedit. These are editors which are generally available for use on high-performance compute clusters. There are also simpler editors available for use on the cluster (e.g. nano), but tend to have limited functionality. Introduction to VimTo write and edit files, we’re going to use a text editor called ‘Vim’. Vim is a very powerful text editor, and it offers extensive text editing options. However, in this introduction we are going to focus on exploring some of the more basic functions.
Vim InterfaceYou can create a document by calling a text editor (in our case
Change directories to the 3 folder and create a document using called 4 using the 2 command: Note the 6 typed at the bottom left-hand section of the screen. This tells you that you just created a new file in vim. Vim ModesVim has two basic modes that will allow you to create documents and edit your text:
Upon creation of a file, vim is automatically in command mode. Let’s change to insert mode by typing i. Note the 7 at the bottom left hand of the screen. Now type in a few lines of text: After you have finished typing, press esc to enter command mode. Note the 7 has now disappeared from the bottom of the screen.
Saving and QuittingTo “write to file” or save the modifications made to the file, type :w when in command mode. You can see the commands you type in the bottom left-hand corner of the screen. After you have saved the file, the total number of lines and characters in the file will print out at the bottom left-hand section of the screen. Alternatively, we can write to file (save changes) and quit all at once by typing :wq. Now, you should have exited vim and returned back to your command prompt. To edit the newly created 4 file, you can open it again with vim: 0. First, change to insert mode and type a few additional lines (you can move around the lines using the arrows on the keyboard). This time we decide to quit without saving by going into command mode by pressing the key, and then typing :q!.
Shortcuts in VimWhile we cannot point and click to navigate the document, we can use the arrow keys to move around. However, navigating with arrow keys can be very slow, so Vim has shortcuts (which are completely unintuitive, but very useful as you get used to them over time). Create a new file called 1 using 2. Go into insert mode and enter the text as shown below in the screenshot: Once you have finished typing, you can display line numbers by changing to command mode and then typing the :set number command. Later, if you choose to remove the line numbers you can reset it with :set nonumber. key (in command mode) action to number lines to remove line numbers Save the document. Check to see what mode you are currently in. While in command mode, try moving around the file 1 and familarizing yourself with some of these shortcuts! Navigating around the file key (in command mode) action to move to top of file to move to bottom of file to move to end of line to move to beginning of line to move to next word to move to previous word Practice some of the editing shortcuts, then quit the document without saving any changes. Editing the file key (in command mode) action to delete word to delete line to undo to redo to search for a pattern (n/N to move to next/previous match) to search for a pattern and replace for all occurences Exercise We have covered some basic commands in vim, but practice is key for getting comfortable with the program. Let’s practice what we just learned in a brief challenge.
This lesson has been developed by members of the teaching team at the Harvard Chan Bioinformatics Core (HBC). These are open access materials distributed under the terms of the Creative Commons Attribution license (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. How do I view the contents of a file in CMD?In the Windows Command shell, type is a built in command which displays the contents of a text file. Use the type command to view a text file without modifying it. In PowerShell, type is a built-in alias to the Get-Content cmdlet, which also displays the contents of a file, but using a different syntax. What is the command to review the contents of a file?You can also use the cat command to display the contents of one or more files on your screen. Combining the cat command with the pg command allows you to read the contents of a file one full screen at a time. You can also display the contents of files by using input and output redirection. What is the command to display the contents of specific file?The cat command is the simplest way to view the contents of a file. It displays the contents of the file(s) specified on to the output terminal. Sometimes, we might want to number the lines in the output. How to check directory contents in CMD?Run “dir” in Command Prompt to list all of the files and folders in the current directory. Dir also take special arguments to sort and select what kinds of files and folders are displayed. For example, “dir /h” will display hidden files. |
