How to add multiple “+” commands into less from the command line

command lineless

What I know and use regularly

I love how I can add commands to less with the +-parameter from the commandline. I like this for instant searching:

$ less +/DHCP /var/log/syslog
# result: syslog at the point of the first occurrence of DHCP

Yet I also like to set it to follow the output like this:

$ less +F /var/log/syslog
# result: a syslog that follows the file, very much like tail -f would.

What I would like to use

But every once in a while I'd like BOTH. But I do not have any Idea how to do it.

$ less +F +/DHCP /var/log/syslog
# result: "Pattern not found" - it will actually bunch up both things to one string.

Bonus Points to anyone who can tell me how I can automatically filter without having to press at the beginning?

$ less +\&DHCP /var/log/syslog
# result: "please press enter" after which the filtering search _is_
# running correctly. I would love to get rid of that extra <enter>

edit2: Funny is, that i can combine these:

$ less +?DHCP +G /var/log/syslog
# result: jumps to the end and reverse-searches for DHCP
# But I have to press enter (which I'd like to avoid)

but i can not do this:

$ less +G +?DHCP /var/log/syslog
# this is being bunched up to ?DHCPG and subsequently not found.

So, the order seems to be important, and all strings are interpreted as if it was one?

Version info

edit here's the version of less installed on my system, but i'd be willing to install another version if neccessary!

$ less --version
less 458 (GNU regular expressions)
Copyright (C) 1984-2012 Mark Nudelman
[...]

Best Answer

I don't think I understand the first part of your question based on your later comments. For me, using less +F +/pattern logfile works and continues to highlight new instances of pattern as they appear in the updated file.

As for the bonus part of your question, you can try one of the following commands:

less +\&DHCP$'\n' /var/log/syslog

less +\&DHCP^M /var/log/syslog

In that second command the ^M is generated by pressing Ctrl-V then Enter. Kinda easier to just press enter when less starts though unless you're looking to script it or something.

Related Solutions

Command Line – Resolve All IP Addresses in Command Output

Here's a quick and dirty solution to this in Python. It does caching (including negative caching), but no threading and isn't the fastest thing you've seen. If you save it as something like rdns, you can call it like this:

zcat /var/log/some-file.gz | rdns
# ... or ...
rdns /var/log/some-file /var/log/some-other-file # ...

Running it will annotate the IP addresses with their PTR records in-place:

$ echo "74.125.132.147, 64.34.119.12." | rdns
74.125.132.147 (rdns: wb-in-f147.1e100.net), 64.34.119.12 (rdns: stackoverflow.com).

And here's the source:

#!/usr/bin/env python

import sys, re, socket

cache = dict()

def resolve(x):
    key = x.group(0)
    try:
        return "%s (rdns: %s)" % (key, cache[key])
    except KeyError:
        try:
            cache[key] = socket.gethostbyaddr(key)[0]
        except socket.herror:
            cache[key] = '?'
        return "%s (rdns: %s)" % (key, cache[key])

for f in [open(x) for x in sys.argv[1:]] or [sys.stdin]:
    for line in f:
        sys.stdout.write(re.sub("\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}", resolve, line))

# End of file.

Please note: this isn't quite what you're after to the letter (using ‘standard tools’). But it probably helps you more than a hack that resolves every IP address every time it's encountered. With a few more lines, you can even make it cache its results persistently, which would help with repeat invocations.

How to echo (a (executable-)string) to the prompt, so that the cursor flashes at the end of the line

If you need the echo_to_prompt() command in a shell script or on the normal command line, you can simply use read:

#!/bin/sh

echo_to_prompt() {
        echo -n "$USER@$HOSTNAME:$PWD $" $@
        read && $@
}

echo_to_prompt rm -R ./tmp/logs/delete_me_every_once_in_a_while/

You can add the echo_to_prompt() function to your .bashrc/.profile/... if you want it on the command line.