Commands using od (26)

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resize all JPG images in folder and create new images (w/o overwriting)
Convert all jpegs in the current directory into ~1024*768 pixels and ~ 150 KBytes jpegs

Find removed files still in use via /proc
Oracle DBA remove some logfiles which are still open by the database and he is complaining the space has not been reclaimed? Use the above command to find out what PID needs to be stopped. Or alternatively recover the file via: $ cp /proc/pid/fd/filehandle /new/file.txt

Create a listing of all possible permissions and their octal representation.

Share a 'screen'-session
Ater person A starts his screen-session with `screen`, person B can attach to the srceen of person A with `screen -x`. Good to know, if you need or give support from/to others.

Suspend, background, and foreground a process
./script.sh # suspend process {ctrl-Z} # background process bg # list all backgrounded jobs jobs # bring it back to foreground fg

Schedule a command while one is already running.
Useful when you have only one terminal session e.g. ssh. and want to queue up another command after the currently running has finished(in case if you forget to run that command). Originally used as ; python-updater when running emerge. When I have noticed that a package failed due to that command not run.

Use a var with more text only if it exists
See "Parameter Expansion" in the bash manpage. They refer to this as "Use Alternate Value", but we're including the var in the at alternative.

Colorized grep in less
Get your colorized grep output in less(1). This involves two things: forcing grep to output colors even though it's not going to a terminal and telling less to handle those properly.

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"

Add line number count as C-style comments
I often find the need to number enumerations and other lists when programming. With this command, create a new file called 'inputfile' with the text you want to number. Paste the contents of 'outputfile' back into your source file and fix the tabbing if necessary. You can also change this to output hex numbering by changing the "%02d" to "%02x". If you need to start at 0 replace "NR" with "NR-1". I adapted this from http://osxdaily.com/2010/05/20/easily-add-line-numbers-to-a-text-file/.


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