# 3. Development Cycle¶

This chapter introduces program development in the YottaDB environment. The YottaDB environment differs from other M implementations in a number of ways. These differences, which include maintaining data and code in separate files and compiling rather than interpreting source code, allow greater programmer control over the development cycle.

In contrast to M environments that interpret M code, YottaDB compiles M code from source files into the target machine language. The YottaDB compiler produces object files, which are dynamically linked into an image. Source files and object files may be managed independently, or placed together in a specific directory. YottaDB permits access to source and object files in multiple directories.

YottaDB databases are UNIX files identified by a small file called a Global Directory. Global Directories allow management of the database files to be independent of the placement of files containing M routines. By changing the Global Directory, you can use the same programs to access different databases.

Program development may utilize both YottaDB and UNIX development tools. The development methodology and environment chosen for a particular installation, and tailored by the individual user, determines the actual mix of tools. These tools may vary from entirely YottaDB with little UNIX, to mostly UNIX with a modest use of YottaDB.

Direct Mode serves as an interactive interface to the YottaDB run-time environment and the compiler. In Direct Mode, the user enters M commands at the YottaDB prompt, and YottaDB compiles and executes the command. This feature provides immediate turnaround for rapid program development and maintenance.

This chapter is based on the tasks that a programmer might perform while developing an application. It provides a “road map” for programmers of varying levels. Some steps may be unnecessary in your environment, so feel free to skip sections that do not apply to your situation.

## Overview of the Program Development Cycle¶

This section provides an overview of the steps involved in generating executable programs in YottaDB.

The steps begin with your initial use of YottaDB. The first two steps are part of your initial setup and will generally be performed only the first time you use YottaDB. The remaining steps are those you will use regularly when generating your programs.

Each of these remaining steps can be performed either from the YottaDB prompt or the shell prompt. To clearly describe the two ways to perform each step, this section is set up in the format of a table with one column illustrating the YottaDB method, and one column illustrating the shell method.

Define Environment Variables (shell)

define:

• ydb_dist
• ydb_gbldir
• ydb_routines
Prepare database

define Global Directory with GDE

create database with MUPIP CREATE

Create/Edit Routine Create file with UNIX editor; assign .m extension ZEDIT “routine” .m extension added by YottaDB
Compile Routine invoke mumps routine.m ZLINK “routine”
Execute Routine

invoke mumps -run routine

calls from other routines invoke auto-ZLINK

Do ^routine calls from other routines invoke auto-ZLINK
Debug Routine edit file with UNIX editor; compile and execute

utilize debug commands such as:

ZGOTO

ZMESSAGE

ZPRINT

ZSHOW

ZSTEP

ZSYSTEM

ZWRITE

compile and execute

The table is presented as an overview of the YottaDB routine generation process, and as a comparison of the available methods. More complete information on each of the steps can be found in the following parts of this manual set.

## Defining Environment Variables¶

YottaDB requires the definition of certain environment variables as part of setting up the environment. These environment variables are used for the following purposes:

• To locate the files that YottaDB provides
• To hold some user-controlled information which YottaDB uses for run-time operation

YottaDB limits environment variables to 8192 bytes, but items they specify such as a path may have a lower limit.

The procedure below describes how to define an environment variable. Use this procedure to define an environment variable either at the shell prompt or in your shell startup file. If you define the variable at the shell prompt, it will be effective only until you logout. If you define it in your .profile file (.cshrc, if using a C shell variant), it will be in effect whenever you log in. Your system manager may have already defined some of these variables.

Note

Each environment variable required by YottaDB is described and illustrated in individual sections following the procedure. Only ydb_dist, and in some cases ydb_gbldir, ydb_principal and ydb_routines, are required by users who do not perform programming activities.

To define an environment variable type the following commands:

$env_variable=env_variable_value$ export env_variable


The example above may differ from the syntax supported by some shells.

The following environment variables hold information that determines some details of YottaDB run-time operation, over which the user has control.

### ydb_dist¶

ydb_dist is used to establish the location of the installed YottaDB program and support files.

