如何使用 perl 脚本从文件中删除选定的重复行

Question

Let's say I am having file a.txt which is having following content.

aa
aa
bb
cc
dd
ee
ff
ee
gg

I want following output -

aa
aa
bb
cc
dd
ee
ff
gg

Note that I want delete particular duplication of lines only: ee . How can I do that following one liner I tried.

perl -ne 'print unless $a{$_}++' a.txt

but it is deleting all duplicated lines.

Answer 1

To remove duplicates of only specific ("target") lines add that condition

perl -lne'$tgt = "ee"; print unless $h{$_}++ and $_ eq $tgt' file

If there may be multiple such targets, then check whether the current line matches any one of them. A nice tool for that is any from List::Util

perl -MList::Util=any -lne'
    $line=$_; 
    @tgt = qw(ee aa); 
    print unless $h{$line}++ and any { $_ eq $line} @tgt
' file

Target(s) can be read from the command line as arguments, if there is a benefit to not have them hardcoded.

Note: In older versions any is in List::MoreUtils , and not in List::Util .