awk/sed solution for printing only next line after it matches a pattern

Question

I have multiple files in a folder. This is how a file look like File1.txt

ghfgh gfghh
  dffd  kjkjoliukjkj
  sdf ffghf
  sf 898575
  sfkj utiith

## 
my data to be extracted

I want to extract the line immediately below "##" pattern from all the files and write them to an output file. I want the file name to be appended too in the output file. Desired output

>File1
My data to be extracted
>File2
My data to be extracted
>File3
My data to be extracted 

This is what i tried 
awk '/##/{getline; print FILENAME; print ">"; print}' *.txt > output.txt

if you're considering using getline in future then make sure you understand everything discussed in http://awk.freeshell.org/AllAboutGetline before deciding to do so. — Ed Morton, Oct 12 '18 at 22:40

score 4 · Answer 1 · answered Oct 12 '18 at 21:15

4

assumes one extract per file (otherwise filename header will be repeated)

$ awk '/##/{f=1; next} f{print ">"FILENAME; print; f=0}' *.txt > output.txt

answered Oct 12 '18 at 21:15

karakfa

66,216
7
41
56

That doesn't produce any output. – akang Oct 12 '18 at 21:20
it writes to `output.txt` – karakfa Oct 12 '18 at 21:21
Output.txt is empty – akang Oct 12 '18 at 21:23
did you try with the posted sample file? I don't see anything wrong with the script. Perhaps your files are not what they are supposed to be? – karakfa Oct 12 '18 at 21:24
I tried with my actual file which is similar to the sample file here – akang Oct 12 '18 at 21:26
2

**similar** is not a synonym for **same**. Save the posted contents in "File1.txt" named file and test the script with that. – karakfa Oct 12 '18 at 21:28
You are right! My bad. Thanks for the solution though. – akang Oct 12 '18 at 21:29

score 2 · Answer 2 · answered Oct 12 '18 at 21:17

2

Perl to the rescue!

perl -ne 'print ">$ARGV\n", scalar <> if /^##/' -- *.txt > output.txt

-n reads the input line by line
$ARGV contains the current input file name
scalar <> reads one line from the input

answered Oct 12 '18 at 21:17

choroba

231,213
25
204
289

score 1 · Answer 3 · answered Oct 12 '18 at 21:19

1

a quick way with grep:

grep -A1 '##' *.txt|grep -v '##' > output.txt

answered Oct 12 '18 at 21:19

Kent

189,393
32
233
301

This is how outpur looks like File1.txt:## File1.txt-my data to be extracted – akang Oct 12 '18 at 21:34
1

I would add the `-H` option, and change the 2nd grep to `sed '/##/d;/--/d;s/^/>/;s/-/\n/'` – glenn jackman Oct 12 '18 at 23:48

dawg · Answer 4 · 2018-10-14T20:11:02.723

0

POSIX or GNU sed:

$ sed -n '/^##/{n;p;}' file
my data to be extracted

grep and sed:

$ grep -A 1 '##' file | sed '1d'
my data to be extracted

edited Oct 14 '18 at 20:11

answered Oct 14 '18 at 20:04

dawg

98,345
23
131
206

awk/sed solution for printing only next line after it matches a pattern

4 Answers4