I have a file like the following and I would like to print the lines between two given patterns PAT1
and PAT2
.
1
2
PAT1
3 - first block
4
PAT2
5
6
PAT1
7 - second block
PAT2
8
9
PAT1
10 - third block
I have read How to select lines between two marker patterns which may occur multiple times with awk/sed but I am curious to see all the possible combinations of this, either including or excluding the pattern.
How can I print all lines between two patterns?
$ awk '/PAT1/,/PAT2/' file
PAT1
3 - first block
4
PAT2
PAT1
7 - second block
PAT2
PAT1
10 - third block
Or, using variables:
awk '/PAT1/{flag=1} flag; /PAT2/{flag=0}' file
How does this work?
/PAT1/
matches lines having this text, as well as /PAT2/
does. /PAT1/{flag=1}
sets the flag
when the text PAT1
is found in a line./PAT2/{flag=0}
unsets the flag
when the text PAT2
is found in a line.flag
is a pattern with the default action, which is to print $0
: if flag
is equal 1 the line is printed. This way, it will print all those lines occurring from the time PAT1
occurs and up to the next PAT2
is seen. This will also print the lines from the last match of PAT1
up to the end of the file.$ awk '/PAT1/{flag=1; next} /PAT2/{flag=0} flag' file
3 - first block
4
7 - second block
10 - third block
This uses next
to skip the line that contains PAT1
in order to avoid this being printed.
This call to next
can be dropped by reshuffling the blocks: awk '/PAT2/{flag=0} flag; /PAT1/{flag=1}' file
.
$ awk '/PAT1/{flag=1} /PAT2/{flag=0} flag' file
PAT1
3 - first block
4
PAT1
7 - second block
PAT1
10 - third block
By placing flag
at the very end, it triggers the action that was set on either PAT1 or PAT2: to print on PAT1, not to print on PAT2.
$ awk 'flag; /PAT1/{flag=1} /PAT2/{flag=0}' file
3 - first block
4
PAT2
7 - second block
PAT2
10 - third block
By placing flag
at the very beginning, it triggers the action that was set previously and hence print the closing pattern but not the starting one.
This is based on a solution by Ed Morton.
awk 'flag{
if (/PAT2/)
{printf "%s", buf; flag=0; buf=""}
else
buf = buf $0 ORS
}
/PAT1/ {flag=1}' file
As a one-liner:
$ awk 'flag{ if (/PAT2/){printf "%s", buf; flag=0; buf=""} else buf = buf $0 ORS}; /PAT1/{flag=1}' file
3 - first block
4
7 - second block
# note the lack of third block, since no other PAT2 happens after it
This keeps all the selected lines in a buffer that gets populated from the moment PAT1 is found. Then, it keeps being filled with the following lines until PAT2 is found. In that point, it prints the stored content and empties the buffer.