[regex] Regex: Remove lines containing "help", etc

I have a long document of commands. Using Notepad++ or regex, I want to delete all lines containing "help" including keyboard_help, etc.

How can this be done?

Easy task with grep:

grep -v help filename

Append > newFileName to redirect output to a new file.

Update

To clarify it, the normal behavior will be printing the lines on screen. To pipe it to a file, the > can be used. Thus, in this command:

grep -v help filename > newFileName

1. grep calls the grep program, obviously
2. -v is a flag to inverse the output. By defaulf, grep prints the lines that match the given pattern. With this flag, it will print the lines that don't match the pattern.
3. help is the pattern to match
4. filename is the name of the input file
5. > redirects the output to the following item
6. newFileName the new file where output will be saved.

As you may noticed, you will not be deleting things in your file. grep will read it and another file will be saved, modified accordingly.

Search with a regular expression:

^.*(help).*$

You can do this using sed: sed '/help/ d' < inputFile > outputFile

If you're on Windows, try findstr. Third-party tools are not needed:

findstr /V /L "searchstring" inputfile.txt > outputfile.txt

It supports regex's too! Just read the tool's help findstr /?.

P.S. If you want to work with big, huge files (like 400 MB log files) a text editor is not very memory-efficient, so, as someone already pointed out, command-line tools are the way to go. But there's no grep on Windows, so...

I just ran this on a 1 GB log file, and it literally took 3 seconds.

Another way to do this in Notepad++ is all in the Find/Replace dialog and with regex:

• Ctrl + h to bring up the find replace dialog.

• In the Find what: text box include your regex: .*help.*\r?\n (where the \r is optional in case the file doesn't have Windows line endings).

• Leave the Replace with: text box empty.

• Make sure the Regular expression radio button in the Search Mode area is selected. Then click Replace All and voila! All lines containing your search term help have been removed.