PERL/C3/File-Handling/English-timed - Revision history

PoojaMoolya at 12:46, 20 February 2017

2017-02-20T12:46:22Z

Sandhya.np14 at 07:38, 15 February 2016

2016-02-15T07:38:49Z

Sandhya.np14 at 12:53, 28 December 2015

2015-12-28T12:53:54Z

Sandhya.np14 at 12:51, 28 December 2015

2015-12-28T12:51:56Z

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Sandhya.np14 at 10:12, 28 December 2015

2015-12-28T10:12:50Z

PoojaMoolya at 07:14, 26 November 2015

2015-11-26T07:14:36Z

PoojaMoolya: Created page with " {| Border = 1 | '''Time''' | '''Narration''' |- | 00:01 | Welcome to the''' Spoken Tutorial''' on''' File Handling in PERL.''' |- | 00:06 | In this tutorial we will..."

2015-11-24T06:18:10Z

Created page with " {| Border = 1 | '''Time''' | '''Narration''' |- | 00:01 | Welcome to the''' Spoken Tutorial''' on''' File Handling in PERL.''' |- | 00:06 | In this tutorial we will..."

New page

{| Border = 1
| '''Time'''
| '''Narration'''

|-
| 00:01
| Welcome to the''' Spoken Tutorial''' on''' File Handling in PERL.'''

|-
| 00:06
| In this tutorial we will learn how to

* Open a file in '''read mode'''
* Write to a file
* Open a file in '''append mode'''
* Close the file handle

|-
| 00:17
| For this tutorial, I am using

* '''Ubuntu Linux 12.04''' operating system
* '''Perl 5.14.2'''
* and the''' gedit''' Text Editor

|-
| 00:28
| You can use any text editor of your choice.

|-
| 00:32
| To follow this tutorial, you should have working knowledge of '''Perl''' programming.

|-
| 00:37
| If not, then go through the relevant''' Perl''' spoken tutorials on the''' spoken tutorial''' website.

|-
| 00:43
| The basic operations we can do with files in '''Perl '''are:
* open a file
* read from a file
* write to a file and
* close a file

|-
|00:54
| The default file handles are

* '''STDIN'''
* '''STDOUT'''
* '''STDERR'''

|-
| 01:02
| This is the syntax for '''open '''function.

|-
| 01:05
| In the syntax''', FILEHANDLE''' is the''' file handle''' returned by the '''open '''function.

|-
| 01:11
| '''MODE''' represents the mode of opening the file. For eg: read, write, etc.

|-
| 01:18
| '''EXPR''' is the physical filename used to read or write. In this case, '''“First.txt” '''is the filename.

|-
| 01:27
| There is another way to write the '''open '''function, as shown here.

|-
| 01:32
| Let us understand how to open an existing file and read the data from it.

|-
| 01:38
| First we will create a text file and store some data in it. Go to the '''terminal''' and type''' gedit first.txt''' and press '''Enter'''.

|-
|01:51
| In the '''first dot txt''' file, type the following text:

|-
| 01:55
| Save the file and close''' gedit'''.

|-
| 01:59
| Now we will look at a '''Perl '''program that opens the file''' first.txt''' and reads the content.

|-
| 02:07
| Let me open the sample program''' openfile.pl''' which I have already saved.

|-
| 02:13
| Type''' gedit openfile dot pl ampersand''' and press''' Enter'''.

|-
| 02:19
| In the '''openfile dot pl''' file, type the following code as displayed on the screen.

|-
| 02:25
| Let us understand the code now.

|-
| 02:28
| The''' open''' '''function''' opens a file for reading.

|-
| 02:33
| The first parameter''' DATA''' is the''' filehandle''' which allows''' Perl''' to refer to the file in future.

|-
| 02:40
| The second parameter '''<nowiki>“<”</nowiki>''' less than symbol denotes the '''READ''' mode.

