Advanced Interchange Topics

Table of Contents

1. Advanced Interchange Topics

2. Maintaining Interchange

Some utilities are supplied in the VendRoot/bin directory:

 compile_link Compiles an Interchange vlink or tlink CGI link
 configdump   Dumps the configuration directives for a particular catalog
 dump         Dumps the session file for a particular catalog
 expire       Expires sessions for a particular catalog
 expireall    Expires all catalogs
 makecat      Make catalog

Some example scripts for other functions are in the eg/ directory of the software distribution.

Some thought should be given to where the databases, error logs, and session files should be located, especially on an ISP that might have multiple users sharing an Interchange server. In particular, put all of the session files and logs in a directory that is not writable by the user. This eliminates the possibility that the catalog may crash if the directory or file is corrupted.

To test the format of user catalog configuration files before restarting the server, set (from VendRoot):

   bin/interchange -test

This will check all configuration files for syntax errors, which might otherwise prevent a catalog from booting. Once a catalog configures properly, user reconfiguration will not crash it. It will just cause an error. But, it must come up when the server is started.

2.1. Starting, Stopping, and Re-starting the Servers

The following commands need to have VENDROOT changed to the main directory where Interchange is installed. If the Interchange base directory is /home/interchange/, the start command would be /home/interchange/bin/interchange.

Do a perldoc VENDROOT/bin/interchange for full documentation.

To start the server with default settings:


Assuming the server starts correctly, the names of catalogs as they are configured will be displayed, along with a message stating the process ID it is running under.

It is usually best to issue a restart instead. It doesn't hurt to do a restart if you're actually starting the first time. And, if a server is already running (from this VENDROOT), a new start attempt will fail. To restart the server:

   VENDROOT/bin/interchange -restart

The -r option is the same as -restart.

This is typically done to force Interchange to re-read its configuration. A message will be displayed stating that a TERM signal has been sent to the process ID the servers are running under. This information is also sent to VENDROOT/error.log. Check the error.log file for confirmation that the server has restarted properly.

To stop the server:

   VENDROOT/bin/interchange -stop

A message will be displayed stating that a TERM signal has been sent to the process ID the server is running under. This information is also sent to VENDROOT/error.log.

Because processes waiting for selection on some operating systems block signals, they may have to wait for HouseKeeping seconds to stop. The default is 60.

To terminate the Interchange server with prejudice, in the event it will not stop:

   VENDROOT/bin/interchange -kill

2.2. UNIX and INET modes

Both UNIX-domain and INET-domain sockets can be used for communication. INET domain sockets are useful when more than one web server, connected via a local-area network (LAN), is used for accessing an Interchange server.

Important note: When sending sensitive information like credit card numbers over a network, always ensure that the data is secured by a firewall, or that the Interchange server runs on the same machine as any SSL-based server used for encryption.

Use the -i and -u flags if you only want to use one communication method:

   # Start only in UNIX mode
   VENDROOT/bin/interchange -r -u

   # Start only in INET mode
   VENDROOT/bin/interchange -r -i

2.3. User Reconfiguration

The individual catalogs can be reconfigured by the user by running the [reconfig] support tag. This should be protected by one of the several forms of Interchange authentication, preferably by HTTP basic authorization. See RemoteUser.

The command line can be reconfigured (as the Interchange user) with:

   VENDROOT/bin/interchange --reconfig=catalog

It is easy for the administrator to manually reconfigure a catalog. Interchange simply looks for a file etc/reconfig (based in the Interchange software directory) at HouseKeeping time. If it finds a script name that matches one of the catalogs, it will reconfigure that catalog.

2.4. Expiring Sessions

If Interchange is using DBM capability to store the sessions, periodically expire old sessions to keep the session database file from growing too large.

   expire -c catalog

There is also an expireall script which reads all catalog entries in interchange.cfg and runs expire on them. The expire script accepts a -r option which tells it to recover lost disk space.

On a UNIX server, add a crontab entry such as the following:

   # once a day at 4:40 am
   40 4 * * *    perl /home/interchange/bin/expireall -r

Interchange will wait until the current transaction is finished before expiring, so this can be done at any time without disabling web access. Any search paging files for the affected session (kept in ScratchDir) will be removed as well.

