BOSS-Linux/C2/Working-with-Regular-Files/English-timed

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.
00:32	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.
00:56	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.
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 Example. 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 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 the name of the file that we want to copy, space /home/anirban/demo2 and press Enter.
03:32	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 whose name is demo2.
03:51	To see that the 'demo2' is there, type: ls space /home/anirban and press Enter.
04:07	And as you can see, here is demo2.
04:12	Before moving ahead, let us clear the screen.
04:17	If you want the file to have the same name in the destination directory, you may not even mention the file name. For example-
04:27	Type: cp space /home/anirban/arc/demo1 space /home/anirban/ and press Enter.
04:55	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.
05:11	As before, to see the demo1, type: ls/home/anirban and press Enter.
05:25	And, as you can see the demo1 file is there.
05:30	Again, before moving ahead, let us clear the screen.
05:37	Another instance when we do not need to give the destination file name is when we want to copy multiple files.
05:44	We assume that we have three files named test1, test2, test3 in our home directory.
05:53	Now, we type: cp space test1 space test2 space test3 space /home/anirban/testdir and press Enter.
06:16	This will copy all the three files named test1,test2 and test3 to the directory /home/anirban/testdir without changing their names.
06:30	To see that these files have actually been copied, we will type: ls space /home/anirban/testdir and press Enter.
06:52	As you can see test1,test2 and test3 are present in this directory.
06:58	There are many options that go with cp. Here, we will see only the most important of them.
07:07	Let us first go back to the slides.
07:12	Among the options, -R (The capital R) is an important one. It causes recursive copying of an entire directory structure.
07:23	Let us see an example.
07:27	Let us try to copy all the contents of the 'testdir' directory to a directory called 'test'.
07:36	For that, we would type: cp space testdir slash test and press Enter.
07:51	As you can see from the output message,
07:54	normally we cannot copy a directory having some contents directly with the 'cp command.
08:02	But using the -R (mius R ) option we can do this.
08:07	Now we type: cp space -R(minus capital R) space testdir/ test and press Enter.
08:25	The files have now been copied. To see that the test directory actually exists, type: ls and press Enter.
08:37	As you can see, the 'test' directory exists. Let us clear the screen.
08:45	To see the contents inside 'test', type: ls test and press Enter.
08:57	You can see the contents of the 'test' directory.
09:01	Now, we go back to the slides.
09:05	We have seen if a file is copied to another file that already exists, the existing file is overwritten.
09:14	Now, what if we inadvertently overwrite an important file?
09:19	To prevent anything like this to occur, we have the '-b' option.
09:25	This makes a backup of each existing destination file.
09:32	We can also use the -i(interactive)option. This always warns us before overwriting any destination file.
09:43	Now, let us see how the mv command works.
09:47	This is used for moving files. Now how is that useful?
09:53	It has two major uses.
09:57	It is used for renaming a file or directory.
10:00	It also moves a group of files to a different directory.
10:05	mv is very similar to cp which we have already seen. So, let us quickly see how mv can be used.
10:17	We open the terminal and type: mv space test1 space test2 and press Enter.
10:32	This will rename the file named test1 which was already present in the home directory to a file named test2.
10:40	If test2 already existed then it would be overwritten silently.
10:49	If we want our warning before the file is overwritten,
10:54	we can use the -i option with the mv command.
10:59	Say we have another file named 'anirban'. This file we also want to renew as 'test2'.
11:08	We will type: mv space -i space anirban space test2 and press Enter.
11:21	As you can see, a warning is provided asking whether test2 should be overwritten or not.
11:30	If we press 'y' and then press Enter, the file would be actually overwritten.
11:37	Like cp, we can use mv with multiple files but in that case the destination should be a directory.
11:47	Before moving ahead, let us clear the screen.
11:52	Suppose we have 3 files named abc.txt, pop.txt and push.txt in our home directory.
12:03	To see their presence, type ls and press Enter.
12:09	Here are the files pop.txt, push.txt and abc.txt. Let us clear the screen.
12:24	Now we want to move these three files to a directory called testdir.
12:32	What we need to do is, type: mv space abc.txt pop.txt push.txt and then the name of the destination folder which is testdir and press Enter.
12:58	To see them, type: ls testdir and press Enter.
13:06	You can see the files abc, pop and push.txt.
13:14	Now, let us see some options that go with mv'. Let us first go back to the slides.