|-
| 02:44
| If you fail to specify the “'''Mode'''”, by default the file will be opened in “'''READ'''” mode.

|-
| 02:50
| The third parameter''' first.txt''' is the''' filename''' from where the data has to be read.

|-
| 02:57
| What will happen if the file''' first.txt''' does not exist?

|-
| 03:02
| The script will die with the appropriate error message stored in the''' dollar exclamation ($!)'''variable.

|-
| 03:08
| The '''while '''loop will read line by line and loop through the'''<nowiki> <</nowiki>DATA>''' file
until all the lines have been read.

|-
| 03:17
| Print''' dollar underscore''' ('''$_)''' variable will print the contents of the current line.

|-
| 03:22
| Lastly, close the file with the''' FILEHANDLE''' name, which we had given in the '''open''' statement.

|-
| 03:29
| Closing a file prevents any accidental file changes or overwriting of the content.

|-
| 03:36
| Now, press''' Ctrl+S''' to save the file.

|-
| 03:40
| Let us execute the program.

|-
| 03:42
| Switch back to the''' terminal''' and type '''perl openfile dot pl''' and press''' Enter'''.

|-
| 03:51
| The output is displayed as shown.

|-
| 03:54
| This is the same content that we saw earlier in '''first dot txt '''file.

|-
| 03:59
| Next we will see how to write data into a file.

|-
| 04:03
| The '''open '''statement with greater than''' (>)''' symbol defines the '''WRITE''' mode.

|-
| 04:08
| '''Filename''' represents the name of the file where the data has to be written.

|-
| 04:13
| Let me open the sample program''' writefile.pl''' which I have already saved.

|-
| 04:19
| Switch to the '''terminal.'''

|-
| 04:21
| Now, type''' gedit writefile dot pl ampersand''' and press '''Enter.'''

|-
| 04:29
| In the '''writefile dot pl''' file, type the following code as displayed on the screen.

|-
| 04:34
| Let me explain the code now.

|-
| 04:37
| The '''open function '''opens a file '''second.txt''' in '''write mode.'''

|-
| 04:44
| “>” Greater than symbol before the filename denotes the '''write mode.'''

|-
| 04:49
| The first parameter '''FILE1''' is the''' FILEHANDLE'''.

|-
| 04:53
| The '''print function''' prints the given text to''' FILEHANDLE'''. i.e''' FILE1'''

|-
| 04:59
| Now, press''' Ctrl+S''' to save the file

|-
| 05:03
| Let us execute the program.

|-
| 05:05
| Switch back to the '''terminal''' and type '''perl writefile dot pl''' and press''' Enter'''.

|-
| 05:12
| Now let us check whether the text has been written in '''second.txt''' file.

|-
| 05:18
| Type''' gedit second.txt''' and press '''Enter'''.

|-
| 05:23
| We can see the text''' Working with files makes data storage and retrieval a simple task! '''In our second.txt file.

|-
|05:32
| Let us close the '''second.txt '''file.

|-
| 05:35
| What will happen if we open the same file again in '''write mode'''? Let us see that.
|-
| 05:41
| In the '''writefile.pl''', Comment the previous '''print''' '''Statement'''.

|-
| 05:46
| Add the below '''print''' command.

|-
| 05:48
| Now, press''' Ctrl+S''' to save the file. Let us execute the program.

|-
| 05:54
| Switch back to the '''terminal''' and type '''perl writefile dot pl''' and press''' Enter'''.

|-
| 06:00
| Now let us check the''' second.txt''' file once again.

|-
| 06:04
| Type''' gedit second.txt''' and press '''Enter'''.

|-
| 06:09
| We can see the output “'''Greater than symbol (>) will overwrite the content of the file!" '''

|-
| 06:14
| The previous content of the '''second.txt''' file has been overwritten.

|-
| 06:19
| This is because we had opened the file in the '''write mode''' again.

|-
| 06:24
| Let us close the '''second.txt''' file.