The syntax for ydb_dist is as follows:

$ydb_dist=<distribution-directory>  The standard installation places these files in /usr/local/lib/yottadb. Example: $ ydb_dist=/usr/local/lib/yottadb/r120
$export ydb_dist  This identifies /usr/local/lib/yottadb/r120 as the location of the installed YottaDB files. Add ydb_dist to your PATH environment variable to have UNIX search the YottaDB installation directory (when processing a command to activate or run an image). This allows you to activate YottaDB and the utilities without explicitly specifying a path. To add ydb_dist to your PATH type the following commands: $ PATH=$PATH:$ydb_dist
$export PATH  Note Most of the examples in this manual assume that you have added ydb_dist to your PATH. ### ydb_gbldir¶ ydb_gbldir defines the path to a Global Directory. A Global Directory maps global variables to physical database files, and is required to locate M global variables. ydb_gbldir provides the initial value for$ZGBLDIR, the intrinsic special variable that connects the YottaDB run-time system to the Global Directory. It also connects the Global Directory to the utilities requiring one.

If you maintain multiple global directories, define ydb_gbldir to the Global Directory you currently want to use.

The syntax of a ydb_gbldir definition is:

$ydb_gbldir=/directory/filename.gld  Example: $ ydb_gbldir=/usr/staff/mumps.gld
$export ydb_gbldir  This specifies /usr/staff as the directory containing the Global Directory file named mumps.gld. ### ydb_principal¶ The ydb_principal environment variable specifies the value for$principal, which designates the absolute pathname of the principal $IO device. This is an MDC Type A enhancement to standard M. The following is an example of ydb_principal definition: $ ydb_principal=/usr/filename
$export ydb_principal  This specifies the /usr/filename as the principal$IO device, effective until changed further or until you logout of the particular session.

### ydb_routines¶

The ydb_routines environment variable specifies a search list of possible locations for M routines. This value is used to initialize $ZROUTINES, (the intrinsic special variable that enables YottaDB to find the routine (program) you want to run). ydb_routines is required for ZLINKing. ydb_routines is particularly helpful in calling percent utilities and the Global Directory Editor (GDE), which are in ydb_dist. $ ydb_routines="directories in search list"


The directories in the search list must be separated by a space and enclosed in quotation marks (” “). Environment variables are accepted in the search list.

The following is an example of ydb_routines definition:

$ydb_routines=".$ydb_dist"
$export ydb_routines  This specifies that YottaDB search for a routine first in the current directory (.), then in the distribution directory (which is identified by the environment variable ydb_dist). The distribution directory is included in the list because it contains the percent routines. You will probably want the search list to contain these two items at a minimum. In addition, you may want to add directories of your own. For additional information about how YottaDB uses the routine search list, see “$ZROutines”.

### Editor¶

The EDITOR environment variable specifies the UNIX text editor used when editing a routine either from the shell or with ZEDIT. Since this is a standard part of establishing your UNIX environment, you will probably only need to define this when you want to use a different editor than the one defined in your shell startup file.

Example:

$EDITOR=/usr/bin/vi$ export EDITOR


This defines the current text editor to vi.

## Preparing the Database¶

YottaDB databases consist of one or more UNIX files. Most database files have a UNIX file structure externally and a YottaDB Database Structure (GDS) internally. Management of the GDS files by the YottaDB run-time system assures high performance and integrity. YottaDB database files are coordinated by a Global Directory. The Global Directory identifies which global names belong in which files, and specifies the creation characteristics for each file. To specify access to a database, each M process must define the ydb_gbldir environment variable to point to the associated Global Directory.

To define and maintain a Global Directory, use the Global Directory Editor (GDE) utility. The GDE utility automatically upgrades existing global directories to the current format. The MUPIP command CREATE uses the characteristics as defined in the Global Directory to create the associated database. In a production environment, the system manager typically maintains Global Directories.

For more information on GDE and MUPIP refer to the “Global Directory Editor” and “MUPIP” chapters in the Administration and Operations Guide.

Example:

This example is a sequence of events that illustrate steps you might typically perform in creating a new global directory, in our example PAYROLL.GLD.

