spec - Local Sector 7 web page

47.FOURC> u vi macro.defs"macro.defs" 3 lines, 20 characters48.FOURC> qdo macro.defsOpened input file ‘macro.defs’ at level 1.49.FOURC>The unix() command (or the u macro) with no argument will spawn a subshell. Youreturn to spec upon exiting the subshell. spec uses the shell environment variableSHELL or shell, ifset, to select the type of UNIX shell. By default, /bin/sh is used.With arguments, unix() uses /bin/sh to execute the one-line command. For somecommon UNIX commands, macros such as the following are defined in the standardlibrary.def cat ’unix("cat $*")’def ls ’unix("ls $*")’def l ’unix("ls -l $*")’def vi ’unix("vi $*")’The working directory of spec can be changed as with the shell.49.FOURC> cd dataNow in ‘data’50.FOURC>The macro cd used above is defined using the built-in function chdir() . Only theworking directory of the program spec is changed; the shell from which you startedspec is not touched.Moving MotorsAprimary purpose of spec is to manipulate an X-ray diffractometer according to acalculated geometry. The automation of the angular settings is accomplishedthrough the use of motor controllers interfaced to the computer. spec can be configuredto control any number of motors.As explained earlier, motor positions are referred to as dial positions and user positions.The diffractometer is operated in user positions. Dial positions are used toprovide a stable point of reference. The two differ possibly by a sign and/or an offset.Dial positions should be set to always agree with the physical dials of the diffractometermotors. The user positions are then set in the line-up procedure of the28 USER MANUAL AND TUTORIALS INTERIM WORK-IN-PROGRESS (8/16/01) NOT FOR GENERAL DISTRIBUTION