|-
| 06:27
| Next, we will see how to append data to an existing file.

|-
| 06:32
| The '''open '''statement with two '''greater than''' (>> ) symbols denotes the '''APPEND''' mode.

|-
| 06:38
| Now I will open the '''writefile dot pl''' again in '''gedit'''.

|-
| 06:44
| In the '''open''' statement, type two '''greater (>>) than''' symbols. This will denote that the file is in '''append mode.'''

|-
| 06:52
|Comment the previous '''print''' '''statement''' as it is already executed.

|-
| 06:57
| Add the line '''print FILE1''' within double quotes ''' Two greater than symbols >> opens the file in append mode''' to append to the existing data.

|-
| 07:07
| Now, press''' Ctrl+S''' to save the file.

|-
| 07:11
| Let us execute the program.

|-
| 07:14
| Switch back to the '''terminal''' and type '''perl writefile dot pl''' and press''' Enter'''.

|-
| 07:20
| Now let us check whether the text has been appended to the''' second.txt''' file.

|-
| 07:26
| Type''' gedit second.txt''' and press '''Enter'''.

|-
| 07:31
| We can see the text has been appended in our''' second.txt''' file.

|-
| 07:36
| Let us close the '''second.txt''' file.

|-
| 07:39
| Similarly, there are other modes also.

|-
| 07:42
| Try out these options on your own and understand what happens.

|-
| 07:49
| This brings us to the end of this tutorial. Let us summarise.

|-
| 07:53
| In this tutorial we learnt to
* Open a file in read mode
* Write to a file
* Open a file in append mode and
* Close the file handle

|-
| 08:03
| Here is an assignment for you.
Change the file attribute to''' +>''' in the''' writefile.pl''' program.

|-
| 08:11
| Save and execute the program.

|-
| 08:14
| Open the''' second.txt''' file to see the output.

|-
| 08:17
| Analyse the usage of file attribute''' +>'''

|-
| 08:22
| The video at the following link summarises the Spoken Tutorial project.
Please download and watch it

|-
| 08:29
| The''' Spoken Tutorial Project''' Team
* conducts workshops using spoken tutorials and
* gives certificates on passing online tests.

|-
| 08:37
| For more details, please write to us.

|-
| 08:41
| Spoken Tutorial project is funded by NMEICT, MHRD, Government of India.

|-
| 08:48
| More information on this mission is available at this link.
|-
| 08:53
| This is Nirmala Venkat from IIT Bombay, signing off. Thanks for watching.

|}

@@ Line 11: / Line 11: @@
 |  00:06
 |  In this tutorial, we will learn how to:
-* Open a file in '''read mode'''
+Open a file in '''read mode'''
-* Write to a file
+Write to a file
-* Open a file in '''append mode'''
+Open a file in '''append mode'''
-* Close the '''file handle'''.
+Close the '''file handle'''.
 |-
 | 00:17
 |  For this tutorial, I am using:
-* '''Ubuntu Linux 12.04''' operating system
+'''Ubuntu Linux 12.04''' operating system
-* '''Perl 5.14.2''' and the
+'''Perl 5.14.2''' and the
-* ''' gedit''' Text Editor.
+''' gedit''' Text Editor.
 |-
@@ Line 38: / Line 38: @@
 |  00:43
 |  The basic operations we can do with files in '''Perl '''are:
-* open a file
+open a file
-* read from a file
+read from a file
-* write to a file and
+write to a file and
-* close a file.
+close a file.
 |-
 |00:54
 |  The default '''file handle'''s are:
-* '''STDIN'''
+'''STDIN'''
-* '''STDOUT'''
+'''STDOUT'''
-* '''STDERR'''
+'''STDERR'''
 |-
@@ Line 356: / Line 356: @@
 |  07:53
 |  In this tutorial, we learnt to:
-* Open a file in "read" mode
+Open a file in "read" mode
-* Write to a file
+Write to a file
-* Open a file in "append" mode and
+Open a file in "append" mode and
-* Close the '''file handle'''.
+Close the '''file handle'''.
 |-
@@ Line 384: / Line 384: @@
 |  08:29
 |  The''' Spoken Tutorial Project''' team:
-* conducts workshops using spoken tutorials and
+conducts workshops using spoken tutorials and
-* gives certificates on passing online tests.
+gives certificates on passing online tests.
 |-

