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send echo to socket network
this command will send a message to the socket 25 on host 192.168.1.2 in tcp. works on udp and icmp understand only IP address, not hostname. on the other side (192.168.1.2), you can listen to this socket and test if you receive the message. easy to diagnose a firewall problem or not.

Watch the progress of 'dd'
The previously-posted one-liner didn't work for me for whatever reason, so I ended up doing this instead.

tar a directory and send it to netcat
tar's directory and sends to netcat listening on port 10000 On the client end: netcat [server ip] 10000 | tar xfvz - This will send it over the network and extract it on the clients machine.

LVM2 Reduce
Just the commands for the lvreduce I keep forgetting.

Find duplicate UID in /etc/passwd
You can use only awk

list files recursively by size

Check if your desired password is already available in haveibeenpwnd database. This command uses the API provided by HIBP

Sort on multiple dis-contiguous keys/fields (can even specify key number/field from the end)
Notes: 1) -n-1 means sort key is the last field 2) -l is important if each separate record is on a new line (usually so for text files) 3) -j tells msort not to create log file (msort.log) in the working directory 4) may need to install msort package. 5) msort does lot more. Check man msort

Print every Nth line
Sometimes commands give you too much feedback. Perhaps 1/100th might be enough. If so, every() is for you. $ my_verbose_command | every 100 will print every 100th line of output. Specifically, it will print lines 100, 200, 300, etc If you use a negative argument it will print the *first* of a block, $ my_verbose_command | every -100 It will print lines 1, 101, 201, 301, etc The function wraps up this useful sed snippet: $ ... | sed -n '0~100p' don't print anything by default $ sed -n starting at line 0, then every hundred lines ( ~100 ) print. $ '0~100p' There's also some bash magic to test if the number is negative: we want character 0, length 1, of variable N. $ ${N:0:1} If it *is* negative, strip off the first character ${N:1} is character 1 onwards (second actual character).

Efficient remote forensic disk acquisition gpg-crypted for multiple recipients
Acquires a bit-by-bit data image, gzip-compresses it on multiple cores (pigz) and encrypts the data for multiple recipients (gpg -e -r). It finally sends it off to a remote machine.


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