pro read_parameters, file_name, redshift=redshift, InitialTime=InitialTime, $
                     InitialRedshift=InitialRedshift, DataDumpNumber=DataDumpNumber, $
                     lengthunit=lengthunit, timeunit=timeunit, velocityunit=velocityunit,  $
                     densityunit=densityunit, temperatureunit=temperatureunit, $ 
                     DomainLeftEdge=DomainLeftEdge, DomainRightEdge=DomainRightEdge, gamma=gamma

     
     fstring = read_ascii_file_return_list_of_strings(file_name, $
                                                      /verbose, nlines=nlines)



     InitialRedshift = 0.D
     InitialTime = 0.D
     ComovingBoxSize = 0
     HubbleConstantNow = 0.
     OmegaNow = 0.
     Gamma=5./3.
     DataDumpNumber = 0
     unitvalue = 0.
     unitlabel=''
     lengthunit = 1.
     timeunit = 1.
     temperatureunit = 1.
     densityunit = 1.
     DomainLeftEdge = [0.,0.,0.]
     DomainRightEdge = [1.,1.,1.]

     if N_elements(fstring) lt 2 then return

     redshift =  -1.D

     whereRed = where(strmatch(fstring, 'CosmologyCurrentRedshift*') eq 1)
     whereIRed = where(strmatch(fstring, 'CosmologyInitialRedshift*') eq 1)
     whereCBS = where(strmatch(fstring, 'CosmologyComovingBoxSize*') eq 1)
     whereH0 = where(strmatch(fstring, 'CosmologyHubbleConstantNow*') eq 1)
     whereOmega0 = where(strmatch(fstring, 'CosmologyOmegaMatterNow*') eq 1)
     whereIt = where(strmatch(fstring, 'InitialTime*') eq 1)
     whereGamma = where(strmatch(fstring, 'Gamma*') eq 1)
     whereDDNum = where(strmatch(fstring, 'DataDumpNumber*') eq 1)
     whereLU = where(strmatch(fstring, 'LengthUnit*') eq 1)
     whereDU = where(strmatch(fstring, 'DensityUnit*') eq 1)
     whereTU = where(strmatch(fstring, 'TimeUnit*') eq 1)
     whereDL = where(strmatch(fstring, 'DomainLeftEdge*') eq 1)
     whereDR= where(strmatch(fstring, 'DomainRightEdge*') eq 1)
     

     if whereLU[0] ge 0 then begin
        hs = fstring[whereLU[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        lengthunit = DOUBLE(value)
     endif
     if whereDU[0] ge 0 then begin
        hs = fstring[whereDU[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        densityunit = DOUBLE(value)
        timeunit = 1.D/(sqrt(6.673e-8*densityunit))  ; this gets overidden if timeunit is in the file:
     endif
     if whereTU[0] ge 0 then begin
        hs = fstring[whereTU[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        timeunit = DOUBLE(value)
     endif

     if whereRed[0] ge 0 then begin
        hs = fstring[whereRed[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        redshift = DOUBLE(value)
     endif
     if whereH0[0] ge 0 then begin
        hs = fstring[whereH0[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        HubbleConstantNow = DOUBLE(value)
     endif
     if whereOmega0[0] ge 0 then begin
        hs = fstring[whereOmega0[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        OmegaNow = DOUBLE(value)
     endif

     if whereIRed[0] ge 0 then begin
        hs = fstring[whereIRed[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        InitialRedshift = DOUBLE(value)
     endif

     if whereCBS[0] ge 0 then begin
        hs = fstring[whereCBS[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        ComovingBoxSize = DOUBLE(value)
        mpc = 3.086d24
        rho0 = 3.D*OmegaNow * HubbleConstantNow^2 * (1d7/Mpc)^2/(8.*!pi*6.673e-8)
        timeunit = 1d/sqrt(4.*!PI*6.673e-8*rho0 * (1.+InitialRedshift)^3)
        temperatureunit = 1.88d6*ComovingBoxSize^2*OmegaNow*(1.+InitialRedshift)
;        densityunit = rho0*(1.+redshift)^3
; leave these comoving so they are the same for every data dump
        densityunit = rho0
;        lengthunit =
;        mpc*ComovingBoxSize/HubbleConstantNow/(1.+redshift)
        lengthunit = mpc*ComovingBoxSize/HubbleConstantNow
        velocityunit = lengthunit/timeunit/(1.+InitialRedshift)
     endif
     
     if whereIt[0] ge 0 then begin
        hs = fstring[whereIt[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        InitialTime = DOUBLE(value)
     endif
     
     if whereGamma[0] ge 0 then begin
        hs = fstring[whereGamma[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        Gamma = FLOAT(value)
     endif
     
     if whereDDNum[0] ge 0 then begin
        hs = fstring[whereDDNum[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        DataDumpNumber = FIX(value)
     endif
     
;;      if whereDCGS[0] ge 0 then begin
;;         nun = N_ELEMENTS(whereDCGS)
;;         unitvalue = fltarr(nun)
;;         unitlabel = STRARR(nun)
;;         unitfield = STRARR(nun)
;;         for i=0, nun-1 do begin
;;            hs = fstring[whereDCGS[i]]
;;            values = str_sep(strtrim(strmid(hs,strpos(hs, '=')+1), 2), ' ')
;;            unitvalue[i] = FLOAT(values[0])
;;            unitlabel[i] = values[1]
;;            hs = fstring[whereDCGS[i]-1]
;;            unitfield[i] = strmid(hs,strpos(hs, '= ')+1)
;;         endfor
;;      endif

     if (redshift eq -1) then begin
;        redshift = -InitialTime
        print, 'Time:', InitialTime, ' from file:', file_name
     end else print, 'Redshift:', Redshift, ' from file:', file_name
        
     if whereDL[0] ge 0 then begin
        hs = fstring[whereDL[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        str_to_flt_arr, value, DomainLeftEdge
     endif
     if whereDR[0] ge 0 then begin
        hs = fstring[whereDR[0]]
        value = strmid(hs,strpos(hs, '=')+1)
        str_to_flt_arr, value, DomainRightEdge
     endif

     if (InitialRedshift eq 0.) then velocityunit = lengthunit/timeunit

end