How to select lines between two marker patterns which may occur multiple times with awk/sed

Question

Using awk or sed how can I select lines which are occurring between two different marker patterns? There may be multiple sections marked with these patterns.

For example: Suppose the file contains:

abc
def1
ghi1
jkl1
mno
abc
def2
ghi2
jkl2
mno
pqr
stu

And the starting pattern is abc and ending pattern is mno So, I need the output as:

def1
ghi1
jkl1
def2
ghi2
jkl2

I am using sed to match the pattern once:

sed -e '1,/abc/d' -e '/mno/,$d' <FILE>

Is there any way in sed or awk to do it repeatedly until the end of file?

Bisayas

Answer 1

Use awk with a flag to trigger the print when necessary:

$ awk '/abc/{flag=1;next}/mno/{flag=0}flag' file
def1
ghi1
jkl1
def2
ghi2
jkl2

How does this work?

• /abc/ matches lines having this text, as well as /mno/ does.
• /abc/{flag=1;next} sets the flag when the text abc is found. Then, it skips the line.
• /mno/{flag=0} unsets the flag when the text mno is found.
• The final flag is a pattern with the default action, which is to print $0: if flag is equal 1 the line is printed.

For a more detailed description and examples, together with cases when the patterns are either shown or not, see How to select lines between two patterns?.

Induce

If you want to print everything between and including the pattern then you can use awk '/abc/{a=1}/mno/{print;a=0}a' file. – Maestoso

Yes, @Maestoso ! or even awk '/abc/{a=1} a; /mno/{a=0}' file - with this, putting a condition before the /mno/ we make it evaluate the line as true (and print it) before setting a=0. This way we can avoid writing print. – Induce

@Maestoso @Induce For including pattern output, you can do awk '/abc/,/mno/' file – Carbide

@scai,@Induce : In the above how can we include abc and exclude mno. – Rebut

@Rebut awk '/abc/{flag=1}/mno/{flag=0}flag' file should make. – Induce

The only drawback of this solution if patterns abc and mno are the same – Integrator

@EirNym that is a weird scenario that can be handled on very different ways: which lines would you like to print? Probably awk 'flag; /PAT1/{flag=1; next} /PAT1/{flag=0}' file would make. – Induce

@EirNym Have a look at seq 100 | awk '/.*1$/{ flag=1-flag }flag' so see a way of doing it. – Janka

Hi @fedorqui, how to stop after first occurance ? – Gossamer

@Gossamer probably /second_pattern/ {exit} should make. – Induce

Hi @Induce I have a doubt . If abc pattern is repeated twice before mno as follows . abc def1 abc ghi1 jkl1 mno abc def2 ghi2 jkl2 mno pqr stu .. Here the command will print lines between abc and mno including abc.How to avoid this and get the result for words between abc and mno only. – Aliber

@EashwarGadanchi the approach in my answer keeps printing while a true condition is happening. To get what you mention we would have to create some kind of buffering, since it needs to into account things that are not known when you are reading a specific line. See other approaches to this problem in a related question I created. – Induce

For newbies like me, there is a doc. 1. A awk "rule" contains a "pattern" and an "action", either of which (but not both) may be omitted. So [pattern] { action } or pattern [{ action }]. 2. An action consists of one or more awk statements, enclosed in braces (‘{…}’). —— So the ending flag is abbr of flag {print $0} – Eleanore

Answer 2

Using sed:

sed -n -e '/^abc$/,/^mno$/{ /^abc$/d; /^mno$/d; p; }'

The -n option means do not print by default.

The pattern looks for lines containing just abc to just mno, and then executes the actions in the { ... }. The first action deletes the abc line; the second the mno line; and the p prints the remaining lines. You can relax the regexes as required. Any lines outside the range of abc..mno are simply not printed.

Electrolysis

@JonathanLeffler can I know what is the purpose of using -e – Teleran

@KasunSiyambalapitiya: Mostly it means I like to use it. Formally, it specifies that the next argument is (part of) the script that sed should execute. If you want or need to use several arguments to include the entire script, then you must use -e before each such argument; otherwise, it's optional (but explicit). – Electrolysis

Nice! (I prefer sed over awk.) When using complex regular expressions, it would be nice not to have to repeat them. Isn't it possible to delete the first / last line of the "selected" range? Or to first apply the d to all lines up to the first match, and then another d to all lines starting with the second match? – Colony

(Replying to my own comment.) If there's only one section to be cut, I could tentatively solve this e.g. for LaTeX using sed -n '1,/\\begin{document}/d;/\\end{document}/d;p'. (This is cheating a little bit, since the second part does not delete up to the document end, and I would not know how to cut multiple parts as the OP asked for.) – Colony

@JonathanLeffler what is the reason for inserting the $ mark, as in /^abc$ and others – Teleran

The ^ matches the start of a line; the $ matches the end of line. Between them, they ensure that only lines containing just abc and mno are matched. – Electrolysis

