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Remove invalid key from the known_hosts file for the IP address of a host
Quick shortcut if you know the hostname and want to save yourself one step for looking up the IP address separately.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Convert tab separate file (TSV) to JSON with jq
With this command you can convert a tab separate file (TSV) into a JSON file with jq. For example, this input.tsv i-0b9adca882e5e6326 172.16.0.188 i-088dd69e5c3624888 172.16.0.102 i-0e70eac180537d4aa 172.16.0.85 will produce the showed output.

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Backup files older than 1 day on /home/dir, gzip them, moving old file to a dated file.
Useful for backing up old files, custom logs, etc. via a cronjob.

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

Complete TCP Handshake on a given host-port
Try to perform a fully TCP 3 way handshake on for a given host-port with a timeout of 1s.

Update a tarball
This will update the tarball, adding files that have changed since the last update. This assumes that the tarball is in the same directory as the files being archived. N.B. This command can't be used on compressed tarballs. N.B. This will add the updated files to the tarball, so that the tarball will have two versions of each file. This will make the tarball larger, but doesn't have any other significant effect.

Binary difference of two files
Upload/download newer version of any file with less size and high speed. To remake the new file use $bspatch

check open ports without netstat or lsof


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