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Contents → REFERENCE MANUAL → Syntax Description → Variables → Built-In Variables

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The following is a list of most of spec's built-in variables. Some site-dependent code, along with most of the standard diffractometer geometry code, will create additional built-in variables. Also, motor and counter mnemonics entered in the hardware configuration file become built-in variables when the config file is read by spec.

A[]

is an array dimensioned to the number of motors as obtained from the config file. The function read_motors(0) fills the array with user angles. The user can assign values to any of the elements. The commands move_all and move_cnt use the values in the array. Also, the various site-dependent, geometry-specific calculations, accessed through the calc() user-hook function, base their results on the values in this array or place new values in it.

COLS

is a number-valued variable set to the number of text columns on the user terminal or workstation window. The value is used for formatting text-mode plots and on-line help files. COLS is generally automatically assigned a value from the system terminal data base when spec starts up, or, if available, by using the TIOCGWINSZ command in the ioctl() system call whenever a value for COLS is needed.

COUNTERS

is the number of counters being used as determined from reading the config file.

CWD

is a string-valued variable that contains the name of the user's current working directory. It is assigned a value when spec starts up, and is updated each time the chdir() function is executed.

DEBUG

is a user-assignable numeric variable that determines the level of debugging messages printed. The level is determined by the sum of the values given in this table:

Hex	Decimal	What is shown
0x1	1	Show input tokens during parsing.
0x2	2	Show node execution while running.
0x4	4	Show node allocate and free.
0x8	8	Show symbol table creation and lookup.
0x10	16	Show value get and set.
0x20	32	Show misc info.
0x40	64	Show hardware related info.
0x80	128	Show more hardware related info.
0x100	256	Show macro substitution.
0x200	512	Show memory allocate and free.
0x400	1024	Show input after macro expansion.
0x800	2048	Print warning messages.
0x1000	4096	Show certain low level hardware info.
0x2000	8192	Show data array allocation.
0x4000		Show signal blocking.
0x8000		Show sleeps and other low level hardware info.
0x10000		Show input file queuing.
0x20000		Show readable runtime debugging.
0x40000		Print input context on execution-time errors.

A change in the value of DEBUG only takes effect after the complete mini-program in which the new value is assigned has been executed. If a debugging log file is open (any file that begins with the characters dlog or ends with the characters .dlog), debugging messages are only written to that file, not to the screen or any other file or device.

DISPLAY

is a user-assignable, string-valued variable. Its value at the time an X-Windows graphics filter process is spawned with the plot_cntl("open") function (with GTERM set to "x11") determines on which host and screen the plot window will be displayed. The initial value for DISPLAY is taken from the environment variable of the same name.

FRESH

is a built-in variable that has an initial nonzero value if spec was invoked with the -f (fresh start) flag or if a fresh start was forced by an incompatible state file version. The value is zero otherwise, and is set to zero in any case after all start-up command files and macros have been read and their commands executed. In the standard start-up macros, the value of FRESH is checked to see if initial default parameter assignments should be made.

GTERM

is a user-assignable, string-valued variable containing a value describing the display type to use for high-resolution graphics. Its value will be taken from an environment variable of the same name when spec starts up, if such a variable exists. Currently supported GTERM types are vga, vpc, ega, epc, herc and cga for various PC console graphics (not linux); x11 for X Window System graphics; and sun for SunView graphics. If GTERM is not set in the environment or has not been assigned a value, it defaults to x11.

HOME

is string valued and is initialized to the user's home directory as taken from the environment variable HOME. If not found in the environment, its value is set to the current directory.

MOTORS

is the number of motors being used as determined from reading the config file.

PAGER

can contain the name of a program to use for paging through spec help files. Such a program can be an alternative to spec's built-in paging code, allowing, for example, searching and line-by-line perusal. On start up, spec examines the environment variables SPEC_PAGER and PAGER, in turn. If one exists, its value is assigned to PAGER. Also, if a version of the less utility greater than version 332 is installed on the spec platform, the standard macros will assign to PAGER a string that invokes less with special flags. Otherwise, PAGER is left unset.

PI

is a number-valued symbol with the value 3.14159....

ROWS

is a number-valued variable set to the number of text rows on the user terminal or workstation window. The value is used for formatting text-mode plots and on-line help files. ROWS is generally automatically assigned a value from the system terminal data base when spec starts up, or, if available, by using the TIOCGWINSZ command in the ioctl() system call whenever a value for ROWS is needed.

S[]

is an array that will be filled with the hardware scaler contents when the command getcounts is executed.

SPEC

is string valued and set to the name by which spec is invoked, such as fourc.

SPECD

is string valued and set to spec's auxiliary file directory. The default name is compiled in when spec is installed, but can be overridden by the -D invocation option or by the SPECD environment variable.

TERM

is a user-assignable, string-valued variable. It is initialized to the user's terminal type as taken from the environment variable TERM. If not found in the environment, it is set to terminal-type vt100.

USER

is string valued and is set to the login name of the current user.

VERSION

is string valued and is set to the version number of spec, as in 3.03.11.

The values of A[], S[], DEBUG, TERM, GTERM, ROWS and COLS can be changed by the user. The other variables are immutable and cannot have their value changed.

Motor mnemonics obtained from the config file become built-in, immutable variables. User-added code, such as the X-ray diffractometer geometry code, typically creates other built-in variables, such as G[], Q[], U[] and Z[].

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