BASH/C2/String-and-File-attributes/English-timed - Revision history

Pratik kamble at 10:49, 23 March 2017

2017-03-23T10:49:42Z

Pratik kamble at 09:58, 7 March 2017

2017-03-07T09:58:59Z

Pratik kamble at 06:03, 5 January 2017

2017-01-05T06:03:18Z

Sandhya.np14 at 09:22, 13 July 2015

2015-07-13T09:22:21Z

Show changes

Sandhya.np14 at 06:45, 13 July 2015

2015-07-13T06:45:54Z

Sandhya.np14 at 11:53, 3 July 2015

2015-07-03T11:53:34Z

Sandhya.np14 at 11:52, 3 July 2015

2015-07-03T11:52:48Z

Show changes

Ranjana at 12:30, 8 December 2014

2014-12-08T12:30:44Z

PoojaMoolya at 05:52, 8 December 2014

2014-12-08T05:52:18Z

Ranjana: Created page with "'''Title of script:''' '''String and File Attributes''' '''comparison in Bash''' '''Author:''' Ashwini Patil '''Keywords: video tutorial, ==, !=, string compare, file attrib..."

2014-11-21T08:00:29Z

Created page with "'''Title of script:''' '''String and File Attributes''' '''comparison in Bash''' '''Author:''' Ashwini Patil '''Keywords: video tutorial, ==, !=, string compare, file attrib..."

New page

'''Title of script:''' '''String and File Attributes''' '''comparison in Bash'''

'''Author:''' Ashwini Patil

'''Keywords: video tutorial, ==, !=, string compare, file attributes.'''

{| border=1
!Time
!Narration

|-
| 00:01
| Dear friends, Welcome to the spoken tutorial on '''String and File Attributes comparison in Bash.'''

|-
| 00:10
| In this tutorial, we will learn

|-
| 00:13
| * '''String comparison''' and '''File attributes comparison'''

|-
| 00:18
| We will do this using a few examples.

|-
| 00:22
| For this tutorial, I am using

|-
| 00:25
| * '''Ubuntu Linux''' 12.04 Operating System and

|-
| 00:30
| * '''GNU BASH''' version 4.1.10

|-
| 00:34
| Please note,''' GNU Bash''' version '''4''' or above, is recommended to practise this tutorial.

|-
| 00:42
| Let us start with an introduction.

|-
| 00:45
| There are two ways to compare a '''string''' in '''Bash'''.

|-
| 00:49
| 1) First: using == (equal to equal to) operator

|-
| 00:53
| To compare two '''equal strings'''.

|-
| 00:56
| 2) Second: != (not equal to) operator.

|-
| 00:59
| To compare two '''not equal strings'''.

|-
| 01:03
| Let us look at an example.

|-
| 01:06
| I have a simple program here, that checks the user ID.

|-
| 01:11
| Open a file in your editor and save it as '''strcompare dot sh'''

|-
| 01:19
| Now, type the code as shown here, in your '''strcompare dot sh''' file.

|-
| 01:26
| Let me explain the code.

|-
| 01:28
| This is '''shebang line.'''

|-
| 01:31
| '''whoami''' command gives the '''username''' of the current '''user.'''

|-
| 01:36
| The '''if''' statement checks the output of the variable '''whoami ''' against the '''string “root”'''.

|-
| 01:44
| We have used '''not-equal to''' operator here to compare the '''strings'''.

|-
| 01:50
| If the current user is not the '''root user,''' then it will '''echo''' this statement -

|-
| 01:57
| '''“You have no permission to run strcompare dot sh as non-root user.”'''

|-
| 02:05
| Here '''$0 (dollar zero)''' is the '''zeroeth''' argument which is a '''filename''' itself.

|-
| 02:13
| If the user is the '''root user''', it will '''echo -''' '''“Welcome root!”'''

|-
| 02:18
| Then we have the '''exit''' statement for the program.

|-
| 02:23
| And here with '''fi ''' we end the '''if statement.'''

|-
| 02:28
| Let us switch back to our slides to know more about the '''exit statement.'''

|-
| 02:34
| Every program returns an '''exit status'''.

|-
| 02:38
| A successful command returns a '''0 (zero)'''.

