From: William James <w_a_x_man@...>
Date: 2007-01-04T06:30:07+09:00
Subject: Re: Delete line from file

dblack@wobblini.net wrote:
> Hi --
>
> On Wed, 3 Jan 2007, Robert Klemme wrote:
>
> > On 03.01.2007 00:11, Jules wrote:
> >> Given a line number, what is the best way to delete this line from a
> >> file?
> >
> > $ cat x
> > 1
> > 2
> > 3
> > 4
> > 5
> > 6
> > 7
> > 8
> > 9
> > 10
> >
> > $ sed -ni -e '5 b;p' x
> >
> > robert@fussel /cygdrive
> > $ cat x
> > 1
> > 2
> > 3
> > 4
> > 6
> > 7
> > 8
> > 9
> > 10
> >
> > Or did you mean with Ruby?
> >
> > $ ruby -n -i.bak -e 'puts $_ unless $. == 5' x
> >
> > $ cat x
> > 1
> > 2
> > 3
> > 4
> > 6
> > 7
> > 8
> > 9
> > 10
> >
> >> And given an array of line numbers, what is the best way to delete
> >> these lines from a file?
> >
> > $ ruby -n -i.bak -e 'puts $_ unless [1,3,4].include? $.' x
> >
> > robert@fussel /cygdrive/c/Temp
> > $ cat x
> > 2
> > 5
> > 6
> > 7
> > 8
> > 9
> > 10
> >
> > $ diff -u x.bak x
> > --- x.bak       2007-01-03 11:03:20.281250000 +0100
> > +++ x   2007-01-03 11:03:46.437500000 +0100
> > @@ -1,7 +1,4 @@
> > -1
> > 2
> > -3
> > -4
> > 5
> > 6
> > 7
> >
> > Inside a script?
> >
> > robert@fussel /cygdrive/c/Temp
> > $ ./del.rb x
> >
> > robert@fussel /cygdrive/c/Temp
> > $ diff -u x.bak x
> > --- x.bak       2007-01-03 11:09:29.437500000 +0100
> > +++ x   2007-01-03 11:09:31.468750000 +0100
> > @@ -2,7 +2,6 @@
> > 2
> > 3
> > 4
> > -5
> > 6
> > 7
> > 8
> >
> > robert@fussel /cygdrive/c/Temp
> > $ cat del.rb
> > #!ruby
> >
> > f = ARGV.shift or raise "Need file name"
> > fb = f + ".bak"
> >
> > File.rename(f, fb)
> >
> > File.open(f, "w") do |out|
> >  File.foreach(fb) {|line| out.puts line unless $. == 5}
> > end
> >
> >
> > Plenty to choose from... :-)
>
> For the script version you can also do:
>
> #!/usr/local/bin/ruby -ni.bak
> puts $_ unless $. == 5

The $_ can go.

print unless $. == 5