Database Definition

Tags: developer advanced


This chapter describes database definitions. The following definitions are described:

  • Menu

  • Record Type

  • Device

  • Driver

  • Registrar

  • Variable

  • Function

  • Breakpoint Table

  • Record Instance

Record Instances are fundamentally different from the other definitions. A file containing record instances should never contain any of the other definitions and vice-versa. Thus the following convention is followed:

Database Definition File

A file that contains any type of definition except record instances.

Record Instance File

A file that contains only record instance definitions.

This chapter also describes utility programs which operate on these definitions.

Any combination of definitions can appear in a single file or in a set of files related to each other via include statements.

Summary of Database Syntax

The following summarizes the Database Definition syntax:

path "path"
addpath "path"
include "filename"
menu(name) {
    include "filename"
    choice(choice_name, "choice_value")

recordtype(record_type) {}

recordtype(record_type) {
    include "filename"
    field(field_name, field_type) {

device(record_type, link_type, dset_name, "choice_string")




breaktable(name) {
    raw_value eng_value

The Following defines a Record Instance

record(record_type, record_name) {
    include "filename"
    field(field_name, "value")
    info(info_name, "value")

General Rules for Database Definition


The following are keywords, i.e. they may not be used as values unless they are enclosed in quotes:


Unquoted Strings

In the summary section, some values are shown as quoted strings and some unquoted. The actual rule is that any string consisting of only the following characters does not need to be quoted unless it contains one of the above keywords:

a-z A-Z 0-9 _ + - : . [ ] < > ;

These are all legal characters for process variable names, although . is not allowed in a record name since it separates the record from the field name in a PV name. Thus in many cases quotes are not needed around record or field names in database files. Any string containing a macro does need to be quoted though.

Quoted Strings

A quoted string can contain any ascii character except the quote character ". The quote character itself can given by using a back-slash (\) as an escape character. For example "\"" is a quoted string containing a single double-quote character.

Macro Substitution

Macro substitutions are permitted inside quoted strings. Macro instances take the form:




There is no distinction between the use of parentheses or braces for delimiters, although the opening and closing characters must match for each macro instance. A macro name can be constructed using other macros, for example:


A macro instance can also provide a default value that is used when no macro with the given name has been defined. The default value can itself be defined in terms of other macros if desired, but may not contain any unescaped comma characters. The syntax for specifying a default value is as follows:


Finally macro instances can also set the values of other macros which may (temporarily) override any existing values for those macros, but the new values are in scope only for the duration of the expansion of this particular macro instance. These definitions consist of name=value sequences separated by commas, for example:


Escape Sequences

The database routines translate standard C escape sequences inside database field value strings only. The standard C escape sequences supported are:

\a \b \f \n \r \t \v \\ \' \" \ooo \xhh

\ooo represents an octal number with 1, 2, or 3 digits. \xhh represents a hexadecimal number which may have any number of hex digits, although only the last 2 will be represented in the character generated.


The comment symbol is “#”. Whenever the comment symbol appears outside of a quoted string, it and all subsequent characters through the end of the line will be ignored.

Define before referencing

In general items cannot be referenced until they have been defined. For example a device definition cannot appear until the recordtype that it references has been defined or at least declared. Another example is that a record instance cannot appear until its associated record type has been defined.

One notable exception to this rule is that within a recordtype definition a menu field may reference a menu that has not been included directly by the record’s .dbd file.

Multiple Definitions

If a menu, device, driver, or breakpoint table is defined more than once, then only the first instance will be used. Subsequent definitions may be compared to the first one and an error reported if they are different (the program does this, the IOC currently does not). Record type definitions may only be loaded once; duplicates will cause an error even if the later definitions are identical to the first. However a record type declaration may be used in place of the record type definition in .dbd files that define device support for that type.

Record instance definitions are (normally) cumulative, so multiple instances of the same record may be loaded and each time a field value is encountered it replaces the previous value.

Filename Extensions

By convention:

  • Record instances files have the extension “.db” or “.vdb” if the file also contains visual layout information

  • Database definition files have the extension “.dbd

Database Definition Statements

path addpath – Path Definition


path "dir:dir...:dir"
addpath "dir:dir...:dir"

The path string follows the standard convention for the operating system, i.e. directory names are separated by a colon “:” on Unix and a semicolon “;” on Windows.

