Passing a shell variable to awk in gnuplot - variables

Question

I need to pass a shell variable to awk in gnuplot but I get error messages :
The variable is set in the sript and is called FILE. This changes according to date.
My code : (in a Gnuplot script)
plot FILE using 1:14 with points pointtype 7 pointsize 1 # this works fine
replot '< awk ''{y1 = y2; y2 = $14; if (NR > 1 && y2 - y1 >= 100) printf("\n") ; if (NR > 1 && y2 -y1 <= -100) printf("\n"); print}'' FILE' using 1:14 with linespoints
Err msg
awk: fatal: cannot open file `FILE' for reading (No such file or directory)
When I hard code the FILE path the replot works.
Could anyone clarify the code I need to pass this variable to awk? Am I on the right track with something like :
% environment_variable=FILE
% awk -vawk_variable="${environment_variable}" 'BEGIN { print awk_variable }' ?
Here is my Gnuplot script code: cobbled together from other posts mostly..
#FILE selection - we want to plot the most recent data file
FILE = strftime('/data/%Y-%m-%d.txt', time(0)) # this is correct
print "FILE is : " .FILE
#set file path variable for awk : (This is where my problem is)
awk -v var="$FILE" '{print var}'
awk '{print $0}' <<< "$FILE"
Thank you in advance

Answer 1

If FILE is a gnuplot variable that contains the path of the file, you can do this:
FILE = 'input'
plot '<awk ''1'' ' . FILE
This concatenates the value of the gnuplot variable FILE onto the end of the awk command. The resulting awk "script" is therefore awk '1' input (which just prints every line of the file); you can substitute the '1' for whatever it is you want to do with awk.
By the way, your awk script can be simplified a little bit to this:
awk '{ y1 = y2; y2 = $14 } NR > 1 && (y2 - y1 >= 100 || y2 - y1 <= -100) { print "" } { print $1, $14 }'
It's not often that you need to use if in awk, as each block { } is executed conditionally (or if no condition is specified, the block is always executed). Assuming you haven't modified the record separator (the RS variable), print "" is the same as printf("\n"). Rather than specifying using 1:14 in gnuplot, you may as well only print the columns that you are interested in using print $1, $14.
So your replot line in gnuplot would be:
replot '<awk ''{ y1 = y2; y2 = $14 } NR > 1 && (y2 - y1 >= 100 || y2 - y1 <= -100) { print "" } { print $1, $14 }'' ' . FILE with linespoints
Of course, this line is getting a bit long. You might want to split it up a bit:
awk_cmd = '{ y1 = y2; y2 = $14 } NR > 1 && (y2 - y1 >= 100 || y2 - y1 <= -100) { print "" } { print $1, $14 }'
replot sprintf("<awk '%s' %s", awk_cmd, FILE) with linespoints