How to recursively replace characters with sed?

up vote
1
down vote

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Is it possible to replace occurrences of a character sequence recursively without iterating over the same sequence again?

By performing a sed as in the following scenarios I can get the mentioned output.

echo XX | sed -e 's/XX/XoX/g' # outputs XoX
echo XXX | sed -e 's/XX/XoX/g' # outputs XoXX
echo XXXX | sed -e 's/XX/XoX/g' # outputs XoXXoX

However, I'm expecting the output to follow the following behavior.
XX -> XoX
XXX -> XoXoX
XXXX -> XoXoXoX

Is it possible to achieve the expected behavior with sed alone?

asked 58 mins ago

Ishan Madhusanka

1084

New contributor

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up vote
1
down vote

favorite

Is it possible to replace occurrences of a character sequence recursively without iterating over the same sequence again?

By performing a sed as in the following scenarios I can get the mentioned output.

echo XX | sed -e 's/XX/XoX/g' # outputs XoX
echo XXX | sed -e 's/XX/XoX/g' # outputs XoXX
echo XXXX | sed -e 's/XX/XoX/g' # outputs XoXXoX

However, I'm expecting the output to follow the following behavior.
XX -> XoX
XXX -> XoXoX
XXXX -> XoXoXoX

Is it possible to achieve the expected behavior with sed alone?

asked 58 mins ago

Ishan Madhusanka

1084

New contributor

add a commentÂ |Â

up vote
1
down vote

favorite

Is it possible to replace occurrences of a character sequence recursively without iterating over the same sequence again?

By performing a sed as in the following scenarios I can get the mentioned output.

echo XX | sed -e 's/XX/XoX/g' # outputs XoX
echo XXX | sed -e 's/XX/XoX/g' # outputs XoXX
echo XXXX | sed -e 's/XX/XoX/g' # outputs XoXXoX

However, I'm expecting the output to follow the following behavior.
XX -> XoX
XXX -> XoXoX
XXXX -> XoXoXoX

Is it possible to achieve the expected behavior with sed alone?

asked 58 mins ago

Ishan Madhusanka

1084

New contributor

Is it possible to replace occurrences of a character sequence recursively without iterating over the same sequence again?

By performing a sed as in the following scenarios I can get the mentioned output.

echo XX | sed -e 's/XX/XoX/g' # outputs XoX
echo XXX | sed -e 's/XX/XoX/g' # outputs XoXX
echo XXXX | sed -e 's/XX/XoX/g' # outputs XoXXoX

However, I'm expecting the output to follow the following behavior.
XX -> XoX
XXX -> XoXoX
XXXX -> XoXoXoX

Is it possible to achieve the expected behavior with sed alone?

linux bash regex sed

asked 58 mins ago

Ishan Madhusanka

1084

New contributor

asked 58 mins ago

Ishan Madhusanka

1084

New contributor

asked 58 mins ago

Ishan Madhusanka

1084

New contributor

asked 58 mins ago

Ishan Madhusanka

1084

asked 58 mins ago

Ishan Madhusanka

1084

New contributor

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

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3 Answers
3

active

oldest

votes

up vote
2
down vote

accepted

You can do:

> echo XXXX | sed -e ':loop' -e 's/XX/XoX/g' -e 't loop'
XoXoXoX

With:

-e ':loop' : Create a "loop" label

-e 't loop' : Jump to the "loop" label if previous substitution was successful

answered 32 mins ago

Gohu

447127

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up vote
1
down vote

In this particular case look-ahead or look-behind would be useful. I think GNU sed doesn't support these. With pearl:

perl -ne 's/X(?=X)/Xo/g; print;'

answered 9 mins ago

Kamil Maciorowski

21.4k155071

add a commentÂ |Â

up vote
0
down vote

I checked if there is any sort of a flag to make this happen.

Even if that behavior was there it is going to be highly resource consuming.

However, in this particular use case, it is possible to have the expression just twice and achieve the required functionality. i.e. with 2 repeating sed expressions.

echo XX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoX
echo XXX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoXoX
echo XXXX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoXoXoX

answered 31 mins ago

Ishan Madhusanka

1084

New contributor

add a commentÂ |Â

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3 Answers
3

active

oldest

votes

3 Answers
3

active

oldest

votes

up vote
2
down vote

accepted

You can do:

> echo XXXX | sed -e ':loop' -e 's/XX/XoX/g' -e 't loop'
XoXoXoX

With:

-e ':loop' : Create a "loop" label

-e 't loop' : Jump to the "loop" label if previous substitution was successful

answered 32 mins ago

Gohu

447127

add a commentÂ |Â

up vote
2
down vote

accepted

You can do:

