StdinVsFiles

stdin vs. temporary files

Data can be passed through gnuplot's stdin like so gp << "plot '-' with lines\n"; gp.send1d(data); or can be passed via a temporary file, gp << "plot" << gp.file1d(data) << "with lines\n"; or even a non-temporary file, gp << "plot" << gp.file1d(data, "file.dat") << "with lines\n";

Binary data can also be passed via stdin or files.

Each has advantages and disadvantages.

• Passing through stdin avoid having to create temporary files. The disadvantage is that if something goes wrong, gnuplot can start interpreting your data as commands. This tends to spew a lot of error messages onto the console.
• Temporary files could possibly be left behind if your program crashes before cleanup can be done.
• If you are rapidly plotting data, as in an animation, you might not want to be creating hundreds of temporary files.
• If your program runs and exits quickly, the temporary files might be cleaned up before gnuplot can read them. Actually, this happens as soon as the Gnuplot object goes out of scope. The pgnuplot program on Windows seems especially prone to this problem, although even on Linux this could happen. The only sure-fire solution is to wait for a keystroke before letting the Gnuplot object go out of scope.
• If you are generating a script, using Gnuplot gp(fopen("script.gp", "w")) then it may make more sense to put the data in separate files rather than inlining it into your script.

Temporary files will automatically be erased when your program exits, or when the Gnuplot object goes out of scope. If you wish to manually wipe them at any time, just call gp.clearTmpfiles(). Be warned that calling gp.clearTmpfiles() just after a plot command can cause trouble since the files can be removed before gnuplot has a chance to read them!