Home » grep inside less?

grep inside less?

Solutons:


less has very powerful pattern matching.  From the man page:

&pattern

    Display only lines which match the pattern;
    lines which do not match the pattern
    are not displayed.  If pattern is empty
    (if you type & immediately followed by ENTER),
    any filtering is turned off, and all lines are displayed. 
    While filtering is in effect,
    an ampersand is displayed at the beginning of the prompt,
    as a reminder that some lines in the file may be hidden.

    Certain characters are special as in the / command:

    ^N or !

      Display only lines which do NOT match the pattern.

    ^R

      Don’t interpret regular expression metacharacters;
      that is, do a simple textual comparison.

    ____________
    Certain characters are special
    if entered at the beginning of the pattern;
    they modify the type of search
    rather than become part of the pattern.

   (Of course ^N and ^R represent Ctrl+N
and Ctrl+R, respectively.) 

So, for example, &dns will display only lines that match the pattern dns,
and &!dns will filter out (exclude) those lines,
displaying only lines that don’t match the pattern.

It is noted in the description of the / command that

    The pattern is a regular expression,
    as recognized by the regular expression library supplied by your system.

So

  • &eth[01]  will display lines containing eth0 or eth1
  • &arp.*eth0 will display lines containing arp followed by eth0
  • &arp|dns  will display lines containing arp or dns

And the ! can invert any of the above. 
So the command you would want to use for the example in your question is:

&!event text|something else|the other thing|foo|bar

Also use /pattern and ?pattern
to search (and n/N to go to next/previous).

Building on orion’s answer, the less(1) man page describes

/pattern

    Search forward in the file for the N-th line
    containing the pattern. 
    N defaults to 1. 
    The pattern is a regular expression,
    as recognized by the regular expression library supplied by your system. 
    The search starts at the second line displayed
    (but see the -a and -j options, which change this).

    Certain characters are special
    if entered at the beginning of the pattern;
    they modify the type of search
    rather than become part of the pattern:

    ^N or !

      Search for lines which do NOT match the pattern.

    ^E or *

      Search multiple files. 
      That is, if the search reaches the END of the current file
      without finding a match,
      the search continues in the next file in the command line list.

    ^F or @

      Begin the search
      at the first line of the FIRST file in the command line list,
      regardless of what is currently displayed on the screen
      or the settings of the -a or -j options.

    ^K

      Highlight any text
      which matches the pattern on the current screen,
      but don’t move to the first match (KEEP current position).

    ^R

      Don’t interpret regular expression metacharacters;
      that is, do a simple textual comparison.

    ____________
    Commands may be preceded by a decimal number,
    called N in the descriptions …

   (Of course ^N and ^E, etc., represent
Ctrl+N and Ctrl+E, etc.) 

It turns out that &pattern
and /pattern work well together. 
For example, the commands

  • &!arp|dnsEnter
  • /Ctrl+Kfail|fatal|fault|sd[a-z][0-9]Enter

typed in either order, will hide (exclude) all lines
containing arp or dns (like grep -v), and then, in the remaining lines,
highlight all occurrences of fail, fatal, fault,
or anything that looks like the name of a SCSI device (sd[a-z][0-9]). 
Note that lines that contain arp or dns,
and also fail or any of the other danger words,
will not be displayed.

Over the last few months, I have become somewhat enamoured of fzf.

In your case, as long as context is not needed (i.e., the equivalent of grep’s -A, -B, or -C is not needed, and by the way, less’s & also has the same limitation), then fzf is a very powerful tool.

Here’s a silly example:

printf "%sn" {aa,bb,cc}{dd,ee,ff}{gg,hh,ii} | fzf

If you run that, and play with inputs like aa | bb dd | ee !gg !hh and so on, you will quickly see what is happening.

Fzf’s documentation on the | operator is sparse, but my best guess is it only applies to the terms immediately before and after, which means, in effect, that OR takes precedence over AND (which is implicit; all terms are AND-ed by default). But in most cases this should not be an issue, and things work out OK in my experience.

Give it a shot. I have found it surprisingly useful when it comes to browsing things when I am not really sure what I am looking for, and when context does not matter.

