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List all symbolic links in current directory
Tested with GNU and BSD ls.

ping MAC ADDRESS
# first install arp-scan if not have it arp-scan 10.1.1.0/24 .... show ip+mac in localnet awk '/00:1b:11:dc:a9:65/ {print $1}' .... get ip associated with MAC ` backtick make do command substitution passing ip to command ping

Changes standard mysql client output to 'less'.
Changes standard mysql client output to 'less'. In another words makes query results of mysql command line client to look much better.

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" }

Search previous commands from your .bash_history
This is not actually a command, it's just a keyboard shortchut. But a very useful one.

Watch the progress of 'dd'
need pv (pipe view) : http://www.ivarch.com/programs/pv.shtml

list block devices
Shows all block devices in a tree with descruptions of what they are.

Command to logout all the users in one command
This command logs out all users - which is way more secure to use ps -ef and "grep" to kill processes. Never ever use ps -ef piped to grep to kill something. If you ever need to ps-something use the UNIX95-directive, which makes sure you will never need "grep" together with "ps".

Merge various PDF files

Execute a command with a timeout
I like much more the perl solution, but without using perl. It launches a backgroup process that will kill the command if it lasts too much. A bigger function: check_with_timeout() { [ "$DEBUG" ] && set -x COMMAND=$1 TIMEOUT=$2 RET=0 # Launch command in backgroup [ ! "$DEBUG" ] && exec 6>&2 # Link file descriptor #6 with stderr. [ ! "$DEBUG" ] && exec 2> /dev/null # Send stderr to null (avoid the Terminated messages) $COMMAND 2>&1 >/dev/null & COMMAND_PID=$! [ "$DEBUG" ] && echo "Background command pid $COMMAND_PID, parent pid $$" # Timer that will kill the command if timesout sleep $TIMEOUT && ps -p $COMMAND_PID -o pid,ppid |grep $$ | awk '{print $1}' | xargs kill & KILLER_PID=$! [ "$DEBUG" ] && echo "Killer command pid $KILLER_PID, parent pid $$" wait $COMMAND_PID RET=$? # Kill the killer timer [ "$DEBUG" ] && ps -e -o pid,ppid |grep $KILLER_PID | awk '{print $1}' | xargs echo "Killing processes: " ps -e -o pid,ppid |grep -v PID | grep $KILLER_PID | awk '{print $1}' | xargs kill wait sleep 1 [ ! "$DEBUG" ] && exec 2>&6 6>&- # Restore stderr and close file descriptor #6. return $RET }

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