If not running DBM sessions, use a Perl script to delete all files not modified in the last one or two days. The following will work if given an argument of a session directory or session files:

   # -- delete files 2 days old or older

   my @files;
   my $dir;
   foreach $dir (@ARGV) {
       # just push files on the list
       if (-f $dir) { push @files, $_; next; }

       next unless -d $dir;

       # get all the file names in the directory
       opendir DIR, $dir or die "opendir $dir: $!\n";
       push @files, ( map { "$dir/$_" } grep(! /^\.\.?$/, readdir DIR));

   for (@files) {
       unless (-f $_) {
           warn "skipping $_, not a file.\n";
       next unless -M $_ >= 2;
       unlink $_ or die "unlink $_: $!\n";

It would be run with a command invocation like:

   perl /home/you/catalogs/simple/session

Multiple directory names are acceptable, if there is more than one catalog.

This script can be adjusted as necessary. Refinements might include reading the file to "eval" the session reference and expire only customers who are not members.

2.5. My session files change to owner root every day!

You have the expireall -r entry in the root crontab, and it should either be in the Interchange user crontab or run as:

44 4 * * * su -c "/ICROOT/bin/expireall -r" ICUSERNAME

3. Interchange Components

Interchange components are merely portions of HTML/ITL that are included into pages within the site depending on options set in the Admin UI. The default component set includes the following:


3.1. Content -> Page Edit

The Interchange Admin UI offers a page editor function that allows component definitions and options to be modified for each page within the catalog.

3.1.1. Template

The choices for the Template drop-down are read from template definition files located in the CATROOT/template directory. These files store the name and description of the template, as well as components and options for the particular template.

To create a new template for use in the admin, it is best to copy an existing template definition to a new file name and edit it's contents to suit. Once the catalog is reconfigured, the new choice will be visible within the Content Page Editor admin function.

Each template option is looped through and a scratch is set using its same name and value.

ITL is used near the bottom of this file to set each option to default values before the page is displayed.

[set page_title][set]
[set page_banner][set]
[set members_only][set]
[set component_before][set]
[set component_after][set]
[set bgcolor]#FFFFFF[/set]

3.1.2. Page Title

Sets the title of the page which is synonymous with the html <title></title> code.

The following code within the template definition file is used to display this option within in the content editor:

page_title: description: Page title

This code dynamically adds the title to the page:

<title>[scratch page_title]</title>

3.1.3. Page Banner

Sets a textual title for each page which is called by [either][scratch page_banner][or][scratch page_title][/either] This results in the Page Banner being displayed if defined. Otherwise, the Page Title is used.

3.1.4. Members Only

The members only function is handled by the following code within each template file:

[if scratch members_only]
    [set members_only][/set]
    [if !session logged_in]
    [set mv_successpage]@@MV_PAGE@@[/set]
    [bounce page=login]

This code says if members only is set to yes and the visitor is logged in, display the page. Otherwise, redirect the visitor to the login page.

3.1.5. Break 1

This code causes a separation in the Content Editor between the next set of options. (A blue line)

3.1.6. Horizontal Before Component

This allows the inclusion of a defined component to be displayed before, or above, the page's content. It is called with the following code within the LEFTRIGHT_TOP template:

[if scratch component_before]
[include file="templates/components/[scratch component_before]"]
[set component_before][/set]

3.1.7. Horizontal After Component

This function allows the inclusion of a defined component to be displayed after or below the page's content. It's called with the following code within the LEFTRIGHT_BOTTOM template:

[if scratch component_after]
[include file="templates/components/[scratch component_after]"]
[set component_after][/set]

3.1.8. Horizontal Item Width

This setting allows you to choose how many items the horizontal components display. For example, the horizontal best sellers component uses this setting to randomly select the best sellers. Notice the default to 2 if nothing is defined.

random="[either][scratch component_hsize][or]2[/either]"

3.1.9. Special Tag

This setting is only viable when a promotion is used for a horizontal component. It tells the promotional component which rows to evaluate in the merchandising table for display within the component. This setting normally correlates to the featured column of the merchandising table as follows:

        [query arrayref=main
                                SELECT sku,timed_promotion,start_date,finish_date
                                FROM merchandising
                                WHERE featured = '[scratch hpromo_type]'

3.1.10. Before/After Banner

Allows a title for the horizontal components to be defined to displayed in a header above the component's items. It is called with the [scratch hbanner] tag.