|-
| 02:42
| An erroneous command returns a '''non-zero''' '''value.'''

|-
| 02:47
| It can be interpreted as an '''error code'''.

|-
| 02:51
| We can customize return value of the '''exit statement '''.

|-
| 02:56
| Now, let's execute the program.

|-
| 02:58
| Open the terminal by pressing '''Ctrl+Alt''' and T '''keys simultaneously on your keyboard.

|-
| 03:08
| First, let's check the current user of the system.

|-
| 03:12
| Type '''whoami'''

|-
| 03:15
| Press '''Enter.'''

|-
| 03:17
| This will output the name of the current user.

|-
| 03:21
| Now let's make our script executable.

|-
| 03:25
| Type '''chmod +x strcompare.sh'''

|-
| 03:32
| Type '''./strcompare.sh'''

|-
| 03:37
| The output is displayed as:

|-
| 03:39
| '''You have no permission to run dot slash strcompare dot sh as non-root user.'''

|-
| 03:47
| Now let's execute the same '''program''' as '''root user.'''

|-
| 03:52
| Type: '''sudo dot slash strcompare.sh '''

|-
| 03:58
| It will prompt for an password.

|-
| 04:01
| Give your password here.

|-
| 04:04
| The output is displayed as: '''Welcome root!. '''

|-
| 04:08
| Now, let's learn about the '''file attributes''' comparison.

|-
| 04:13
| I already have a working example of the code.

|-
| 04:17
| In this program, we will check whether a given file exists or not.

|-
| 04:23
| '''file1''' is the variable in which we save the path of the file.

|-
| 04:29
| Then '''-(hyphen) f''' command checks whether the file exists or not.

|-
| 04:33
| And whether it is a normal file.

|-
| 04:37
| If the condition is '''true,''' it will '''echo'" File exists and is a normal file"'

|-
| 04:44
| Else, it will '''echo"' File does not exis '''

|-
| 04:48
| Back to the '''terminal''' let us execute our file.

|-
| 04:53
| Type '''chmod plus x fileattrib dot sh'''

|-
| 05:00
| Type: '''dot slash fileattrib dot sh'''

|-
| 05:05
| The output is displayed as:

|-
| 05:07
| '''File exists and is a normal file'''.

|-
| 05:11
| Now we will check whether the file is empty or not.

|-
| 05:12
| Before executing our program, I will create an empty file named as '''empty dot sh'''.

|-
| 05:24
| Type '''gedit empty dot sh ampersand sign'''

|-
| 05:31
| Click on '''Save''' close the file.

|-
| 05:35
| |Let us replace '''- (hyphen) f''' attrib with '''- (hyphen) s''' attribute.

|-
| 05:41
| Replace the filename here as well.

|-
| 05:45
| Type ''' empty.sh '''

|-
| 05:47
| Now, replace the first '''echo statement''' with:

|-
| 05:51
| “File exists and is not empty”'''

|-
| 05:54
| And the second '''echo statement''' with:

|-
| 05:57
| “File is empty”'''

|-
| 05:59
| Click on '''Save'''.

|-
| 06:01
| Come back to the terminal.

|-
| 06:03
| Let me clear the prompt.

|-
| 06:06
| Let's execute.

|-
| 06:08
| Type '''dot slash fileattrib dot sh''' press '''Enter.'''

|-
| 06:13
| The output is '''File is empty.'''

|-
| 06:17
| Now, let us see another file attribute, which will check the '''write premission''' of any file.

|-
| 06:24
| Come back to our program.

|-
| 06:26
| Let us replace the '''- (hyphen) s''' attribute with '''- (hyphen) w'''.

|-
| 06:32

| Now replace the first '''echo statement''' with:

|-
| 06:36
| '''“User has write permission to this file”'''

|-
| 06:40
| And the second '''echo statement''' with:

|-
| 06:43
| '''“User doesn't have write permission to this file”'''

|-
| 06:47
| Click on '''Save'''.

|-
| 06:49
| I will use a different file for this example.

|-
| 06:53
| I will select a file, which is not a readable file or which does not have '''write permission'''.

|-
| 07:01
| Let me change the '''filepath''' to

|-
| 07:04
| '''“slash etc slash mysql slash debian dot cnf”'''

|-
| 07:10
| Click on '''Save'''.

