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Need regex to replace the whole line, but the last optional character

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;

0

It sounds like it should be trivial task, but I cannot figure it out, so I decided to ask. I need to replace the whole line, but optional last character. For instance, I want:
abcd to become efgh but
abcd, to become efgh,

How can I create regex like that? It seems optional character cannot be back-referenced, i.e something like: s/.*(,)?$/efgh1 won't work (I tried :) )
To make it clear, the lines are arbitrary length with arbitrary characters. The only condition in my case is to preserve comma at the end of the line after the replacement if one existed there or drop it if line did not end up with comma

regular-expression

share|improve this question

edited 2 days ago

Shimon Pozin

asked 2 days ago

Shimon PozinShimon Pozin

1012

New contributor

Shimon Pozin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Any length lines? Always abcd? Always a comma? How do we tell whether or not the last character should be kept?
  
  – roaima
  2 days ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  What tool are you using to apply the RE? Different tools use different variants (unfortunately).
  
  – roaima
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  .* is greedy, meaning it will match the whole string first then try the rest of the match, which since the next group is optional it will never get matched. Some regex flavors have a reluctant quantifier which will try matching the least amount of characters.
  
  – Torin
  2 days ago
  

  
  
  
  

add a comment | 

0

It sounds like it should be trivial task, but I cannot figure it out, so I decided to ask. I need to replace the whole line, but optional last character. For instance, I want:
abcd to become efgh but
abcd, to become efgh,

How can I create regex like that? It seems optional character cannot be back-referenced, i.e something like: s/.*(,)?$/efgh1 won't work (I tried :) )
To make it clear, the lines are arbitrary length with arbitrary characters. The only condition in my case is to preserve comma at the end of the line after the replacement if one existed there or drop it if line did not end up with comma

regular-expression

share|improve this question

edited 2 days ago

Shimon Pozin

asked 2 days ago

Shimon PozinShimon Pozin

1012

New contributor

Shimon Pozin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Any length lines? Always abcd? Always a comma? How do we tell whether or not the last character should be kept?
  
  – roaima
  2 days ago
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  What tool are you using to apply the RE? Different tools use different variants (unfortunately).
  
  – roaima
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  .* is greedy, meaning it will match the whole string first then try the rest of the match, which since the next group is optional it will never get matched. Some regex flavors have a reluctant quantifier which will try matching the least amount of characters.
  
  – Torin
  2 days ago
  

  
  
  
  

add a comment | 

It sounds like it should be trivial task, but I cannot figure it out, so I decided to ask. I need to replace the whole line, but optional last character. For instance, I want:
abcd to become efgh but
abcd, to become efgh,

How can I create regex like that? It seems optional character cannot be back-referenced, i.e something like: s/.*(,)?$/efgh1 won't work (I tried :) )
To make it clear, the lines are arbitrary length with arbitrary characters. The only condition in my case is to preserve comma at the end of the line after the replacement if one existed there or drop it if line did not end up with comma

regular-expression

share|improve this question

edited 2 days ago

Shimon Pozin

asked 2 days ago

Shimon PozinShimon Pozin

1012

New contributor

Shimon Pozin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited 2 days ago

Shimon Pozin

asked 2 days ago

Shimon PozinShimon Pozin

1012

New contributor

Shimon Pozin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited 2 days ago

Shimon Pozin

asked 2 days ago

Shimon PozinShimon Pozin

1012

New contributor

Shimon Pozin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 2 days ago

Shimon PozinShimon Pozin

1012

New contributor

Shimon Pozin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 2 days ago

Shimon PozinShimon Pozin

1012

2 Answers
2

active

oldest

votes

1

Another one:

$ echo -e "abcdnabcd," | sed 's/.*($|,)/efgh1/'
efgh
efgh,

This matches the end of the line $ or the comma , in the captured group.

share|improve this answer

edited 2 days ago

answered 2 days ago

FreddyFreddy

1,612210

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you so much! That's exactly what I was looking for. I totally forgot that capturing group may have more than 1 character! I hope this solution will save time for somebody else in the future as well.
  
  – Shimon Pozin
  2 days ago
  

  
  
  
  

add a comment | 

0

I believe you are referring to something like:

's/[a-z]+([^a-z]0,1)$/efgh1/g' 

Complete sed commands + output:

$ echo "abcd," | sed 's/[a-z]+([^a-z]0,1)$/efgh1/g'
efgh,

$ echo "abcd" | sed 's/[a-z]+([^a-z]0,1)$/efgh1/g'
efgh

share|improve this answer

answered 2 days ago

PMartPMart

1

New contributor

PMart is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I think this works for specific example I gave, but I am not sure about arbitrary line (i search for specific pattern in the line, but then replace it entirely, preserving only comma at the end of the line) So, if I read it correct, we capture end of line that is not a letter and appears 0 or 1 times, right? But if it's a period, it will preserve it too? I only need to preserve it if it's comma. If it's ending of json statement, for example ("xxx}") I don't want to preserve the last character. But if it's "xxx}," then I do want to transfer comma into replacement. Sorry if I was not clear.
  
  – Shimon Pozin
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @ShimonPozin You are correct in your comment here. You could change [^a-z] to just , in the given regular expression (and delete the g at the end as the substitution would by necessity only match once ever).
  
