Linux/C2/Working-with-Regular-Files/English-timed
From Script | Spoken-Tutorial
Time | Narration |
00:00 | Welcome to this spoken tutorial on Working with Regular Files in Linux. |
00:07 | Files and directories together form the Linux File System. |
00:13 | In a previous tutorial, we have already seen how to work with directories. You can find the tutorial at this website. |
00:25 | In this tutorial, we will see how to handle regular files. |
00:31 | We have already seen in another tutorial how we can create a file using the 'cat' command. For details, please visit this website. |
00:46 | Let us see how to copy a file from one place to another. For this we have the 'cp' command. |
00:55 | Let us see how the command is used. |
01:00 | To copy a single file, we type: cp space one or more of the [OPTIONS]... space the name of the SOURCE file space the name of the destination file (DEST). |
01:15 | To copy multiple files at the same time,
We write cp space one or more of the [OPTIONS]...the name of the SOURCE files that we want to copy and the name of the destination DIRECTORY in which these files would be copied. |
01:34 | Let us now see an eg.First we open a terminal. |
01:42 | We already have a file named 'test1' in our home directory. |
01:49 | To see what is in test1, we type:$ cat space test1 and press Enter. |
02:00 | As we can see, the content of test1 is shown. Now if we want to copy it into another file called 'test2' we would write:
$ cp space test1 space test2 and press Enter. |
02:22 | Now the file has been copied. |
02:25 | If 'test2' doesn't exist, it would be first created and then the content of 'test1' will be copied to it. |
02:35 | If it already existed then it would be silently overwritten. To see the copied file, type:
$ cat space test2 and press Enter. |
02:52 | We can also copy files from and to different directories. For example,
type: $ cp space /home/anirban/arc/demo1 (which is th name of the file we want to copy) space /home/anirban/demo2 and press Enter. |
03:31 | What this will do is that it will copy the file 'demo1' from source diretory /home/anirban/arc to the destination directory /home/anirban, it will copy to a file name 'demo2'. |
03:51 | To see that the 'demo2' is there, type:
ls space /home/anirban and press Enter. |
04:13 | We scroll up as you can see here is 'demo2'. |
04:19 | Before moving ahead let us clear the screen. |
04:25 | If you want the file to have the same name in the destination directory, you may not even mention the file name. For example |
04:35 | Type $ cp space /home/anirban/arc/demo1 space /home/anirban/ and press Enter. |
05:03 | This will again copy the file 'demo1' presenting the /home/anirban/arc directory to /home/anirban directory to a file whose name will be 'demo1' as well. |
05:20 | As before, to see the 'demo1' type:
ls /home/anirban and press Enter. |
05:33 | Here again we would scroll up and as you can see the 'demo1' file is there. |
05:40 | Again, before moving ahead let us clear the screen. |
05:48 | Another instance when we do not need to give the destination file name is when we want to copy multiple files. |
05:56 | We assume that we have three files named test1, test2, test3 in our home directory. |
06:04 | Now we type: $ cp space test1 space test2 space test3 space /home/anirban/testdir and press Enter. |
06:27 | This will copy all the three files named test1,test2 and test3 to the directory /home/anirban/testdir without changing their names. |
06:41 | To see that these files have actually been copied. We will type: ls space /home/anirban/testdir and press Enter. |
07:03 | As you can see test1, test2 and test3 are present in this directory. |
07:10 | There are many options that go with cp. Here we will see only the most important of them. |
07:18 | Let us first go back to the slides. |
07:23 | Among the options, -R is an important one. It causes recursive copying of an entire directory structure. |
07:33 | Let us see an example. |
07:38 | Let us try to copy all the contents of the 'testdir' directory to a directory called 'test'. |
07:48 | For that, we would type: cp space testdir/ space test and press Enter. |
08:02 | As you can see from the output message, |
08:06 | normally we cannot copy a directory having some content directly with cp command. |