$ls payroll.gld payroll.gld not found  The ls command verifies that there are no existing files with the name payroll.gld. $ ydb_gbldir=payroll.gld
$export ydb_gbldir  This establishes the current value of the environment variable ydb_gbldir as payroll.gld. YottaDB uses ydb_gbldir to identify the current Global Directory. When defined at the shell prompt, ydb_gbldir maintains the defined value only for the current login session. The next time you log into UNIX, you must again define the value of ydb_gbldir as payroll.gld to use it as the current Global Directory. This example defines ydb_gbldir without a full pathname. The environment variable points to the payroll.gld file in the current working directory. Therefore if the default directory changes, YottaDB attempts to locate the Global Directory in the new default directory and cannot use the original file. If you intend for the Global Directory to consistently point to this file, even if the default directory changes, use a full file-specification for ydb_gbldir. $ /usr/local/lib/yottadb/r120/ydb
YDB>do ^GDE
%GDE-I-VERIFY, Verification OK
GDE>


This invokes the Global Directory Editor by entering GDE from the YottaDB prompt and produces an informational message.

GDE> show all

*** Templates ***
Region                        Def Coll    Rec Size   Key Size   Null Subs    Std Null Coll   Journaling
--------------------------------------------------------------------------------------------------------
<default>                       0           4080       255       NEVER             Y             Y

Jnl File (def ext: .mjl)    Before   Buff    Alloc   Exten
------------------------------------------------------------------------------------------------
<default>                    <based on DB file-spec>      Y       128     2048    2048

Segment              Active          Acc   Typ   Block   Alloc   Exten     Options
--------------------------------------------------------------------------------------
<default>             *              BG    DYN   4096    5000    10000     GLOB=1000
LOCK = 40
RES = 0
ENCR = OFF
<default>                            MM    DYN   4096    5000    10000     DEFER
LOCK=40

*** Names ***
Global                                              Region
----------------------------------------------------------------
*                                                  DEFAULT

*** Regions ***
Region          Dynamic Segment     Def Coll    Rec Size   Key Size   Null Subs   Std Null Coll   Journaling
---------------------------------------------------------------------------------------------------------------
DEFAULT         DEFAULT               0          4080       255        NEVER          Y              Y

*** Journaling Information ***
Region                          Jnl File (def ext: .mjl)     Before   Buff   Alloc   Exten
------------------------------------------------------------------------------------------------------
DEFAULT                   $gtmdir/$ydb_rel/g/payroll.mjl    Y        128    2048     2048

*** Segments ***
Segment                      File (def ext: .dat)           Acc  Typ  Block   Alloc  Exten   Options
---------------------------------------------------------------------------------------------------------
DEFAULT                    $gtmdir/$ydb_rel/g/payroll.dat  BG   DYN  4096    5000   10000   GLOB=1000
LOCK=40
RES=0
ENCR=OFF

*** MAP ***
--------------------------------Names----------------------------------------------
From              Up to              Region / Segment / File(def ext: .dat)
---------------------------------------------------------------------------------------
%                 ...                REG = DEFAULT
SEG = DEFAULT
FILE = $gtmdir/$ydb_rel/g/payroll.dat

LOCAL LOCKS                          REG = DEFAULT
SEG = DEFAULT
FILE = $gtmdir/$ydb_rel/g/payroll.dat


The GDE SHOW command displays the default Global Directory.

GDE> change -segment default -allocation=1000 file=payroll.dat


The GDE CHANGE command sets the database file name to payroll.dat, and specifies a file size of 1000 blocks (of 1024 bytes).

GDE>exit
%GDE-I-VERIFY, Verification OK
%GDE-I-GDCREATE, Creating Global Directory file /usr/lib/yottadb/r120/payroll.gld
%GDE-I-GDEIS, Global Directory


The GDE EXIT command terminates GDE. The Global Directory Editor creates a default Global Directory and displays a confirmation message.

