Do base 10 arithmetic in bash instead of octal

((newvar = 10#$var + 10))

Remove leading zeros in bash

newvar=${var#0}

Find processes & threads for users (useful if running into nproc limits)

ps h -Led -o user | sort | uniq -c | sort -n

Show threads per process for user bob

ps -o nlwp,pid,lwp,args -u bob | sort -n

Delete files when rm/bash says too many arguments

No xargs

find . -name '*.pdf' -exec rm {} +

Using xargs

find . -name "*.pdf" -print0 | xargs -0 rm

Pretty tree of processes

ps -eo 'pid,args' --forest

Scan/re-scan a fibre channel adapter and scsi host

FC host

echo 1 > /sys/class/fc_host/host/issue_lip

SCSI host

echo "- - -" > /sys/class/scsi_host/host/scan

Individual disk

echo 1 > /sys/class/scsi_disk/0\:0\:0\:0/device/rescan

Check for open tcp ports from bash without telnet or nc

Replace <hostname> and <port> with your host and port you are checking

timeout 1 bash -c "cat < /dev/null > /dev/tcp/<hostname>/<port>"

Check the return result (echo $?) afterward and if it is 0 we had a successful connection, 1 means there was an error connecting before the timeout expired, 124 means the timeout expired and there was no connection

Display info from istheinternetonfire.com in a pretty way

Requires cowsay and the lolcat ruby gem (gem install lolcat)

case $- in *i*)dig +short txt istheinternetonfire.com | cowsay -f moose | lolcat; esac

Show connection settings for a single port

ss -tnl '( sport = :80 )'

Check for network stats on a system. Look here for things such as SYN overflow.

netstat -s

Tar and compress files with multiple threads. -T0 makes it use all threads available.

tar -c -I 'xz -T0' -f file.tar.xz <files>