The path statement specifies the current search path for use when loading database and database definition files. The addpath statement appends directories to the current path. The path is used to locate the initial database file and included files. An empty path component at the beginning, middle, or end of a non-empty path string means search the current directory. For example:

nnn::mmm    # Current directory is between nnn and mmm
:nnn        # Current directory is first
nnn:        # Current directory is last

Utilities which load database files (dbExpand, dbLoadDatabase, etc.) allow the user to specify an initial path. The path and addpath commands can be used to change or extend that initial path.

The initial path is determined as follows:

  1. If path is provided with the command, it is used. Else:

  2. If the environment variable EPICS_DB_INCLUDE_PATH is defined, it is used. Else:

  3. the path is “.”, i.e. the current directory.

The search path is not used at all if the filename being searched for contains a / or \ character. The first instance of the specified filename is used.

include – Include Statement


include "filename"

An include statement can appear at any place shown in the summary. It uses the search path as described above to locate the named file.

recordtype – Record Type Definition


recordtype(record_type) {}

recordtype(record_type) {
    field(field_name, field_type) {

A record type statement that provides no field descriptions is a declaration, analagous to a function declaration (prototype) or forward definition in C. It allows the given record type name to be used in circumstances where the full record type definition is not needed.

Field Descriptor Rules


Sets the Access Security Level for the field. Access Security is discussed in chapter [Access Security].


Provides an initial (default) value for the field.


The group to which the field belongs, for database configuration tools.


A prompt string for database configuration tools. Optional if promptgroup is not defined.


If specified, special processing is required for this field at run time.


Whether a passive record should be processed when Channel Access writes to this field.


Interest level for the field.


For integer fields, the number base to use when converting the field value to a string.


Must be specified for DBF_STRING fields.


Must be specified for DBF_NOACCESS fields.


Must be specified for DBF_MENU fields. It is the name of the associated menu.


Must be YES or NO (default). Indicates that the field holds Channel Access meta-data.



The unique name of the record type. Duplicate definitions are not allowed and will be rejected.


The field name, which must be a valid C and C++ identifier. When include files are generated, the field name is converted to lower case for use as the record structure member name. If the lower-case version of the field name is a C or C++ keyword, the original name will be used for the structure member name instead. Previous versions of EPICS required the field name be a maximum of four all upper-case characters, but these restrictions no longer apply.


This must be one of the following values:










This must be one of the following values:

  • ASL0

  • ASL1 (default value)

Fields which operators normally change are assigned ASL0. Other fields are assigned ASL1. For example, the VAL field of an analog output record is assigned ASL0 and all other fields ASL1. This is because only the VAL field should be modified during normal operations.


A legal value for data type.


A prompt value for database configuration tools.


A string used by database configuration tools (DCTs) to group related fields together.

A promptgroup should only be set for fields that can sensibly be configured in a record instance file.

The set of group names is no longer fixed. In earlier versions of Base the predefined set of choices beginning GUI_ were the only group names permitted. Now the group name strings found in the database definition file are collected and stored in a global list. The strings given for group names must match exactly for fields to be grouped together.

To support sorting and handling of groups, the names used in Base have the following conventions:

  • Names start with a two-digit number followed by a space-dash-space sequence.

  • Names are designed to be presented in ascending numerical order.

  • The group name (or possibly just the part following the dash) may be displayed by the tool as a title for the group.

  • In many-of-the-same-kind cases (e.g. 21 similar inputs) fields are distributed over multiple groups. Once-only fields appear in groups numbered in multiples of 5 or 10. The groups with the multiple instances follow in +1 increments. This allows more sophisticated treatment, e.g. showing the first group open and the other groups collapsed.

Record types may define their own group names. However, to improve consistency, records should use the following names from Base where possible. (This set also demonstrates that the group names used in different record types may share the same number.)

  • General fields that are common to all or many record types

  • Scanning mechanism, priority and related properties

  • Record type specific behavior and processing action

  • Links and related properties

  • Input links and properties

  • Output links and properties

  • Conversion between raw and engineering values

  • Alarm related properties, severities and thresholds

  • Client related configuration, strings, deadbands

  • Simulation mode related properties

NOTE: Older versions of Base contained a header file guigroup.h defining a fixed set of group names and their matching index numbers. That header file has been removed. The static database access library now provides functions to convert between group index keys and the associated group name strings. See [subsec:Get Field Prompt] for details.


