Useful CLI one-liners (Linux)

bash_oneliners.sh

# Number of open file descriptors per process (replace 'httpd' with process name)
lsof -p $( echo `ps -o pid= -C httpd` | tr ' ' ',' ) | awk '{ print $2 }' | uniq -c

# Show swap usage per process, >=1000 kB
cat /proc/*/status | egrep -B30 '^VmSwap:[[:space:]]+[[:digit:]]{4,}' | egrep '^Name|^Pid|^VmSwap'

# generate password
head -c12 /dev/urandom | base64 | tr '+/' '_-' | tr -d '='

# days to web server certificate expiry
echo $(( ( $( date -d "`openssl s_client -servername example.com -connect example.com:443 < /dev/null 2> /dev/null | openssl x509 -noout -enddate | grep notAfter | cut -d= -f2`" '+%s') - `date '+%s'` ) / 60 / 60 / 24 ))

# list virtio block devices with PCI IDs (not exactly one-liner, but useful anyway)
for dev in /sys/bus/virtio/drivers/virtio_blk/virtio* ; do
 echo $( readlink "$dev" | sed -r 's#.*/(pci.*)#\1#' ) $( ls "${dev}/block" )
done