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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" }

Count files beneath current directory (including subfolders)

Generate diff of first 500 lines of two files
Useful for massive files where doing a full diff would take too long. This just runs diff on the first 500 lines of each. The use of subshells to feed STDIN is quite a useful construct.

Run local bash script on remote server
Run local scripts on remote server. "-T Disable pseudo-tty allocation"

convert ascii string to hex
Even adds a newline.

Show File System Hierarchy
Curious about differences between /bin, /usr/bin, and /usr/local/bin? What should be in the /sbin dir? Try this command to find out. Tested against Red Hat & OS X

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

Download SSL server certificate with opsnessl
Useful when we need to create new certificate for site when current one is near expiry. This downloaded cert can be used to provide organisational data directly to new cert. using below command. e.g. openssl x509 -x509toreq -in /tmp/example.com.cert -out example.com.csr -signkey example.com-key.pem

display a smiling smiley if the command succeeded and a sad smiley if the command failed
you could save the code between if and fi to a shell script named smiley.sh with the first argument as and then do a smiley.sh to see if the command succeeded. a bit needless but who cares ;)

output your microphone to a remote computer's speaker
This will output the sound from your microphone port to the ssh target computer's speaker port. The sound quality is very bad, so you will hear a lot of hissing.


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