Must be one of the following:

  • SPC_MOD – Notify record support when modified. The record support special routine will be called whenever the field is modified by the database access routines.

  • SPC_NOMOD – No external modifications allowed. This value disables external writes to the field, so it can only be set by the record or device support module.

  • SPC_DBADDR – Use this if the record support’s cvt_dbaddr routine should be called to adjust the field description when code outside of the record or device support makes a connection to the field.

    The following values are for database common fields. They must not be used for record specific fields:

  • SPC_SCAN – Scan related field.

  • SPC_ALARMACK – Alarm acknowledgment field.

  • SPC_AS – Access security field.

    The following values are deprecated, use SPC_MOD instead:

  • An integer value greater than 103.

  • SPC_RESET – a reset field is being modified.

  • SPC_LINCONV – A linear conversion field is being modified.

  • SPC_CALC – A calc field is being modified.


Should a passive record be processed when Channel Access writes to this field? The allowed values are:

  • FALSE (default)

  • TRUE


An interest level for the dbpr command.


For integer type fields, the default base. The legal values are:

  • DECIMAL (Default)

  • HEX


The number of characters for a DBF_STRING field.


For DBF_NOACCESS fields, this is the C language definition for the field. The definition must end with the fieldname in lower case.


A percent sign % inside the record body introduces a line of code that is to be included in the generated C header file.


The following is the definition of the event record type:

recordtype(event) {
    include "dbCommon.dbd"
    field(VAL,DBF_STRING) {
        prompt("Event Name To Post")
        promptgroup("40 - Input")
    field(EPVT, DBF_NOACCESS) {
        prompt("Event private")
        extra("EVENTPVT epvt")
    field(INP,DBF_INLINK) {
        prompt("Input Specification")
        promptgroup("40 - Input")
    field(SIOL,DBF_INLINK) {
        prompt("Sim Input Specifctn")
        promptgroup("90 - Simulate")
    field(SVAL,DBF_STRING) {
        prompt("Simulation Value")
    field(SIML,DBF_INLINK) {
        prompt("Sim Mode Location")
        promptgroup("90 - Simulate")
    field(SIMM,DBF_MENU) {
        prompt("Simulation Mode")
    field(SIMS,DBF_MENU) {
        prompt("Sim mode Alarm Svrty")
        promptgroup("90 - Simulate")

device – Device Support Declaration


device(record_type, link_type, dset_name, "choice_string")



Record type. The combination of record_type and choice_string must be unique. If the same combination appears more than once, only the first definition is used.


Link type. This must be one of the following:



  • VME_IO


  • AB_IO





  • RF_IO

  • VXI_IO


The name of the device support entry table for this device support.


The DTYP choice string for this device support. A choice_string value may be reused for different record types, but must be unique for each specific record type.


device(ai,CONSTANT,devAiSoft,"Soft Channel")
device(ai,VME_IO,devAiXy566Se,"XYCOM-566 SE Scanned")

driver – Driver Declaration





If duplicates are defined, only the first is used.



registrar – Registrar Declaration





The name of an C function that accepts no arguments, returns void and has been marked in its source file with an epicsExportRegistrar declaration, e.g.

static void myRegistrar(void);

This can be used to register functions for use by subroutine records or that can be invoked from iocsh. The example application described in Section [Example IOC Application], “Example IOC Application” gives an example of how to register functions for subroutine records.



variable – Variable Declaration


variable(variable_name[, type])



The name of a C variable which has been marked in its source file with an epicsExportAddress declaration.


The C variable’s type. If not present, int is assumed. Currently only int and double variables are supported.

This registers a diagnostic/configuration variable for device or driver support or a subroutine record subroutine. This variable can be read and set with the iocsh var command (see Section [Utility Commands]. The example application described in Section [Example IOC Application] shows how to register a debug variable for use in a subroutine record.


In an application C source file:

#include <epicsExport.h>

static double myParameter;
epicsExportAddress(double, myParameter);

In an application database definition file:

variable(myParameter, double)

function – Function Declaration





The name of a C function which has been exported from its source file with an epicsRegisterFunction declaration.

