Re: Regular expression to read non-commented lines from a file
- From: Jonny <www.mail@xxxxxxxxxxxx>
- Date: Fri, 12 Aug 2005 18:40:39 GMT
Mario Winterer wrote:
> Here's the code snippet that prints all lines that are not comments and
> do not start with whitespace.
> The input is a String (more general: CharSequence) containing the entire
> file content. DO NOT USE FOR LARGE FILES!
>
> /* BEGIN */
> String testLine = "This\n is\na\n#test";
>
> Pattern pattern = Pattern.compile("^[^\\s#].*$", Pattern.MULTILINE);
> Matcher matcher = pattern.matcher(testLine);
> while (matcher.find()) {
> String l = matcher.group();
> System.out.println(l);
> }
> /* END */
>
> In your case, it might be better to read lines using the
> BufferedReader's "readLine" method and just test if it starts with
> whitespace or "#":
>
> BufferedReader reader = new BufferedReader(new FileReader(yourFile));
> try {
> String line = null;
> while ((line = reader.readLine()) != null) {
> if (line.length() == 0) continue; /* skip line in case it is empty
> (is this correct?) */
>
> char c = line.charAt(0);
> if ((c == '#') || Character.isWhitespace(c)) continue;
> System.out.println(line);
> }
> } finally {
> reader.close();
> }
>
> Best regards,
> Tex
>
> "Jonny" <www.mail@xxxxxxxxxxxx> wrote in message
> news:XKZKe.3247$2C5.797@xxxxxxxxxxxxxxxxxxxxxxx
> > Hi,
> >
> > I would like to use a regular expression in Java to read those lines
> > from a file which are not comments and do not start with whitespace.
> > Commented lines start with #
> >
> > Currently with grep, I am using the command:
> >
> > grep -E "^[^#\ \t]" myfile
> >
> > to get the lines I want, but I am having problems converting this
> > regular expression for use in Java. I don't get any lines returned.
> >
> > If I replace the above regular expression with ".*" in my Java code,
> > then all lines of myfile are returned, as you might expect, so it would
> > appear that the problem is only with the regular expression shown in the
> > above grep example.
> >
> > Please can you help.
Thanks for a comprehensive response Mario. It is much appreciated.
I can see that I needed to use ^ and $, and also \\s for whitespace.
These were the two problems I was having.
Incidentally, the file I am reading is very small, so I used the
following code to read the file:
String fileAsString = new Scanner(new
File(myFile)).useDelimiter("\\A").next();
where myFile is the path to the file to be read.
Regards,
Jonny
.
- References:
- Regular expression to read non-commented lines from a file
- From: Jonny
- Re: Regular expression to read non-commented lines from a file
- From: Mario Winterer
- Regular expression to read non-commented lines from a file
- Prev by Date: Re: Regular expression to read non-commented lines from a file
- Next by Date: regex help
- Previous by thread: Re: Regular expression to read non-commented lines from a file
- Next by thread: regex help
- Index(es):
Relevant Pages
|
