Linux/C3/Basics-of-awk/Khasi

Time	Narration
00:01	Pdiang sngewbha sha kane ka spoken tutorial halor ka awk command.
00:05	Ha kane ka tutorial, ngin pule iaka jingpyndonkam In this tutorial we will learn awk command.
00:09	We will do this through some examples.
00:12	To record this tutorial, I am using: Ubuntu Linux 12.04 OS GNU BASH v. 4.2.24
00:23	Please note, GNU Bash version 4 or above is recommended to practice this tutorial.
00:29	Let us start with an introduction to awk.
00:33	The awk command is a very powerful text manipulation tool.
00:38	It is named after its authors, Aho, Weinberger and Kernighan.
00:44	It can perform several functions.
00:46	It operates at the field level of a record.
00:51	So, it can easily access and edit the individual fields of the record.
00:56	Let us see some examples.
00:59	For demonstration purpose, we use the awkdemo.txt file.
01:04	Let us see the contents of awkdemo.txt file.
01:09	Now open the terminal window by pressing Ctrl + Alt and T keys simultaneously on your keyboard.
01:17	Let us see how to print using awk command.
01:22	Type: awk space (within single quote) (front slash) '/Pass (front slash)/(opening curly bracket) {print (closing curly bracket)} (after the quotes) space awkdemo.txt
01:38	Press Enter.
01:40	Here, Pass is the selection criteria.
01:44	All the lines of the awkdemo where Pass occurs are printed.
01:49	The action here is print.
01:52	We can also use regular expressions in awk.
01:56	Say, we want to print records of students with name "Mira."
02:01	We would type: awk space '/M (opening square bracket) [ ei (closing square bracket) ]*ra */{print}' space awkdemo.txt
02:27	Press Enter.
02:29	"*" will give one or more occurrences of previous character.
02:33	Thus, entries with more than one occurrence for i, e and a will be listed.
02:40	For example,
02:42	Mira with M I R A
02:45	Meera with M double E R A
02:47	and Meeraa with M double E R double A
02:52	awk supports the extended regular expressions (ERE)
02:58	Which means we can match multiple patterns separated by a PIPE.
03:03	Let me clear the prompt.
03:05	electrical(front slash)space (opening curly brackets)/{print}(closing curly brackets) after the quotes spaceawkdemo.txt
03:23	Press Enter.
03:26	Now entries for both "civil" and "electrical" are given.
03:31	Let us go back to our slides.
03:34	Parameters: awk has some special parameters to identify individual fields of a line.
03:41	$1(Dollar 1) would indicate the first field.
03:45	Similarly we can have $2, $3 and so on for respective fields.
03:53	$0 represents the entire line.
03:56	come back to our terminal.
03:59	Note that each word is separated by PIPE in the file awkdemo.txt.
04:05	In this case PIPE is called a delimiter.
04:09	A delimiter separates words from each other.
04:13	A delimiter can also be a single white space.
04:16	To specify a delimiter, we have to give - capital F flag followed by a delimiter.
04:24	Let us see. Type: awk space minus capital F space within double quotes PIPE space within single quote front-slash civil PIPE electrical front-slash opening curly bracket print space dollar0 closing curly bracket after the quotes space awkdemo.txt
04:51	Press Enter.
04:53	This prints the entire line since we have used $0.
04:58	Notice that names and stream of students are the second and third fields.
05:04	Say we only want to print two fields.
05:08	We will replace $0 with $2 and $3 in the above command.
05:15	Press Enter .
05:18	Only two fields are shown.
05:21	Though it gives the right result, the display is all jagged and un-formatted.
05:26	We can provide formatted output by using the C style printf statement.
05:32	We can also provide a serial number by using a built-in variable NR.
05:40	We will see more about built-in variables later.
05:44	Now Type awk space minus capital F within double quotes (Pipe) after the double quotes space 'front-slash Pass front slash opening curly bracket printf (within double quotes) "percentage sign 4d space percentage sign -25s space percentage sign minus 15s space backslash n”, after the double quotes NR, $2, $3 closing curly bracket' after the single quote space awkdemo.txt
06:33	Press Enter. We see the difference.
06:37	Here, NR stands for number of records.
06:41	Records are integers, hence we have written %d.
06:45	Name and Stream are strings. So we have used %s.
06:50	Here 25s will reserve 25 spaces for Name field.
06:55	15s will reserve 15 spaces for Stream field.
07:01	The minus sign is used to left justify the output.
07:05	This brings us to the end of this tutorial.
07:08	Let us move back to our slides.
07:10	Let us summarize. In this tutorial we learnt: * To print using awk
07:16	Regular expression in awk * To list the entries for a particular stream
07:21	To list only the second and the third fields
07:24	To display a formatted output.
07:28	As an assignment, display roll no., stream and marks of Ankit Saraf.
07:34	Watch the video available at the link shown below.
07:37	It summarizes the Spoken Tutorial project.
07:40	If you do not have good bandwidth, you can download and watch it.
07:45	The Spoken Tutorial Project Team: Conducts workshops using spoken tutorials.
07:48	Gives certificates to those who pass an online test.
07:52	For more details, please write to contact@spoken-tutorial.org
07:58	Spoken Tutorial Project is a part of the Talk to a Teacher project.
08:01	It is supported by the National Mission on Education through ICT,MHRD,Government of India.
08:07	More information on this Mission is available at: [1]
08:12	This is Ashwini Patil from IIT Bombay, signning off. Thank you for joining.

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