How Perl CLI code can get a line appended directly
so below is wrong as lines need its newline char get dropped

$ for i in {1..7}; { echo $i ;} |perl -npe '$_= "=".$_."=" '
=1
==2
==3
==4
==5
==6
==7
=

by needing to stick on-np option, then can't get it work right:

$ for i in {1..7} ;{ echo $i ;} |perl -npe '$_= "=".chop($_)."=\n" '
=
=
=
=
=
=
=
=
=
=
=
=
=
=

Please solve it out, thanks much.

CodePudding user response：

You didn't specify what output you are trying to achieve. I'm guessing you want

=1=
=2=
=3=
=4=
...

chop returned the removed character, not the remaining string. It modifies the variable in-place. So the following is the correct usage:

perl -npe'chop( $_ ); $_ = "=$_=\n"'

But we can improve this.

• It's safer to use chomp instead of chop to remove trailing line feeds.
• -n is implied by -p, and it's customary to leave it out when -p is used.
• chomp and chop modify $_ by default, so we don't need to explicitly pass $_.

perl -pe'chomp; $_ = "=$_=\n"'

Finally, we can get the same exact behaviour out of -l.

perl -ple'$_ = "=$_="'