Difference between revisions of "BASH/C3/Here-document-and-Here-string/English-timed"

|  Dear friends, Welcome to the spoken tutorial on''' HERE document and strings'''

| * special-purpose redirection called '''Here documents '''and '''Here strings'''

| * With the help of some examples  

|  To follow this tutorial you should have knowledge of '''Shell Scripting''' in''' BASH.'''

|If not, for relevant tutorials please visit our website which is as shown,'''(http://www.spoken-tutorial.org)'''

|  For this tutorial I am using''' '''

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

|* '''GNU BASH''' version 4.2

|Please note,''' GNU Bash''' '''version 4''' or above is recommended for practice.

|  Let us learn about '''Here document'''.

|* It is a special-purpose block of text or code.  

|* It is a form of I/O redirect.

|* It feeds a command list to an interactive program or command line.

|* It can be treated as a separate file.

|* It can also be treated as multiple line input redirected to a shell script.

|  Syntax is,

 

|-

|'''command space less than less than space HERE'''.

|After this on the next line, we can give the text inputs.  

|Here, '''text1, text2, textN''' are the text inputs.

|I will open a file named '''here dot sh '''

|  Let me put a block of code after this line.

| wc represents word count  

| '''wc hyphen w counts the number of words in the '''HERE''' document

|The block of code or text until the second occurance of '''HERE''' will be treated as a file  

|The content present in '''HERE''' document is an input to the command '''wc hyphen w'''

|  '''HERE''' acts as a delimiter for '''wc hyphen w''' command while reading multi-line input.

|If we try to execute the same command in the '''terminal''', we should get ''''4'''' as an output.

|This is because we have passed four words to the command ''''wc hyphen w''''.  

|Now click on '''Save''' to save the file.

|Type '''dot slash here dot sh'''

|  We can see the output as '''4.'''

|That is, number of words in '''Here document '''is '''4.'''

|  Come back to the program.

|Let us add two more words here at the beginning of the text.

|'''Hello and welcome to Bash learning'''

|Let us execute the program again.

|  On the '''terminal, type '''dot slash here dot sh'''

|  We can also pass an argument to the '''Here document.'''

|Let me open a file named '''hereoutput dot sh'''

|  The command '''cat''' will concatenate files and print the standard output.

|  Note that we have used the string '''this''' instead of '''HERE.'''

|You can use any other delimiter also.

|  This line will display the '''0th (zeroeth) argument'''.

|The '''0th (zeroeth) argument''', by default, is the '''filename'''.

|  This line will display the '''1st argument''' passed to the program.

|  And this line will display the '''2nd argument''' passed to the program.

|  Here we have to close the document using the same delimiter, '''this.'''

|  Save the file.

 

|  Let us now execute the program.

|On the '''terminal''' type: '''chmod space plus x space hereoutput dot sh'''

|Type '''dot slash hereoutput dot sh space Sunday space Monday'''

|  The output is dispalyed as:

|'''0'th argument is: dot salsh hereoutput dot sh ''' which is the '''filename.'''

|'''1st argument is: Sunday'''

|'''2nd argument is: Monday '''

|  Let us learn about '''Here string''' now.

|* '''Here string '''is used for input redirection from text or a variable.

|* The input is mentioned in the same line within single quotes.

|  The syntax is, '''command space three less than symbols space''' within single quotes write '''string'''

|I will open the same file '''here dot sh'''

|  Here at the end, I will type: '''wc space hyphen w three less than symbols space''' within single quotes '''Welcome to Bash learning'''

|This will redirect the string within quotes to the command '''wc hyphen w.'''

|Now Click on '''Save '''to save the changes.

|  Now type: '''dot slash here dot sh'''

|  We can see the output as '''6''' and '''4'''

|Number of words in '''here document''' is '''6''' and number of words in '''here string''' is''' 4.'''

|  Likewise, you can write your own '''Here strings.'''

|Let us summarise.  

|In this tutorial we learnt about

|* '''HERE document'''

|* '''HERE string'''  

|  As an assignment, convert a string to uppercase using:

|* '''Here document'''

 

|* '''Here string'''

|This is the command to convert characters from lower to upper case.

|It summarises the Spoken Tutorial project.

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|This is Ashwini Patil from IIT Bombay. Signing off