URWEB(1) General Commands Manual URWEB(1)

urweb - compiler for the Ur/Web programming language

urweb [option ...] [project-name]
urweb daemon (start|stop)

This manual page briefly documents the urweb compiler. Extensive documentation is available in the Ur/Web reference manual.

urweb is an optimizing compiler for Ur/Web, a functional, pure, statically typed, strictly evaluated programming language designed for constructing dynamic Web applications backed by SQL databases. urweb produces very efficient object code that does not use garbage collection; compiled programs will often be even more efficient than what most programmers would bother to write in C.

The first invocation described compiles an Ur/Web project, while the second invocation controls the type inference daemon (see TYPE INFERENCE DAEMON). For simple projects, only familiarity with the first invocation is required.

urweb is a whole-program compiler (i.e., incremental compilation is not supported). Thus, it operates at project granularity, and it is run from the command line with a collection of options and a project name. The simplest case is to run urweb foo, where the file foo.ur contains a valid Ur/Web program, in which case urweb will compile the program to the file foo.exe. (Despite the extension of the generated files, urweb does not necessarily produce COFF executables; rather, it produces the default object format of the default C compiler.)

Larger programs, spanning many files, may be compiled by specifying an .urp (i.e., an Ur/Web project) file. The syntax of an .urp file is relatively simple; see section 3.1 of the Ur/Web reference manual for details.

With no arguments, urweb prints the version number and exits.

Sets the executable name corresponding to the C compiler. urweb uses gcc(1) by default, but clang(1) should also work.
Sets database information using the format expected by Postgres's PQconnectdb. If the database backend is MySQL or SQLite, urweb will parse the information string to set connection parameters appropriately. For MySQL, the only relevant parameters are host, hostaddr, port, dbname, user, and password; for SQLite, the only relevant parameter is dbname, which is interpreted as the file system path to the database file. All unrecognized parameters are silently ignored.
Sets the database backend. If requested, urweb will also emit initialization code for the selected backend; see the -sql option.
Instructs urweb to emit the generated C code as /tmp/webapp.c. Additionally, urweb will print the command-line options it passes to the C compiler and linker as it executes.
Instructs urweb to print a text-based form of the current intermediate representation (IR) when compilation fails. Output will likely be extremely long and not very human-readable.
Instructs urweb to print a text-based form of every intermediate representation it generates during compilation. Output will likely be extremely long and not very human-readable.
If specified, urweb will print the types of all named values it finds during compilation.
Identical to -dumpTypes, but only prints the types if compilation fails.
Enables verbose error messages when urweb is unable to embed server-side values in client-side code.
Sets a resource usage limit for generated applications. The limit class will be set to the non-negative integer num. The classes are:
maximum number of cleanup operations (e.g., entries recording the need to deallocate certain temporary objects) that may be active at once per request
maximum number of clients that can be simultaneously blocked waiting for new messages (sent by Basis.send)
maximum size of database file (currently only used by SQLite), in units of database pages
maximum number of messages sendable in a single request handler with Basis.send
maximum number of global variables that FFI libraries may set in a single request context
maximum size (in bytes) of per-request buffer used to hold HTTP headers for generated pages
maximum size (in bytes) of per-request heap for dynamically allocated data
maximum number of top-level form fields per request
maximum size (in bytes) of per-request buffer used to hold a single outgoing message sent with Basis.send
maximum size (in bytes) of per-request buffer used to hold HTML content of generated pages
maximum size (in bytes) of per-request buffer used to hold JavaScript content of generated pages
maximum number of form fields per request, excluding top-level fields
maximum running time of a single page request, in units of approximately 0.1 seconds
maximum number of custom transactional actions (e.g., sending an e-mail) that may be run in a single page generation
Sets where urweb will store the compiled executable.
Defines a new path alias for use in .urp files. In particular, this option specifies that all occurrences of $name in any .urp files processed will be replaced with value. You may specify this option more than once.
Sets the application prefix. This controls how Ur/Web functions are bound to URIs; in particular, if prefix is /directory/myapp.exe/, then URIs of the form //example.com/directory/myapp.exe/Module/function will resolve to the function Module.function in Ur/Web.
Instructs urweb to produce an executable which speaks the specified protocol:
HTTP 1.1. urweb will generate a standalone server executable.
The Common Gateway Interface, cgi(5). This is the classic protocol that Web servers use to generate dynamic content by spawning new processes. While Ur/Web programs may in general use message-passing with the send and recv functions, that functionality is not yet supported in CGI, since CGI needs a fresh process for each request, and message-passing needs to use persistent sockets to deliver messages.
Since Ur/Web treats paths in an unusual way, you will need to configure Ur/Web specially by setting the prefix directive in your .urp file or passing the -prefix option on the command line. For example, if you deploy a Web application at //example.com/directory/myapp.exe, you should specify /directory/myapp.exe/ as the application prefix. See section 3.2 of the Ur/Web reference manual for more information.
The faster, newer protocol inspired by CGI, wherein Web servers can start and reuse persistent external processes to generate dynamic content. Ur/Web doesn't implement the whole protocol, but Ur/Web's support has been tested to work with both Apache and lighttpd.
Applications which use message-passing, while supported, require special configuration. In particular, if you're using Apache, be sure to specify a large idle-timout; if you're using lighttpd, be sure to set max-procs to 1. The rationale for these configuration changes is detailed in section 3.2 of the Ur/Web reference manual.
static
The simplest possible protocol. urweb will generate an output executable which expects a single command-line argument giving the URI of a page to generate. For instance, this argument might be /main, in which case a static HTTP response for that page will be written to standard output.
Triggers an alternate module convention for all source files found in directory path or any of its subdirectories. In particular, any file path/foo.ur will define a module called Name.Foo instead of the usual Foo. Any file path/subdir/foo.ur will define a module called Name.Subdir.Foo, and so on for arbitrary nesting of subdirectories. You may specify this option more than once.
If specified, the compiled application will look at path for a key to use in cryptographic signing. This is used to prevent cross-site request forgery attacks for any form handler that both reads a cookie and creates side effects. If the referenced file doesn't exist, the application will create it and read its saved data on future invocations. You can also initialize the file manually with any contents at least 16 bytes long; the first 16 bytes will be treated as the key.
Requests that urweb generate database initialization code for the selected database backend, storing it in file. If file already exists, urweb will overwrite it.
Note that the generated instructions will not create the application database; you must do that yourself.
Instructs urweb to statically link the generated executable.
If specified, urweb will print a timing report at the end of compilation showing the number of seconds required for each stage of the compilation process.
Instructs urweb's type inference engine to make best-effort guesses rather than immediately failing when performing type inference. If -dumpTypes shows unresolved unification variables in positions where you would like to see urweb make best-guesses effort instead, specify this option.
Correct programs compiled with -unifyMore will be identical to their counterparts compiled without it; however, urweb will likely generate many more (and potentially more useful) error messages at a time when asked to compile an incorrect program with this flag.
Instructs urweb to announce the stages of the compilation process as it performs them.