  – Kusalananda♦
  yesterday
  
  

  
  
  
  

add a comment | 

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1

Another one:

$ echo -e "abcdnabcd," | sed 's/.*($|,)/efgh1/'
efgh
efgh,

This matches the end of the line $ or the comma , in the captured group.

share|improve this answer

edited 2 days ago

answered 2 days ago

FreddyFreddy

1,612210

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you so much! That's exactly what I was looking for. I totally forgot that capturing group may have more than 1 character! I hope this solution will save time for somebody else in the future as well.
  
  – Shimon Pozin
  2 days ago
  

  
  
  
  

add a comment | 

1

Another one:

$ echo -e "abcdnabcd," | sed 's/.*($|,)/efgh1/'
efgh
efgh,

This matches the end of the line $ or the comma , in the captured group.

share|improve this answer

edited 2 days ago

answered 2 days ago

FreddyFreddy

1,612210

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you so much! That's exactly what I was looking for. I totally forgot that capturing group may have more than 1 character! I hope this solution will save time for somebody else in the future as well.
  
  – Shimon Pozin
  2 days ago
  

  
  
  
  

add a comment | 

Another one:

$ echo -e "abcdnabcd," | sed 's/.*($|,)/efgh1/'
efgh
efgh,

This matches the end of the line $ or the comma , in the captured group.

share|improve this answer

edited 2 days ago

answered 2 days ago

FreddyFreddy

1,612210

$ echo -e "abcdnabcd," | sed 's/.*($|,)/efgh1/'
efgh
efgh,

share|improve this answer

edited 2 days ago

answered 2 days ago

FreddyFreddy

1,612210

answered 2 days ago

FreddyFreddy

1,612210

answered 2 days ago

FreddyFreddy

1,612210

0

I believe you are referring to something like:

's/[a-z]+([^a-z]0,1)$/efgh1/g' 

Complete sed commands + output:

$ echo "abcd," | sed 's/[a-z]+([^a-z]0,1)$/efgh1/g'
efgh,

$ echo "abcd" | sed 's/[a-z]+([^a-z]0,1)$/efgh1/g'
efgh

share|improve this answer

answered 2 days ago

PMartPMart

1

New contributor

PMart is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I think this works for specific example I gave, but I am not sure about arbitrary line (i search for specific pattern in the line, but then replace it entirely, preserving only comma at the end of the line) So, if I read it correct, we capture end of line that is not a letter and appears 0 or 1 times, right? But if it's a period, it will preserve it too? I only need to preserve it if it's comma. If it's ending of json statement, for example ("xxx}") I don't want to preserve the last character. But if it's "xxx}," then I do want to transfer comma into replacement. Sorry if I was not clear.
  
  – Shimon Pozin
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @ShimonPozin You are correct in your comment here. You could change [^a-z] to just , in the given regular expression (and delete the g at the end as the substitution would by necessity only match once ever).
  
  – Kusalananda♦
  yesterday
  
  

  
  
  
  

add a comment | 

0

I believe you are referring to something like:

's/[a-z]+([^a-z]0,1)$/efgh1/g' 

Complete sed commands + output:

$ echo "abcd," | sed 's/[a-z]+([^a-z]0,1)$/efgh1/g'
efgh,

$ echo "abcd" | sed 's/[a-z]+([^a-z]0,1)$/efgh1/g'
efgh

share|improve this answer

answered 2 days ago

PMartPMart

1

New contributor

PMart is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I think this works for specific example I gave, but I am not sure about arbitrary line (i search for specific pattern in the line, but then replace it entirely, preserving only comma at the end of the line) So, if I read it correct, we capture end of line that is not a letter and appears 0 or 1 times, right? But if it's a period, it will preserve it too? I only need to preserve it if it's comma. If it's ending of json statement, for example ("xxx}") I don't want to preserve the last character. But if it's "xxx}," then I do want to transfer comma into replacement. Sorry if I was not clear.
  
  – Shimon Pozin
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @ShimonPozin You are correct in your comment here. You could change [^a-z] to just , in the given regular expression (and delete the g at the end as the substitution would by necessity only match once ever).
  
  – Kusalananda♦
  yesterday
  
  

  
  
  
  

add a comment | 

I believe you are referring to something like:

's/[a-z]+([^a-z]0,1)$/efgh1/g' 

Complete sed commands + output:

$ echo "abcd," | sed 's/[a-z]+([^a-z]0,1)$/efgh1/g'
efgh,

$ echo "abcd" | sed 's/[a-z]+([^a-z]0,1)$/efgh1/g'
efgh

share|improve this answer

answered 2 days ago

PMartPMart

1

New contributor

PMart is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

's/[a-z]+([^a-z]0,1)$/efgh1/g' 

$ echo "abcd," | sed 's/[a-z]+([^a-z]0,1)$/efgh1/g'
efgh,

$ echo "abcd" | sed 's/[a-z]+([^a-z]0,1)$/efgh1/g'
efgh

share|improve this answer

answered 2 days ago

PMartPMart

1

New contributor

PMart is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

answered 2 days ago

PMartPMart

1

New contributor

PMart is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

answered 2 days ago

PMartPMart

1