YAWS_API(5) User API YAWS_API(5)
NAME
yaws_api - api available to yaws web server programmers
SYNOPSIS
yaws_api:Function(...)
DESCRIPTION
This is the api available to yaws web server programmers. The Erlang
module yaws_api contains a wide variety of functions that can be used
inside yaws pages.
Each chunk of yaws code is executed while the yaws page is being deliv‐
ered from the server. We give a very simple example here to show the
basic idea. Imagine the following HTML code:
<html>
<body>
<h1> Header 1</h1>
<erl>
out(Arg) ->
{html, "<p> Insert this text into the document"}.
</erl>
</body>
</html>
The out(Arg) function is supplied one argument, an #arg{} structure.
We have the following relevant record definitions:
-record(arg, {
clisock, % the socket leading to the peer client
client_ip_port, % {ClientIp, ClientPort} tuple
headers, % headers
req, % request
orig_req, % original request
clidata, % The client data (as a binary in POST requests)
server_path, % The normalized server path
% (pre-querystring part of URI)
querydata, % For URIs of the form ...?querydata
% equiv of cgi QUERY_STRING
appmoddata, % (deprecated - use pathinfo instead) the remainder
% of the path leading up to the query
docroot, % Physical base location of data for this request
docroot_mount, % virtual directory e.g /myapp/ that the docroot
% refers to.
fullpath, % full deep path to yaws file
cont, % Continuation for chunked multipart uploads
state, % State for use by users of the out/1 callback
pid, % pid of the yaws worker process
opaque, % useful to pass static data
appmod_prepath, % (deprecated - use prepath instead) path in front
% of: <appmod><appmoddata>
prepath, % Path prior to 'dynamic' segment of URI.
% ie http://some.host/<prepath>/<script-point>/d/e
% where <script-point> is an appmod mount point,
% or .yaws,.php,.cgi,.fcgi etc script file.
pathinfo % Set to '/d/e' when calling c.yaws for the request
% http://some.host/a/b/c.yaws/d/e
% equiv of cgi PATH_INFO
}).
The headers argument is also a record:
-record(headers, {
connection,
accept,
host,
if_modified_since,
if_match,
if_none_match,
if_range,
if_unmodified_since,
range,
referer,
user_agent,
accept_ranges,
cookie = [],
keep_alive,
location,
content_length,
content_type,
content_encoding,
authorization,
transfer_encoding,
x_forwarded_for,
other = [] % misc other headers
}).
The out/1 function can use the Arg to generate any content it likes. We
have the following functions to aid that generation.
API
ssi(DocRoot, ListOfFiles)
Server side include. Just include the files as is in the docu‐
ment. The files will not be parsed and searched for <erl> tags.
pre_ssi_files(DocRoot, ListOfFiles) ->
Server side include of pre-indented code. The data in Files
will be included but contained in a <pre> tag. The data will be
htmlized.
pre_ssi_string(String)
Include htmlized content from String.
f(Fmt, Args)
The equivalent of io_lib:format/2. This function is automati‐
cally -included in all erlang code which is a part of a yaws
page.
htmlize(Binary | List | Char)
Htmlize an IO list object.
set_cookie(Name, Value, Options])
Sets a cookie to the browser. Options are:
{expires, UtcTime} - Cookie expiration time, where UtcTime is
a tuple returned by calendar:universal_time/0.
{max_age, Age} - Defines the lifetime of the cookie, in seconds,
where age is an integer >= 0.
{path, Path} - Path is a string that specifies the subset of URLs to
which this cookie applies.
{domain, Domain} - Domain is a string that specifies the domain for which
the cookie is valid.
{comment, Comment} - Comment is a string that doccuments the server's
intended use of the cookie.
secure - Directs the user agent to use only secure means to
contact the origin server whenever it sends back this
cookie.
http_only - Restricts cookie access from other non-HTTP APIs.
setcookie(Name, Value, [Path, [ Expire, [Domain , [Secure]]]])
Sets a cookie to the browser. This function is deprecated by
set_cookie/3.
find_cookie_val(Cookie, Header)
This function can be used to search for a cookie that was previ‐
ously set by setcookie/2-6. For example if we set a cookie as
yaws_api:setcookie("sid",SomeRandomSid), then on subsequent
requests from the browser we can call:
find_cookie("sid",(Arg#arg.headers)#headers.cookie)
The function returns [] if no cookie was found, otherwise the
actual cookie is returned as a string.
parse_set_cookie(Str)
This function parses the value of a Set-Cookie header, following
the RFC6265. Because old RFCs (2109 and 2965) are still used, it
is backward compatible. So this function returns a #setcookie{}
record when only one cookie is found. If multiple cookies are
set in a single Set-Cookie header, it returns a list of #set‐
cookie{} records. If no cookie was found or if an error
occurred, it returns [].
