Linux/C2/The-Linux-Environment/English-timed - Revision history

PoojaMoolya at 12:01, 23 March 2017

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PoojaMoolya at 06:44, 10 March 2017

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Sandhya.np14 at 10:36, 12 March 2015

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Sandhya.np14 at 10:00, 11 March 2015

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Sandhya.np14 at 07:07, 11 March 2015

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PoojaMoolya at 11:15, 1 September 2014

2014-09-01T11:15:30Z

PoojaMoolya at 11:14, 1 September 2014

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Pratik kamble at 11:34, 9 July 2014

2014-07-09T11:34:54Z

Minal: Created page with '{| border=1 !Time !Narration |- |00:00 |Welcome to this spoken tutorial on the Linux environment and ways to manupulate it. |- |00:07 |A working linux system, preferably Ubuntu …'

2012-12-28T09:38:59Z

Created page with '{| border=1 !Time !Narration |- |00:00 |Welcome to this spoken tutorial on the Linux environment and ways to manupulate it. |- |00:07 |A working linux system, preferably Ubuntu …'

New page

{| border=1
!Time
!Narration
|-

|00:00
|Welcome to this spoken tutorial on the Linux environment and ways to manupulate it.
|-
|00:07
|A working linux system, preferably Ubuntu will be required to try out the examples illustrated in this tutorial.
|-
|00:13
|We assume that you know how to get started with the Linux operating system and have some basic idea about commands, file systems and shell .
|-
|00:22
|If you are interested, or need to brush these concepts up , please feel free to do so through another spoken tutorial available on our website.
|-
|00:32
|Please note that Ubuntu 10.10 was used for recording this tutorial.
|-
|00:36
|Please also note that Linux is case sensitive and all the commands used in this tutorial are in lower case unless otherwise mentioned.
|-
|00:46
|The Linux environment determines how the operating system behaves with you, how it responds to your commands, how it interprets your actions and so on.
|-
|00:55
|Linux can be highly customized by changing the settings of the shell.
|-
|00:58
|Let us understand how all this can be done.
|-
|00:59
|The behaviour of the shell is generally determined by the shell variables.
|-
|01:04
|There are mainly two kinds of shell variables:

Environment Variables and

Local Variables
|-
|01:12
|Environment variables, named so because they are available entirely in the user's total environment.
|-
|01:19
|These are also available in subshells spawned by the shell like the ones for running shell scripts.
|-
|01:24
|Local Variables , which as the name suggests have a more restricted or limited availability.
|-
|01:31
|These are not available in the subshells spawned by the shell.
|-
|01:36
|While in this tutorial, we will mainly talk about environment variables, let us first see how the value of these shell variables can be seen.
|-
|01:48
|To see all the variables available in the current shell , we run the command set.
|-
|01:53
| '''Type at the terminal'''
"set space 'vertical-bar' more" and press enter.
|-
|02:00
|We can see all the current shell variables ,
|-
|02:04
|For example : take a look at the HOME environment variable also notice the value assigned to it.
|-
|02:15
|press Enter to move through the list and in order to come out press q
|-
|02:21
|Here the output from set was pipelined to more in order to display a more systematic multipage output of the variable list.
|-
|02:38
|To see only the environment variables run the command env
|-
|02:45
|'''Type at the terminal'''

"env space 'vertical-bar' more" and press enter
|-
|02:52
|For example,

Notice the SHELL variable whose value is slash bin slash bash .
|-
|03:00
|Again, you may press q to come out of the list.
|-
|03:07
|Now let us discuss some of the more important environment variables in linux.
|-
|03:11
|We would be using the bash shell for all our demonstrations here.
|-
|03:15
|Different shells are customized in slightly different ways.
|-
|03:19
|To see what a variable actually stores we have to prefix a dollar sign to the name of that variable and use the echo command along with it.
|-
|03:30
|The first environment variable that we would see is the SHELL variable.
|-
|03:35
|It stores the name of the current shell.
|-
|03:37
|To see what is the value of the SHELL variable, type

