Regular expression to exclude lines?

[Shannon Jacobs]

Sorry to ask what is surely a trivial question. Also sorry that I don't have
my current code version on hand, but... Anyway, must be some problem with
trying to do the negative. It seems like I get into these ruts each time I
try to deal with regular expressions.

All I'm trying to do is delete the lines which don't contain a particular
string. Actually a filter to edit a log file. I can find and replace a thing
with null, but can't figure out how to find the lines which do not contain
the thing.

Going further, I want to generalize and use a JavaScript variable containing
the decision string, but first I need to worry about the not-within-a-line
problem.

[Mark Szlazak]

Try this to exclude lines that don't have "something" in them:

rx = /^(?:(?!\bsometh ing\b).)*$/gm;
output = input.replace(r x,'');

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[Dr John Stockton]

JRS: In article <3f************ *********@news3 .asahi-net.or.jp>, seen
in news:comp.lang. javascript, Shannon Jacobs <sh****@my-deja.com> posted
at Mon, 24 Nov 2003 21:50:22 :-

All I'm trying to do is delete the lines which don't contain a particular
string. Actually a filter to edit a log file. I can find and replace a thing
with null, but can't figure out how to find the lines which do not contain
the thing.

Of course, for a *particular* string, not requiring a RegExp, DOS batch
provides the answer, and there must surely be a UNIX equivalent.

find "mystring" < old.log > new.log

It seems likely that someone has written a version of DOS find that
accepts RegExps; given RegExp code in library form, the job seems
trivial. UNIX has grep, which should do; and there are ports of grep to
DOS & Windows. Also, WSH has file I/O and RegExps, AIUI.

The important thing seems to be to not bother with a RegExp
substitution, but to work line-by-line and do a RegExp (or other) test
of acceptability.

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk DOS 3.3, 6.20; Win98. ©
Web <URL:http://www.merlyn.demo n.co.uk/> - FAQqish topics, acronyms & links.
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[Thomas 'PointedEars' Lahn]

Dr John Stockton wrote:

Of course, for a *particular* string, not requiring a RegExp, DOS batch
provides the answer, and there must surely be a UNIX equivalent.

find "mystring" < old.log > new.log

grep -v 'mystring' old.log >new.log 2>&1

The single quotes are only required if special shell expressions are
used but not escaped. 2>&1 captures (error) messages in new.log, too.
If you do not want that, leave it out.
PointedEars

[Dr John Stockton]

JRS: In article <3F************ **@PointedEars. de>, seen in
news:comp.lang. javascript, Thomas 'PointedEars' Lahn
<Po*********@we b.de> posted at Wed, 26 Nov 2003 17:27:13 :-

Dr John Stockton wrote:

Of course, for a *particular* string, not requiring a RegExp, DOS batch
provides the answer, and there must surely be a UNIX equivalent.

find "mystring" < old.log > new.log

grep -v 'mystring' old.log >new.log 2>&1

The single quotes are only required if special shell expressions are
used but not escaped. 2>&1 captures (error) messages in new.log, too.
If you do not want that, leave it out.

I'm not aware of 2>&1 being valid in either DOS or Win98, and GREP is
not part of those systems but must be imported.

Why did you cut the part where I wrote "UNIX has grep, which should do;
and there are ports of grep to DOS & Windows." ?

IMHO, MiniTrue is more useful than GREP and SED; see my reply to your
earlier post.

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 MIME. ©
Web <URL:http://www.merlyn.demo n.co.uk/> - FAQish topics, acronyms, & links.
I find MiniTrue useful for viewing/searching/altering files, at a DOS prompt;
free, DOS/Win/UNIX, <URL:http://www.idiotsdelig ht.net/minitrue/> Update soon?

[Thomas 'PointedEars' Lahn]

Dr John Stockton wrote:

Thomas 'PointedEars' Lahn wrote:

Dr John Stockton wrote:

Of course, for a *particular* string, not requiring a RegExp, DOS batch
provides the answer, and there must surely be a UNIX equivalent.

find "mystring" < old.log > new.log
grep -v 'mystring' old.log >new.log 2>&1

The single quotes are only required if special shell expressions are
used but not escaped. 2>&1 captures (error) messages in new.log, too.
If you do not want that, leave it out.