|-
| 07:12
| Let us execute our program.

|-
| 07:15
| Press the '''up-arrow key'''. Press '''Enter'''.

|-
| 07:19
| We see that the output is displayed as:

|-
| 07:21
| '''User doesn't have write permission to this file.'''

|-
| 07:26
| Now, let us see another example based on file attributes.

|-
| 07:31
| In this example, we will check whether '''file1''' is newer than '''file2.'''

|-
| 07:38
| Let us see the program.

|-
| 07:40
| Note that our filename is '''fileattrib2.sh'''

|-
| 07:46
| Let's go through the code.

|-
| 07:48
| Here we have two variables '''file1''' and '''file2.'''

|-
| 07:53
| The two files have already been created and are empty.

|-
| 07:58
| Here we check whether '''file1''' is newer than '''file2.'''

|-
| 08:04
| If the '''condition''' is '''true''', we print '''file1 is newer than file2.'''

|-
| 08:09
| Else, '''file2 is newer than file1.'''

|-
| 08:14
| This is another '''if statement.'''

|-
| 08:16
| Here we check whether '''file1''' is older than '''file2.'''

|-
| 08:21
| If the '''condition''' is '''true''', we print '''file1 is older than file2.'''

|-
| 08:27
| Else, we print '''file2 is older than file1.'''

|-
| 08:32
| Come back to our '''terminal.'''

|-
| 08:35
| First, we will edit '''empty1.sh''' file

|-
| 08:39
| I will just add an '''echo statement''' in it.

|-
| 08:42
| Type: '''echo within doubel quotes Hiii after the double quotes greater than sign empty one dot sh''' Press '''Enter'''.

|-
| 08:53
| Now, let us make our script executeable.

|-
| 08:57
| Type - '''chmod plus x fileattrib2 dot sh'''

|-
| 09:03
| Now type '''dot slash fileattrib2 dot sh'''

|-
| 09:09
| We see the output as:

|-
| 09:11
| '''file1 is newer than file2'''

|-
| 09:15
| '''file2 is older than file1'''

|-
| 09:19
| Now let's edit '''empty2.sh''' file.

|-
| 09:23
| Here also I will add an '''echo statement.'''

|-
| 09:27
| Type echo within double quotes '''How are you''' after the quotes greater than sign >'''empty2.sh'''.

|-
| 09:38
| Let me clear the prompt.

|-
| 09:41
| Now let us execute our script again.

|-
| 09:45
| Press the up-arrow key.

|-
| 09:45
| Go to '''./fileattrib2.sh''' Press '''Enter.'''

|-
| 09:53
| Now the output is displayed as:

|-
| 09:55
| '''file2 is newer than file1'''

|-
| 09:59
| And '''file1 is older than file2'''

|-
| 10:03
| This brings us to the end of this tutorial.

|-
| 10:06
| Let us summarise.

|-
| 10:08
| In this tutorial we learnt,

|-
| 10:11
| '''String comparison'''

'''file attributes'''

'''<nowiki>==</nowiki>'''

'''!='''

'''-f '''

'''-s'''

'''-w'''

'''-nt'''

and '''-ot ''' attributes.

|-
| 10:25
| As an assignment

|-
| 10:26
| Explore some more attributes.

|-
| 10:29
| Ex: '''-r '''

'''-x'''

and '''-o'''

|-
| 10:33
| Watch the video available at the link shown below

|-
| 10:36
| It summarises the Spoken Tutorial project

|-
| 10:40
| If you do not have good bandwidth, you can download and watch it

|-
| 10:45
| The Spoken Tutorial Project Team

|-
| 10:47
| Conducts workshops using spoken tutorials

|-
| 10:51
| Gives certificates to those who pass an online test

|-
| 10:55
| For more details, please write to contact@spoken-tutorial.org

|-
| 11:02
| Spoken Tutorial Project is a part of the Talk to a Teacher project

|-
| 11:06
| It is supported by the National Mission on Education through ICT, MHRD, Government of India

|-
| 11:14
| More information on this Mission is available at the link shown below .

|-
| 11:19
| The script has been contributed by Fossee and spoken-tutorial team.

|-
| 11:25
| This is Ashwini Patil from IIT Bombay signning off.