3.1.11. Break 2

This code causes a separation in the Content Editor between the next set of options. (A blue line)

3.1.12. Vertical Component

Defines a component to be displayed along the right side of the LEFTRIGHT_BOTTOM template. It is called from the template with the following code:

[include file="templates/components/[scratch component_right]"]

3.1.13. Vertical Items Height

Sets the number of items to display within the vertical component. Called with the following code:

random="[either][scratch component_vsize][or]3[/either]"

3.1.14. Right Banner

Allows a title to be set for a vertical component which is displayed as a header above the items in the vertical component. It's called with the [scratch vbanner] tag.

3.1.15. Special Tag

Essentially the same as the Special Tag setting described in item number 9 above.

3.1.16. Background Color

Allows the background color of the page to be selected. The choices are stored within the page or template definition as in:

        options: #FFFFFF=White,pink=Pink
        widget: select
        description: Background color

3.1.17. Content

Allows the page code to be downloaded, uploaded and viewed/edited. Only the code between <!-- BEGIN CONTENT --> and <!-- END CONTENT --> is displayed or can be edited here.

3.1.18. Preview, Save, and Cancel buttons

Allows the changes to the edited page to be previewed in a pop-up browser window, or saved. Cancel returns you to the page editor selection page.

3.1.19. Save template in page

Template settings are stored in the template definitions by default. This allows a common set of choices for template settings for all pages. If specific setting options are desired for a page, the template can be saved within the page so that it may have individual options.

The in-page template definition must be surrounded by [comment] [/comment].

3.2. Custom Admin UI Options

Other options may be added to the template by defining them in the default definition file, or using in-page definitions.

When the following lines are added to the template definition, the new option is added to the Admin UI.

options: 1,2*,3
widget: select
description: Option Description
help: Other Details

Each time the template is used, an option_name scratch variable is created. (Called with: [scratch option_name].) This scratch value will be equal to what's selected here in the admin tool.

The possible widgets include:

break - produces the blue line separator.
radio - produces radio button type selections.
select - standard drop-down selector.
move_combo - select drop down with options and text input for new option.

4. Administrative Pages

With Interchange's GlobalSub capability, very complex add-on schemes can be implemented with Perl subroutines. And with the new writable database, pages that modify the catalog data can be made. See MasterHost, RemoteUser, and Password.

In addition, any Interchange page subdirectory can be protected from access by anyone except the administrator if a file called '.access' is present and non-zero in size.

4.1. Controlling Access to Certain Pages

If the directory containing the page has a file .access and that file's size is zero bytes, access can be gated in one of several ways.

  1. If the file .access_gate is present, it will be read and scanned for page-based access. The file has the form:
  page: condition
  *: condition
 -rw-rw-r--   1 mike     mike            0 Jan  8 14:19 .access
 -rw-rw-r--   1 mike     mike          185 Jan  8 16:00 .access_gate
 -rw-rw-r--   1 mike     mike          121 Jan  8 14:59 any.html
 -rw-rw-r--   1 mike     mike          104 Jan  8 14:19 bar.html
 -rw-rw-r--   1 mike     mike          104 Jan  8 14:19 baz.html
 -rw-rw-r--   1 mike     mike          104 Jan  8 14:19 foo.html
   foo.html: [if session username eq 'flycat']
   bar:      [if session username eq 'flycat']
             [or scratch allow_bar]
   baz:      yes
   *:        [data session logged_in]
  1. If the Variable MV_USERDB_REMOTE_USER is set (non-zero and non-blank), any user logged in via the UserDB feature will receive access to all pages in the directory. NOTE: If there is a .access_gate file, it overrides this.
  2. If the variables MV_USERDB_ACL_TABLE is set to a valid database identifier, the UserDB module can control access with simple ACL logic. See USER DATABASE. NOTE: If there is a .access_gate file, it overrides this. Also, if MV_USERDB_REMOTE_USER is set, this capability is not available.

