BOSS-Linux/C2/Working-with-Regular-Files/English-timed
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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 [OPTION]... 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 [OPTION]...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 /home/anirban/arc/ |
01:49 | To see what is in test1.We type
$ cat 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 test1 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 test2 and press enter. |
02:52 | You can also copy files from and to different directories.For example.
$ cp /home/anirban/arc/demo1 /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 a head 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 /home/anirban/arc/demo1 /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 a head 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 test1 test2 test3 /home/anirban/testdir and press enter. |
06:27 | This will copy all the three files test1,test2 and test3 to the directory /home/anirban/testdir without changing their names. |
06:41 | You see that this files have actually been copied.We will type ls /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 will 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 testdir/ test and press enter. |
08:02 | As you can see from the output message. |
08:06 | Normally we cannot copy a directory having a some content directly with cp command. |
08:14 | But using the -R option we can do this. |
08:19 | Now we type cp -R testdir/ test and press enter. |
08:36 | The files have now been copied, to see that the test directory actually exist 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 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 rename 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 test1 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 -i anirban 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 this three files to a directory called testdir. |
12:46 | What we need to do is type mv abc.txt pop.txt push.txt and then the name of the destination folder which is testdir and press enter. |
13:14 | To see them type ls 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 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 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 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 this files abc1 and abc2. |
15:23 | For this we would type rm testdir/abc1 testdir/abc2 and press enter. |
15:45 | This remove the files abc1 and abc2 from testdir directory. |
15:53 | To see that they have been removed type ls 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 do delete a single file we write rm and than 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 -rf 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 file1 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 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 this two files. |
20:11 | We will write cmp sample1 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 content, for that we will type cat 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 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. |