#setcookie{} record is defined in yaws_api.hrl:
-record(setcookie, {key,
value,
quoted = false,
domain,
max_age,
expires,
path,
secure = false,
http_only = false,
extensions = []}).
parse_cookie(Str)
This function parses the value of Cookie header, following the
RFC6265. It returns a list of #cookie{} records. If no cookie
was found or if an error occurred, it returns [].
#cookie{} record is defined in yaws_api.hrl:
-record(cookie, {key,
value,
quoted = false}).
format_set_cookie(SetCookie)
Build a cookie string from a #setcookie{} record like returned
by parse_set_cookie/1.
format_cookie(Cookie | [Cookie])
Build a cookie string from a #cookie{} record (or a list or
records) like returned by parse_cookie/1.
redirect(Url)
This function generates a redirect to the browser. It will
clear any previously set headers. So to generate a redirect and
set a cookie, we need to set the cookie after the redirect as
in:
out(Arg) ->
... do some stuff
Ret = [{redirect, "http://www.somewhere.com"},
setcookie("sid", Random)
].
redirect_self(Arg)
If we want to issue a redirect to ourselves, this function is
useful. It returns a record #redir_self{} defined in
yaws_api.hrl. The record contains fields to construct a URL to
ourselves.
-record(redir_self, {
host, % string() - our own host
scheme, % http | https
scheme_str, % "https://" | "http://"
port, % integer() - our own port
port_str % "" | ":<int>" - the optional port part
% to append to the url
}).
get_line(String)
This function is convenient when getting \r\n terminated lines
from a stream of data. It returns:
{line, Line, Tail} or {lastline, Line, Tail}
The function handles multilines as defined in e.g. SMTP or HTTP
mime_type(Scope, FileName)
Returns the MIME type as defined by the extension of FileName.
Scope can have following values:
global - returns the result obtained from the global con‐
text.
#sconf{} | {ServerName, Port} - returns the result obtained
from the virtual server's context. If no MIME type is found
in this scope, it falls back on the global one.
mime_type(FileName)
Tries to determine the right Scope before calling mime_type/2.
stream_chunk_deliver(YawsPid, Data)
When a yaws function needs to deliver chunks of data which it
gets from a process. The other process can call this function to
deliver these chunks. It requires the out/1 function to return
the value {streamcontent, MimeType, FirstChunk} to work.
YawsPid is the process identifier of the yaws process delivering
the original .yaws file. That is self() in the yaws code. The
Pid must typically be passed (somehow) to the producer of the
stream.
stream_chunk_deliver_blocking(YawsPid, Data)
A synchronous version of the above function. This synchronous
version must always be used when the producer of the stream is
faster than the consumer. This is usually the case since the
client is the WWW browser.
stream_chunk_end(YawsPid)
When the process discussed above is done delivering data, it
must call this function to let the yaws content delivering
process finish up the HTTP transaction.
stream_process_deliver(Socket, IoList)
Yaws allows application processes to deliver data directly to
the client. The application tells yaws about such a process by
returning {streamcontent_from_pid, MimeType, Pid} from its out/1
function. In this case, Pid uses the stream_process_deliver/2
function to deliver data to the client. The application gets
Socket from Arg#arg.clisock, and IoList is the data to be sent
to the client.
stream_process_deliver_chunk(Socket, IoList)
Same as above but delivers IoList using HTTP chunked transfer
format. IoList must have a size greater than zero. The applica‐
tion process delivering the data will have had to have make sure
that the HTTP headers of the response indicate chunked transfer
mode, either by ensuring no Content-Length header is set or by
specifically setting the Transfer-Encoding header to chunked.
stream_process_deliver_final_chunk(Socket, IoList)
If the application process delivering data to the client uses
chunked transfer mode, it must call this to deliver the final
chunk of the transfer. This tells yaws to create a special final
chunk in the format required by the HTTP specification (RFC
2616). IoList may be empty, but if its size is greater than
zero, that data will be sent as a separate chunk before the
final chunk.
stream_process_end(Socket, YawsPid)
Application processes delivering data directly to clients must
call this function to inform yaws that they've finished using
Socket. The YawsPid argument will have been passed to the
process earlier when yaws sent it a message telling it to pro‐
ceed with data delivery. Yaws expects Socket to be open.
stream_process_end(closed, YawsPid)
Same as the previous function but the application calls this if
it closes the client socket as part of its data delivery
process. This allows yaws to continue without assuming the
socket is still open and encountering errors due to that assump‐
tion. The YawsPid argument will have been passed to the applica‐
tion process earlier when yaws sent it a message telling it to
proceed with data delivery.
parse_query(Arg)
This function will parse the query part of the URL. It will
return a {Key, Value} list.