Related Solutions

Joining bash arguments into single string with spaces

[*] I believe that this does what you want. It will put all the arguments in one string, separated by spaces, with single quotes around all: str="'$*'" $* produces all the scripts arguments separated by the first character of $IFS which, by default, is a space....

AddTransient, AddScoped and AddSingleton Services Differences

TL;DR Transient objects are always different; a new instance is provided to every controller and every service. Scoped objects are the same within a request, but different across different requests. Singleton objects are the same for every object and every...

How to download package not install it with apt-get command?

Use --download-only: sudo apt-get install --download-only pppoe This will download pppoe and any dependencies you need, and place them in /var/cache/apt/archives. That way a subsequent apt-get install pppoe will be able to complete without any extra downloads....

What defines the maximum size for a command single argument?

Answers Definitely not a bug. The parameter which defines the maximum size for one argument is MAX_ARG_STRLEN. There is no documentation for this parameter other than the comments in binfmts.h: /* * These are the maximum length and maximum number of strings...

Bulk rename, change prefix

I'd say the simplest it to just use the rename command which is common on many Linux distributions. There are two common versions of this command so check its man page to find which one you have: ## rename from Perl (common in Debian systems -- Ubuntu, Mint,...

Output from ls has newlines but displays on a single line. Why?

When you pipe the output, ls acts differently. This fact is hidden away in the info documentation: If standard output is a terminal, the output is in columns (sorted vertically) and control characters are output as question marks; otherwise, the output is...

mv: Move file only if destination does not exist

mv -vn file1 file2. This command will do what you want. You can skip -v if you want. -v makes it verbose - mv will tell you that it moved file if it moves it(useful, since there is possibility that file will not be moved) -n moves only if file2 does not exist....

Is it possible to store and query JSON in SQLite?

SQLite 3.9 introduced a new extension (JSON1) that allows you to easily work with JSON data . Also, it introduced support for indexes on expressions, which (in my understanding) should allow you to define indexes on your JSON data as well. PostgreSQL has some...

Combining tail && journalctl

You could use: journalctl -u service-name -f -f, --follow Show only the most recent journal entries, and continuously print new entries as they are appended to the journal. Here I've added "service-name" to distinguish this answer from others; you substitute...

how can shellshock be exploited over SSH?

One example where this can be exploited is on servers with an authorized_keys forced command. When adding an entry to ~/.ssh/authorized_keys, you can prefix the line with command="foo" to force foo to be run any time that ssh public key is used. With this...

Why doesn’t the tilde (~) expand inside double quotes?

The reason, because inside double quotes, tilde ~ has no special meaning, it's treated as literal. POSIX defines Double-Quotes as: Enclosing characters in double-quotes ( "" ) shall preserve the literal value of all characters within the double-quotes, with the...

What is GNU Info for?

GNU Info was designed to offer documentation that was comprehensive, hyperlinked, and possible to output to multiple formats. Man pages were available, and they were great at providing printed output. However, they were designed such that each man page had a...

Set systemd service to execute after fstab mount

a CIFS network location is mounted via /etc/fstab to /mnt/ on boot-up. No, it is not. Get this right, and the rest falls into place naturally. The mount is handled by a (generated) systemd mount unit that will be named something like mnt-wibble.mount. You can...

Merge two video clips into one, placing them next to each other

To be honest, using the accepted answer resulted in a lot of dropped frames for me. However, using the hstack filter_complex produced perfectly fluid output: ffmpeg -i left.mp4 -i right.mp4 -filter_complex hstack output.mp4 ffmpeg -i input1.mp4 -i input2.mp4...

How portable are /dev/stdin, /dev/stdout and /dev/stderr?

It's been available on Linux back into its prehistory. It is not POSIX, although many actual shells (including AT&T ksh and bash) will simulate it if it's not present in the OS; note that this simulation only works at the shell level (i.e. redirection or...

How can I increase the number of inodes in an ext4 filesystem?

It seems that you have a lot more files than normal expectation. I don't know whether there is a solution to change the inode table size dynamically. I'm afraid that you need to back-up your data, and create new filesystem, and restore your data. To create new...

Why doesn’t cp have a progress bar like wget?

The tradition in unix tools is to display messages only if something goes wrong. I think this is both for design and practical reasons. The design is intended to make it obvious when something goes wrong: you get an error message, and it's not drowned in...