Gsyfuy

Could the Saturn V actually have launched astronauts around Venus?

What is the purpose or proof behind chain rule?

et qui - how do you really understand that kind of phraseology?

How should I state my peer review experience in the CV?

Have the tides ever turned twice on any open problem?

The German vowel “a” changes to the English “i”

Bach's Toccata and Fugue in D minor breaks the "no parallel octaves" rule?

Most cost effective thermostat setting: consistent temperature vs. lowest temperature possible

Aluminum electrolytic or ceramic capacitors for linear regulator input and output?

Counting models satisfying a boolean formula

Official degrees of earth’s rotation per day

How do I hide Chekhov's Gun?

Welcoming 2019 Pi day: How to draw the letter π?

Do I need to be arrogant to get ahead?

Knife as defense against stray dogs

Why does overlay work only on the first tcolorbox?

What's the meaning of a knight fighting a snail in medieval book illustrations?

Why do passenger jet manufacturers design their planes with stall prevention systems?

Is "upgrade" the right word to use in this context?

PTIJ: Who should I vote for? (21st Knesset Edition)

What is the adequate fee for a reveal operation?

Happy pi day, everyone!

What is the relationship between relativity and the Doppler effect?

Brexit - No Deal Rejection

How to get the n-th line after a grepped one?

How can I set up an alias or shortcut to do the *nix find command?Awk responds differently based on how an empty argument is specifiedHow do different operators deal with a given stringConverting multiple files using programs that accepts stdin and output to stdoutBash script not waiting for wget to finish downloadSeeing actual commands typed in bash historyQueue a Bash script to run after currently job finishes?regex to match any combination of text of indeterminate lengthbash: how to print multiple arrays valuesSetting environment variables for Windows cmd temporarily, to run a program, in a single line?

1

1

Consider the following text file

one 1

two 2

three 3

four 4

five 5

six 6

seven 7

eight 8

I would like to access to the second line after the one which matched four. This would be the line

six 6

The resulting line (so the one above) would then be piped for further processing (say, a | cut -d' ' -f2).

Is there a way to do this in bash and other typical utilities? (otherwise I will script it in Python)

linux command-line bash grep

share|improve this question

asked 4 hours ago

WoJWoJ

82232238

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Will there always only be one occurrence of what you are trying to match? Will it always be two lines after?
  
  – Nasir Riley
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Use awk? But if you're more familiar with Python that would be quicker.
  
  – MZB
  3 hours ago
  

  
  
  
  

add a comment | 

1

1

Consider the following text file

one 1

two 2

three 3

four 4

five 5

six 6

seven 7

eight 8

I would like to access to the second line after the one which matched four. This would be the line

six 6

The resulting line (so the one above) would then be piped for further processing (say, a | cut -d' ' -f2).

Is there a way to do this in bash and other typical utilities? (otherwise I will script it in Python)

linux command-line bash grep

share|improve this question

asked 4 hours ago

WoJWoJ

82232238

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Will there always only be one occurrence of what you are trying to match? Will it always be two lines after?
  
  – Nasir Riley
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Use awk? But if you're more familiar with Python that would be quicker.
  
  – MZB
  3 hours ago
  

  
  
  
  

add a comment | 

Consider the following text file

one 1

two 2

three 3

four 4

five 5

six 6

seven 7

eight 8

I would like to access to the second line after the one which matched four. This would be the line

six 6

The resulting line (so the one above) would then be piped for further processing (say, a | cut -d' ' -f2).

Is there a way to do this in bash and other typical utilities? (otherwise I will script it in Python)

linux command-line bash grep

share|improve this question

asked 4 hours ago

WoJWoJ

82232238

one 1

two 2

three 3

four 4

five 5

six 6

seven 7

eight 8

six 6

share|improve this question

asked 4 hours ago

WoJWoJ

82232238

share|improve this question

asked 4 hours ago

WoJWoJ

82232238

asked 4 hours ago

WoJWoJ

82232238

asked 4 hours ago

WoJWoJ

82232238

4 Answers
4

active

oldest

votes

3

There is nothing wrong with the previous two answers, but I thought I would make you aware that finding the third line after a pattern can be done in a single sed call:

sed -n "/four/ { n; n; p }" SourceData.txt

Because a single program does the work, this is more efficient than running multiple filters. The above command outputs the third line after every instance of "four", except where this occurs again in one of the two lines following a match (the other solutions don't handle this case in the expected manner either); also, no output is generated if the pattern is in the last or second-last line of the file, which may or may not be what you want.

