oneliners.md

Oneliners

Delete all backups except from Sundays

If you have a filename in a YYYYMMDD-<something> format you can delete all the files except (for example) Sunday:

for i in $(ls | sed 's/-.*//g'); do [[ $(date --date=$i +'%w') != 0 ]] && rm -fv ${i}*; done

Delete multiple matcing lines from a file

sed -i -e ':a;N;$!ba;s/line1 match\nline2 match\n//' file

Kill all processes of user

kill -TERM $(ps -u <username> -o "pid=")

Find and remove dead symlinks

find /usr/bin -type l ! -xtype f ! -xtype d -ok rm -f {} \;

Drop Linux caches

To free pagecache:

echo 1 > /proc/sys/vm/drop_caches

To free dentries and inodes:

echo 2 > /proc/sys/vm/drop_caches

To free pagecache, dentries and inodes:

echo 3 > /proc/sys/vm/drop_caches

Test TCP port with bash only (exit should be 0):

echo -e 'test' > /dev/tcp/<ip>/<port>