How to grep -v and also exclude the next line after the match?

Question

How to filter out 2 lines for each line matching the grep regex?
this is my minimal test:

SomeTestAAAA
EndTest
SomeTestABCD
EndTest
SomeTestDEFG
EndTest
SomeTestAABC
EndTest
SomeTestACDF
EndTest

And obviously I tried e.g. grep -vA 1 SomeTestAA which doesn't work.

desired output is:

SomeTestABCD
EndTest
SomeTestDEFG
EndTest
SomeTestACDF
EndTest

Answer 1

You can use grep with -P (PCRE) :

grep -P -A 1 'SomeTest(?!AA)' file.txt

(?!AA) is the zero width negative lookahead pattern ensuring that there is no AA after SomeTest.

Test :

$ grep -P -A 1 'SomeTest(?!AA)' file.txt 
SomeTestABCD
EndTest
SomeTestDEFG
EndTest
SomeTestACDF
EndTest

Answer 2

You can use GNU sed's d command to delete a line, and prefix it with /pat/,+N to select lines matching the pattern and the subsequent N lines. In your case, N = 1 since you only want to delete the single subsequent line after a matching line:

sed -e '/SomeTestAAAA/,+1d'

Answer 3

Tried with below GNU sed command and it worked fine

command

sed  '/SomeTestAA/,+1d' filename

output

SomeTestABCD
EndTest
SomeTestDEFG
EndTest
SomeTestACDF
EndTest

Answer 4

Here's a sed solution (with -n i.e. no auto-printing) that works with arbitrary input:

sed -n '/SomeTestAA/!p          # if line doesn't match, print it
: m                             # label m
//{                             # if line matches
$!{                             # and if it's not the last line
n                               # empty pattern space and read in the next line
b m                             # branch to label m (so n is repeated until a
}                               # line that's read in no longer matches) but
}                               # nothing is printed
' infile

so with an input like

SomeTestAAXX
SomeTestAAYY
+ one line
SomeTestONE
Message body
EndTest
########
SomeTestTWO
something here
EndTest
SomeTestAABC
+ another line
SomeTestTHREE
EndTest
SomeTestAA
+ yet another line

running

sed -n -e '/SomeTestAA/!p;: m' -e '//{' -e '$!{' -e 'n;b m' -e '}' -e'}' infile

outputs

SomeTestONE
Message body
EndTest
########
SomeTestTWO
something here
EndTest
SomeTestTHREE
EndTest

that is, it removes exactly the lines that grep -A1 SomeTestAA infile would select:

SomeTestAAXX
SomeTestAAYY
+ one line
--
SomeTestAABC
+ another line
--
SomeTestAA
+ yet another line

Answer 5

One option is to use perl compatible regular expression grep:

pcregrep -Mv 'SomeTestAA.*\n' file

The option -M allows pattern to match more then one line.

Answer 6

Using standard sed:

$ sed '/SomeTestAA/{ N; d; }' file
SomeTestABCD
EndTest
SomeTestDEFG
EndTest
SomeTestACDF
EndTest

The sed script parses the input file line by line, and when a line matches the pattern SomeTestAA, the two sed editing commands N and d are executed. The N command appends the next line of input to the pattern space (the buffer that sed can edit), and the d deletes the pattern space and starts the next cycle.

Answer 7

You might have better luck with something that looks at multi-line regions as single records. There's an sgrep which I haven't used much.

There's also awk, where you can set the input record separator, and output record separator, to whatever you like.

pat="^SomeTestAA"
awk  'BEGIN{ RS=ORS="\nEndTest\n"} !/'"$pat/" foo

Most of the awk program is single-quoted, but I change to double quotes at the end so the $pat shell variable can be expanded.