$ls payroll.gld payroll.gld  This ls command shows the new Global Directory has been created. In the simplest case, running the Global Directory Editor and immediately EXITing creates a Global Directory with a default single file database. To create the database file payroll.dat, use the MUPIP CREATE utility. Example: $ mupip create
Created file payroll.dat


The MUPIP CREATE command generates the database file. Notice that the MUPIP CREATE syntax does not include the file name. MUPIP uses the environment variable ydb_gbldir to find the Global Directory payroll.dat and obtains the file name from that Global Directory. MUPIP then checks to make sure that payroll.dat does not already exist and creates payroll.dat with the characteristics described in payroll.dat.

Example:

$mupip load payroll.gld MUPIP EXTRACT 02-MAY-2013 22:21:37 ZWR Beginning LOAD at record number: 3 LOAD TOTAL Key Cnt: 279 Max Subsc Len: 28 Max Data Len: 222 Last LOAD record number: 281  This uses the MUPIP LOAD command to load a sequential file into the database. Because MUPIP uses the environment variable ydb_gbldir to locate a Global Directory, which identifies the database file(s), the LOAD command does not require any information about the target database. With few exceptions, the YottaDB utilities work in the same way. ## Creating and Editing a Source Program¶ The first step in developing a YottaDB program is to create a source file. In most cases, the user can create and modify YottaDB source programs using UNIX text editors. When the program is very simple (and its lines do not need revision after they are entered), you can use the cat command to direct input from your terminal to your source file. ### Editing from YottaDB¶ If you focus on program development outside the YottaDB environment, skip this section and continue with the section “Editing from the Shell”. Invoke Direct Mode to create and edit a source program in YottaDB. At the YDB> prompt, invoke the editor by typing: ZEDIT <filename>  ZEDIT invokes the editor specified by the EDITOR environment variable, which creates a seperate file for each M source module. The YottaDB environment works most efficiently if the file has the same name as the M routine it contains, and has an .m extension. Since ZEDIT automatically defaults the .m extension, it is not necessary to specify an extension unless you require a different one. If you use another extension, you must specify that extension with every reference to the file. Multiple character file extensions are permitted for M source file names. Example: $ ydb
YDB>ZEDIT "payroll"


This syntax uses the ydb script to enter YottaDB from the shell, and uses ZEDIT to initiate an editing session on payroll.m Because ZEDIT defaults the extension to .m, it is not necessary to provide an extension. If payroll.m does not already exist, YottaDB creates it in the first source directory identified by $ZROUTINES. If$ZROUTINES is null, ZEDIT places the source file in the process’s current working directory.

$ZROUTINES is a read-write special variable containing an ordered list of directories that certain YottaDB functions use to locate source and object files. Generally, a system manager sets up the environment to define the environment variable ydb_routines. At image invocation, YottaDB initializes$ZROUTINES to the value of ydb_routines. Once you are running M, you can SET and refer to $ZROUTINES using the format: YDB>SET$ZROUTINES=expr


Where:

• The expression may contain a list of UNIX directories and/or file-specifications delimited by spaces.
• The expression specifies one or more directories to search.
• An element of the expression contains an environment variable evaluating to a directory specification.
• If $ZROUTINES contains an environment variable that evaluates to a list, YottaDB uses the first name in that list. For more information on$ZROUTINES, see Chapter 8: “Intrinsic Special Variables”.

### Editing from the Shell¶

To create and edit a source program from the shell, invoke any text editor at the shell prompt and specify a UNIX file as the source. The YottaDB environment works best when you give a file the name of the M routine that it contains, and a .m extension.

Example:

$vi payroll.m  The vi command initiates an editing session for payroll.m from the shell prompt. If payroll.m does not already exist, vi creates it. Because this example uses UNIX rather than YottaDB tools, we must specify the .m file extension. ## Compiling a Source Program¶ If you wish to focus on program development outside the YottaDB environment, skip the next section and continue with the section “Compiling from the Shell”. YottaDB compiles M source code files and produces object files for complete integration into the UNIX enviroment. The object modules have the same name as the compiled M source file with an .o file extension, unless otherwise specified. The object files contain machine instructions and information necessary to connect the routine with other routines, and map it into memory. An M routine source file must be compiled after it is created or modified. You can compile explicitly with the ZLINK command or implicitly with auto-ZLINK. At the shell command line, compile by issuing the mumps command. The compiler checks M code for syntax errors and displays error messages on the terminal, when processing is complete. Each error message provides the source line in error with an indicator pointing to the place on the line where the error is occurring. For a list and description of the compiler error messages, refer to the Messages and Recovery Procedures Reference Manual. You can generate a listing file containing the compile results by including the -list qualifier as a modifier to the argument to the ZLINK command in Direct Mode. This can also be done by redirecting the compiler messages to a file by adding >filename 2>&1 to the mumps command when compiling a program from the shell. See “Compiling from the Shell” for an explanation of the M command describing -list, and other valid qualifiers for the M and ZLINK commands. The compiler stops processing a routine line when it detects an error on that line. Under most conditions the compiler continues processing the remaining routine lines. This allows the compiler to produce a more complete error analysis of the routine and to generate code that may have valid executable paths. The compiler does not report multiple syntax errors on the same line. When it detects more than 127 syntax errors in a source file, the compiler ceases to process the file. ### Compiling from YottaDB¶ In Direct Mode, YottaDB provides access to the compiler explicitly through the ZLINK and ZCOMPILE commands, and implicitly through automatic invocation of ZLINK functionality (auto-ZLINK) to add required routines to the image. ZCOMPILE is a YottaDB routine compilation command, it compiles the routine and creates a new object module. The primary task of ZLINK is to place the object code in memory and “connect” it with other routines. However, under certain circumstances, ZLINK may first use the YottaDB compiler to create a new object module. The difference between ZCOMPILE and ZLINK is that ZCOMPILE creates a new object module on compiling, whereas the ZLINK command links the object module with other routines and places the object code in memory. ZLINK compiles under these circumstances: • ZLINK cannot locate a copy of the object module but can locate a copy of the source module. • ZLINK can locate both object and source module, and finds the object module to be older than the source module. • The file-specification portion of the ZLINK argument includes an explicit extension of .m. Auto-ZLINK compiles under the first two circumstances, but can never encounter the last one. When a command refers to an M routine that is not part of the current image, YottaDB automatically attempts to ZLINK and, if necessary, compile that routine. In Direct Mode, the most common method to invoke the compiler through an auto-ZLINK is to enter DO ^routinename at the YDB> prompt. When the current image does not contain the routine, YottaDB does the following: • Locates the source and object • Determines whether the source has been edited since it was last compiled • Compiles the routine, if appropriate • Adds the object to the image By using the DO command, you implicitly instruct YottaDB to compile, link, and execute the program. With this method, you can test your routine interactively. For complete descriptions of ZLINK and auto-ZLINK, see Chapter 6: “Commands” . Example: YDB>do ^payroll YDB>do ^taxes  This uses the M DO command to invoke the YottaDB compiler implicitly from the YDB> prompt if the routine requires new object code. When the compiler runs, it produces two object module files, payroll.o and taxes.o. If you receive error messages from the compilation, you may fix them immediately by returning to the editor and correcting the source. By default, the YottaDB compiler operates in “compile-as-written” mode, and produces object code even when a routine contains syntax errors. This code includes all lines that are correct and all commands on a line with an error, up to the error. Therefore, you may decide to tailor the debugging cycle by running the program without removing the syntax errors. Note The DO command does not add an edited routine to the current image if the image already includes a routine matching the DO argument routine name. When the image contains a routine, YottaDB simply executes the routine without examining whether a more recent version of the module exists. If you have a routine in your image, and you wish to change it, you must explicitly ZLINK that routine. Example: YDB>zlink "payroll" YDB>zlink "taxes.m"  The first ZLINK compiles payroll.m if it cannot locate payroll, or if it finds that payroll.m has a more recent date/time stamp than payroll.o. The second ZLINK always compiles taxes.m producing a new taxes.o. For more information on debugging in Direct Mode, see Chapter 4: “Operating and Debugging in Direct Mode”. ### Compiling from the Shell¶ From the shell, invoke the compiler by entering mumps file-name at the shell prompt. Example: $ mumps payroll.m

#### -[no]i[gnore]¶

Instructs the compiler to produce an object file even when the compiler detects errors in the source code (-ignore), or not to produce an object file when the compiler encounters an error (-noignore).

