Difference between revisions of "BASH/C2/String-and-File-attributes/English-timed"

!Time  

!Narration  

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

|   In this tutorial, we will learn

| * '''String comparison''' and '''File attributes comparison'''

|  For this tutorial, I am using  

| * '''Ubuntu Linux''' 12.04 Operating System and  

| * '''GNU BASH''' version 4.1.10

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

| To compare two '''equal strings'''.

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

| To compare two '''not equal strings'''.

 

|  I have a simple program here, that checks the user ID.

 

|  Open a file in your editor and save it as '''strcompare dot sh'''

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

|  Let me explain the code.   

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

 

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

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

 

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

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

| And here with '''fi ''' we end the '''if statement.'''

 

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

| A successful command returns a '''0 (zero)'''.

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

|   02:56

|   Now, let's execute the program.

|   02:58  

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

| Type '''whoami'''

| This will output the name of the current user.

| Type '''chmod +x strcompare dot sh'''

 

| Type '''dot slash strcompare dot sh'''

 

|  The output is displayed as:

|  Now let's execute the same '''program''' as '''root user.'''

|  It will prompt for an password.   

|  '''file1''' is the variable in which we save the path of the file.  

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

| And whether it is a normal file.

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

|  Else, it will '''echo "File does not exis" '''

| Switch back to the '''terminal''' let us execute our file.

|  Type '''chmod  plus x fileattrib dot sh'''

 

| '''File exists and is a normal file'''.

 

| Type '''gedit empty dot sh ampersand sign'''

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

| Type ''' empty dot sh '''

|   05:47

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

| And the second '''echo statement''' with:

| ''' “File is empty”'''

 

|  Come back to the terminal.   

| Let me clear the prompt.

| Let's execute.

| Type '''dot slash fileattrib dot sh''' press '''Enter.'''

| The output is '''File is empty.'''

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

 

| '''“User has write permission to this file”'''

| '''“User doesn't have write permission to this file”'''

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

|   Let me change the '''filepath''' to

| Let us execute our program.

| '''User doesn't have write permission to this file.'''

|  Now, let us see another example based on file attributes.

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

| Note that our filename is '''fileattrib2 dot sh'''

| Let's go through the code.

|  Here we have two variables '''file1''' and '''file2.'''

|  Here we check whether '''file1'''  is newer than '''file2.'''

|  If the '''condition''' is '''true''', we print '''file1 is newer than  file2.'''

| '''Else''', '''file2 is newer than  file1.'''

| If the '''condition''' is '''true''', we print '''file1 is older than  file2.'''

| Else, we print '''file2 is older than  file1.'''

| First, we will edit '''empty1 dot sh''' file

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

|  Now, let us make our script executeable.

| Type '''chmod plus x fileattrib2 dot sh'''

|  Now type '''dot slash fileattrib2 dot sh'''

 

| '''file2 is older than file1'''

|  Type echo within double quotes '''How are you''' after the quotes (greater than sign) >'''empty2 dot sh'''.  

| Let me clear the prompt.

|  Now let us execute our script again.  

| Press the up-arrow key.  

|  Now the output is displayed as:

| '''file2 is newer than file1'''

| And '''file1 is older than file2'''

|  Let us summarise.

| In this tutorial we learnt,

| '''String comparison'''

 

|'''file attributes'''

|'''!= (not equal to)'''

 

|'''-f (hyphen f) '''

|'''-s'''(hyphen s)

 

|'''-w'''(hyphen w)

|'''-nt'''(hyphen nt)

 

|and '''-ot '''(hyphen ot)attributes.

|   As an assignment

 

|-

| Explore some more attributes.

| Ex: '''-r '''

 

'''-x'''

 

and '''-o'''

|  Watch the video available at the link shown below

| It summarises the Spoken Tutorial project  

| If you do not have good bandwidth, you can download and watch it

|  The Spoken Tutorial Project Team

| Conducts workshops using spoken tutorials  

| Gives certificates to those who pass an online test  

| 11:02

|   Spoken Tutorial Project is a part of the Talk to a Teacher project

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

| More information on this Mission is available at the link shown below .

| This is Ashwini Patil from IIT Bombay signning off.