When run with any of these options, urweb will not produce executable output.

Dumps generated CSS properties and classes. The first output line is a list of categories of CSS properties that would be worth setting on the document body. The remaining lines are space-separated pairs of CSS class names and categories of properties that would be worth setting for that class. The category codes are divided into two varieties. Codes that reveal properties of a tag or its (recursive) children are
for block-level elements,
for table captions,
for table cells,
for lists, and
for tables.
Codes that reveal properties of the precise tag that uses a class are
for block-level elements,
for tables,
for table cells,
-
for table rows,
for the possibility to set a height,
for non-replaced inline-level elements,
for replaced inline elements, and
for the possibility to set a width.
Prints the Ur module name corresponding to the source file file.
Prints the version of the compiler executable without any associated English text. Suitable for use in scripts.
Prints the executable name of the compiler that urweb will use.
Prints the file system location in which urweb will look for C headers.
If specified, urweb will stop after the typechecking phase. Liberal use of this option can substantially speed development, as urweb's optimization passes can take quite a while.
Prints the version of the compiler executable. Output is identical to urweb output when run without arguments.

These options customize Ur/Web's documentation generator.

Performs demo-style formatting.
Performs demo-style formatting, but sizes frames to allocate less space to explanatory text. Useful for generating presentations.
When used with -demo, causes urweb to not use Emacs to syntax-highlight code. The resulting code will not be highlighted.
Performs tutorial-style formatting.

These options are not meant for users; they are used to build urweb releases and to debug the compiler.

Places urweb into bootstrap mode. Used when building the standard library for the first time.
Causes urweb to exit after the specified phase of compilation.

Since Ur/Web type inference can take a significant amount of time, it can be helpful to cache type-inferred versions of source files. This mode can be activated by running

urweb daemon start
Further urweb invocations in the same working directory will send requests to a background daemon process that reuses type inference results whenever possible, tracking source file dependencies and modification times.

To stop the background daemon, run

urweb daemon stop
Communication happens via a Unix domain socket in file .urweb_daemon in the working directory.

urweb is a product of research; while it is intended to be usable for real work, it may occasionally fail to produce optimal results. If you believe you've found a bug (e.g., the compiler throws an unhandled exception), contact the Ur/Web mailing list,

urweb is copyright © 2008-2017 Adam Chlipala and licensed under the

This manual page is copyright © 2013, 2015—2017 Benjamin Barenblat and licensed under the Apache License, Version 2.0.

2017-07-20