queryvar(Arg, VarName)
This function is automatically included from yaws_api in all
.yaws pages. It is used to search for a variable in the query‐
part of the url. Returns {ok, Val} or undefined. If a variable
is defined multiple times, the function may also return {Val1,
Val2...}.
parse_post(Arg)
If the browser has set the Content-Type header to the value
"application/x-www-form-urlencoded", this function will parse
the request's body. It will return a {Key, Value} list.
postvar(Arg, VarName)
This function is automatically included from yaws_api in all
.yaws pages. It is used to search for a variable in the
request's body sent by the client. Returns {ok, Val} or unde‐
fined. If a variable is defined multiple times, the function may
also return {Val1, Val2...}.
getvar(Arg, VarName)
This function is used to search a variable in the query part of
the URL and in the request's body. it invokes queryvar/2 and
postvar/2 and merges the results.
parse_multipart_post(Arg)
If the browser has set the Content-Type header to the value
"multipart/form-data", which is the case when the browser wants
to upload a file to the server the following happens:
If the function returns {result, Res} no more data will come
from the browser.
If the function returns {cont, Cont, Res} the browser will sup‐
ply more data. (The file was too big to come in one read)
This indicates that there is more data to come and the out/1
function should return {get_more, Cont, User_state} where
User_state might usefully be a File Descriptor. The Res value
is a list of either: {head, {Name, Headers}} | {part_body,
Binary} | {body, Binary}
The function returns {error, Reason} when an error occurred dur‐
ing the parsing.
Example usage could be:
<erl>
out(A) ->
case yaws_api:parse_multipart_post(A) of
{cont, Cont, Res} ->
St = handle_res(A, Res),
{get_more, Cont, St};
{result, Res} ->
handle_res(A, Res),
{html, f("<pre>Done </pre>",[])};
{error, Reason} ->
{html, f("An error occured: ~p", [Reason])}
end.
handle_res(A, [{head, {Name, _Hdrs}}|T]) ->
io:format("head:~p~n",[Name]),
handle_res(A, T);
handle_res(A, [{part_body, Data}|T]) ->
io:format("part_body:~p~n",[Data]),
handle_res(A, T);
handle_res(A, [{body, Data}|T]) ->
io:format("body:~p~n",[Data]),
handle_res(A, T);
handle_res(A, []) ->
io:format("End_res~n").
</erl>
new_cookie_session(Opaque)
Create a new cookie-based session. Yaws will either generate the
cookie itself or, if a ysession_cookiegen module is configured,
call new_cookie() on that module to get a new cookie. The new
cookie is returned from this function. The Opaque argument will
typically contain user data such as user name and password
new_cookie_session(Opaque, TTL)
As above, but allows to set a session specific time-out value,
overriding the system specified time-out value.
new_cookie_session(Opaque, TTL, CleanupPid)
As above, but also sends a message {yaws_session_end, Reason,
Cookie, Opaque} to the provided CleanupPid where Reason can be
either of timeout or normal. The Cookie is the HTTP cookie as
returned by new_session() and Opaque is the user-provided Opaque
parameter to new_session(). The purpose of the feature is to
cleanup resources assigned to the session.
cookieval_to_opaque(CookieVal)
print_cookie_sessions()
replace_cookie_session(Cookie, NewOpaque)
delete_cookie_session(Cookie)
setconf(Gconf, Groups)
This function is intended for embedded mode in yaws. It makes it
possible to load a yaws configuration from another data source
than /etc/yaws.conf, such as a database. If yaws is started
with the environment {embedded, true}, yaws will start with an
empty default configuration, and wait for some other program to
execute a setconf/2 The Gconf is a #gconf{} record and the Group
variable is a list of lists of #sconf{} records. Each sublist
must contain #sconf{} records with the same IP/Port listen
address. To create a suitable initial #gconf{} record see the
code in yaws_config:make_default_gconf/2. Especially the
yaws_dir parameter is important to get right.
url_decode(Str)
Decode url-encoded string. A URL encoded string is a string
where all alfa numeric characters and the the character _ are
preserved and all other characters are encode as "%XY" where X
and Y are the hex values of the least respective most signifi‐
cant 4 bits in the 8 bit character.
url_encode(Str)
Url-encodes a string. All URLs in HTML documents must be URL
encoded.
get_sslsocket(Socket)
Returns a socket for SSL sockets or the atom undefined for non-
SSL sockets. Useful for applications that have to deal with both
SSL and non-SSL sockets.
get_listen_port(Sconf)
Return the actual port number used by the listen socket of the
virtual server indicated by the function argument, an #sconf{}
record instance. If successful, returns the requested port num‐
ber, or returns {error, not_found} if the function argument does
not match any known virtual server. This function is useful for
retrieving the actual port number when, e.g. for testing pur‐
poses, a virtual server is configured to use port 0, which will
cause it to have an ephemeral port assigned by the operating
system.