|-
| 11:29
| Thank You for joining.

|}

@@ Line 13: / Line 13: @@
 |-
 | 00:13
-| * '''String''' comparison and '''File attributes''' comparison.
+|'''String''' comparison and '''File attributes''' comparison.
 |-
@@ Line 25: / Line 25: @@
 |-
 | 00:25
-| * '''Ubuntu Linux''' '''12.04''' Operating System and
+|'''Ubuntu Linux''' '''12.04''' Operating System and
 |-
 | 00:30
-| * '''GNU BASH''' version '''4.1.10'''
+|'''GNU BASH''' version '''4.1.10'''
 |-
@@ Line 545: / Line 545: @@
 |-
 | 10:11
-|* '''String''' comparison'''file attributes'''
+|'''String''' comparison'''file attributes'''
 |-
 | 10:14
-|* '''==(equal to equal to)'''
+|'''==(equal to equal to)'''
 |-
 | 10:16
-|* '''!= (not equal to)'''* '''-f''' (hyphen f)
+|'''!= (not equal to)'''* '''-f''' (hyphen f)
 |-
 | 10:18
-|* '''-s''' (hyphen s)* '''-w''' (hyphen w)
+|'''-s''' (hyphen s)* '''-w''' (hyphen w)
 |-
 | 10:21
-|* '''-nt''' (hyphen nt) and '''-ot '''(hyphen ot) '''attribute'''s.
+|'''-nt''' (hyphen nt) and '''-ot '''(hyphen ot) '''attribute'''s.
 |-

@@ Line 144: / Line 144: @@
 |-
-|   02:56
+|02:56
-|   Now, let's '''execute''' the program.
+|Now, let's '''execute''' the program.
 |-
-|   02:58
+|02:58
-|  Open the '''terminal window''' by pressing '''Ctrl+Alt''' and '''T''' keys simultaneously on your keyboard.
+|Open the '''terminal window''' by pressing '''Ctrl+Alt''' and '''T''' keys simultaneously on your keyboard.
 |-
@@ Line 288: / Line 288: @@
 |-
-|   05:47
+|05:47
-|   Now, replace the first '''echo statement''' with:
+|Now, replace the first '''echo statement''' with:
 |-
@@ Line 329: / Line 329: @@
 |-
 |  06:17
-|   Now, let us see another file attribute which will check the '''write permission''' of any file.
+|Now, let us see another file attribute which will check the '''write permission''' of any file.
 |-
@@ Line 545: / Line 545: @@
 |-
 | 10:11
-|* '''String''' comparison
+|* '''String''' comparison'''file attributes'''
-−
-|-
-| 10:12
-|* '''file attributes'''
 |-
@@ Line 557: / Line 553: @@
 |-
 | 10:16
-|* '''!= (not equal to)'''
+|* '''!= (not equal to)'''* '''-f''' (hyphen f)
-−
-|-
-| 10:17
-|* '''-f''' (hyphen f)
 |-
 | 10:18
-|* '''-s''' (hyphen s)
+|* '''-s''' (hyphen s)* '''-w''' (hyphen w)
-−
-|-
-| 10:19
-|* '''-w''' (hyphen w)
 |-
 | 10:21
-|* '''-nt''' (hyphen nt) and
+|* '''-nt''' (hyphen nt) and '''-ot '''(hyphen ot) '''attribute'''s.
-−
-|-
-| 10:22
-|* '''-ot '''(hyphen ot) '''attribute'''s.
 |-
 |  10:25
-| As an assignment-
+| As an assignment-explore some more attributes.
-−
-|-
-| 10:26
-| explore some more attributes.
 |-
@@ Line 620: / Line 600: @@
 |-
-|  11:02
+|11:02
-|   '''Spoken Tutorial''' project is a part of the '''Talk to a Teacher''' project.
+|'''Spoken Tutorial''' project is a part of the '''Talk to a Teacher''' project.
 |-

@@ Line 1: / Line 1: @@
 {| border=1
-!Time
+|'''Time'''
-!Narration
+|'''Narration'''
 |-

@@ Line 540: / Line 540: @@
 |-
-| 09:45
+| 09:47
 | Go to '''dot slash fileattrib2 dot sh''' Press '''Enter.'''