This registers a function so that it can be found in the function registry for use by record types such as sub or aSub which refer to the function by name. The example application described in Section [Example IOC Application] shows how to register functions for a subroutine record.


In an application C source file:

#include <registryFunction.h>
#include <epicsExport.h>

static long myFunction(void *argp) {
    /* my code ... */

In an application database definition file:


breaktable – Breakpoint Table


breaktable(name) {
    raw_value eng_value



Name, which must be alpha-numeric, of the breakpoint table. If duplicates are specified the first is used.


The raw value, i.e. the actual ADC value associated with the beginning of the interval.


The engineering value associated with the beginning of the interval.


breaktable(typeJdegC) {
    0.000000 0.000000
    365.023224 67.000000
    1000.046448 178.000000
    3007.255859 524.000000
    3543.383789 613.000000
    4042.988281 692.000000
    4101.488281 701.000000

record – Record Instance


record(record_type, record_name) {
    field(field_name, "field_value")
    info(info_name, "info_value")
alias(record_name, alias_name)



The record type, or "*" (see discussion under record_name below).


The record name. This must be composed out of only the following characters:

a-z A-Z 0-9 _ - + : [ ] < > ;

NOTE: If macro substitutions are used the name must be quoted.

Duplicate definitions are normally allowed for a record as long as the record type is the same. The last value given for each field is the value used. If the duplicate definitions are being used and the record has already been loaded, subsequent definitions may use "*" in place of the record type in the record instance.

The variable dbRecordsOnceOnly can be set to any non-zero value using the iocsh var command to make loading duplicate record definitions into the IOC illegal.


An alternate name for the record, following the same rules as the record name.


A field name.


A value for the named field, appropriate for its particular field type. When given inside double quotes the field value string may contain escaped characters which will be translated appropriately when loading the database. See section 1.3.5 for the list of escaped characters supported. Permitted values for the various field types are as follows:

    Any ASCII string. If it exceeds the field length, it will be truncated.
    A string that represents a valid integer. The standard C conventions are applied, i.e. a leading 0 means the value is given in octal and a leading 0x means that value is given in hex.
    The string must represent a valid floating point number. Infinities or NaN are also allowed.
    The string must be one of the valid choices for the associated menu.
    The string must be one of the valid device choice strings.
    • If the field name is INP or OUT then this field is associated with DTYP, and the permitted values are determined by the link type of the device support selected by the current DTYP choice string. Other DBF_INLINK and DBF_OUTLINK fields must be either CONSTANT or PV_LINKs.

    • A device support that specifies a link type of CONSTANT can be given either a constant or a PV_LINK.

    The allowed values for the field depend on the device support’s link type as follows:

      A numeric literal, valid for the field type it is to be read into.
    • PV_LINK
      A value of the form:
      record.field process maximize

      record is the name of a record that exists in this or another IOC.

      The .field, process, and maximize parts are all optional.

      The default value for .field is .VAL.

      process can have one of the following values:

      • NPP – No Process Passive (Default)

      • PP – Process Passive

      • CA – Force link to be a channel access link

      • CP – CA and process on monitor

      • CPP – CA and process on monitor if record is passive


        CP and CPP are valid only for DBF_INLINK fields.

        DBF_FWDLINK fields can use PP or CA. If a DBF_FWDLINK is a channel access link it must reference the target record’s PROC field.

      maximize can have one of the following values:

      • NMS – No Maximize Severity (Default)

      • MS – Maximize Severity

      • MSS – Maximize Severity and Status

      • MSI – Maximize Severity if Invalid

    • VME_IO
      #Ccard Ssignal @parm
      card – the card number of associated hardware module
      signal – signal on card
      parm – An arbitrary character string of up to 31 characters. This field is optional and is device specific.
    • CAMAC_IO
      #Bbranch Ccrate Nstation Asubaddress Ffunction @parm

      branch, crate, station, subaddress, and function should be obvious to camac users. subaddress and function are optional (0 if not given). parm is also optional and is device specific (25 characters max).