I'm not aware of 2>&1 being valid in either DOS or Win98,

It is only available in Cmd.exe of Windows NT-based systems and
Unices, generally saying in POSIX-compatible shells, of course.
and GREP is not part of those systems but must be imported.
Of course. My posting was only regarding "there must
surely be a UNIX equivalent". Here you are :)
Why did you cut the part where I wrote "UNIX has grep, which should do;
and there are ports of grep to DOS & Windows." ?
Just oversaw it.
IMHO, MiniTrue is more useful than GREP and SED; see my reply to your
earlier post.

MiniTrue is not part of a basic installation of Unices,
though. (Instead, mtr refers to Matt's Traceroute.)
F'up2 poster

PointedEars

[Dr John Stockton]

JRS: In article <3F************ **@PointedEars. de>, seen in
news:comp.lang. javascript, Thomas 'PointedEars' Lahn
<Po*********@we b.de> posted at Thu, 27 Nov 2003 01:27:41 :-

Dr John Stockton wrote:

Thomas 'PointedEars' Lahn wrote:

grep -v 'mystring' old.log >new.log 2>&1

The single quotes are only required if special shell expressions are
used but not escaped. 2>&1 captures (error) messages in new.log, too.
If you do not want that, leave it out.

I'm not aware of 2>&1 being valid in either DOS or Win98,

It is only available in Cmd.exe of Windows NT-based systems and
Unices, generally saying in POSIX-compatible shells, of course.

There is no reason to assume that the OP is aware of that; or even of
that part of that that is applicable to the system in question. a
plausible but inapplicable or incorrect "solution" is worse than
useless".

IMHO, MiniTrue is more useful than GREP and SED; see my reply to your
earlier post.

MiniTrue is not part of a basic installation of Unices,
though. (Instead, mtr refers to Matt's Traceroute.)

Indeed; nor of DOS; which is sufficiently clearly indicated by my
signature to that article.

--
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No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

[Thomas 'PointedEars' Lahn]

Dr John Stockton wrote:

Thomas 'PointedEars' Lahn wrote:

Dr John Stockton wrote:

Thomas 'PointedEars' Lahn wrote:
grep -v 'mystring' old.log >new.log 2>&1

The single quotes are only required if special shell
expressions are used but not escaped. 2>&1 captures (error)
messages in new.log, too. If you do not want that, leave it
out.

I'm not aware of 2>&1 being valid in either DOS or Win98,
It is only available in Cmd.exe of Windows NT-based systems and
Unices, generally saying in POSIX-compatible shells, of course.

There is no reason to assume that the OP is aware of that;

There is no reason that she is interested in it, either.
or even of that part of that that is applicable to the system in
question.
The system in question is unknown.
a plausible but inapplicable or incorrect "solution" is worse than
useless".

This is a JavaScript newsgroup, not a shell script newsgroup. As the
OP has not provided the system on which solutions are supposed to work,
she will test if the provided solutions will work on her system.
PointedEars

[Shannon Jacobs]

Thomas 'PointedEars' Lahn wrote:

Dr John Stockton wrote:

<snip>

There is no reason to assume that the OP is aware of that;

There is no reason that she is interested in it, either.

<snip>

Return of the original poster... Sorry I've been rather busy and haven't
been able to follow this very interesting thread more closely. (The OP is
male, by the way.) However, judging by the complexity of the discussion, it
seems that there was some reason for my original perplexity, though I
thought it a trivial notion.

First let me try to clarify what I'm doing. I know that JavaScript has no
access to the file system. The files are to be handled directly by the user
of the utility. In the Windows environment, this is trivial with ^A, ^C, and
^V. I didn't mention that part because it's almost mindless now (for me).
The actual steps for the file part are:

Open the converter JavaScript form, then open the target file, ^A, ^C, click
in the form, ^V, click on the convert button of the form, ^A, ^C, click back
in the original file, ^A, ^V, and save the file. Done. (If anyone is curious
and the results of these steps are not obvious enough, I can explain.)

Now to clarify the JavaScript part. This example is from an existing utility
that converts raw HTML into JavaScript. The variable HtmlText is the body of
the file from an input field in the form. The critical function is:

function jsFromHtml(Html Text) {
HtmlText = HtmlText.replac e(/\"/g,"\\\"");
HtmlText = HtmlText.replac e(/[\r\n]+/g,"\");\r\ndocu ment.writeln(\" ");
return "document.write ln(\"" + HtmlText + "\");";
}

I know this is rather ugly code, and I'd also be interested in improvements,
or even a completely different approach. My JavaScript skills are obviously
rather limited, but this was adequate for my purposes at the time. Since
it's probably not IOttMCO, I'll explain what it does. In the first
executable line, the regular expression escapes all of the double quotes in
the original HTML. In the next line, all of the embedded line breaks are
replaced with the end and start of document.writel n statements, and then the
last line puts one more start and end around the entire thing. The result is
a block of JavaScript code which outputs the arbitrary HTML input. You stick
that into a JavaScript function to create that block of HTML under program
control wherever it is required. (I was especially unhappy with my treatment
of line breaks, and believe this is not a properly general method, though it
works.)

