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Perform a reverse DNS lookup
Performs a reverse DNS lookup, variants include: $ nslookup 74.125.45.100 or: $ host 74.125.45.100

Copy your SSH public key on a remote machine for passwordless login - the easy way

Want to known what time is it in another part of the world ?
available timezone can be found in /usr/share/zoneinfo. Other examples: $ TZ=Europe/Paris date; TZ=Australia/Sydney date; TZ=America/New_York date this is based on zoneinfo files on macosx. Your mileage my vary on other unix dialects

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" }

Show LAN IP with ip(8)
$ ip address show | grep eth0 | sed '1d' | awk '{print $2}' does the same, but shows network-prefix.

Disconnect telnet
You are stuck with testing a tcp port using telnet, and must kill the telnet session from another terminal... Or, press ctrl+5 and write close/quit to force the current connection to close..

Buffer in order to avoir mistakes with redirections that empty your files
A common mistake in Bash is to write command-line where there's command a reading a file and whose result is redirected to that file. It can be easily avoided because of : 1) warnings "-bash: file.txt: cannot overwrite existing file" 2) options (often "-i") that let the command directly modify the file but I like to have that small function that does the trick by waiting for the first command to end before trying to write into the file. Lots of things could probably done in a better way, if you know one...

locating packages held back, such as with "aptitude hold "
locating packages held back, such as with "aptitude hold "

Backup trought SSH


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