    • AB_IO
      #Llink Aadapter Ccard Ssignal @parm
      link – Scanner, i.e. vme scanner number
      adapter – Adapter. Allen Bradley also calls this rack
      card – Card within Allen Bradley Chassis
      signal – signal on card
      parm – optional device-specific character string (27 char max)
    • GPIB_IO
      #Llink Aaddr @parm
      link – gpib link, i.e. interface
      addr – GPIB address
      parm – device-specific character string (31 char max)
      #Llink Nnode Pport Ssignal @parm
      link – link, i.e. vme bitbus interface
      node – bitbus node
      port – port on the node
      signal – signal on port
      parm – device specific-character string (31 char max)
    • INST_IO @parm

      parm – Device dependent character string

      #Llink Bbbaddr Ggpibaddr @parm
      link – link, i.e. vme bitbus interface
      bbadddr – bitbus address
      gpibaddr – gpib address
      parm – optional device-specific character string (31 char max)
    • RF_IO
      #Rcryo Mmicro Ddataset Eelement
    • VXI_IO
      #Vframe Cslot Ssignal @parm (Dynamic addressing)
      #Vla Signal @parm (Static Addressing)
      frame – VXI frame number
      slot – Slot within VXI frame
      la – Logical Address
      signal – Signal Number
      parm – device specific character string(25 char max)

The name of an Information Item related to this record. See section 1.5 below for more on Information Items.


Any ASCII string. IOC applications using this information item may place additional restrictions on the contents of the string.


record(ai,STS_AbAiMaS0) {
    field(SCAN,".1 second")
    field(INP,"#L0 A2 C0 S0 F0 @")
record(ao,STS_AbAoMaC1S0) {
    field(OUT,"#L0 A2 C1 S0 F0 @")
record(bi,STS_AbDiA0C0S0) {
    field(SCAN,"I/O Intr")
    field(DTYP,"AB-Binary Input")
    field(INP,"#L0 A0 C0 S0 F0 @")

Record Information Item

Information items provide a way to attach named string values to individual record instances that are loaded at the same time as the record definition. They can be attached to any record without having to modify the record type, and can be retrieved by programs running on the IOC (they are not visible via Channel Access at all). Each item attached to a single record must have a unique name by which it is addressed, and database access provides routines to allow a record’s info items to be scanned, searched for, retrieved and set. At runtime a void* pointer can also be associated with each item, although only the string value can be initialized from the record definition when the database is loaded.

Record Attributes

Each record type can have any number of record attributes. Each attribute is a psuedo field that can be accessed via database and channel access. Each attribute has a name that acts like a field name but returns the same value for all instances of the record type. Two attributes are generated automatically for each record type: RTYP and VERS. The value for RTYP is the record type name. The default value for VERS is “none specified”, which can be changed by record support. Record support can call the following routine to create new attributes or change existing attributes:

long dbPutAttribute(char *rtype, char *name, char *value);

The arguments are:

rtype – The name of recordtype.

name – The attribute name, i.e. the psuedo field name.

value – The value assigned to the attribute.

Breakpoint Tables – Discussion

The menu menuConvert is used for field LINR of the ai and ao records. These records allow raw data to be converted to/from engineering units via one of the following:

  1. No Conversion.

  2. Slope Conversion.

  3. Linear Conversion.

  4. Breakpoint table.

Other record types can also use this feature. The first choice specifies no conversion; the second and third are both linear conversions, the difference being that for Slope conversion the user specifies the conversion slope and offset values directly, whereas for Linear conversions these are calculated by the device support from the requested Engineering Units range and the device support’s knowledge of the hardware conversion range. The remaining choices are assumed to be the names of breakpoint tables. If a breakpoint table is chosen, the record support modules calls cvtRawToEngBpt or cvtEngToRawBpt. You can look at the ai and ao record support modules for details.

If a user wants to add additional breakpoint tables, then the following should be done:

  • Copy the menuConvert.dbd file from EPICS base/src/ioc/bpt

  • Add definitions for new breakpoint tables to the end

  • Make sure modified menuConvert.dbd is loaded into the IOC instead of EPICS version.

It is only necessary to load a breakpoint file if a record instance actually chooses it. It should also be mentioned that the Allen Bradley IXE device support misuses the LINR field. If you use this module, it is very important that you do not change any of the EPICS supplied definitions in menuConvert.dbd. Just add your definitions at the end.

