/(.+)n1/ works but /(.*)n1/ doesn't when they should both work
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I was playing around with sed after answering another question and I noticed that .+ and .* are not giving the same result when they both match multiple characters in a context address.
The following command1:
sed -E '$!N;/(.+)n1/!P;D' <<IN
one
one_more
two
two_more
IN
prints
one_more
two_more
OK, that's the expected output.
Changing the regex from .+ to .* (i.e. from one or more characters to zero or more characters) should give the same result but it does not:
sed -E '$!N;/(.*)n1/!P;D' <<IN
one
one_more
two
two_more
IN
prints just one line
two_more
It appears to work fine in the left hand side of a substitution e.g.
sed -E '$!N;s/(.*)n1/1/' <<IN
one
one_more
two
two_more
IN
prints
one_more
two_more
just not in a context address...
What's going on here ?
1: I'm using ERE for simplicity/readability, the same happens when using BRE
sed regular-expression
asked 41 mins ago
don_crissti
48.1k15127157
add a comment |Â
up vote
0
down vote
favorite
I was playing around with sed after answering another question and I noticed that .+ and .* are not giving the same result when they both match multiple characters in a context address.
The following command1:
sed -E '$!N;/(.+)n1/!P;D' <<IN
one
one_more
two
two_more
IN
prints
one_more
two_more
OK, that's the expected output.
Changing the regex from .+ to .* (i.e. from one or more characters to zero or more characters) should give the same result but it does not:
sed -E '$!N;/(.*)n1/!P;D' <<IN
one
one_more
two
two_more
IN
prints just one line
two_more
It appears to work fine in the left hand side of a substitution e.g.
sed -E '$!N;s/(.*)n1/1/' <<IN
one
one_more
two
two_more
IN
prints
one_more
two_more
just not in a context address...
What's going on here ?
1: I'm using ERE for simplicity/readability, the same happens when using BRE
sed regular-expression
asked 41 mins ago
don_crissti
48.1k15127157
add a comment |Â
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I was playing around with sed after answering another question and I noticed that .+ and .* are not giving the same result when they both match multiple characters in a context address.
The following command1:
sed -E '$!N;/(.+)n1/!P;D' <<IN
one
one_more
two
two_more
IN
prints
one_more
two_more
OK, that's the expected output.
Changing the regex from .+ to .* (i.e. from one or more characters to zero or more characters) should give the same result but it does not:
sed -E '$!N;/(.*)n1/!P;D' <<IN
one
one_more
two
two_more
IN
prints just one line
two_more
It appears to work fine in the left hand side of a substitution e.g.
sed -E '$!N;s/(.*)n1/1/' <<IN
one
one_more
two
two_more
IN
prints
one_more
two_more
just not in a context address...
What's going on here ?
1: I'm using ERE for simplicity/readability, the same happens when using BRE
sed regular-expression
asked 41 mins ago
don_crissti
48.1k15127157
I was playing around with sed after answering another question and I noticed that .+ and .* are not giving the same result when they both match multiple characters in a context address.
The following command1:
sed -E '$!N;/(.+)n1/!P;D' <<IN
one
one_more
two
two_more
IN
prints
one_more
two_more
OK, that's the expected output.
Changing the regex from .+ to .* (i.e. from one or more characters to zero or more characters) should give the same result but it does not:
sed -E '$!N;/(.*)n1/!P;D' <<IN
one
one_more
two
two_more
IN
prints just one line
two_more
It appears to work fine in the left hand side of a substitution e.g.
sed -E '$!N;s/(.*)n1/1/' <<IN
one
one_more
two
two_more
IN
prints
one_more
two_more
just not in a context address...
What's going on here ?
1: I'm using ERE for simplicity/readability, the same happens when using BRE
sed regular-expression
sed regular-expression
asked 41 mins ago
don_crissti
48.1k15127157
asked 41 mins ago
don_crissti
48.1k15127157
asked 41 mins ago
don_crissti
48.1k15127157
asked 41 mins ago
don_crissti
48.1k15127157
asked 41 mins ago
don_crissti
48.1k15127157
48.1k15127157
add a comment |Â
add a comment |Â
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