at the terminal "echo space dollar S-H-E-L-L in capital"and press enter.
|-
|03:55
|Here slash bin slash bash is the shell where we are currently operating.
|-
|04:02
|The next variable is the HOME.
|-
|04:05
|When we login into Linux, it normally places us in a directory named after our user name.
|-
|04:11
|This directory is called the home directory and this is exactly what is available in HOME variable.
|-
|04:17
|To see the value, type at the terminal "echo space dollar H-O-M-E in capital"and press enter
|-
|04:29
|The next environment variable is PATH.
|-
|04:32
|The PATH variable contains the absolute paths of the directories that the shell is supposed to search for locating any executable command.
|-
|04:40
|Lets see the value of the path variable.
|-
|04:43
|Again, type at the terminal "echo space dollar P-A-T-H " in capitals and press enter
|-
|04:51
|On my computer it shows the directories

slash user slash local slash sbin slash user slash local slash bin slash user slash sbin slash user slash bin etc.
|-
|05:04
|This may slightly vary from one system to other.
|-
|05:07
|It is actually a list of directories separated by the :(colon) delimiter, that the shell would search in this order for finding an executable command.
|-
|05:18
|We can also add our own directory to this list so that our directory is also searched by the shell.
|-
|05:25
|In order to add our own directory type at the terminal
|-
|5:29
|"P-A-T-H in capital 'equal-to' dollar P-A-T-H again in capital colon slash home slash the name of my own home directory and press enter.
|-
|05:54
|Now if we echo the value of PATH,
|-
|06:04
|our added directory will also be a part of the PATH variable.
|-
|06:10
|See the directory is now present here.
|-
|06:16
|Another interesting variable is the LOGNAME.
|-
|06:20
|It stores the username of the currently active user.
|-
|06:24
|In order to see the value type "echo space dollar LOGNAME" and press enter.
|-
|06:35
|When we open the terminal we can see the dollar sign, which is the prompt at which we enter all our commands.
|-
|06:42
|This is the primary prompt string represented by the environment variable PS1.
|-
|06:47
|There is a secondary prompt string also
|-
|06:50
|If our command is long and it spans for more than one line then from the second line onwards we can see a greater than sign “>” as the prompt
|-
|07:00
|This is the secondary prompt string represented by the environment variable PS2.
|-
|07:05
|To see the value of the secondary command prompt, type at the terminal "echo space dollar PS2 and press enter.
|-
|07:20
|We may change our primary prompt string to say “at the rate” <@> at the prompt.
|-
|07:28
|In order to get this done

Type "PS1 'equal-to' now within quotes 'at the rate' “ and press enter.
|-
|07:41
|Now instead of the dollar sign we can see the at the rate sign as the prompt.
|-
|07:50
|We may do something more interesting. Like we may display our username at the prompt.
|-
|07:56
|Just type "PS1in capital 'equal-to' within quotes dollar LOGNAME " and press enter
|-
|08:12
|Now my username is my prompt.
|-
|08:16
|To revert back type "PS1 'equal-to' dollar within quotes and press enter."
|-
|08:28
|We have assigned values to many of the environment variables.
|-
|08:32
|But, remember one thing that these modifications are only applicable for the current session.
|-
|08:37
|Like we had just added our directory to the PATH variable.
|-
|08:40
|If we close the terminal and open it again or open a new terminal altogether and check the path variable by echoing its value
|-
|09:00
|we will be surprised to see that our modifications are no longer present.
|-
|09:05
|The way by which we can make these modifications permanent will be covered in some advanced tutorial.
|-
|09:13
|Often we want to re-execute a command that we had executed in the recent past. What do we do? Do we have to type the entire command again?
|-
|9:22
| No, there are a number of solutions.
|-
|09:26
|First, normally if you press the up key on your keyboard then it will show the last command that you typed.
|-
|09:33
|Keep pressing and it will keep scrolling through the previous commands.
|-
|09:37
|To go back press the down key.
|-
|09:42
|But when you have to scroll through many commands this becomes a little clumsy and tedious. A better way is to use the history command.
|-
|09:52
|Type at the prompt "history"
|-
|09:58
|and press enter, see a list of previously executed commands appears
|-
|10:04
|If instead of the large list you want to see, only the last ten
|-
|10:08
|Type "history space 10" and press enter
|-
|10:20
|Notice, in this list, there is a number assigned to each of the previously executed commands.
|-
|10:27
|In order to repeat a particular command.
|-
|10:32
|Just type exclamation mark followed by the number of the command for example 442 in my case would execute echo space dollar path
|-
|10:51
|If you need to re execute the last command simply type exclamation mark twice and press enter.
|-
|11:03
|The next thing we would see is called tilde substitution