Answer 3

This might work for you (GNU sed):

sed '/^abc$/,/^mno$/{//!b};d' file

Delete all lines except for those between lines starting abc and mno

Cabrera

!d;//d golfs 2 characters better :-) https://mcmap.net/q/149210/-how-to-select-lines-between-two-marker-patterns-which-may-occur-multiple-times-with-awk-sed – Heimdall

This is awesome. The {//!b} prevents the abc and mno from being included in the output, but I can't figure out how. Could you explain? – Robinson

@Robinson the instruction //!b reads if the current line is neither one of the lines that match the range, break and therefore print those lines otherwise all other lines are deleted. – Cabrera

Answer 4

From the previous response's links, the one that did it for me, running ksh on Solaris, was this:

sed '1,/firstmatch/d;/secondmatch/,$d'

• 1,/firstmatch/d: from line 1 until the first time you find firstmatch, delete.
• /secondmatch/,$d: from the first occurrance of secondmatch until the end of file, delete.
• Semicolon separates the two commands, which are executed in sequence.

Tactful

Just curious, why does the range limiter (1,) come before /firstmatch/? I'm guessing this could also be phrased '/firstmatch/1,d;/secondmatch,$d'? – Tyndareus

With "1,/firstmatch/d" you are saying "from line 1 until the first time you find 'firstmatch', delete". Whereas, with "/secondmatch/,$d" you say "from the first occurrance of 'secondmatch' until the end of file, delete". the semicolon separates the two commands, which are executed in sequence. – Tactful

Answer 5

sed '/^abc$/,/^mno$/!d;//d' file

golfs two characters better than ppotong's {//!b};d

The empty forward slashes // mean: "reuse the last regular expression used". and the command does the same as the more understandable:

sed '/^abc$/,/^mno$/!d;/^abc$/d;/^mno$/d' file

This seems to be POSIX:

If an RE is empty (that is, no pattern is specified) sed shall behave as if the last RE used in the last command applied (either as an address or as part of a substitute command) was specified.

Heimdall

I think the second solution will end up with nothing as the second command is also a range. However kudos for the first. – Cabrera

@Cabrera true! I have to study more why the first one works. Thanks! – Heimdall

Answer 6

Don_crissti's answer from Show only text between 2 matching pattern?

firstmatch="abc"
secondmatch="cdf"
sed "/$firstmatch/,/$secondmatch/!d;//d" infile

which is much more efficient than AWK's application, see here.

Systematology

I don't think linking the time comparisons makes much sense here, since the requirements of the questions are quite different, hence the solutions. – Induce

I disagree because we should have some criterias to compare answers. Only a few has SED applications. – Haehaecceity

Answer 7

something like this works for me:

file.awk:

BEGIN {
    record=0
}

/^abc$/ {
    record=1
}

/^mno$/ {
    record=0;
    print "s="s;
    s=""
}

!/^abc|mno$/ {
    if (record==1) {
        s = s"\n"$0
    }   
}

using: awk -f file.awk data...

edit: O_o fedorqui solution is way better/prettier than mine.

Verbose

In GNU awk if (record=1) should be if (record==1), i.e. double = - see gawk comparison operators – Acarpous

Answer 8

perl -lne 'print if((/abc/../mno/) && !(/abc/||/mno/))' your_file

Barling

Good to know perl equivalent as it is a pretty good alternative to both awk and sed. – Scaphoid

Answer 9

I tried to use awk to print lines between two patterns while pattern2 also match pattern1. And the pattern1 line should also be printed.

e.g. source

package AAA
aaa
bbb
ccc
package BBB
ddd
eee
package CCC
fff
ggg
hhh
iii
package DDD
jjj

should has an ouput of

package BBB
ddd
eee

Where pattern1 is package BBB, pattern2 is package \w*. Note that CCC isn't a known value so can't be literally matched.

In this case, neither @scai 's awk '/abc/{a=1}/mno/{print;a=0}a' file nor @fedorqui 's awk '/abc/{a=1} a; /mno/{a=0}' file works for me.

Finally, I managed to solve it by awk '/package BBB/{flag=1;print;next}/package \w*/{flag=0}flag' file, haha

A little more effort result in awk '/package BBB/{flag=1;print;next}flag;/package \w*/{flag=0}' file, to print pattern2 line also, that is,

package BBB
ddd
eee
package CCC

Eleanore

Answer 10

This can also be done with logical operations and increment/decrement operations on a flag:

awk '/mno/&&--f||f||/abc/&&f++' file

Schaumberger

I'm absolutely certain that i've used awk in the past for this problem, and it was nothing like this complex. – Denicedenie

Obviously the accepted answer in awk that predates my answer by more than 7 years is much more readable, and I saw that answer before I posted mine. I'm just throwing this one here because it is one byte shorter than the accepted answer even after renaming its variable flag to f, in the spirit of some good ol' code golf fun. :-) – Schaumberger