Steering gd1 or gd1.pp from a shell script

We can steer gd1 or gd1.pp by adding an option -Dname=value when starting the program. gd1 then defines a symbolic variable with name name to have the value value. The effect is therefore the same as if in the very first line of its input, the line sdefine(name, value) would occur. We write a small shell script that starts gd1 three times with three different values for the option.

#!/bin/sh

 for POS1 in 0e-3 25e-3 50e-3
 do
     gd1 -Dposition1=$POS1 -Dposition2=0 \
        < /usr/local/gd1/Tutorial-SRRC/wPlunger04.gdf | tee out.pos1=$POS1
 done

This shell-script can be found as '/usr/local/gd1/Tutorial-SRRC/many-pos1.x'. The inputfile 'wPlunger04.gdf' now calls the macros as follows:

 #
 # Model the tube and the plunger at phi=17 degrees:
 #
 call OuterPlunger( (130.75e-3/2)          , 17 )
 call InnerPlunger( (OuterRadius-position1), 17 )

 #
 # model the tube and the plunger at phi=-90+22.5 degrees:
 #
 call OuterPlunger( (110e-3/2)             , (-90+22.5) )
 call InnerPlunger( (OuterRadius-position2), (-90+22.5) )

The actual positions are output as annotations by specifying in the section -general:

 -general
    text()= position1 : Position of the first plunger  grep
    text()= position2 : Position of the second plunger grep

When gd1 reads this, it will substitute the 'position1' with the value that was supplied to it via its commandline option -Dposition1=$POS1, the corresponding happens to the string 'position2'. The strings 'grep' are supplied so that the outputfiles out.pos1=$POS1 can be 'grep'ed for the string 'grep'. The full inputfile can be found as /usr/local/gd1/Tutorial-SRRC/wPlunger04.gdf'.

When we run our shell script, we get three files

   out.pos1=0e-3, out.pos1=25e-3, out.pos1=50e-3

where the computed frequencies can be found in. The relevant lines can be easily extracted with the UNIX-command 'grep'. To show all lines in the files out.pos* that contain the string 'grep', you say

 grep grep out.pos*

The result is:

out.pos1=0e-3: general>     text()= 0e-3 : Position of the first plunger  grep
out.pos1=0e-3: general>     text()= 0 : Position of the second plunger grep
 Position of the first plunger: 0e-3  grep
 Position of the second plunger: 0 grep
out.pos1=0e-3:    1   52.7470e+06  1.0090174050  0.3438316719       # "grep" for me
out.pos1=0e-3:    2  502.5682e+06  0.0000031370  0.0000025505       # "grep" for me
out.pos1=0e-3:    3  778.1484e+06  0.0000000660  0.0000000914       # "grep" for me
out.pos1=0e-3:    4  779.3503e+06  0.0000000163  0.0000000249       # "grep" for me
out.pos1=0e-3:    5    1.0554e+09  0.0000000001  0.0000000002       # "grep" for me
out.pos1=0e-3:    6    1.0591e+09  0.0000000003  0.0000000045       # "grep" for me
out.pos1=0e-3:    7    1.0971e+09  0.0000000012  0.0000000173       # "grep" for me
out.pos1=0e-3:    8    1.0973e+09  0.0000000045  0.0000000428       # "grep" for me
out.pos1=0e-3:    9    1.1560e+09  0.0000000521  0.0000005213       # "grep" for me
out.pos1=0e-3:   10    1.1976e+09  0.0000001260  0.0000013792       # "grep" for me
out.pos1=0e-3:   11    1.2515e+09  0.0004255555  0.0049426207       # "grep" for me
out.pos1=0e-3:   12    1.2656e+09  0.0016319888  0.0731105041       # "grep" for me
out.pos1=0e-3:   13    1.2668e+09  0.0025985547  1.0000000000       # "grep" for me
out.pos1=25e-3: general>     text()= 25e-3 : Position of the first plunger  grep
out.pos1=25e-3: general>     text()= 0 : Position of the second plunger grep
out.pos1=25e-3: 25e-3 : Position of the first plunger  grep
out.pos1=25e-3: 0 : Position of the second plunger grep
out.pos1=25e-3:    1  503.7682e+06  0.0000024488  0.0000019899       # "grep" for me
out.pos1=25e-3:    2  779.4209e+06  0.0000000124  0.0000000171       # "grep" for me
out.pos1=25e-3:    3  781.0514e+06  0.0000000431  0.0000000660       # "grep" for me
out.pos1=25e-3:    4    1.0575e+09  0.0000000027  0.0000000051       # "grep" for me
out.pos1=25e-3:    5    1.0595e+09  0.0000000002  0.0000000024       # "grep" for me
out.pos1=25e-3:    6    1.0968e+09  0.0000000062  0.0000000913       # "grep" for me
out.pos1=25e-3:    7    1.0975e+09  0.0000000018  0.0000000174       # "grep" for me
out.pos1=25e-3:    8    1.1555e+09  0.0000000372  0.0000003780       # "grep" for me
out.pos1=25e-3:    9    1.2018e+09  0.0000002208  0.0000025548       # "grep" for me
out.pos1=25e-3:   10    1.2529e+09  0.0007020442  0.0086314595       # "grep" for me
out.pos1=25e-3:   11    1.2675e+09  0.0009580488  0.0414770393       # "grep" for me
out.pos1=25e-3:   12    1.2746e+09  0.0020655866  0.1865897939       # "grep" for me
out.pos1=50e-3: general>     text()= 50e-3 : Position of the first plunger  grep
out.pos1=50e-3: general>     text()= 0 : Position of the second plunger grep
out.pos1=50e-3: 50e-3 : Position of the first plunger  grep
out.pos1=50e-3: 0 : Position of the second plunger grep
out.pos1=50e-3:    1   99.6144e+06  0.9656790469  0.3479304400       # "grep" for me
out.pos1=50e-3:    2  505.2467e+06  0.0000031189  0.0000025741       # "grep" for me
out.pos1=50e-3:    3  779.6769e+06  0.0000000046  0.0000000065       # "grep" for me
out.pos1=50e-3:    4  781.9646e+06  0.0000000537  0.0000000853       # "grep" for me
out.pos1=50e-3:    5    1.0479e+09  0.0000000086  0.0000000166       # "grep" for me
out.pos1=50e-3:    6    1.0605e+09  0.0000000016  0.0000000236       # "grep" for me
out.pos1=50e-3:    7    1.0955e+09  0.0000000193  0.0000003011       # "grep" for me
out.pos1=50e-3:    8    1.0983e+09  0.0000000036  0.0000000400       # "grep" for me
out.pos1=50e-3:    9    1.1477e+09  0.0000000200  0.0000001945       # "grep" for me
out.pos1=50e-3:   10    1.2055e+09  0.0000001903  0.0000020180       # "grep" for me
out.pos1=50e-3:   11    1.2473e+09  0.0031135695  0.0463915760       # "grep" for me
out.pos1=50e-3:   12    1.2570e+09  0.0168888927  0.6785522929       # "grep" for me
out.pos1=50e-3:   13    1.2726e+09  0.0118906521  0.4821503838       # "grep" for me

This usage of gd1 is the reason, why gd1 writes the string

   "grep" for me

in the table of the frequencies.