@@ Line 21: / Line 21: @@
 |-
 | 00:13
-| * '''String comparison''' and '''File attributes comparison'''.
+| * '''String''' comparison and '''File attributes''' comparison.
 |-
@@ Line 61: / Line 61: @@
 |-
 | 00:56
-| 2) Second: != (not equal to) operator.
+| 2) Second: != (not equal to) operator
 |-
@@ Line 73: / Line 73: @@
 |-
 |  01:06
-|  I have a simple program here that checks the user ID.
+|  I have a simple program here that checks the '''user ID'''.
 |-
@@ Line 93: / Line 93: @@
 |-
 | 01:31
-|  '''whoami''' '''command''' gives the '''username''' of the current '''user.'''
+|  '''whoami''' command gives the '''username''' of the current '''user.'''
 |-
@@ Line 101: / Line 101: @@
 |-
 |  01:44
-| We have used '''not-equal to''' operator here to compare the '''strings'''.
+| We have used '''not-equal to''' operator here to compare the strings.
 |-
@@ Line 114: / Line 114: @@
 |-
 | 02:05
-| Here '''$0 (dollar zero)''' is the '''zeroth''' argument which is a 'file-name' itself.
+| Here, '''$0 (dollar zero)''' is the zeroth '''argument''' which is a 'file-name' itself.
 |-
 |  02:13
-|   If the user is the '''root user''', it will '''echo -''' '''“Welcome root!”'''.
+|   If the user is the '''root user''', it will '''echo -''' “Welcome root!”.
 |-
@@ Line 126: / Line 126: @@
 |-
 | 02:23
-| And here with '''fi ''' we end the '''if statement.'''
+| And here with '''"fi" ''' we end the '''if statement.'''
 |-
@@ Line 138: / Line 138: @@
 |-
 | 02:38
-| A successful command returns a '''0 (zero)'''.
+| A successful command returns a '''0 '''(zero).
 |-
 | 02:42
-| An erroneous command returns a '''non-zero''' '''value.'''
+| An erroneous command returns a non-zero '''value.'''
 |-
@@ Line 158: / Line 158: @@
 |-
 |   02:58
-|  Open the '''terminal''' by pressing '''Ctrl+Alt''' and '''T''' keys simultaneously on your keyboard.
+|  Open the '''terminal window''' by pressing '''Ctrl+Alt''' and '''T''' keys simultaneously on your keyboard.
 |-
@@ Line 166: / Line 166: @@
 |-
 |  03:12
-| Type '''whoami'''.
+| Type: '''whoami'''.
 |-
@@ Line 190: / Line 190: @@
 |-
 | 03:37
-|  The output is displayed as:
+|  The '''output''' is displayed as:
 |-
@@ Line 198: / Line 198: @@
 |-
 | 03:47
-|  Now let's execute the same '''program''' as '''root user.'''
+|  Now let's execute the same program as '''root user.'''
 |-
@@ Line 206: / Line 206: @@
 |-
 |  03:58
-|  It will prompt for an password.
+|  It will prompt for a password.
 |-

@@ Line 33: / Line 33: @@
 |-
 | 00:25
-| * '''Ubuntu Linux''' 12.04 Operating System and
+| * '''Ubuntu Linux''' '''12.04''' Operating System and
 |-
 | 00:30
-| * '''GNU BASH''' version 4.1.10
+| * '''GNU BASH''' version '''4.1.10'''
 |-

