# awk script 
#
# the begin command is executed BEFORE anything else is done
BEGIN {FS=" ";
"date" | getline date;
print date
}
# ------------------------ File reading sequence
{N=N+1}
{if(N==1) {printf "Input file [ %12s ]\n",FILENAME ;
print "#----------------------Input---------------------#"}}
{if($1=="Weight") {mass=$2/386.04;print$0}}
{if($1=="Spring") {kspring=$3;print$0}}
{if($1=="Damping") {dratio=$3;print$0}}
{if($1=="X0") {x0=$2;print$0}}
{if($1=="V0") {v0=$2;print$0}}
{if($1=="F0") {f0=$2;print$0}}
{if($1=="alpha") {alpha=$2;print$0}}
#
# ------------------------Start of calculation sequence
END {
#natlfreq will be in Hz
{natlfreq=sqrt(kspring/mass)/2/3.14159}
{dmpdnatlfreq=natlfreq*sqrt(1-dratio^2)}
{freqratio=alpha/natlfreq}
{statdefl=f0/kspring}
{scratch1=(1-freqratio^2)^2}
{scratch2=(2*dratio*freqratio)^2}
{scratch3=sqrt(scratch1+scratch2)}
{displ=statdefl/scratch3}
#
# response plot calculations..........
# x[ ] is the varying frequency ratio 
# y[ ] is the response
# frequency step are refined near resonance
# scratches are throw-away calcs
# 
{x[1]=0.;scratch4=(1-x[1]^2)^2;scratch5=(2*dratio*x[1])^2;scratch6=sqrt(scratch4+scratch5);y[1]=statdefl/scratch6}
#
{for(jk=2;jk<=10;jk++) {x[jk]=x[jk-1]+.10;scratch4=(1-x[jk]^2)^2;scratch5=(2*dratio*x[jk])^2;
scratch6=sqrt(scratch4+scratch5);y[jk]=statdefl/scratch6}}
{for(jk=11;jk<=14;jk++) {x[jk]=x[jk-1]+.05;scratch4=(1-x[jk]^2)^2;scratch5=(2*dratio*x[jk])^2;
scratch6=sqrt(scratch4+scratch5);y[jk]=statdefl/scratch6}}
{for(jk=15;jk<=23;jk++) {x[jk]=x[jk-1]+.10;scratch4=(1-x[jk]^2)^2;scratch5=(2*dratio*x[jk])^2;
scratch6=sqrt(scratch4+scratch5);y[jk]=statdefl/scratch6}}
#
# crude plotting routine (max stars = 20):
{for(jk=1;jk<=23;jk++) {if(y[jk]>ymax) {ymax=y[jk]}}}
{for(jk=1;jk<=23;jk++) {yratio[jk]=int(20*y[jk]/ymax)}}
{for(jk=1;jk<=23;jk++)
{km=0;scratch="";
while(km<=yratio[jk]) {scratch=scratch "#";km=km+1};
ystars[jk]=scratch}}
#
# start printing output 
{print "#---------------------------------Output--------------------------------------#"}
{print" "}
{printf("%s %-8.2f %-s\n","Undamped natural frequency =",natlfreq,"Hz")}
{printf("%s %-8.2f %-s\n","Damped natural frequency =",dmpdnatlfreq,"Hz")}
{printf("%s %-8.3f\n","Applied frequency ratio=",alpha/natlfreq)}

{printf("%s %-8.4f %-s\n","Amplitude at specified frequency =",displ,"inches")}
{printf("%s %-8.4f %-s\n","Applied F0 / k =",statdefl,"inches")}
{print" "}
{print"Response Plot: "}
{printf("%-8s %-8s %-10s\n","FR","Hz","Ampl")}
{for(jk=1;jk<=23;jk++) {printf("%-8.2f %-8.2f %-10.4f %s\n",x[jk],x[jk]*natlfreq,y[jk],ystars[jk])}}
#
{print "#-----------------------------End of File---------------------------------------#"}
}