If a breakpoint table is chosen, then the corresponding breakpoint file must be loaded into the IOC before iocInit is called.

Normally, it is desirable to directly create the breakpoint tables. However, sometimes it is desirable to create a breakpoint table from a table of raw values representing equally spaced engineering units. A good example is the Thermocouple tables in the OMEGA Engineering, INC Temperature Measurement Handbook. A tool makeBpt is provided to convert such data to a breakpoint table.

The format for generating a breakpoint table from a data table of raw values corresponding to equally spaced engineering values is:

!comment line
<header line>
<data table>

The header line contains the following information:


An alphanumeric ascii string specifying the breakpoint table name

Low Value Eng

Engineering Units Value for first breakpoint table entry

Low Value Raw

Raw value for first breakpoint table entry

High Value Eng

Engineering Units: Highest Value desired

High Value Raw

Raw Value for High Value Eng


Allowed error (Engineering Units)

First Table

Engineering units corresponding to first data table entry

Last Table

Engineering units corresponding to last data table entry

Delta Table

Change in engineering units per data table entry

An example definition is:

"TypeKdegF" 32 0 1832 4095 1.0 -454 2500 1
<data table>

The breakpoint table can be generated by executing


The input file must have the extension of data. The output filename is the same as the input filename with the extension of .dbd.

Another way to create the breakpoint table is to include the following definition in a Makefile:

BPTS += bptXXX.dbd

NOTE: This requires the naming convention that all data tables are of the form bpt<name>.data and a breakpoint table bpt<name>.dbd. [-D] [-I dir] [-S mac=sub] [-o out.dbd] in.dbd ...

This program reads and combines the database definition from all the input files, then writes a single output file containing all information from the input files. The output content differs from the input in that comment lines are removed, and all defined macros and include files are expanded. Unlike the previous dbExpand program, this program does not understand database instances and cannot be used with .db or .vdb files.

Multiple -I options can be provided to specify directories that must be searched when looking for included files. Multiple -S options are allowed for macro substitution, or multiple macros can be specified within a single option. If no output filename is specified with the -o out.dbd option then the output will go to stdout.

The -D option causes the program to output Makefile dependency information for the output file to standard output, instead of actually performing the functions describe above.


dbLoadDatabase(char *dbdfile, char *path, char *substitutions)

This IOC command loads a database file which may contain any of the Database Definitions described in this chapter. The dbdfile string may contain environment variable macros of the form ${MOTOR} which will be expanded before the file is opened. Both the path and substitutions parameters can be null or empty, and are usually ommitted. Note that dbLoadDatabase should only used to load Database Definition (.dbd) files, although it is currently possible to use it for loading Record Instance (.db) files as well.

As each line of the file is read, the substitutions specified in substitutions are performed. Substitutions are specified as follows:


Variables are used in the file with the syntax $(var) or ${var}. If the substitution string

"a=1,b=2,c=\"this is a test\""

were used, any variables $(a), $(b), $(c) in the database file would have the appropriate values substituted during parsing.


dbLoadRecords(char* dbfile, char* substitutions)

This IOC command loads a file containing record instances, record aliases and/or breakpoint tables. The dbfile string may contain environment variable macros of the form ${MOTOR} which will be expanded before the file is opened. The substitutions parameter can be null or empty, and is often ommitted. Note that dbLoadRecords should only used to load Record Instance (.db) files, although it is currently possible to use it for loading Database Definition (.dbd) files as well.


For example, let the file test.db contain:

record(ai, "$(pre)testrec1")
record(ai, "$(pre)testrec2")
record(stringout, "$(pre)testrec3") {
    field(VAL, "$(STR)")
    field(SCAN, "$(SCAN)")

Then issuing the command:

dbLoadRecords("test.db", "pre=TEST,STR=test,SCAN=Passive")

gives the same results as loading:

record(ai, "TESTtestrec1")
record(ai, "TESTtestrec2")
record(stringout, "TESTtestrec3") {
    field(VAL, "test")
    field(SCAN, "Passive")


dbLoadTemplate(char *subfile, char *substitutions)

This IOC command reads a template substitutions file which provides instructions for loading database instance files and gives values for the $(xxx) macros they may contain. This command performs those substitutions while loading the database instances requested.