To match the first instance only:

sed -n "/four/ { n; n; p; q }" SourceData.txt

I add this solution because it is worth getting to know sed and, despite its rather off-putting syntax (regular expressions are bad enough!), it can often be extremely useful. This tutorial is a good introduction.

share|improve this answer

answered 2 hours ago

AFHAFH

14.4k31938

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  "the other solutions don't handle this case in the expected manner either" – No longer true. :)
  
  – Kamil Maciorowski
  40 mins ago
  

  
  
  
  

add a comment | 

1

You can use this expression (input.txt):

grep "four" -A 2 input.txt | tail -n 1

Output is:

six 6

The grep option "-A 2" states that two lines after the matched line are outputted.

And the tail option "-n 1" states that only the last 1 lines of this result are returned.

share|improve this answer

answered 4 hours ago

zx485zx485

1,0211913

add a comment | 

0

For multiple occurences, and assumming that no lines start with --:

( grep -A 2  pattern data.txt; echo '--' ) | grep -E -B1 '^--' | grep -Ev '^--'

In slo-mo:

• 
  ( grep -A 2 pattern data.txt; echo '--' ) prints the pattern and the next two lines, and inserts a -- line between the groups. echo '--' makes sure that the last group is also followed by --.


• 
  grep -E -B1 '^--' print the separators and the lines just before (whoch are the ones we are looking for)


• 
  grep -Ev '^--' drops the separators, leaving only the lines we are looking for.

share|improve this answer

answered 3 hours ago

xenoidxenoid

3,8193719

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  if you use the -A, -B or -C option then grep automatically use -- to separate matches, no need to print it yourself
  
  – phuclv
  2 hours ago
  

  
  
  
  

add a comment | 

0

This solution prints the current line iff there was a match two lines ago. It is slightly different from other answers (so far) because it won't miss another match even if it occurs soon after the previous match.

awk -v delay=2 '{for (i=delay; i>=0; i--) t[i]=t[i-1]}; /four/ {t[0]="m"}; {if (t[delay]) print}'

Whenever there's a match, the information is stored in t[0]. With each line the t array is shifted (including shifting t[-1] to t[0] to reset the value of t[0]). The line is printed iff the array indicates there was a match two lines ago.

You can easily set a different delay (e.g. delay=7) or use another pattern (e.g. /sda[[:digit:]]/)

share|improve this answer

answered 43 mins ago

Kamil MaciorowskiKamil Maciorowski

28.3k156186

add a comment | 

Your Answer

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "3"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fsuperuser.com%2fquestions%2f1414661%2fhow-to-get-the-n-th-line-after-a-grepped-one%23new-answer', 'question_page');
}
);

Post as a guest

Name

Email

Required, but never shown

3

There is nothing wrong with the previous two answers, but I thought I would make you aware that finding the third line after a pattern can be done in a single sed call:

sed -n "/four/ { n; n; p }" SourceData.txt

Because a single program does the work, this is more efficient than running multiple filters. The above command outputs the third line after every instance of "four", except where this occurs again in one of the two lines following a match (the other solutions don't handle this case in the expected manner either); also, no output is generated if the pattern is in the last or second-last line of the file, which may or may not be what you want.

To match the first instance only:

sed -n "/four/ { n; n; p; q }" SourceData.txt

I add this solution because it is worth getting to know sed and, despite its rather off-putting syntax (regular expressions are bad enough!), it can often be extremely useful. This tutorial is a good introduction.

share|improve this answer

answered 2 hours ago

AFHAFH

14.4k31938

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  "the other solutions don't handle this case in the expected manner either" – No longer true. :)
  
  – Kamil Maciorowski
  40 mins ago
  

  
  
  
  

add a comment | 

3

There is nothing wrong with the previous two answers, but I thought I would make you aware that finding the third line after a pattern can be done in a single sed call:

sed -n "/four/ { n; n; p }" SourceData.txt

Because a single program does the work, this is more efficient than running multiple filters. The above command outputs the third line after every instance of "four", except where this occurs again in one of the two lines following a match (the other solutions don't handle this case in the expected manner either); also, no output is generated if the pattern is in the last or second-last line of the file, which may or may not be what you want.

