gnuplot
To launch a batch session using two command files "input1" and "input2":
gnuplot input1 input2
To launch an interactive session after an initialization file "header" and followed by another command file "trailer":
gnuplot header - trailer
To give gnuplot commands directly in the command line, using the "-persist" option so that the plot remains on the screen afterwards:
gnuplot -persist -e "set title 'Sine curve'; plot sin(x)"
To set user-defined variables a and s prior to executing commands from a file:
gnuplot -e "a=2; s='file.png'" input.gpl