[SOLVED] How this command works

Swathi Prasad · 01-23-2018, 04:48 PM

Hi

I am bit new to Linux.

Can anybody explain How this command works

Code:

$ awk '/./{line=$0} END{print line}' file1

I know the above command prints the last non empty line.

for ex:file1 has text as shown below.

Code:

PGW|PGW_CDR_|2017-06-23 141946|2017-07-17 131633|2017-08-21 
PGW|PGW_CDR_|2017-06-23 141946|2017-07-17 131633|2017-08-21 
PGW|PGW_CDR_|2017-06-23 141946|2017-07-17 131633|2017-08-21 
PGW|PGW_CDR_|2017-06-23 141946|2017-07-17 131633|2017-08-21 
PGW|PGW_CDR_|2017-06-23 141946|2017-07-17 131633|2017-08-21 
Total number of rows: 5

last 2 lines in the file are empty lines.

and the above comand prints

Total number of rows: 5

Can anybody please decode the command and explain me.

Thanks

rknichols · 01-23-2018, 05:01 PM

Quote:

Originally Posted by Swathi Prasad

Can anybody explain How this command works

Code:

$ awk '/./{line=$0} END{print line}' file1

Putting the two code blocks on separate lines

Code:

/./ { line=$0 }
END { print line }

The first block matches any line that contains any character. The action block stores that entire line in the "line" variable, replacing whatever was there before.

The second block executes when end-of-file is reached on the input. The action block prints whatever is stored in the "line" variable.

MadeInGermany · 01-23-2018, 05:02 PM

The main loop (runs once per input line):
the regular expression . is true if there is any character met, then the following { block } is executed: the input line $0 is saved into the variable line.
At the END of the input file, the variable line is printed.

Swathi Prasad · 01-23-2018, 05:34 PM

Thank you for your elegant explanations!!

I want to delete the same line(Total number of rows: 5) and copy the remaining lines to file2.file1 content should not change at all.
file1 should be as it is.

file2 should look like

Code:

PGW|PGW_CDR_|2017-06-23 141946|2017-07-17 131633|2017-08-21 
PGW|PGW_CDR_|2017-06-23 141946|2017-07-17 131633|2017-08-21 
PGW|PGW_CDR_|2017-06-23 141946|2017-07-17 131633|2017-08-21 
PGW|PGW_CDR_|2017-06-23 141946|2017-07-17 131633|2017-08-21 
PGW|PGW_CDR_|2017-06-23 141946|2017-07-17 131633|2017-08-21

To achieve above ,does my below code makes sense

Code:

$ awk '/./{line=$0} END{delete}' file1 >file2

If not how to achieve this?

Thanks

keefaz · 01-23-2018, 06:01 PM

Code:

grep -v '^Total' file1 > file2

Swathi Prasad · 01-23-2018, 06:09 PM

I don't want to hard code any thing here,want to delete the last non empty line and copy the remaining text to the new file

keefaz · 01-23-2018, 06:45 PM

Input file is no consistant? No way to find a pattern to keep or a pattern to leave?
There can be blank lines in the middle too?

rknichols · 01-23-2018, 09:17 PM

An answer was given in your other thread. This thread should be locked as a duplicate. (reported)

rtmistler · 01-24-2018, 07:36 AM

Please post your thread in only one forum. Posting a single thread in the most relevant forum will make it easier for members to help you and will keep the discussion in one place. This thread is being closed because it is a duplicate.