When used with the -noobject qualifier, the -ignore qualifier has no effect.

Execution of a routine that compiles with errors produces run-time errors when the execution path encounters any of the compile time errors.

This compile-as-written mode facilitates a flexible approach to debugging and expedites conversion to YottaDB from an interpreted environment. Many M applications from an interpreted environment contain syntax abnormalities. This feature of compiling and later executing a routine provides the feel of developing in an interpreted environment.

By default, the compiler operates in -ignore mode and produces an object module even when the source routine contains errors.

#### -le[ngth]=lines¶

Controls the page length of the listing file.

The M compiler ignores the -length qualifier unless it appears with the -list qualifier.

By default, the listing has -length=66.

#### -[no]li[st][=filename]¶

Instructs the compiler to produce a source program listing file, and optionally specifies a name for the listing file. The listing file contains numbered source program text lines. When the routine has errors, the listing file also includes an error count, information about the location, and the cause of the errors.

When you do not specify a file name for the listing file, the compiler produces a listing file with the same name as the source file with a .lis file extension.

The -length and -space qualifiers modify the format and content of the listing file. The M compiler ignores these qualifiers unless the command includes the -list qualifier.

By default, the compiler operates -nolist and does not produce listings.

#### -noin[line_literals]¶

Compiles routines to use library code in order to load literals instead of generating in-line code thereby reducing the routine size. At the cost of a small increase in CPU, the use of -NOINLINE_LITERAL may help counteract growth in object size due to -DYNAMIC_LITERALS.

Note

Both -DYNAMIC_LITERALS and -NOINLINE_LITERALS help optimize performance and virtual memory usage for applications whose source code includes literals. As the scalability and performance from reduced per-process memory usage may or may not compensate for the incremental cost of dynamically loading and unloading the data structures, and as the performance of routines vs. inline code can be affected by the availability of routines in cache, YottaDB suggests benchmarking to determine the combination of qualifiers best suited to each workload. Note that applications can freely mix routines compiled with different combinations of qualifiers.

#### -[no]o[bject][=filename]¶

Instructs the compiler to produce an output object file and optionally specifies a name for the object file using the optional filename argument.

When you do not specify a file name, the compiler produces an object file with the same file name as the source file and an .o file extension.

When forming routine names, the compiler truncates object filenames to a maximum length of 31 characters. For example, for a source file called Adatabaseenginewithscalabilityproven.m the compiler generates an object file called Adatabaseenginewithscalabilityp.o. Ensure that first 31 characters of source file names are unique.

The -noobject qualifier suppresses the production of an object file and is usually used with the -list qualifier to produce only a listing file.

By default, the compiler produces object modules.

#### -[no]w[arning]¶

Instructs the compiler to suppress error output; the default is -warning.

When used with the -list qualifier, the -nowarning qualifier does not affect errors in the listing.

Note

When used with the -noobject qualifier, the -nowarning qualifier instructs the compiler to produce no object with no indication of the fact or the cause of any errors.

#### -r[un]¶

The next argument is taken to be an M entryref. That routine is immediately executed, bypassing Direct Mode. Depending on the shell, you may need to put the entryref in quotation marks (“”). This qualifier does not invoke the M compiler and is not compatible with any other qualifier.

#### -s[pace]=lines¶

Controls the spacing of the output in the listing file. -space=n specifies n-1 blank lines separating every source line in the listing file. If n<1, the M command uses single spacing in the listing.

If this qualifier appears without the -list qualifier, the M compiler ignores the -space qualifier.

By default, listings use single spaced output (-space=1).

MUMPS Command Qualifiers Summary

Qualifier Default
“-di[rect_mode]” N/A
“-dy[namic_literals]” N/A
“-[no]embed_source” -noembedsource
“-[no]i[gnore]” -ignore
“-le[ngth]=lines” -length=66
“-[no]li[st][=filename]” -nolist
“-noin[line_literals]” N/A
“-[no]o[bject][=filename]” -object
“-r[un]” N/A
“-s[pace]=lines” -space=1

## Executing a Source Program¶

M source programs can be executed either from the shell or from YottaDB (Direct Mode).

