$ # wrong output
$ # sed -nE '/(\<co){2}/p' and awk '/(\<co){2}/' has the buggy behavior too
$ # but grep -E '(\<co){2}' correctly doesn't give ouput
$ echo 'cocoa' | sed -nE '/(\bco){2}/p'
cocoa
$ # correct behavior, no output
$ echo 'cocoa' | sed -nE '/\bco\bco/p'
$ # wrong output, there's only 1 whole word 'it' after 'with'
$ echo 'it line with it here sit too' | sed -E 's/with(.*\bit\b){2}/XYZ/'
it line XYZ too
$ # correct behavior, input isn't modified
$ echo 'it line with it here sit too' | sed -E 's/with.*\bit\b.*\bit\b/XYZ/'
it line with it here sit too
$ # changing word boundaries to \< and \> results in a different problem
$ # this correctly doesn't modify the input
$ echo 'it line with it here sit too' | sed -E 's/with(.*\<it\>){2}/XYZ/'
it line with it here sit too
$ # this correctly modifies the input
$ echo 'it line with it here it too' | sed -E 's/with(.*\<it\>){2}/XYZ/'
it line XYZ too
$ # but this one fails to modify the input
$ echo 'it line with it here it too sit' | sed -E 's/with(.*\<it\>){2}/XYZ/'
it line with it here it too sit
sed -nE '/(\<co){2}/p' and awk '/(\<co){2}/' has the buggy behavior too, but grep -E '(\<co){2}' correctly doesn't give ouput
Correct behavior, no output:
$ echo 'cocoa' | sed -nE '/\bco\bco/p'
Wrong output: there's only 1 whole word it after with
$ echo 'it line with it here sit too' | sed -E 's/with(.*\bit\b){2}/XYZ/'
it line XYZ too
Correct behavior, input isn't modified
$ echo 'it line with it here sit too' | sed -E 's/with.*\bit\b.*\bit\b/XYZ/'
it line with it here sit too
Changing word boundaries to \< and \> results in a different problem.
This correctly doesn't modify the input:
$ echo 'it line with it here sit too' | sed -E 's/with(.*\<it\>){2}/XYZ/' it line with it here sit too
This correctly modifies the input
$ echo 'it line with it here it too' | sed -E 's/with(.*\<it\>){2}/XYZ/' it line XYZ too
But this one fails to modify the input
$ echo 'it line with it here it too sit' | sed -E 's/with(.*\<it\>){2}/XYZ/' it line with it here it too sit
Also, the problematic behavior is seen only if the conflicting word has extra characters at the beginning. For example, it and sit. But not if there are characters at the end. For example, it and site and item.
$ echo 'it line with it here item too' | sed -E 's/with(.*\bit\b){2}/XYZ/'
it line with it here item too
$ echo 'it line with it here it too item' | sed -E 's/with(.*\<it\>){2}/XYZ/'
it line XYZ too item
$ echo 'it line with it here item too' | sed -E 's/with(.*\bit\b){2}/XYZ/'
it line with it here item too
$ echo 'it line with it here it too item' | sed -E 's/with(.*\<it\>){2}/XYZ/'
it line XYZ too item