The subfile parameter gives the name of the template substitution file to be used. The optional substitutions parameter may contain additional global macro values, which can be overridden by values given within the substitution file.

The MSI program can be used to expand templates at build-time instead of using this command at run-time; both understand the same substitution file syntax.

Template File Syntax

The template substitution file syntax is described in the following Extended Backus-Naur Form grammar:

substitution-file ::= ( global-defs | template-subs )+

global-defs ::= 'global' '{' variable-defs? '}'

template-subs ::= template-filename '{' subs? '}'
template-filename ::= 'file' file-name
subs ::= pattern-subs | variable-subs

pattern-subs ::= 'pattern' '{' pattern-names? '}' pattern-defs?
pattern-names ::= ( variable-name ','? )+
pattern-defs ::= ( global-defs | ( '{' pattern-values? '}' ) )+
pattern-values ::= ( value ','? )+

variable-subs ::= ( global-defs | ( '{' variable-defs? '}' ) )+
variable-defs ::= ( variable-def ','? )+
variable-def ::= variable-name '=' value

variable-name ::= variable-name-start variable-name-char*
file-name ::= file-name-char+ | double-quoted-str | single-quoted-str
value ::= value-char+ | double-quoted-str | single-quoted-str

double-quoted-str ::= '"' (double-quoted-char | escaped-char)* '"'
single-quoted-str ::= "'" (single-quoted-char | escaped-char)* "'"
double-quoted-char ::= [^"\]
single-quoted-char ::= [^'\]
escaped-char ::= '\' .

value-char ::= [a-zA-Z0-9_+:;./\<>[] | '-' | ']'
variable-name-start ::= [a-zA-Z_]
variable-name-char ::= [a-zA-Z0-9_]
file-name-char ::= [a-zA-Z0-9_+:;./\] | '-'

Note that the current implementation may accept a wider range of characters for the last three definitions than those listed here, but future releases may restrict the characters to those given above.

Any record instance file names must appear inside quotation marks if the name contains any environment variable macros of the form ${ENV_VAR_NAME}, which will be expanded before the named file is opened.

Template File Formats

Two different template formats are supported by the syntax rules given above. The format is either:

file name.template {
    { var1=sub1_for_set1, var2=sub2_for_set1, var3=sub3_for_set1, ... }
    { var1=sub1_for_set2, var2=sub2_for_set2, var3=sub3_for_set2, ... }
    { var1=sub1_for_set3, var2=sub2_for_set3, var3=sub3_for_set3, ... }


file name.template {
pattern { var1, var2, var3, ... }
    { sub1_for_set1, sub2_for_set1, sub3_for_set1, ... }
    { sub1_for_set2, sub2_for_set2, sub3_for_set2, ... }
    { sub1_for_set3, sub2_for_set3, sub3_for_set3, ... }

The first line (file name.template) specifies the record instance input file. The file name may appear inside double quotation marks; these are required if the name contains any characters that are not in the following set, or if it contains environment variable macros of the form ${VAR_NAME} which must be expanded to generate the file name:

a-z A-Z 0-9 _ + - . / \ : ; [ ] < >

Each set of definitions enclosed in {} is variable substitution for the input file. The input file has each set applied to it to produce one composite file with all the completed substitutions in it. Version 1 should be obvious. In version 2, the variables are listed in the pattern{} line, which must precede the braced substitution lines. The braced substitution lines contains sets which match up with the pattern{} line.


Two simple template file examples are shown below. The examples specify the same substitutions to perform: this=sub1 and that=sub2 for a first set, and this=sub3 and that=sub4 for a second set.

file test.template {
    { this=sub1,that=sub2 }
    { this=sub3,that=sub4 }

file test.template {
    {sub3,sub4 }

Assume that the file test.template contains:

record(ai,"$(this)record") {
    field(DESC,"this = $(this)")
record(ai,"$(that)record") {
    field(DESC,"this = $(that)")

Using dbLoadTemplate with either input is the same as defining the records:

record(ai,"sub1record") {
    field(DESC,"this = sub1")
record(ai,"sub2record") {
    field(DESC,"this = sub2")

record(ai,"sub3record") {
    field(DESC,"this = sub3")
record(ai,"sub4record") {
    field(DESC,"this = sub4")