> echo XXXX | sed -e ':loop' -e 's/XX/XoX/g' -e 't loop'
XoXoXoX

With:

-e ':loop' : Create a "loop" label

-e 't loop' : Jump to the "loop" label if previous substitution was successful

answered 32 mins ago

Gohu

447127

add a commentÂ |Â

up vote
2
down vote

accepted

You can do:

> echo XXXX | sed -e ':loop' -e 's/XX/XoX/g' -e 't loop'
XoXoXoX

With:

-e ':loop' : Create a "loop" label

-e 't loop' : Jump to the "loop" label if previous substitution was successful

answered 32 mins ago

Gohu

447127

You can do:

> echo XXXX | sed -e ':loop' -e 's/XX/XoX/g' -e 't loop'
XoXoXoX

With:

-e ':loop' : Create a "loop" label

-e 't loop' : Jump to the "loop" label if previous substitution was successful

answered 32 mins ago

Gohu

447127

answered 32 mins ago

Gohu

447127

answered 32 mins ago

Gohu

447127

answered 32 mins ago

Gohu

447127

add a commentÂ |Â

up vote
1
down vote

In this particular case look-ahead or look-behind would be useful. I think GNU sed doesn't support these. With pearl:

perl -ne 's/X(?=X)/Xo/g; print;'

answered 9 mins ago

Kamil Maciorowski

21.4k155071

add a commentÂ |Â

up vote
1
down vote

In this particular case look-ahead or look-behind would be useful. I think GNU sed doesn't support these. With pearl:

perl -ne 's/X(?=X)/Xo/g; print;'

answered 9 mins ago

Kamil Maciorowski

21.4k155071

add a commentÂ |Â

up vote
1
down vote

In this particular case look-ahead or look-behind would be useful. I think GNU sed doesn't support these. With pearl:

perl -ne 's/X(?=X)/Xo/g; print;'

answered 9 mins ago

Kamil Maciorowski

21.4k155071

In this particular case look-ahead or look-behind would be useful. I think GNU sed doesn't support these. With pearl:

perl -ne 's/X(?=X)/Xo/g; print;'

answered 9 mins ago

Kamil Maciorowski

21.4k155071

answered 9 mins ago

Kamil Maciorowski

21.4k155071

answered 9 mins ago

Kamil Maciorowski

21.4k155071

answered 9 mins ago

Kamil Maciorowski

21.4k155071

add a commentÂ |Â

up vote
0
down vote

I checked if there is any sort of a flag to make this happen.

Even if that behavior was there it is going to be highly resource consuming.

However, in this particular use case, it is possible to have the expression just twice and achieve the required functionality. i.e. with 2 repeating sed expressions.

echo XX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoX
echo XXX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoXoX
echo XXXX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoXoXoX

answered 31 mins ago

Ishan Madhusanka

1084

New contributor

add a commentÂ |Â

up vote
0
down vote

I checked if there is any sort of a flag to make this happen.

Even if that behavior was there it is going to be highly resource consuming.

However, in this particular use case, it is possible to have the expression just twice and achieve the required functionality. i.e. with 2 repeating sed expressions.

echo XX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoX
echo XXX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoXoX
echo XXXX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoXoXoX

answered 31 mins ago

Ishan Madhusanka

1084

New contributor

add a commentÂ |Â

up vote
0
down vote

I checked if there is any sort of a flag to make this happen.

Even if that behavior was there it is going to be highly resource consuming.

However, in this particular use case, it is possible to have the expression just twice and achieve the required functionality. i.e. with 2 repeating sed expressions.

echo XX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoX
echo XXX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoXoX
echo XXXX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoXoXoX

answered 31 mins ago

Ishan Madhusanka

1084

New contributor

I checked if there is any sort of a flag to make this happen.

Even if that behavior was there it is going to be highly resource consuming.

However, in this particular use case, it is possible to have the expression just twice and achieve the required functionality. i.e. with 2 repeating sed expressions.

echo XX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoX
echo XXX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoXoX
echo XXXX | sed -e 's/XX/XoX/g' -e 's/XX/XoX/g' # outputs XoXoXoX

answered 31 mins ago

Ishan Madhusanka

1084

New contributor

answered 31 mins ago

Ishan Madhusanka

1084

New contributor

answered 31 mins ago

Ishan Madhusanka

1084

answered 31 mins ago

Ishan Madhusanka

1084

New contributor

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

add a commentÂ |Â

Ishan Madhusanka is a new contributor. Be nice, and check out our Code of Conduct.

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