To match the first instance only:

sed -n "/four/ { n; n; p; q }" SourceData.txt

I add this solution because it is worth getting to know sed and, despite its rather off-putting syntax (regular expressions are bad enough!), it can often be extremely useful. This tutorial is a good introduction.

share|improve this answer

answered 2 hours ago

AFHAFH

14.4k31938

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  "the other solutions don't handle this case in the expected manner either" – No longer true. :)
  
  – Kamil Maciorowski
  40 mins ago
  

  
  
  
  

add a comment | 

There is nothing wrong with the previous two answers, but I thought I would make you aware that finding the third line after a pattern can be done in a single sed call:

sed -n "/four/ { n; n; p }" SourceData.txt

Because a single program does the work, this is more efficient than running multiple filters. The above command outputs the third line after every instance of "four", except where this occurs again in one of the two lines following a match (the other solutions don't handle this case in the expected manner either); also, no output is generated if the pattern is in the last or second-last line of the file, which may or may not be what you want.

To match the first instance only:

sed -n "/four/ { n; n; p; q }" SourceData.txt

I add this solution because it is worth getting to know sed and, despite its rather off-putting syntax (regular expressions are bad enough!), it can often be extremely useful. This tutorial is a good introduction.

share|improve this answer

answered 2 hours ago

AFHAFH

14.4k31938

sed -n "/four/ { n; n; p }" SourceData.txt

sed -n "/four/ { n; n; p; q }" SourceData.txt

share|improve this answer

answered 2 hours ago

AFHAFH

14.4k31938

answered 2 hours ago

AFHAFH

14.4k31938

answered 2 hours ago

AFHAFH

14.4k31938

1

You can use this expression (input.txt):

grep "four" -A 2 input.txt | tail -n 1

Output is:

six 6

The grep option "-A 2" states that two lines after the matched line are outputted.

And the tail option "-n 1" states that only the last 1 lines of this result are returned.

share|improve this answer

answered 4 hours ago

zx485zx485

1,0211913

add a comment | 

1

You can use this expression (input.txt):

grep "four" -A 2 input.txt | tail -n 1

Output is:

six 6

The grep option "-A 2" states that two lines after the matched line are outputted.

And the tail option "-n 1" states that only the last 1 lines of this result are returned.

share|improve this answer

answered 4 hours ago

zx485zx485

1,0211913

add a comment | 

You can use this expression (input.txt):

grep "four" -A 2 input.txt | tail -n 1

Output is:

six 6

The grep option "-A 2" states that two lines after the matched line are outputted.

And the tail option "-n 1" states that only the last 1 lines of this result are returned.

share|improve this answer

answered 4 hours ago

zx485zx485

1,0211913

grep "four" -A 2 input.txt | tail -n 1

six 6

share|improve this answer

answered 4 hours ago

zx485zx485

1,0211913

answered 4 hours ago

zx485zx485

1,0211913

answered 4 hours ago

zx485zx485

1,0211913

0

For multiple occurences, and assumming that no lines start with --:

( grep -A 2  pattern data.txt; echo '--' ) | grep -E -B1 '^--' | grep -Ev '^--'

In slo-mo:

• 
  ( grep -A 2 pattern data.txt; echo '--' ) prints the pattern and the next two lines, and inserts a -- line between the groups. echo '--' makes sure that the last group is also followed by --.


• 
  grep -E -B1 '^--' print the separators and the lines just before (whoch are the ones we are looking for)


• 
  grep -Ev '^--' drops the separators, leaving only the lines we are looking for.

share|improve this answer

answered 3 hours ago

xenoidxenoid

3,8193719

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  if you use the -A, -B or -C option then grep automatically use -- to separate matches, no need to print it yourself
  
  – phuclv
  2 hours ago
  

  
  
  
  

add a comment | 

0

For multiple occurences, and assumming that no lines start with --:

( grep -A 2  pattern data.txt; echo '--' ) | grep -E -B1 '^--' | grep -Ev '^--'

In slo-mo:

• 
  ( grep -A 2 pattern data.txt; echo '--' ) prints the pattern and the next two lines, and inserts a -- line between the groups. echo '--' makes sure that the last group is also followed by --.


