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Sometimes in a script you want to make sure that a directory is in the path, and add it in if it's not already there. In this example, $dir contains the new directory you want to add to the path if it's not already present.
There are multiple ways to do this, but this one is a nice clean shell-internal approach. I based it on http://stackoverflow.com/a/1397020.
You can also do it using tr to separate the path into lines and grep -x to look for exact matches, like this:
$ if ! $(echo "$PATH" | tr ":" "\n" | grep -qx "$dir") ; then PATH=$PATH:$dir ; fi
which I got from http://stackoverflow.com/a/5048977.
Or replace the "echo | tr" part with a shell parameter expansion, like
$ if ! $(echo "${PATH//:/$'\n'}" | grep -qx "$dir") ; then PATH=$PATH:$dir ; fi
which I got from http://www.commandlinefu.com/commands/view/3209/.
There are also other more regex-y ways to do it, but I find the ones listed here easiest to follow.
Note some of this is specific to the bash shell.
Middle click on titlebar to minimize apps
Will track your mouse and save it to a file.
You can use gnuplot to graph it:
$ gnuplot -persist
Friday is the 5th day of the week, monday is the 1st.
Output may be affected by locale.
Start printing the contents of filename to stdout, until a matching line to regex is found, then stop.
You can do some boolean logic like
A or B then C else D using
or : ||
and : &&
So you can do some :
# false || false && echo true || echo false
false
# true || false && echo true || echo false
true
# false || true && echo true || echo false
true
# true || true && echo true || echo false
true
and so on ...
I use it like :
$(ssh example.com 'test something') || $(ssh example.net 'test something') && echo ok || echo ko
Run as root. Path may vary depending on laptop model and video card (this was tested on an Acer laptop with ATI HD3200 video).
$ cat /proc/acpi/video/VGA/LCD/brightness
to discover the possible values for your display.