4.2. display tag and mv_metadata

Interchange can store meta information for selected columns of tables in a site's database. This meta information is used when the user interacts with the database. For example, the meta information for a Hide Item field might specify that a checkbox be displayed when the user edits that field, since the only reasonable values are on and off. Or, the meta information might specify a filter on data entered for a Filename field which makes sure that the characters entered are safe for use in a filename.

Widget type specifies the HTML INPUT tag type to use when displaying the field in, say, the item editor.

Width and Height only apply to some of the Widget type options, for instance the Textarea widget.

Label is displayed instead of the internal column name. For example, the category column of the products table might have a label of Product Category.

Help is displayed below the column label, and helps describe the purpose of the field to the user.

Help url can be used to link to a page giving more information on the field.

Lookup can be used when a field is acting like a foreign key into another table. In that case, use some sort of select box as the widget type, and if referencing multiple rows in the destination table, use a multi select box, with colons_to_null as the pre_filter, and :: as the lookup_exclude.

Filter and pre_filter can be used to filter data destined for that field or data read from that field, respectively.

Repeat?: The Interchange back office UI uses the mv_metadata table to discover formatting information for field, table, and view display. The information is kept in fields in the mv_metadata table, and is used to select the display, the HTML input type, the size (height and width where appropriate), label, help text, additional help URL, and default value display.

It works in conjunction with the [display ...] usertag defined in the Interchange UI as well as in specific pages in the UI. The [display] tag has this syntax:

[display table=tablename column=fieldname key=key arbitrary=tag filter=op ...]

In the simplest use, the formatting information for a table form field is called with:

The mv_metadata table is scanned for the following keys:


If a row is found with one of those keys, then the information in the row is used to set the display widget. If no row is found, an INPUT TYPE=TEXT widget is displayed. If the data is all digits, a size of 8 is used, otherwise the size is 60.

If the following row were found (not all fields shown, would be tab-separated in the actual data):

  code                type   width height label     options
  products::category  text   20           Category

Then this would be output:

<INPUT TYPE=text SIZE=20 VALUE="*category*">

If the following row were found:

  code                type   width height label     options
  products::category  select              Category  =none, product=Hardware

Then the following would be output:

        <SELECT NAME=category>
        <OPTION VALUE="">none
        <OPTION VALUE="product">Hardware

The standard widget types are:


    width   size of input box


        width   COLS for textarea
        height  ROWS for textarea


  height          SIZE for select
  default         Default for SELECTED
  options         Options for a fixed list (or prepended to a lookup)
  lookup          signals a lookup (used as field name if "field" empty)
  field           field to look up possible values in
  db              table to look up in if not current table
  lookup_exclude  regular expression to exclude certain values from lookup

5. Usertag Reference

Admin Tool-specific usertags.

6. Admin Tool Database Tables

6.1. mv_metadata.asc

        Table::Column to be operated on.
        Database table
        Widget type (Select the basic display type for the field)
            textarea = Textarea
            text = Text Entry (default)
            select = Select Box
            yesno = Yes/No (Yes=1)
            noyes = No/Yes (No=1)
            multiple = Multiple Select
            combo = Combo Select
            reverse_combo = Reverse Combo
            move_combo = Combo move
            display = Text of option
            hidden_text = Hidden(show text)
            radio = Radio box
            radio_nbsp = Radio (nbsp)
            checkbox = Checkbox
            check_nbsp = Checkbox (nbsp)
            imagedir = Image listing
            imagehelper = Image upload
            date = Date selector
            value = Value
            option_format = Option formatter
            show = Show all options
        Width (SIZE for TEXT, COLS for TEXTAREA, Label limit for SELECT)
        Height (SIZE for SELECT, ROWS for TEXTAREA)
        Field for lookup (can be two comma separated fields, in which
        case second is used as the label text. Both must be in the
        same table.)
        Variable name (normally left empty, changes variable name to
        send in form)
        Select directory for image listing widget
        options in the format <blockquote>value=label*</blockquote>
        Column name (Do not set this.)
        Help (displays at top of page)
        Lookup select (Whether lookup is performed to get options for a
        select type. If nothing is in the field, then used as the name
        of the field to lookup in. Use lookup table if you want to look
        up in a different table.
        Filters (Filters which can transform or constrain your data.
        Some widgets require filters.)
        Help URL (links below help text)
        A URL which will provide more help
        ADVANCED: regular expression that excludes certain keys from the lookup
        Append HTML (HTML to be appended to the widget. Will substitute
        in the macros _UI_TABLE_, _UI_COLUMN_, _UI_KEY_, and _UI_VALUE_,
        and will resolve relative links with absolute links.)

