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I tried out on my Mac, jot to generate sequence ( 0,25,50,..), you can use 'seq' if it is linux to generate numbers, need curl installed on the machine, then it rocks. @Satya

make 100 directories with leading zero, 001...100, using bash3.X

Selecting a random file/folder of a folder
random file from files in directory

Check whether laptop is running on battery or cable
The original proc file doesn't exist on my system.

validate the syntax of a perl-compatible regular expression
Place the regular expression you want to validate between the forward slashes in the eval block.

Remove specific entries from iptables
Then you can remove the specific entry: iptables -D INPUT 10 Just make sure these are set: IPTABLES_SAVE_ON_STOP="yes" IPTABLES_SAVE_ON_RESTART="yes" Else your changes won't stick when you restart iptables.

List your largest installed packages (on Debian/Ubuntu)
The other commands were good, but they included packages that were installed and then removed. This command only shows packages that are currently installed, sorts smallest to largest, and formats the sizes to be human readable.

Touch a file using a timestamp embedded in the file name.
tstouch takes two arguments: a filename containing a timestamp, and an extended regular expression with the parenthesized section matching a timestamp of the form YYYYMMDDhhmm or YYYYMMDDhhmm.ss. It then touches the file with that timestamp.

Blackhole any level zones via dnsmasq
Explanation It creates dnsmasq-com-blackhole.conf file with one line to route all domains of com zones to 0.0.0.0 You might use "address=/home.lab/127.0.0.1" to point allpossiblesubdomains.home.lab to your localhost or some other IP in a cloud.

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" }


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