The tilde(~) character is a shorthand for the home directory.
|-
|11:12
|So say you have a directory with name testtree in your home directory. You can move to it by typing "cd space 'tilde' slash testtree".
|-
|11:25
|One may also toggle between the current working directory and the last directory used by giving the command
cd 'tilde' minus or only cd minus
|-
|11:35
|Like now that we are in the testtree directory, the last directory we visited was the home directory.
|-
|11:41
|So if we run "cd space minus" and press enter. It will go to the home directory.
|-
|11:47
|Run it again and it will take us back to the testtree directory.
|-
|11:55
|The last but quite important command we will see is the alias command.
|-
|11:59
|It may happen that you have a large command that needs to be run again and again.
|-
|12:04
|In this case we can give it a short alias name and use the alias name instead ,to invoke it.
|-
|12:11
|Assuming that you have such a long directory hierarchy that you frequently visit for music, you may create an alias for it like this
|-
|12:20
|Type " alias space cdMusic 'equal-to' within double quotes cd space slash home slash arc slash files slash entertainment slash music " and press enter
|-
|12:47
|Now every time you need to switch to this directory simply write cdMusic and press enter.
|-
|12:55
|See, we are in the music directory now.
|-
|12:58
|Now, you may type "cd space minus" at the prompt to go back to the previous working directory.
|-
|13:08
|To unset an alias simply write unalias space cdMusic and press enter
|-
|13:20
|Now again if you fire cdMusic from the terminal, you will get an error stating that the command was not found.
|-
|13:30
|Suppose we have two files, test1 and test2 in our present working directory
|-
|13:38
|and if we fire rm test1, test1 is silently deleted.
|-
|13:45
|We know that “hyphen i” option of the rm command makes the removal process interactive.
|-
|13:52
|So we may set an alias like, alias rm equal-to, now within quotes “rm space hyphen i”
|-
|14:03
|Now when we run “rm” ,” rm hyphen i” will actually be run.
|-
|14:13
|So we saw that while test1 was silently deleted, system asked before deleting test2.
|-
|14:20
|So, in this tutorial, you have learned about environment variables, history and aliasing.
|-
|14:25
|This brings me to the end of this tutorial.
|-
|14:28
|Spoken Tutorials are a part of the Talk to a Teacher project, supported by the National Mission on Education through ICT.
|-
|14:36
|More information on the same is available from our website.
|-
|14:39
|The Script for this tutorial was created by Anirban
|-
|14:42
|This script has been contributed by ----------------------(name of the translator) and this is -----------------------(name of the recorder) from --------------------------(name of the place)signing off.
|}

@@ Line 27: / Line 27: @@
 |00:55
 |Linux can be highly customized by changing the settings of the '''shell'''.
 |-
 |00:58
-|Let us understand how all this can be done.
+|Let us understand how all this can be done.The behavior of the shell is generally determined by the '''shell variables'''.
-|-
-|00:59
-|The behavior of the shell is generally determined by the '''shell variables'''.
 |-
 |01:04

@@ Line 34: / Line 34: @@
 |-
 |01:04
-|There are mainly two kinds of shell variables:
+|There are mainly two kinds of shell variables: '''Environment Variables''' and '''Local Variables'''.
 '''Environment Variables''' and
 '''Local Variables'''.
 |-
 |01:12
@@ Line 78: / Line 76: @@
 |-
 |02:52
-|For example,
+|For example, notice the '''SHELL''' variable whose value is '''slash bin slash bash'''.
 notice the '''SHELL''' variable whose value is '''slash bin slash bash'''.
 |-
 |03:00
@@ Line 228: / Line 225: @@
 |Often we want to re-execute a command that we had executed in the recent past. What do we do? Do we have to type the entire command again?
 |-
-|9:22
+|09:22
 | No, there are a number of solutions.
 |-
@@ Line 274: / Line 271: @@
 |-
 |11:25
-|One may also toggle between the current working directory and the last directory used by giving the command
+|One may also toggle between the current working directory and the last directory used by giving the command '''cd  '~(tilde)' minus''' or only '''cd  minus'''
 '''cd  '~(tilde)' minus''' or only '''cd  minus'''
 |-
 |11:35
@@ Line 308: / Line 304: @@
 |-
 |12:58
-|Now, you may type '''cd space minus
+|Now, you may type '''cd space minus ''' at the prompt to go back to the previous working directory.
 ''' at the prompt to go back to the previous working directory.
 |-
 |13:08