7. makecat - Set Up a Catalog from a Template

After Interchange is installed, you need to set up at least one catalog. Interchange will not function properly until a catalog is created.

The supplied makecat script, which is in the Interchange program directory bin, is designed to set up a catalog based on the user's server configuration. It interrogates the user for parameters like which directories to use, a URL to base the catalog in, HTTP server definitions, and file ownership. It gives relevant examples of the entries it expects to receive.

Note: A catalog can only be created once. All further configuration is done by editing the files within the catalog directory.

The makecat script requires a catalog skeleton to work from. The Foundation demo is distributed with Interchange. See the icfoundation document for information on building the Foundation demo store. Other demo catalogs are available at

It is not normally necessary for you to understand how to build catalog skeletons for use with makecat, but the following information will help you if you should ever need to.

7.1. Catalog Skeletons

A catalog skeleton contains an image of a configured catalog. The best way to see what the makecat program does is to configure the simple demo and then run a recursive diff on the template and configured catalog directories:

    cd /usr/local/interchange
    diff -r construct catalogs/construct

The files are mostly identical, except that certain macro strings have been replaced with the answers given to the script. For example, if was answered at the prompt for a server name, this difference would appear in the catalog.cfg file:

    # template

    # configured catalog
    Variable SERVER_NAME

The macro string __MVC_SERVERNAME__ was substituted with the answer to the question about server name. In the same way, other variables are substituted, and include:


Note: Not all of these variables are present in the "construct" template, and more may be defined. In fact, any environment variable that is set and begins with MVC_ will be substituted for by the makecat script. For example, to set up a configurable parameter to customize the COMPANY variable in catalog.cfg, run a pre-qualifying script that set the environment variable MVC_COMPANY and then place in the catalog.cfg file:


All files within a template directory are substituted for macros, not just the catalog.cfg file. There are two special directories named html and images. These will be recursively copied to the directories defined as SampleHTML and ImageDir.

Note: The template directory is located in the Interchange software directory, i.e., where interchange.cfg resides. Avoid editing files in the template directory. To create a new template, it is recommended that it should be named something besides 'construct' and a copy of the construct demo directory be used as a starting point. Templates are normally placed in the Interchange base directory, but can be located anywhere. The script will prompt for the location if it cannot find a template.

In addition to the standard parameters prompted for by Interchange, and the standard catalog creation procedure, four other files in the config directory of the template may be defined:

 additional_fields -- file with more parameters for macro substitution
 additional_help   -- extended description for the additional_fields
 precopy_commands  -- commands passed to the system prior to catalog copy
 postcopy_commands -- commands passed to the system after catalog copy

All files are paragraph-based. In other words, a blank line (with no spaces) terminates the individual setting.

7.1.1. Additional fields

The additional_fields file contains:

    The prompt. Set PARAM to?
    The default value of PARAM^IAlternate value of PARAM

This would cause a question during makecat:

    The prompt. Set PARAM to?.....[The default value of PARAM]

The default value line can contain alternate values, separated by tabs from the default value. (The default value may not contain a TAB character.) This will allow command-line editing to cycle between the different values -- usually with the UP and DOWN arrow keys.

If you wish to set the parameter to the default value in this file without a prompt, precede the parameter with an exclamation point, i.e.:

    The prompt.  Set PARAM to?
    default value^Ialternate value

If you wish only to prompt for a value if a previous parameter was set, put the previous parameter to set in curly brackets before the actual parameter:

    Data source name (DSN) for MySQL?

The above will be ignored if the MYSQL parameter was not previously set to a true value.

