|
Re: Save all but line 32!
by davorg (Chancellor) on Sep 18, 2002 at 16:11 UTC
|
perl -i.bak -ne 'print unless $. == 32' filename
--
<http://www.dave.org.uk>
"The first rule of Perl club is you do not talk about
Perl club."
-- Chip Salzenberg
| [reply]
[d/l] |
Re: Save all but line 32!
by jmcnamara (Monsignor) on Sep 18, 2002 at 17:00 UTC
|
Here is another way:
perl -i -pe '$_=$}if$.==32' file
Update: To handle multiple files it needs to be a little longer:
perl -i -pe '$_=$}if$.==32;$.=$[if+eof' file1 file2 ...
But this is probably the cleanest way:
awk 'FNR != 32' file1 file2 ...
--
John.
| [reply]
[d/l]
[select] |
Re: Save all but line 32!
by perrin (Chancellor) on Sep 18, 2002 at 16:30 UTC
|
Not as fast and doesn't handle a list of files, but for entertainment value:
perl -MTie::File -e 'tie @file, 'Tie::File', $ARGV[0]; splice @file, 3
+1, 1;' filename
(Tie::File is in the standard lib now.) | [reply]
[d/l] |
|
|
| [reply]
[d/l] |
|
|
I thought $. only resets on a close call? meaning the <> operator doesn't reset it, since it never closes the filehandles. So the following code will omit the 35th line only for the first file, but not for any other file:
perl -ne 'print unless $. == 35' file1 file2
Is that correct?
-- Dan | [reply]
[d/l]
[select] |
Re: Save all but line 32!
by zigdon (Deacon) on Sep 18, 2002 at 16:14 UTC
|
not very different, but should be slightly faster:
perl -i.bak -ne 'if ($. < 32) { print } elsif ($. > 32) { print <>}' f
+ilename
I think it'll be faster since once you pass the 32nd line, you don't need to check anymore, you can just dump out the rest of the file.
Note that $. might not do what you expect, depending on the value of $/. See perlvar.
-- Dan | [reply]
[d/l] |
|
|
Penny wise but pound foolish.
Your program will read in all
lines after line 32 before printing them. Usually that
will be a lot slower than the comparison you save.
I do not understand your remark about $/.
You aren't setting it, nor does any of the switches influence it.
How could $/ be any different from the default?
My suggestion for the program:
perl -i -nwe 'print unless 32 .. 32' filename
Abigail | [reply]
[d/l]
[select] |
|
|
This confuses me. I don't see how this would work. It looks like it will print no lines since 32 .. 32 should return either 1 (the number of elements in the list) or 32 (the last element in the list) both of which are "true". I am betting the later, but I am not sure. Would you kindly point out where I am wrong?
perl -- executes perl
-i -- in-place editing
-n -- implict loop
-w -- turn on warnings (why?)
-e -- execute the following string as the program
print -- print what is in $_ (only executed if the unless is false)
unless -- execute the previous command if the result of the following
expression is 0, undef, or '' (or the equivalent)
32 .. 32 -- construct a list containing the numbers 32 through 32
filename -- the file to edit
| [reply]
[d/l] |
|
|
|
|
|
Re: Save all but line 32!
by cephas (Pilgrim) on Sep 18, 2002 at 17:18 UTC
|
perl -pe '$.-32or$_=$' -i file
cephas | [reply]
[d/l] |
|
|
$ perl -MO=Deparse -pe '$_=$'
LINE: while (defined($_ = <ARGV>)) {
$_ = $;
}
continue {
die "-p destination: $!\n" unless print $_;
}
It shows that in this case $ gets interpreted as $; the subscript separator. However, this means that your code inserts an extra character in the file as shown by this:
perl -pe '$.-32or$_=$' file | cat -A
But I'm still not sure why perl inserts that semicolon. It doesn't in other cases:
$ perl -MO=Deparse -pe '$_=$.'
LINE: while (defined($_ = <ARGV>)) {
$_ = $.
}
continue {
die "-p destination: $!\n" unless print $_;
}
Anyone have an explanation for this last point?
Update: blakem's answer below is right. This last case is a perl 5.005 issue with B::Deparse.
--
John.
| [reply]
[d/l]
[select] |
|
|
I seem to get the semicolon with your second case:
% perl5.6.1 -MO=Deparse -pe '$_=$.'
LINE: while (defined($_ = <ARGV>)) {
$_ = $.;
}
continue {
die "-p destination: $!\n" unless print $_;
}
% perl5.8.0 -MO=Deparse -pe '$_=$.'
LINE: while (defined($_ = <ARGV>)) {
$_ = $.;
}
continue {
die "-p destination: $!\n" unless print $_;
}
Update: Response to above update: with 5.00503 I get:
% perl5.00503 -MO=Deparse -pe '$_=$.'
LINE: while (defined($_ = <ARGV>)) {
$_ = $.
}
continue {
die "-p destination: $!\n" unless print $_;
}
-Blake
| [reply]
[d/l]
[select] |
|
|
won't "32or" get interpreted as a single token?
| [reply] |
|
|
| [reply]
[d/l] |
(OT) Re: Save all but line 32!
by JayBonci (Curate) on Sep 19, 2002 at 07:59 UTC
|
Offtopic for the site, but sed's a much better tool for that job. It's very easy to do with sed addressing:
sed -n 32\!p filename
Sadly, I don't have a clever or shorter way to do it in perl. The number 32 can be anything, of course
--jb
| [reply]
[d/l] |
|
|
| [reply]
[d/l] |
|
|
t filename^G32^M^D^S
T is my editor
^G32 := goto line 32
^M := return to terminate/execute the goto
^D := delete the line
^S := Save and exit!
Cor! Like yer ring! ... HALO dammit! ... 'Ave it yer way! Hal-lo, Mister la-de-da. ... Like yer ring! | [reply]
[d/l] |
|
|
|
|
|
|
|
Way OT....
by ellem (Hermit) on Sep 19, 2002 at 02:35 UTC
|
# Another Perl edition of a song:
# The End, by The Beatles
END {
$you->take($love) eq $you->made($love) ;
}
John and Paul wrote:
# Another Perl edition of a song:
# The End, by The Beatles
END {
$you->take($love) eq $you->make($love) ;
}
--
ellem@optonline.net
There's more than one way to do it, but only some of them actually work. | [reply]
[d/l]
[select] |