@@ Line 176: / Line 176: @@
 |-
 |06:47
-|There is a secondary prompt string also
+|There is a secondary prompt string also.
 |-
 |06:50
@@ Line 206: / Line 206: @@
 |-
 |08:16
-|To revert back, type: '''PS1''' 'equal-to' dollar within quotes and press Enter."
+|To revert back, type: '''PS1''' 'equal-to' dollar within quotes and press Enter.
 |-
 |08:28
@@ Line 251: / Line 251: @@
 |-
 |10:04
-|If instead of the large list you want to see, only the last ten
+|If instead of the large list you want to see only the last ten,
 |-
 |10:08
-|Type '''history space 10''' and press ''Enter'''.
+|type '''history space 10''' and press ''Enter'''.
 |-
 |10:20
@@ Line 260: / Line 260: @@
 |-
 |10:27
-|In order to repeat a particular command.
+|In order to repeat a particular command,
 |-
 |10:32
-|Just type exclamation mark followed by the number of the command for example 442 in my case would execute '''echo space dollar PATH'''
+|just type exclamation mark followed by the number of the command for example 442 in my case would execute '''echo space dollar PATH'''
 |-
 |10:51
@@ Line 300: / Line 300: @@
 |-
 |12:20
-|Type: '''alias''' space '''cdMusic''' 'equal-to' within double quotes '''cd''' space '''slash home slash arc slash files slash entertainment slash music ''' and press Enter.
+|Type: '''alias''' space '''cdMusic''' 'equal-to' within double quotes '''cd space slash home slash arc slash files slash entertainment slash music''' and press Enter.
 |-
 |12:47
@@ Line 331: / Line 331: @@
 |-
 |14:03
-|Now when we run '''rm''' ,''' rm hyphen i'''will actually be run.
+|Now when we run '''rm''' ,'''rm hyphen i'''will actually be run.
 |-
 |14:13

