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Execute a command with a timeout
In this example the command "somecommand" will be executed and sent a SIGALARM signal if it runs for more than 10 seconds. It uses the perl alarm function. It's not 100% accurate on timing, but close enough. I found this really useful when executing scripts and commands that I knew might hang E.g. ones that connect to services that might not be running. Importantly this can be used within a sequential script. The command will not release control until either the command completes or the timeout is hit.

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"

Recursively remove .svn directories

Number of connections to domains on a cPanel server

Get the size of all the directories in current directory
OSX's BSD version of the du command uses the -d argument instead of --max-depth.

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" }

list files recursively by size

Look for IPv4 address in files.
It finds a SNMP OID too :-(

Pass TAB as field separator to sort, join, cut, etc.
Use this BASH trick to create a variable containing the TAB character and pass it as the argument to sort, join, cut and other commands which don't understand the \t notation. $ sort -t $'\t' ... $ join -t $'\t' ... $ cut -d $'\t' ...

Merge tarballs
Requires the GNU tar ignore zeros option. http://www.gnu.org/software/tar/manual/html_section/Blocking.html


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