@@ Line 251: / Line 251: @@
 |-
 |  05:41
-| In the 'writefile.pl', ''' comment'''  the previous '''print''' Statement.
+| In the 'writefile.pl', ''' comment'''  the previous '''print''' statement.
 |-
 | 05:46
-|  Add the below '''print''' command.
+| Add the '''print''' command shown below.
 |-
@@ Line 271: / Line 271: @@
 |-
 |  06:04
-|  Type: ''' gedit second.txt''' and press '''Enter'''.
+|  Type: "gedit second.txt" and press '''Enter'''.
 |-
@@ Line 299: / Line 299: @@
 |-
 |  06:38
-|  Now I will open the '''writefile dot pl''' again in '''gedit'''.
+|  Now, I will open the '''writefile dot pl''' again in '''gedit'''.
 |-

@@ Line 145: / Line 145: @@
 |  03:22
 |  Lastly, close the file with the''' FILEHANDLE''' name which we had given in the '''open''' statement.
 |-
@@ Line 301: / Line 300: @@
 |  06:38
 |  Now I will open the '''writefile dot pl''' again in '''gedit'''.
 |-

@@ Line 6: / Line 6: @@
 |-
 |  00:01
-|  Welcome to the''' Spoken Tutorial''' on''' File Handling in PERL.'''
+|  Welcome to the''' Spoken Tutorial''' on''' File Handling''' in '''PERL.'''
 |-
 |  00:06
-|  In this tutorial we will learn how to
+|  In this tutorial, we will learn how to:
-−
 * Open a file in '''read mode'''
 * Write to a file
 * Open a file in '''append mode'''
-* Close the file handle
+* Close the '''file handle'''.
 |-
 | 00:17
-|  For this tutorial, I am using
+|  For this tutorial, I am using:
-−
 * '''Ubuntu Linux 12.04''' operating system
-* '''Perl 5.14.2'''
+* '''Perl 5.14.2''' and the
-* and the''' gedit''' Text Editor
+* ''' gedit''' Text Editor.
 |-
 | 00:28
-|  You can use any text editor of your choice.
+|  You can use any '''text editor''' of your choice.
 |-
@@ Line 43: / Line 41: @@
 * read from a file
 * write to a file and
-* close a file
+* close a file.
 |-
 |00:54
-|  The default file handles are
+|  The default '''file handle'''s are:
-−
 * '''STDIN'''
 * '''STDOUT'''
@@ Line 59: / Line 56: @@
 |-
 | 01:05
-|  In the syntax''', FILEHANDLE''' is the''' file handle''' returned by the '''open '''function.
+|  In the syntax, '''FILEHANDLE''' is the''' file handle''' returned by the '''open '''function.
 |-
@@ Line 67: / Line 64: @@
 |-
 | 01:18
-|  '''EXPR''' is the physical filename used to read or write. In this case, '''“First.txt” '''is the filename.
+|  '''EXPR''' is the physical filename used to read or write. In this case, “First.txt” is the filename.
 |-
@@ Line 79: / Line 76: @@
 |-
 |  01:38
-|  First we will create a text file and store some data in it. Go to the '''terminal''' and type''' gedit first.txt''' and press '''Enter'''.
+|  First we will create a text file and store some data in it. Go to the '''terminal''' and type: '''gedit first.txt''' and press '''Enter'''.
 |-
@@ Line 87: / Line 84: @@
 |-
 | 01:55
-|  Save the file and close''' gedit'''.
+|  '''Save''' the file and close''' gedit'''.
 |-
 |  01:59
-|  Now we will look at a '''Perl '''program that opens the file''' first.txt''' and reads the content.
+|  Now we will look at a '''Perl '''program that opens the file 'first.txt' and reads the content.
 |-
 |  02:07
-|  Let me open the sample program''' openfile.pl''' which I have already saved.
+|  Let me open the sample program 'openfile.pl' which I have already saved.