08:14 | But using the -R option we can do this. |
08:19 | Now we type: cp space -R space testdir/ space test and press Enter. |
08:36 | The files have now been copied. To see that the 'test' directory actually exists, type ls and press Enter. |
08:47 | As you can see, the 'test' directory exists. Let us clear the screen. |
08:57 | To see the contents inside 'test', type: ls space test and press Enter. |
09:08 | You can see the contents of the 'test' directory. |
09:13 | Now we go back to the slides. |
09:16 | We have seen if a file is copied to another file that already exists, the existing file is overwritten. |
09:25 | Now what if we inadvertently overwrite an important file? |
09:30 | To prevent anything like this to occur, we have the -b option. |
09:36 | This makes a backup of each exiting destination file. |
09:41 | We can also use the -i (interactive)option, this always warns us before overwriting any destination file. |
09:54 | Now let us see how the mv command works. |
09:59 | This is used for moving files. Now how is that useful? |
10:04 | It has two major uses. |
10:07 | It is used for renaming a file or directory. |
10:11 | It also moves a group of files to a different directory. |
10:17 | mv is very similar to cp which we have already seen. So let us quickly see how mv can be used. |
10:29 | We open the terminal and type: $ mv space test1 space test2 and press Enter. |
10:43 | This will rename the file named 'test1' which was already present in the home directory to a file named 'test2'. |
10:52 | If 'test2' already existed then it would be overwritten silently. |
11:00 | If we want our warning before the file is overwritten, |
11:05 | we can use the -i option with the mv command. |
11:10 | Say we have another file named 'anirban'. This file we also want to renew as 'test2'. |
11:20 | We will type: mv space -i space anirban space test2 and press Enter. |
11:32 | As you can see, a warning is provided asking whether 'test2' should be overwritten or not. |
11:41 | If we press y and then press Enter, the file would be actually overwritten. |
11:49 | Like cp we can use mv with multiple files but in that case the destination should be a directory. |
11:58 | Before moving ahead let us clear the screen. |
12:03 | Suppose we have 3 files named abc.txt, pop.txt and push.txt in our home directory. |
12:14 | To see there presence, type ls and press Enter. |
12:21 | Here are the files pop.txt, push.txt and abc.txt Let us clear the screen. |
12:36 | Now we want to move these three files to a directory called 'testdir'. |
12:46 | What we need to do is type: mv space abc.txt space pop.txt space push.txt and then the name of the destination folder which is 'testdir' and press Enter. |
13:14 | To see them, type ls space testdir and press Enter. |
13:20 | You can see the files abc, pop and push.txt. |
13:27 | Now let us see some options that go with mv. Let us first go back to the slides. |
13:37 | Then -b or –backup option is present with the mv command. It will backup every file in the destination before it is overwritten. |
13:48 | The -i option that we have already seen warns us before overwriting any destination file. |
13:58 | The next command we will see is the rm command. This command is used for deleting files. |
14:06 | Go back to the terminal and type: ls space testdir |
14:15 | We can see a file name 'faq.txt' present. Say, we want to delete it. |
14:23 | For this, we type:
$ rm space testdir/faq.txt and press Enter. |
14:37 | This command will remove the file 'faq.txt' from the '/testdir' directory. |
14:46 | To see that the file has been actually removed or not, let us again press:ls space testdir and press Enter. |
15:00 | We can no longer see the file 'faq.txt'. |
15:05 | We can use the rm command with multiple files as well. |
15:10 | The 'testdir' directory contains two files 'abc2' and 'abc1'. |
15:17 | Suppose we want to remove these files abc1 and abc2. |
15:23 | For this, we would type: rm space testdir/abc1 space testdir/abc2 and press Enter. |
15:45 | This removes the files 'abc1' and 'abc2' from 'testdir' directory. |
15:53 | To see that they have been removed, type ls space testdir again. You can no longer see 'abc1' and 'abc2'. |