Note that information collected in the main makecat run (in this case, the catalog name) can be inserted via macro substitution.

7.1.2. Additional help

If the additional_help file is present, additional instructions for PARAM may be provided.


    These are additional instructions for PARAM, and they
    may span multiple lines up to the first blank line.

The prompt would now be:

    These are additional instructions for PARAM, and they
    may span multiple lines up to the first blank line.

    The prompt. Set PARAM to?.....[The default value of PARAM]

7.1.3. Command files

If the file config/precopy_commands exists, it will be read as a command followed by the prompt/help value.

    mysqladmin create __MVC_CATALOGNAME__
    We need to create an SQL database for your Interchange
    database tables.

This will cause the prompt:

    We need to create an SQL database for your Interchange
    database tables.

    Run command "mysqladmin create simple"?

If the response is "y" or "yes," the command will be run by passing it through the Perl system() function. As with any of the additional configuration files, MVC_PARAM macro substitution is performed on the command and help. Proper permissions for the command are required.

The file config/postcopy_commands is exactly the same as <precopy_commands>, except the prompt occurs after the catalog files are copied and macro substitution is performed on all files.

There may also be SubCatalog directives:

    SubCatalog easy simple /home/catalogs/simple /cgi-bin/easy



The remaining parameters are similar to the Catalog directive.

Additional interchange.cfg parameters set up administrative parameters that are catalog wide. See the server configuration file for details on each of these.

Each catalog can be completely independent with different databases, or catalogs can share pages, databases, and session files. This means that several catalogs can share the same information, allowing "virtual malls."

7.2. Manual Installation of Catalogs

An Interchange installation is complex, and requires quite a few distinct steps. Normally you will want to use the interactive catalog builder, makecat, described above. It makes the process much easier. Please see the iccattut document for a full tutorial on building a catalog by hand.

8. Link Programs

Interchange requires a web server that is already installed on a system. It does have an internal server which can be used for administration, testing, and maintenance, but this will not be useful or desirable in a production environment.

As detailed previously, Interchange is always running in the background as a daemon, or resident program. It monitors either a UNIX-domain file-based socket or a series of INET-domain sockets. The small CGI link program, called in the demo simple, is run to connect to one of those sockets and provide the link to a browser.

Note: Since Apache is the most popular web server, these instructions will focus on it. If using another type of web server, some translation of terms may be necessary.

A ScriptAlias or other CGI execution capability is needed to use the link program. (The default ScriptAlias for many web servers is /cgi-bin.) If ExecCGI is set for all directories, then any program ending in a particular file suffix (usually .cgi) will be seen as a CGI program.

Interchange, by convention, names the link program the same name as the catalog ID, though this is not required. In the distribution demo, this would yield a program name or SCRIPT_PATH of /cgi-bin/simple or /simple.cgi. This SCRIPT_PATH can be used to determine which Interchange catalog will be used when the link program is accessed.

8.1. UNIX-Domain Sockets

This is a socket which is not reachable from the Internet directly, but which must come from a request on the server. The link program vlink is the provided facility for such communication with Interchange. This is the most secure way to run a catalog, for there is no way for systems on the Internet to interact with Interchange except through its link program.

The most important issue with UNIX-domain sockets on Interchange is the permissions with which the CGI program and the Interchange server run. To improve security, Interchange normally runs with the socket file having 0600 permissions (rw-------), which mandates that the CGI program and the server run as the same user ID. This means that the vlink program must be SUID to the same user ID as the server executes under. (Or that CGIWRAP is used on a single catalog system).

With Interchange's multiple catalog capability, the permissions situation gets a bit tricky. Interchange comes with a program, makecat, which configures catalogs for a multiple catalog system. It should properly set up ownership and permissions for multiple users if run as the superuser.

8.2. INET-Domain Sockets

These are sockets which are reachable from the Internet directly. The link program tlink is the provided facility for such communication with Interchange. Other browsers can talk to the socket directly if mapped to a catalog with the global TcpMap directive. To improve security, Interchange usually checks that the request comes from one of a limited number of systems, defined in the global TcpHost directive. (This check is not made for the internal HTTP server.)