### Executing in the Direct Mode¶

As discussed in the section on compiling source programs, the YottaDB command ZLINK compiles the source code into an object module and adds the object module to the current image.

The run-time system also invokes auto-ZLINKing when an M command, in a program or in Direct Mode, refers to a routine that is not part of the current image.

M commands and functions that may initiate auto-ZLINKing are:

• DO
• GOTO
• ZBREAK
• ZGOTO
• ZPRINT
• $TEXT() YottaDB auto-ZLINKs the routine only under these conditions: • The routine has the same name as the source file. • ZLINK can locate the routine file using$ZROUTINES, or the current directory if $ZROUTINES is null.$ZROUTINES is a read-write special variable that contains a directory search path used by ZLINK and auto-ZLINK to locate source and object files.

When the argument to a ZLINK command includes a pathname, $ZSOURCE maintains that pathname as a default for ZEDIT and ZLINK.$ZSOURCE is a read-write special variable.

Once you use the ZEDIT or ZLINK commands, $ZSOURCE can contain a partial file specification. The partial file specification can be a directory path (full or relative), a file name, and a file extension. You can set$ZSOURCE with an M SET command. A ZLINK without an argument is equivalent to ZLINK $ZSOURCE. For additional information on$ZSOURCE and $ZROUTINES, refer to Chapter 8: “Intrinsic Special Variables”. Example: YDB>ZLINK "taxes"  If ZLINK finds taxes.m or taxes.o, the command adds the routine taxes to the current image. When ZLINK cannot locate taxes.o, or when it finds taxes.o is older than taxes.m, it compiles taxes.m, producing a new taxes.o. Then, it adds the contents of the new object file to the image. ### Locating the Source File Directory¶ A ZLINK command that does not specify a directory uses$ZROUTINES to locate files. When $ZROUTINES is null, ZLINK uses the current directory.$ZROUTINES is initialized to the value of the ydb_routines environment variable.

When the file being linked includes an explicit directory, ZLINK and auto-ZLINK searches only that directory for both the object and the source files. If compilation is required, ZLINK places the new object file in the named directory.

A subsequent ZLINK searching for this object file will never find the object file in the specified directory unless the directory is added to the search path in $ZROUTINES, or the object file is moved to another directory already in the search path. ZLINK cannot change a currently active routine, (e.g., a routine displayed in a ZSHOW “S” of the stack). ZLINK a currently active routine by first removing it from the M stack, using ZGOTO, or one or more QUITs. For additional information on the functionality of ZGOTO and ZSHOW, see their entries in Chapter 6: “Commands”. To maintain compatibility with other editions of YottaDB that do not permit the percent sign (%) in a file name, YottaDB uses an underscore (_) in place of the percent in the file name. Example: YDB>zlink "_MGR"  This ZLINK links the M routine %MGR into the current image. ## Executing from the Shell¶ You can run a program from the shell prompt using the following command: $ mumps -run ^filename


The mumps command searches the directories specified by the environment variable ydb_routines to locate the specified file name.

Example:

$mumps -run ^payroll  This executes a routine named payroll. ## Processing Errors from Direct Mode and Shell¶ Executing in Direct Mode Executing from the Shell (mumps -run ^routine) Usage Suitable for Development and Debugging Suitable for production Error Handling Not invoked for code entered at the direct mode prompt; Note that XECUTE code is treated as not entered at the Direct Mode prompt. The default$ZTRAP=”B” brings a process to the Direct Mode for debugging.

Errors are suppressed and cause a silent process exit. Set the environment variable ydb_etrap which overrides the default $ZTRAP=”B”. If needed, error handlers can include appropriate error notification to$PRINCIPAL. For example, the ydb_env_set script sets a default $ETRAP value of “Write:(0=$STACK) “”Error occurred: “”,\$ZStatus,!” which you can customize to suit your needs.

stderr

YottaDB processes send error messages to stderr only under the following conditions:

• The error is fatal which means that the process is about to terminate
• During compilation except of indirection or XECUTE
• The process is about to enter direct mode due to a BREAK command
• The erroneous code was entered at the direct mode prompt