13:22	The '-b' or '–backup' option is present with the mv command. It will backup every file in the destination before it is overwritten.
13:34	The '-i' (minus i) option that we have already seen, warns us before overwriting any destination file.
13:44	The next command we will see is the rm command. This command is used for deleting files.
13:52	Go back to the terminal and type: ls testdir.
14:00	We can see a file name 'faq.txt' present. Say we want to delete it.
14:09	For this, we type: rm space testdir/faq.txt and press Enter.
14:23	This command will remove the file 'faq.txt' from the /testdir directory.
14:32	To see that the file has been actually removed or not, let us again press ls space testdir and press Enter.
14:47	We can no longer see the file 'faq.txt'.
14:51	We can use the rm command with multiple files as well.
14:57	The testdir directory contains two files 'abc2' and 'abc1.'
15:03	Suppose, we want to remove these files- 'abc1' and 'abc2.'
15:09	For this, we would type: rm space testdir/abc1 space testdir/abc2 and press Enter.
15:31	This removes the files 'abc1' and 'abc2' from testdir directory.
15:39	To see that they have been removed, type: ls space testdir again. You can no longer see abc1' and abc2.
15:53	Let us clear the screen before moving ahead.
15:58	Now, let us go back to the slides.
16:02	Let us summarize what we just said.
16:04	That is, to delete a single file we write rm and then the name of the file.
16:11	To delete multiple files, we write rm and the name of the multiple files that we want to delete.
16:19	Now, let us look into some of the options of the rm command.
16:24	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.
16:41	The other common option is the -r option. Let us see where these option are useful?
16:52	Let us switch back to the terminal.
16:57	rm command is not normally used for deleting directories. For that, we have the rmdir command.
17:05	But rmdir command normally deletes a directory only when it is empty.
17:12	What if we want to delete a directory that has a number of files and sub-directories inside?
17:19	Let us try the rm command to do this.
17:23	Let us type rm and the directory that we want to delete which is testdir and press Enter.
17:31	From the output message, we can see that we can not use the rm directory to delete 'testdir'.
17:39	But if we combine the '-r' and '-f' options then we can do this.
17:47	Press rm -rf testdir and then press Enter.
18:00	Now, the testdir directory has been successfully deleted.
18:06	Let us now go back to the slides to study the next command-
18:11	the cmp command.
18:13	Sometimes we need to check whether two files are same. If they are same then we may delete one of them.
18:22	Also we may want to see whether a file has changed since the last version.
18:28	For these and many other purposes, we can use the cmp command.
18:33	It compares two files byte by byte.
18:38	To compare 'file1' and 'file2', we would write cmp space file1 space file2.
18:47	If the two files have exactly the same contents then no message would be shown.
18:55	Only the prompt will be printed.
18:58	If there are differences in their contents then the location of the first mismatch will be printed on the terminal.
19:10	Let us see how cmp works. We have two files named sample1 and sample2 in our home directory.
19:19	Let us see what they contain?
19:22	Type: cat sample1 and press Enter. It contains the text- "This is a Linux file to test the cmp command".
19:34	The other file sample2 will contain the text and to see that we will type: cat sample2 and press Enter.
19:44	It will contain the text- "This is a Unix file to test the cmp command".
19:50	Now we would apply the cmp command on these two files.
19:55	We will write: cmp space sample1 space sample2 and press Enter.
20:08	As we can see, the first difference between the two files sample1 and sample2 is pointed out.
20:16	Let us clear the screen before moving ahead to the next command.
20:22	The next command we will see is the wc command.
20:26	This command is used to count the number of characters, words and lines in a file.
20:34	We have a file named "sample3" in our home directory.
20:39	Let us see its contents. For that, we will type: cat space sample3 and press Enter.
20:50	This is the content of sample3.
20:54	Now, let us use the wc command on this file.
20:59	For that, we would write wc space sample3 and press Enter.
21:10	This command points out that the file has 6 lines, 67 words and 385 characters.
21:22	These were some of the commands that help us to work with files.
21:27	There are many more commands. Moreover each of the command that we saw has many other options.
21:36	I encourage you to see more about them using the man command.
21:44	This brings me to the end of this tutorial at last.
21:48	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.
22:02	More information on the same is available at the following link- http://spoken-tutorial.org/NMEICT-Intro.
22:18	This is Anirban, signing off . Thanks for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14