8.3. Internal HTTP Server

If the socket is contacted directly (only for INET-domain sockets), Interchange will perform the HTTP server function itself, talking directly to the browser. It can monitor any number of ports and map them to a particular catalog. By default, it only maps the special catalog mv_admin, which performs administrative functions. The default port is 7786, which is the default compiled into the distribution tlink program. This port can be changed via the TcpMap directive.

To prevent catalogs that do not wish access to be made in this way from being served from the internal server, Interchange has a fixed SCRIPT_PATH of /catalogname (/simple for the distribution demo) which needs to be placed as an alias in the Catalog directive to enable access. See TcpMap for more details.

8.4. Setting Up VLINK and TLINK

The vlink and tlink programs, compiled from vlink.c and tlink.c, are small C programs which contact and interface to a running Interchange daemon. The VLINK executable is normally made setuid to the user account which runs Interchange, so that the UNIX-domain socket file can be set to secure permissions (user read-write only). It is normally not necessary for the user to do anything. They will be compiled by the configuration program. If the Interchange daemon is not running, either of the programs will display a message indicating that the server is not available. The following defines in the produced config.h should be set:





8.5. Compiling VLINK and TLINK

There is a compile_link program which will assist with this. Do:

   perldoc VENDROOT/bin/compile_link

for its documentation.

8.6. Manually Compiling VLINK and TLINK

Change directories to the src directory, then run the GNU configure script:

   cd src

There will be some output displayed as the configure script checks the system. Then, compile the programs:


To compile manually:

   cc vlink.c -o vlink
   cc tlink.c -o tlink

On manual compiles, ensure that the C compiler will be invoked properly with this little ditty:

   perl -e 'do "syscfg"; system("$CC $LIBS $CFLAGS $DEFS -o tlink tlink.c");'
   perl -e 'do "syscfg"; system("$CC $LIBS $CFLAGS $DEFS -o vlink vlink.c");'

On some systems, the executable can be made smaller with the strip program, if available. It is not required.

   strip vlink
   strip tlink

If Interchange is to run under a different user account than the individual configuring the program, make that user the owner of vlink. Do not make vlink owned by root, because making vlink SETUID root is an huge and unnecessary security risk. It should also not normally run as the default Web user (often nobody or http)).

   chown interchange vlink

Move the vlink executable to the cgi-bin directory:

   mv vlink /the/cgi-bin/directory

Make vlink SETUID:

   chmod u+s /the/cgi-bin/directory/vlink

Most systems unset the SUID bit when moving the file, so change it after moving.

The SCRIPT_NAME, as produced by the HTTP server, must match the name of the program. (As usual, let the makecat program do the work.)

8.7. VLINK or TLINK Compile Problems

The latest version of vlink.c and tlink.c have been compiled on the following systems:

   AIX 4.1
   BSD2.0 (Pentium/x86)
   Debian GNU/Linux
   Digital Unix (OSF/Alpha)
   FreeBSD 2.x, 3.x, 4.x
   IRIX 5.3, IRIX 6.1
   OpenBSD 2.7
   Red Hat Linux 6.2, 7.0, 7.1, 7.2, 7.3, 8.0
   SCO OpenServer 5.x
   Solaris 2.x (Sun compiler and GCC)
   Solaris 7 (Sun compiler and GCC)
   SunOS 4.1.4

Some problems may occur. In general, ignore warnings about pointers.

Make sure that you have run the configure program in the src directory. If you use Interchange's makecat program, it will try to compile an appropriate link at that time, and will substitute if that doesn't work.

You can compile manually with the proper settings with this series of commands:

   cd src
   perl -e 'do "syscfg"; system ("$CC $CFLAGS $DEFS $LIBS -o tlink tlink.c")'
   perl -e 'do "syscfg"; system ("$CC $CFLAGS $DEFS $LIBS -o vlink vlink.c")'

There is also a compile_link program which has documentation embedded and which will compile an appropriate link. If you cannot compile, try using the script, written in Perl instead of C, which should work on most any system. Since vlink needs to have values set before compilation, a pre-compiled version will not work unless it has the exact values you need on your system. If you can use the defaults of 'localhost' and port 7786, you may be in luck.