@@ Line 185: / Line 185: @@
 |-
 |07:05
-|To see the value of the secondary command prompt, type at the terminal '''echo''' space '''dollar PS2'''  and press '''enter.'''
+|To see the value of the secondary command prompt, type at the terminal: '''echo''' space '''dollar PS2'''  and press '''Enter.'''
 |-
 |07:20
@@ Line 191: / Line 191: @@
 |-
 |07:28
-|In order to get this done Type ''' PS1'''  'equal-to' now within quotes 'at the rate' “ and press enter.
+|In order to get this done, type ''' PS1'''  'equal-to' now within quotes 'at the rate' “@"and press Enter.
 |-
 |07:41
@@ Line 200: / Line 200: @@
 |-
 |07:56
-|Just type '''PS1''' in capital 'equal-to' within quotes '''dollar LOGNAME''' and press '''enter'''
+|Just type: '''PS1''' in capital 'equal-to' within quotes '''dollar LOGNAME''' and press '''Enter'''.
 |-
 |08:12
@@ Line 206: / Line 206: @@
 |-
 |08:16
-|To revert back type '''PS1''' 'equal-to' dollar within quotes and press enter."
+|To revert back, type: '''PS1''' 'equal-to' dollar within quotes and press Enter."
 |-
 |08:28
@@ Line 218: / Line 218: @@
 |-
 |08:40
-|If we close the terminal and open it again or open a new terminal altogether and check the path variable by echoing its value
+|If we close the terminal and open it again or open a new terminal altogether and check the path variable by echoing its value,
 |-
 |09:00
@@ Line 233: / Line 233: @@
 |-
 |09:26
-|First, normally if you press the up  key on your keyboard then it will show the last command that you typed.
+|First, normally if you press the 'up  key' on your keyboard then it will show the last command that you typed.
 |-
 |09:33
@@ Line 245: / Line 245: @@
 |-
 |09:52
-|Type at the prompt '''history'''
+|Type at the prompt '''history'''.
 |-
 |09:58
-|and press enter, see a list of previously executed commands appears
+|and press Enter, see a list of previously executed commands appear.
 |-
 |10:04
@@ Line 254: / Line 254: @@
 |-
 |10:08
-|Type '''history space 10''' and press ''enter'''
+|Type '''history space 10''' and press ''Enter'''.
 |-
 |10:20
-|Notice, in this list, there is a number assigned to each of the previously executed commands.
+|Notice, in this list there is a number assigned to each of the previously executed commands.
 |-
 |10:27
@@ Line 266: / Line 266: @@
 |-
 |10:51
-|If you need to re execute the last command simply type exclamation mark twice and press enter.
+|If you need to re-execute the last command simply type exclamation mark twice and press Enter.
 |-
 |11:03
-|The next thing we would see is called tilde substitution. The tilde(~) character is a shorthand for the home directory.
+|The next thing we would see is called 'tilde' substitution. The tilde(~) character is a shorthand for the home directory.
 |-
 |11:12
-|So say you have a directory with name testtree in your home directory. You can move to it by typing '''cd''' space '''~(tilde)''' slash '''testtree'''.
+|So, say you have a directory with name testtree in your home directory. You can move to it by typing: '''cd''' space '''~(tilde)''' slash '''testtree'''.
 |-
 |11:25
@@ Line 282: / Line 282: @@
 |-
 |11:41
-|So if we run '''cd space minus''' and press enter. It will go to the home directory.
+|So if we run '''cd space minus''' and press Enter, it will go to the home directory.
 |-
 |11:47
@@ Line 294: / Line 294: @@
 |-
 |12:04
-|In this case we can give it a short '''alias''' name and use the '''alias''' name instead ,to invoke it.
+|In this case we can give it a short '''alias''' name and use the '''alias''' name instead, to invoke it.
 |-
 |12:11
-|Assuming that you have such a long directory hierarchy that you frequently visit for music, you may create an alias for it like this
+|Assuming that you have such a long directory hierarchy that you frequently visit for music, you may create an alias for it like this.
 |-
 |12:20
-|Type '''alias''' space '''cdMusic''' 'equal-to' within double quotes '''cd''' space '''slash home slash arc slash files slash entertainment slash music ''' and press enter
+|Type: '''alias''' space '''cdMusic''' 'equal-to' within double quotes '''cd''' space '''slash home slash arc slash files slash entertainment slash music ''' and press Enter.
 |-
 |12:47
-|Now every time you need to switch to this directory simply write '''cdMusic''' and press enter.
+|Now every time you need to switch to this directory simply write '''cdMusic''' and press Enter.
 |-
 |12:55
@@ Line 313: / Line 313: @@
 |-
 |13:08
-|To unset an '''alias''' simply write '''unalias space cdMusic''' and press enter
+|To unset an '''alias''', simply write '''unalias space cdMusic''' and press Enter.
 |-
 |13:20
@@ Line 337: / Line 337: @@
 |-
 |14:20
-|So, in this tutorial, you have learned about environment variables, history and aliasing.
+|So, in this tutorial, you have learned about '''environment variables''', '''history''' and '''aliasing'''.
 |-
 |14:25
@@ Line 349: / Line 349: @@
 |-
 |14:39
-|The Script for this tutorial was created by Anirban
+|The Script for this tutorial was created by Anirban.
 |-
 |14:42
 |This script has been contributed by ----------------------(name of the translator) and this is -----------------------(name of the recorder) from --------------------------(name of the place)signing off.
 |}

@@ Line 320: / Line 320: @@
 |-
 |13:20
-|Now again if you fire cdMusic from the terminal, you will get an error stating that the command was not found.
+|Now again if you fire '''cdMusic''' from the terminal, you will get an error stating that the command was not found.
 |-
 |13:30

@@ Line 1: / Line 1: @@
 {| border=1
-!Time
+|'''Time'''
-!Narration
+|'''Narration'''
 |-
@@ Line 158: / Line 158: @@
 |In order to add our own directory type at the terminal
 |-
-|5:29
+|05:29
 |"P-A-T-H in capital 'equal-to' dollar P-A-T-H again in capital colon  slash home slash the name of my own home directory and press enter.
 |-