• 
  grep -E -B1 '^--' print the separators and the lines just before (whoch are the ones we are looking for)


• 
  grep -Ev '^--' drops the separators, leaving only the lines we are looking for.

share|improve this answer

answered 3 hours ago

xenoidxenoid

3,8193719

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  if you use the -A, -B or -C option then grep automatically use -- to separate matches, no need to print it yourself
  
  – phuclv
  2 hours ago
  

  
  
  
  

add a comment | 

For multiple occurences, and assumming that no lines start with --:

( grep -A 2  pattern data.txt; echo '--' ) | grep -E -B1 '^--' | grep -Ev '^--'

In slo-mo:

• 
  ( grep -A 2 pattern data.txt; echo '--' ) prints the pattern and the next two lines, and inserts a -- line between the groups. echo '--' makes sure that the last group is also followed by --.


• 
  grep -E -B1 '^--' print the separators and the lines just before (whoch are the ones we are looking for)


• 
  grep -Ev '^--' drops the separators, leaving only the lines we are looking for.

share|improve this answer

answered 3 hours ago

xenoidxenoid

3,8193719

( grep -A 2  pattern data.txt; echo '--' ) | grep -E -B1 '^--' | grep -Ev '^--'

share|improve this answer

answered 3 hours ago

xenoidxenoid

3,8193719

answered 3 hours ago

xenoidxenoid

3,8193719

answered 3 hours ago

xenoidxenoid

3,8193719

0

This solution prints the current line iff there was a match two lines ago. It is slightly different from other answers (so far) because it won't miss another match even if it occurs soon after the previous match.

awk -v delay=2 '{for (i=delay; i>=0; i--) t[i]=t[i-1]}; /four/ {t[0]="m"}; {if (t[delay]) print}'

Whenever there's a match, the information is stored in t[0]. With each line the t array is shifted (including shifting t[-1] to t[0] to reset the value of t[0]). The line is printed iff the array indicates there was a match two lines ago.

You can easily set a different delay (e.g. delay=7) or use another pattern (e.g. /sda[[:digit:]]/)

share|improve this answer

answered 43 mins ago

Kamil MaciorowskiKamil Maciorowski

28.3k156186

add a comment | 

0

This solution prints the current line iff there was a match two lines ago. It is slightly different from other answers (so far) because it won't miss another match even if it occurs soon after the previous match.

awk -v delay=2 '{for (i=delay; i>=0; i--) t[i]=t[i-1]}; /four/ {t[0]="m"}; {if (t[delay]) print}'

Whenever there's a match, the information is stored in t[0]. With each line the t array is shifted (including shifting t[-1] to t[0] to reset the value of t[0]). The line is printed iff the array indicates there was a match two lines ago.

You can easily set a different delay (e.g. delay=7) or use another pattern (e.g. /sda[[:digit:]]/)

share|improve this answer

answered 43 mins ago

Kamil MaciorowskiKamil Maciorowski

28.3k156186

add a comment | 

This solution prints the current line iff there was a match two lines ago. It is slightly different from other answers (so far) because it won't miss another match even if it occurs soon after the previous match.

awk -v delay=2 '{for (i=delay; i>=0; i--) t[i]=t[i-1]}; /four/ {t[0]="m"}; {if (t[delay]) print}'

Whenever there's a match, the information is stored in t[0]. With each line the t array is shifted (including shifting t[-1] to t[0] to reset the value of t[0]). The line is printed iff the array indicates there was a match two lines ago.

You can easily set a different delay (e.g. delay=7) or use another pattern (e.g. /sda[[:digit:]]/)

share|improve this answer

answered 43 mins ago

Kamil MaciorowskiKamil Maciorowski

28.3k156186

awk -v delay=2 '{for (i=delay; i>=0; i--) t[i]=t[i-1]}; /four/ {t[0]="m"}; {if (t[delay]) print}'

share|improve this answer

answered 43 mins ago

Kamil MaciorowskiKamil Maciorowski

28.3k156186

answered 43 mins ago

Kamil MaciorowskiKamil Maciorowski

28.3k156186

answered 43 mins ago

Kamil MaciorowskiKamil Maciorowski

28.3k156186