16:07 | Let us clear the screen before moving ahead. |
16:14 | Now let us go back to the slides. |
16:18 | Let us summarize what we just said? |
16:20 | That is, to delete a single file we write rm and then the name of the file. |
16:27 | To delete multiple files we write rm and the name of the multiple files that we want to delete. |
16:34 | Now let us look into some of the options of the rm command. |
16:40 | Sometimes a file is write protected, using rm will not delete the file then. In this case we have the -f option which can be used to force delete a file. |
16:57 | The other common option is the -r option. Let us see where this options are useful? |
17:07 | Let us switch back to the terminal. |
17:12 | rm command is not normally used for deleting directories, for that we have the rmdir command. |
17:21 | But rmdir command normally deletes a directory, only then it is empty. |
17:27 | What if we want to delete a directory that has a number of files and subdirectories inside. |
17:35 | Let us try the rm command to do this. |
17:38 | Let us type rm and the directory that we want to delete which is 'testdir' and press Enter. |
17:47 | From the output message we can see that we can not use the 'rm directory' to delete 'testdir'. |
17:55 | But if we combine the -r and -f option then we can do this. |
18:03 | Press: rm space -rf space testdir and then press Enter. |
18:16 | Now the 'testdir' directory has been successfully deleted. |
18:22 | Let us now go back to the slides to study the next command. |
18:27 | The cmp command. |
18:29 | Sometimes we need to check whether two files are same. If they are same then we may delete one of them. |
18:37 | Also we may want to see whether a file has changed since the last version. |
18:44 | For these and many other purposes we can use the cmp command. |
18:49 | It compares two files byte by byte. |
18:54 | To compare file1 and file2, we would write cmp space file1 space file2. |
19:03 | If the two files have exactly same content then no message would be shown. |
19:11 | Only the prompt will be printed. |
19:14 | If there are differences in their contents then the location of the first mismatch will be printed on the terminal. |
19:25 | Let us see how 'cmp' works. We have two files named 'sample1' and 'sample2' in our home directory. |
19:35 | Let us see what they contain? |
19:38 | Type cat space sample1 and press Enter. It contains the text “This is a Linux file to test the cmp command” |
19:50 | The other file 'sample2' will contain the text and to see that we will type cat sample2 and press Enter. |
20:00 | It will contain the text “This is a Unix file to test the cmp command.” |
20:06 | Now we would apply the cmp command on these two files. |
20:11 | We will write: cmp space sample1 space sample2 and press Enter. |
20:23 | As we can see, the first difference between the two files 'sample1' and 'sample2' is pointed out. |
20:32 | Let us clear the screen before moving ahead to the next command. |
20:38 | The next command we will see is the wc command. |
20:43 | This command is used to count the number of characters, words and lines in a file. |
20:50 | We have a file named 'sample3' in our home directory. |
20:56 | Let us see its contents. For that, we will type: cat space sample3 and press Enter. |
21:05 | This is the content of sample3. |
21:10 | Now let us use the wc command on this file. |
21:14 | For that, we would write: wc space sample3 and press Enter. |
21:25 | The command points out that the file has 6 lines, 67 words and 385 characters. |
21:38 | These were some of the commands that help us to work with files. |
21:43 | There are many more commands. Moreover each of the command that we saw has many other options. |
21:51 | I encourage you to see more about them using the man command. |
22:00 | This brings me to the end of this tutorial at last. |
22:04 | Spoken Tutorial Project is a part of the Talk to a Teacher project, supported by the National Mission on Education through ICT, MHRD, Government of India. |
22:17 | More information on the same is available at the following link http://spoken-tutorial.org/NMEICT-Intro. |
22:34 | This is Anirban signing off . Thanks for joining. |
Contributors and Content Editors
Gaurav, Minal, Pratik kamble, Sandhya.np14, Vasudeva ahitanal