@@ Line 117: / Line 117: @@
 |-
 | 02:05
-| Here '''$0 (dollar zero)''' is the '''zeroeth''' argument which is a '''filename''' itself.
+| Here '''$0 (dollar zero)''' is the '''zeroeth''' argument which is a filename itself.
 |-
@@ Line 163: / Line 163: @@
 |-
 |   02:58
-|  Open the terminal by pressing '''Ctrl+Alt''' and T '''keys simultaneously on your keyboard.
+|  Open the terminal by pressing '''Ctrl+Alt''' and '''T''' keys simultaneously on your keyboard.
 |-
@@ Line 187: / Line 187: @@
 |-
 | 03:25
-| Type '''chmod +x strcompare.sh'''
+| Type '''chmod +x strcompare dot sh'''
 |-
 | 03:32
-| Type '''./strcompare.sh'''
+| Type '''dot slash strcompare dot sh'''
@@ Line 209: / Line 209: @@
 |-
 | 03:52
-| Type: '''sudo dot slash strcompare.sh '''
+| Type: '''sudo dot slash strcompare dot sh '''
 |-
@@ Line 241: / Line 241: @@
 |-
 |  04:29
-|   Then '''-(hyphen) f''' command checks whether the file exists or not.
+|  '''-(hyphen) f''' command checks whether the file exists or not.
 |-
@@ Line 249: / Line 249: @@
 |-
 |  04:37
-|   If the condition is '''true,'''  it will '''echo'" File exists and is a normal file"'
+|   If the condition is '''true,'''  it will '''echo "File exists and is a normal file" '''
 |-
 |   04:44
-|   Else, it will '''echo"' File does not exis '''
+|   Else, it will '''echo "File does not exis" '''
 |-
 |   04:48
-| Back to the '''terminal''' let us execute our file.
+| Switch back to the '''terminal''' let us execute our file.
 |-
@@ Line 283: / Line 283: @@
 |-
-| 05:12
+| 05:16
 |   Before executing our program, I will create an empty file named as '''empty dot sh'''.
@@ Line 292: / Line 292: @@
 |-
 | 05:31
-| Click on '''Save'''  close the file.
+| Click on '''Save''',  close the file.
 |-
@@ Line 304: / Line 304: @@
 |-
 |  05:45
-| Type ''' empty.sh '''
+| Type ''' empty dot sh '''
 |-
@@ Line 312: / Line 312: @@
 |-
 |  05:51
-|  “File exists and is not empty”'''
+|  ''' “File exists and is not empty”'''
 |-
@@ Line 320: / Line 320: @@
 |-
 | 05:57
-| “File is empty”'''
+| ''' “File is empty”'''
@@ Line 362: / Line 362: @@
 |-
 |  06:32
 |   Now replace the first '''echo statement''' with:
@@ Line 432: / Line 431: @@
 |-
 |  07:40
-| Note that our filename is '''fileattrib2.sh'''
+| Note that our filename is '''fileattrib2 dot sh'''
 |-
@@ Line 456: / Line 455: @@
 |-
 | 08:09
-| Else, '''file2 is newer than  file1.'''
+| '''Else''', '''file2 is newer than  file1.'''
 |-
@@ Line 480: / Line 479: @@
 |-
 |   08:35
-| First, we will edit '''empty1.sh''' file
+| First, we will edit '''empty1 dot sh''' file
 |-
@@ Line 488: / Line 487: @@
 |-
 | 08:42
-| Type: '''echo within doubel quotes Hiii after the double quotes greater than sign empty one dot sh''' Press '''Enter'''.
+| Type: '''echo within doubel quotes Hiii after the double quotes greater than sign empty one dot sh'''. Press '''Enter'''.
 |-
@@ Line 496: / Line 495: @@
 |-
 | 08:57
-| Type - '''chmod plus x fileattrib2 dot sh'''
+| Type  '''chmod plus x fileattrib2 dot sh'''
 |-
@@ Line 517: / Line 516: @@
 |-
 |  09:19
-|   Now let's edit '''empty2.sh''' file.
+|   Now let's edit '''empty2 dot sh''' file.
 |-
@@ Line 526: / Line 525: @@
 |-
 |  09:27
-|   Type echo within double quotes '''How are you''' after the quotes greater than sign >'''empty2.sh'''.
+|   Type echo within double quotes '''How are you''' after the quotes (greater than sign) >'''empty2 dot sh'''.
 |-
@@ Line 542: / Line 541: @@
 |-
 | 09:45
-| Go to '''./fileattrib2.sh''' Press '''Enter.'''
+| Go to '''dot slash fileattrib2 dot sh''' Press '''Enter.'''
@@ Line 574: / Line 573: @@
 | '''String comparison'''
-'''file attributes'''
+|-
-'''<nowiki>==</nowiki>'''
+|-
-'''!='''
+|-
-'''-f '''
+|-
-'''-s'''
+|-
-'''-w'''
+|-
-'''-nt'''
+|-
-  and  '''-ot ''' attributes.
+  |-
 |-