9. Installing Perl Modules without Root Access

Installing Interchange without root access is no problem. However, installing Perl modules without root access is a little trickier.

You must build your makefile to work in your home dir. Something like:

PREFIX=~/usr/local \
INSTALLPRIVLIB=~/usr/local/lib/perl5 \
INSTALLSCRIPT=~/usr/local/bin \
INSTALLSITELIB=~/usr/local/lib/perl5/site_perl \
INSTALLBIN=~/usr/local/bin \
INSTALLMAN1DIR=~/usr/local/lib/perl5/man \

Put this in a file, say 'installopts', and use it for the Makefile.PL.

perl Makefile.PL `cat installopts`

Then, forget ./config. Just do:

make test
make install

Some of the tests may fail, but that's probably ok.

Also make sure to install Bundle::Interchange, which will need the same config data as you put into 'installopts'.

10. Installation Troubleshooting

Interchange uses the services of other complex programs, such as Perl, Web servers, and relational databases, to work. Therefore, when there is a problem, check these programs before checking Interchange. Many more basic installation problems have to do with those than with Interchange itself.

If an error message is received about not being able to find libraries, or a core dump has occurred, or a segment fault message, it is always an improperly built or configured Perl. Contact the system administrator or install a new Perl.

The makecat program is intended to be used to create the starting point for the catalog. If the demo does not work the first time, keep trying. If it still does not work, try running in INET mode.

Check the two error log files: error.log in the Interchange home directory (where interchange.cfg resides) and error.log in the catalog directory (where catalog.cfg resides; there can be many of these). Many problems can be diagnosed quickly if these error logs are consulted.

Check the README file, the FAQ, and mail list archive at the official Interchange web site for information:

Double check the following items:

  1. Using UNIX sockets?
    • Check that the vlink program is SUID, or the appropriate changes have been made in the SocketPerms directive. Unless the files are world-writable, the vlink program and the Interchange server must run as the same user ID! If running CGI-WRAP or SUEXEC, the vlink program must not be SUID.
    • If having trouble with the vlink program (named construct in the demo configuration), try re-running makecat and using INET mode instead. (Or copy the tlink INET mode link program over vlink). This should work unchanged for many systems.
    • If using an ISP or have a non-standard network configuration, some changes to interchange.cfg are necessary. For tlink to work, the proper host name(s) must be configured into the TcpHost directive in interchange.cfg. The program selects port 7786 by default (the ASCII codes for "M" and "V", for MiniVend). If another port is used, it must be set to the same number in both the tlink program (by running compile_link) and the interchange.cfg file. The tlink program does not need to be SUID.
  2. Proper file permissions?
    • The Interchange server should not run as the user nobody! The program files can be owned by anyone, but any databases, ASCII database source files, error logs, and the directory that holds them must be writable by the proper user ID, that is the one that is executing the Interchange program.
    • The best way to operate in multi-user, multiple catalog setups is to create a special interch user, then put that user in the group that contains each catalog user. If a group is defined for each individual user, this provides the best security. All associated files can be in 660 or 770 mode. There should be no problems with permissions and no problems with security.
  3. Is the vlink program being executed on a machine that has the socket file etc/socket on a directly attached disk?
    • UNIX-domain sockets will not work on NFS-mounted file systems! This means that the Interchange server and the CGI program vlink must be executing on the same machine.
    • The tlink program does not have this problem, but it must have the proper host name(s) and TCP ports set in the TcpHost and TcpMap directives in interchange.cfg. Also, be careful of security if sensitive information, like customer credit card numbers, is being placed on a network wire.

11. Usertracking

Several actions from the user are recorded by Interchange's usertracking facility. The usertracking data is logged at two locations, depending on your setup.

The first location is the one specified by the TrackFile configuration directive, e.g. logs/usertrack in the foundation demo.

The second location are the HTTP headers. You can configure Apache to write this header into the access logs.

LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" \
                        %T %v \"%{X-Track}o\"" track
CustomLog /var/log/apache/access.log track

Copyright 2002-2004 Interchange Development Group. Copyright 2001-2002 Red Hat, Inc. Freely redistributable under terms of the GNU General Public License.