Commands tagged bash (821)

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Generate Random Passwords
If you want a password length longer than 6, changing the -c6 to read -c8 will give you 8 random characters instead of 6. To end up with a line-feed, use this with echo: # echo `< /dev/urandom tr -dc _A-Z-a-z-0-9 | head -c6` Modern systems need higher strenght, so add some special characters: # < /dev/urandom tr -dc '12345!@#$%qwertQWERTasdfgASDFGzxcvbZXCVB' | head -c8

Calculate pi with specific scale
a() function in bc is for arctangent, available if using -l option included.

Reset hosed terminal,
stty sane resets the tty to basic usable function. The ^J is a newline -- sometimes CR/LF interpretation is broken so use the ^J explicitly.

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" }

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" }

Short and sweet output from dig(1)
Turn off almost all of dig's output except for what you'd see in a zone file. This can also be put into ~/.digrc.

watch iptables counters
Watch the number of packets/bytes coming through the firewall. Useful in setting up new iptables rules or chains. Use this output to reorder rules for efficiency.

journalctl -f
a tail -f variant of systemd journal. Follow the most recent updates or if events are appended to the journal

Display a cool clock on your terminal
This command displays a clock on your terminal which updates the time every second. Press Ctrl-C to exit. A couple of variants: A little bit bigger text: $ watch -t -n1 "date +%T|figlet -f big" You can try other figlet fonts, too. Big sideways characters: $ watch -n 1 -t '/usr/games/banner -w 30 $(date +%M:%S)' This requires a particular version of banner and a 40-line terminal or you can adjust the width ("30" here).

Generat a Random MAC address
Original author unknown (I believe off of a wifi hacking forum). Used in conjuction with ifconfig and cron.. can be handy (especially spoofing AP's)


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