 |-
 | 02:13
-|  Type''' gedit openfile dot pl ampersand''' and press''' Enter'''.
+|  Type: '''gedit openfile dot pl ampersand''' and press''' Enter'''.
 |-
@@ Line 111: / Line 108: @@
 |-
 | 02:28
-|  The''' open''' '''function''' opens a file for reading.
+|  The''' open''' function opens a file for reading.
 |-
@@ Line 123: / Line 120: @@
 |-
 | 02:44
-|  If you fail to specify the “'''Mode'''”, by default the file will be opened in “'''READ'''” mode.
+|  If you fail to specify the '''Mode''', by default the file will be opened in “READ” mode.
 |-
 | 02:50
-|  The third parameter''' first.txt''' is the''' filename''' from where the data has to be read.
+|  The third parameter 'first.txt' is the filename from where the data has to be read.
 |-
 | 02:57
-|  What will happen if the file''' first.txt''' does not exist?
+|  What will happen if the file 'first.txt' does not exist?
 |-
 | 03:02
-|  The script will die with the appropriate error message stored in the''' dollar exclamation ($!)'''variable.
+|  The script will die with the appropriate '''error message''', stored in the''' dollar exclamation ($!)'''variable.
 |-
 |  03:08
-|  The '''while '''loop will  read line by line  and loop through the'''<nowiki> <</nowiki>DATA>''' file  until all the lines have been read.
+|  The '''while '''loop will  read line by line  and loop through the '''<nowiki> <</nowiki>DATA>''' file  until all the lines have been read.
 |-
 | 03:17
-|  Print''' dollar underscore''' ('''$_)''' variable will print the contents of the current line.
+|  '''Print dollar underscore''' ('$_') variable will print the contents of the current line.
 |-
 |  03:22
-|  Lastly, close the file with the''' FILEHANDLE''' name, which we had given in the '''open''' statement.
+|  Lastly, close the file with the''' FILEHANDLE''' name which we had given in the '''open''' statement.
@@ Line 156: / Line 153: @@
 |-
 |  03:36
-|  Now, press''' Ctrl+S''' to save the file.
+|  Now, press''' Ctrl+S''' to '''save''' the file.
 |-
 |  03:40
-|  Let us execute the program.
+|  Let us '''execute''' the program.
 |-
 | 03:42
-|  Switch back to the''' terminal''' and type '''perl openfile dot pl''' and press''' Enter'''.
+|  Switch back to the terminal and type '''perl openfile dot pl''' and press''' Enter'''.
 |-

@@ Line 1: / Line 1: @@
 {| Border = 1
 |  '''Time'''
@@ Line 140: / Line 139: @@
 |-
 |  03:08
-|  The '''while '''loop will  read line by line  and loop through the'''<nowiki> <</nowiki>DATA>''' file
+|  The '''while '''loop will  read line by line  and loop through the'''<nowiki> <</nowiki>DATA>''' file  until all the lines have been read.
   until all the lines have been read.
 |-
@@ Line 246: / Line 244: @@
 |-
 |  05:23
-|  We can see the text''' Working with files makes data storage and retrieval a simple task! '''In our second.txt file.
+|  We can see the text''' Working with files makes data storage and retrieval a simple task! '''In our '''second.txt''' file.
 |-
@@ Line 281: / Line 279: @@
 |-
 | 06:09
-|  We can see the output  “'''Greater than symbol (>) will overwrite the content of the file!" '''
+|  We can see the output  “'''Greater than symbol (>) overwrites the content of the file!" '''
 |-