Commands by pornel (2)

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Pick a random line from a file

get you public ip address

watch your network load on specific network interface
-n means refresh frequency you could change eth0 to any interface you want, like wlan0

extract column from csv file
extracts the 5th column using the delimiter ','

list block devices
Shows all block devices in a tree with descruptions of what they are.

concatenate compressed and uncompressed logs
I use zgrep because it also parses non gzip files. With ls -tr, we parse logs in time order. Greping the empty string just concatenates all logs, but you can also grep an IP, an URL...

Insert the last argument of the previous command
for example if you did a: $ ls -la /bin/ls then $ ls !$ is equivalent to doing a $ ls /bin/ls

Create a mirror of a local folder, on a remote server
Create a exact mirror of the local folder "/root/files", on remote server 'remote_server' using SSH command (listening on port 22) (all files & folders on destination server/folder will be deleted)

Limit memory usage per script/program
When I'm testing some scripts or programs, they end up using more memory than anticipated. In that case, computer nearly halts due to swap space usage, and sometimes I have to press Magic SysRq+REISUB to reboot. So, I was looking for a way to limit memory usage per script and found out that ulimit can limit memory. If you run it this way: $ $ ulimit -v 1000000 . $ $ scriptname Then the new memory limit will be valid for that shell. I think changing the limit within a subshell is much more flexible and it won't interfere with your current shell ulimit settings. note: -v 1000000 corresponds to approximately 1GB of RAM

Perl One Liner to Generate a Random IP Address
A bash version.

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