Problems "stdio and gnuplot"

1. Write a program main-stdio that reads a set of numbers from the standard input and writes these numbers together with their cosines in a table form into the standard output.
   Hint:

   double x;
   while( scanf("%lg",&x) != EOF ) printf("%lg \t %lg\n",x,cos(x));
   

2. Test the program by sending some numbers to it's standard input and observing its standard output, for example,

   echo 1 2 3 4 5 | ./main-stdio > test.io.out.txt
   

   and

   seq 1 0.5 4 | ./main-stdio > test.io.out.txt
   

   If you have Danish locale, and if your seq produces decimal commas, try seq 1 0.5 4 | sed -e 's/,/./g'. Read man sed.

3. Write a program main-cmdline that reads a set of numbers from its command-line-arguments and writes these numbers together with their sines in a table form into the standard output.

   Note: the length of the command-line string is limited by something like 2Mb so big data-sets should be read via standard input.

   Hint:

   for(int i=1;i<argc;i++) {
   	double x=atof(argv[i]);
   	printf("%lg \t %lg\n",x,sin(x));
   }
   

4. Test the program by sending some numbers to it's command line and observing its standard output, for example,

   ./main-cmdline 1 2 3 4 5 6 > test.cmd.out.txt
   

   and

   ./main-cmdline `seq 0 0.5 2` > test.cmd.out.txt
   

   Note the backquotes around the command `seq 0 0.5 2`. Read about backquotes in man bash, section "Command Substitution".

5. Prepare an input file with some numbers to make a plot of sine and cosine, for example (you only need sed if your seq produces decimal commas),

   seq 0 0.2 5 | sed -e 's/,/./g' > input.data.txt
   

6. Feed this file inout your prorams and produce tables of sine and cosine, for example,

   cat input.data.txt | ./main-stdio > out.io.txt
   

   or

   ./main-stdio < input.data.txt > out.io.txt
   

   and

   ./main-cmdline `cat input.data.txt` > out.cmd.txt
   

7. Make a plot of these sine and cosine tables using gnuplot/pyxplot. For example by creating a scipt file, plot.gpi,

   set terminal svg
   set output "plot.svg"
   plot "out.io.txt", "out.cmd.txt"
   

   and the running gnuplot on it,

   gnuplot plot.gpi