Print the last column of a row in a file

Question

I have a file that is constantly being written to / updated. I want to find the last row containing a specific word, then print the last column of that row.

The file looks something like this. Over time, additional lines A1 / B1 / C1 will be added.

A1 123 456 B1 234 567 C1 345 678 A1 098 766 B1 987 6545 C1 876 5434 

I tried to use

 tail -f file | grep A1 | awk '{print $NF}' 

to print the value 766 but nothing is output.

Is there any way to do this?

Answer 1

You do not see anything due to buffering. The output is displayed when there are enough lines or the end of the file is reached. tail -f means waiting for more input, but there are no more lines in file , and therefore the channel to grep never closes.

If you omit -f from tail output will be shown immediately:

 tail file | grep A1 | awk '{print $NF}' 

---

@Edmorton is, of course, right. Awk can also search for A1 , which shortens the command line to

 tail file | awk '/A1/ {print $NF}' 

or without tail, showing the last column of all rows containing A1

 awk '/A1/ {print $NF}' file 

---

Thanks to the comment, @MitchellTracy tail can skip a record containing A1 and thus, you won’t get anything at all. This problem can be solved by switching tail and awk , awk search first in the file, and then showing the last line:

 awk '/A1/ {print $NF}' file | tail -n1 

Answer 2

To print the last column of a row, simply use $ (NF):

 awk '{print $(NF)}' 

Answer 3

You can do this without awk with just a few pipes.

 tac file | grep -m1 A1 | rev | cut -d' ' -f1 | rev 

Answer 4

One way: awk :

 tail -f file.txt | awk '/A1/ { print $NF }' 

Answer 5

Maybe it works?

 grep A1 file | tail -1 | awk '{print $NF}' 

Answer 6

You can do it all in awk :

 <file awk '$1 ~ /A1/ {m=$NF} END {print m}' 

Answer 7

Run this in the file:

 awk 'ORS=NR%3?" ":"\n"' filename 

and you get what you are looking for.

Answer 8

  grep A1 aaa.txt|tail -1|awk '{print $NF}' 

Answer 9

ls -l | awk '{print $9}' | tail -n1

Answer 10

awk -F " " '($1=="A1") {print $NF}' FILE | tail -n 1

Use awk with the -F field separator set to space "".

Use the template $1=="A1" and the action {print $NF} , this will print the last field in each record, where the first field is "A1". -n 1 result in tail and use the -n 1 option to show only the last line.

Answer 11

Using Perl

 $ cat rayne.txt A1 123 456 B1 234 567 C1 345 678 A1 098 766 B1 987 6545 C1 876 5434 $ perl -lane ' /A1/ and $x=$F[2] ; END { print "$x" } ' rayne.txt 766 $