My goal now is to do something similar, but excluding the lines that do not
contain some string. I'm most interested in an elegant solution, though the
discussion so far seems to suggest that there may be no better approach than
parsing the input one line at a time...

An additional wrinkle is that I'd like to generalize a bit by treating the
decision string as a parameter returned in another field of the form.

[Lasse Reichstein Nielsen]

"Shannon Jacobs" <sh****@my-deja.com> writes:

First let me try to clarify what I'm doing. I know that JavaScript has no
access to the file system. The files are to be handled directly by the user
of the utility. In the Windows environment, this is trivial with ^A, ^C, and
^V.
I have pages like that too, for colorizing HTML and Javascript :)
Now to clarify the JavaScript part. This example is from an existing utility
that converts raw HTML into JavaScript. The variable HtmlText is the body of
the file from an input field in the form. The critical function is:

function jsFromHtml(Html Text) {
HtmlText = HtmlText.replac e(/\"/g,"\\\"");
HtmlText = HtmlText.replac e(/[\r\n]+/g,"\");\r\ndocu ment.writeln(\" ");
return "document.write ln(\"" + HtmlText + "\");";
} I know this is rather ugly code, and I'd also be interested in improvements,
or even a completely different approach.
I would use split:

function jsFromHtml(Html Text) { // I would write HTML in all caps :)
var inputLines = HtmlText.split(/[\r\n]+/);
var outputLines = [];
for (var i=0;i<inputLine s.length;i++) {
var safeLine = inputLines[i].replace(/[\\"]/g,"\\$&");
outputLines[i] = "document.write ln(\"" + safeLine + "\");" ;
}
return outputLine.join ("\n");
}

(I put a backslash in front of both double quotes and backslashes,
since neither can occour alone in a string. If there are other
characters that makes no sense in a string, they should be
handled as well. Examples could be \t or \b).
My JavaScript skills are obviously rather limited,
Not obviously. It works, and it's something I could find myself doing if
I didn't have split available. It's possibly even faster to change all
the quotes from the beginning instead of doing one replace per line.
but this was adequate for my purposes at the time. Since it's
probably not IOttMCO,
You lost me there :) IOttMCO?
I'll explain what it does.
It's fairly easy to read, as long as you can see what's inside a string
and what's not :)
My goal now is to do something similar, but excluding the lines that do not
contain some string. I'm most interested in an elegant solution, though the
discussion so far seems to suggest that there may be no better approach than
parsing the input one line at a time...
Nothing wrong with one line at a time. If you use the code I showed above,
all you need is to wrap the content of the for loop in an if statement:

if (!/badWord/.test(inputLine s[i])) {
... add to output ...
}

or

if (inputLines[i].indexOf("badWo rd") == -1) {
... add to output ...
}

An additional wrinkle is that I'd like to generalize a bit by treating the
decision string as a parameter returned in another field of the form.

var testRE = RegExp(form.ele ments['otherField'].value);
if (! testRE.test(inp utLines[i])) {
...
}

(To avoid problems or crashes, you might want to screen the other field's
values for characters that are meaningful in regular expressions)
or

var testWord = form.elements['otherField'].value;
if (inputLines[i].indexOf(testWo rd)==-1) {
... add to output ...
}
Good luck
/L
--
Lasse Reichstein Nielsen - lr*@hotpop.com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>
'Faith without judgement merely degrades the spirit divine.'

[Thomas 'PointedEars' Lahn]

Lasse Reichstein Nielsen wrote:

"Shannon Jacobs" <sh****@my-deja.com> writes:

but this was adequate for my purposes at the time. Since it's
probably not IOttMCO,

You lost me there :) IOttMCO?

Intuitively Obvious to the Most Casual Observer

http://babylon.com/ (the tool) or http://online.babylon.com/combo/
(the website) are sometimes quite handy :)
HTH

PointedEars