From Newsgroup: gnu.emacs.help

I have a log file in which most lines are not interesting most of the
time. These line all contain a certain string. Is there a way to
display only those lines that do not contain a certain string?
--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof
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From Newsgroup: gnu.emacs.help

On Wed, 18 May 2022 13:39:26 +0200, Cecil Westerhof <Cecil@decebal.nl>
wrote:

I have a log file in which most lines are not interesting most of the
time. These line all contain a certain string. Is there a way to
display only those lines that do not contain a certain string?

I use M-x delete-matching-lines but this changes the buffer, so be careful
not to accidentally save...

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From Newsgroup: gnu.emacs.help

USEnet <jvromans@squirrel.nl> writes:

On Wed, 18 May 2022 13:39:26 +0200, Cecil Westerhof <Cecil@decebal.nl>
wrote:

I have a log file in which most lines are not interesting most of the
time. These line all contain a certain string. Is there a way to
display only those lines that do not contain a certain string?

I use M-x delete-matching-lines but this changes the buffer, so be careful not to accidentally save...

The problem with that is that when it is a log file that is still
written to, that does not work anymore.

But I could write a little script that copies to a temp file and then
uses delete-matching-lines.
--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof
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From Newsgroup: gnu.emacs.help

Cecil Westerhof <Cecil@decebal.nl> writes:

I have a log file in which most lines are not interesting most of the
time. These line all contain a certain string. Is there a way to
display only those lines that do not contain a certain string?

I'd use grep (the Emacs command that runs grep) but using the -v
argument that show only non-matching lines.

But out of Emacs, I'd use

$ tail -f logfile | grep -v boring-string

since that "follows" the file, showing new lines as they appear. (When
I say "out of Emacs" you can, of course, run this in a Emacs shell
window.)
--
Ben.
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From Newsgroup: gnu.emacs.help

If you're going to copy the file you might as well grep out the boring
string lines, as per Ben's recipe.

-- Johan

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From Newsgroup: gnu.emacs.help

Ben <ben.usenet@bsb.me.uk> writes:

Cecil Westerhof <Cecil@decebal.nl> writes:

I have a log file in which most lines are not interesting most of the
time. These line all contain a certain string. Is there a way to
display only those lines that do not contain a certain string?

I'd use grep (the Emacs command that runs grep) but using the -v
argument that show only non-matching lines.

But out of Emacs, I'd use

$ tail -f logfile | grep -v boring-string

since that "follows" the file, showing new lines as they appear. (When
I say "out of Emacs" you can, of course, run this in a Emacs shell
window.)

That would also be an option, but at the moment I chose the following
function:
(defun dcbl-reduced-logfile (filter-string)
(interactive "s Filter String: ")
(message filter-string)
(let ((buffer-name (generate-new-buffer-name "reduced-logfile"))
(text (buffer-substring (point-min) (point-max))))
(switch-to-buffer buffer-name)
(insert text)
(beginning-of-buffer)
(delete-matching-lines filter-string)
))

Just whipped it up, so I am open for improvements.
(Should probably put name of current buffer in the new buffer name.)
--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof
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From Newsgroup: gnu.emacs.help

Cecil Westerhof <Cecil@decebal.nl> writes:

Ben <ben.usenet@bsb.me.uk> writes:

Cecil Westerhof <Cecil@decebal.nl> writes:

I have a log file in which most lines are not interesting most of the
time. These line all contain a certain string. Is there a way to
display only those lines that do not contain a certain string?

That would also be an option, but at the moment I chose the following function:
(defun dcbl-reduced-logfile (filter-string)
(interactive "s Filter String: ")
(message filter-string)
(let ((buffer-name (generate-new-buffer-name "reduced-logfile"))
(text (buffer-substring (point-min) (point-max))))
(switch-to-buffer buffer-name)
(insert text)
(beginning-of-buffer)
(delete-matching-lines filter-string)
))

Just whipped it up, so I am open for improvements.
(Should probably put name of current buffer in the new buffer name.)

A little bit better version:
(defun dcbl-reduced-logfile (filter-string)
(interactive "sFilter String: ")
(message filter-string)
(let ((buffer-name (generate-new-buffer-name
(concat "reduced-logfile"
"#"
filter-string
"#"
(file-name-sans-extension (buffer-name)))))
(text (buffer-substring (point-min) (point-max))))
(switch-to-buffer buffer-name)
(insert text)
(beginning-of-buffer)
(delete-matching-lines filter-string)
))

My log files are often like 2022-05-18.log, so it is handy to have the
filter string included.
--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof
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