gnuplot output of a pipe

Question

Inspired by this question I tried to pipe output to gnuplot and then plot it.

My pipe is:

cat file.txt |
grep CU | 
perl -e 'while(<>){print +(split)[3], "\n"}' | 
gnuplot file.gp 

Where file.gp contains the following:

set terminal dumb
plot '<perl' using 1

The output of the pipe is:

-77.8333771886
-77.8333771886
-77.8333771886
-77.8333771886
-77.8333771886
-77.8333771886
-77.8333771886
-77.8333771886
-77.8333771886
-7.78333787544e+01
-7.78333787544e+01

Now I got this error:

plot '<perl' using 1
               ^
"file.gp", line 3: warning: Skipping data file with no valid points

plot '<perl' using 1
                ^
"file.gp", line 3: x range is invalid

Piping the output into a file and then doing gnuplot file.gp with file.gp modified to contain the filename works as expected.

What am I doing wrong here?

Answer 1

My internet connection went down when I was about to post this question, so I had to try some more things on my own and eventually figured out how to do it. But since I had already written the question I feel I might as well share my new-found knowledge. I also encourage other answers that provide more insight.

My solution was to change file.gp to

set terminal dumb
plot '<cat' using 1

and then adjust the pipe chain like this

cat file.txt |
grep CU | #I put an identifier in the file 
perl -ne 'print +(split)[3], "\n"' | #strip the identifier
cat | #this makes gnuplot accept the output from the pipe
gnuplot file.gp