reformat_header(H)
Returns a list of reformatted header values from a #headers{}
record. The return list is suitable for retransmit.
reformat_header(H, FormatFun)
Returns a list of reformatted header values from a #headers{}
record, with each element of the list formatted via a call to
FormatFun. This enables converting #headers{} records into vari‐
ous lists of headers and their values. Note that sometimes the
Set-Cookie header will contain a tuple value of the form {multi,
ValueList} — see merge_header/2 below for details — so format‐
ting functions should be prepared to handle such a tuple. They
should handle it by formatting each member of ValueList as a
separate Set-Cookie header, then returning all such header-value
pairs in a list. Note that this implies that sometimes the
return values of reformat_header/1 and reformat_header/2 can be
a multi-level list. The {multi, ValueList} construct results
only from calls to merge_header/2 or merge_header/3, where mul‐
tiple values are set in separate calls for the same header.
set_header(Headers, {Header, Value})
Sets header Header with value Value in the #headers{} record
Headers, and returns a new #headers{} record. Using the atom
undefined for Value effectively deletes the header, same as
delete_header/2.
set_header(Headers, Header, Value)
Same as set_header/2 above, except Header and Value are not
passed in a tuple.
merge_header(Headers, {Header, Value})
Merges value Value for header Header with any existing value for
that header in the #headers{} record Headers, and returns a new
#headers{} record. Using the atom undefined for Value simply
returns Headers. Otherwise, Value is merged with any existing
value already present in the Headers record for header Header,
comma-separated from that existing value. If no such value
exists in the Headers record, the effect is the same as
set_header/2. Note that for the Set-Cookie header, values are
not comma-separated but are instead collected into a tuple
{multi, ValueList} where ValueList is the collection of Set-
Cookie values. This implies that any formatting fun passed to
reformat_header/2 must be prepared to handle such tuples.
merge_header(Headers, Header, Value)
Same as merge_header/2 above, except Header and Value are not
passed in a tuple.
get_header(Headers, Header)
Gets the value of header Header from the #headers{} record Head‐
ers and returns it. If the header isn't set, the atom undefined
is returned.
delete_header(Headers, Header)
Deletes any value set for header Header in the #headers{} record
Headers, and returns a new #headers{} record.
request_url(ARG)
Return the url as requested by the client. Return value is a
#url{} record as defined in yaws_api.hrl
parse_url(Str)
Parse URL in a string, returns a #url record
format_url(UrlRecord)
Takes a #url record a formats the Url as a string
call_cgi(Arg, Scriptfilename)
Calls an executable CGI script, given by its full path. Used to
make `.yaws' wrappers for CGI programs. This function usually
returns streamcontent.
call_cgi(Arg, Exefilename, Scriptfilename)
Like before, but calls Exefilename to handle the script. The
file name of the script is handed to the executable via a CGI
meta variable.
call_fcgi_responder(Arg)
Calls a FastCGI responder. The address and port of the FastCGI
application server are taken from the server configuration (see
yaws.conf). Used to make `.yaws' wrappers for FastCGI respon‐
ders. Returns the same return values as out/1 (see below).
call_fcgi_responder(Arg, Options)
Same as above, but Options overrides the defaults from the
server configuration:
Options = [Option]
Option -- one of the following:
{app_server_host, string() | ip_address()} The hostname or the
IP address of the FastCGI application server.
{app_server_port, 0..65535} The TCP port number of the FastCGI
application server.
{path_info, string()} Override default pathinfo in
Arg#arg.pathinfo.
{extra_env, ExtraEnv} Extra environment variables to be passed
to the FastCGI application server, as a list of name-value
pairs.
ExtraEnv = [Var]
Var = {Name, Value}
Name = string() | binary()
Value = string() | binary()
{trace_protocol, boolean()} Enable or disable tracing of FastCGI
protocol messages as info log messages.
{log_app_error, boolean()} Enable or disable logging of applica‐
tion error messages: output to stderr and non-zero exit value.
call_fcgi_authorizer(Arg) -> {allowed, Out} | {denied, Out}
Calls a FastCGI authorizer. The address and port of the FastCGI
application server are taken from the server configuration (see
yaws.conf). Used to make `.yaws' wrappers for FastCGI authoriz‐
ers. Variables contains the values of the variables returned by
the FastCGI application server in the "Variable-XXX: YYY" head‐
ers.
If access is denied, Out contains the complete response returned
by the FastCGI application server. This response is typically
returned as-is to the HTTP client.
If access is allowed, Out contains the response returned by the
FastCGI application server minus the body (i.e. minus the con‐
tent) which should be ignored per the FastCGI specification.
This response is typically not returned to the HTTP client. The
calling application module may wish to inspect the response, for
example by extracting variables (see fcgi_extract_variables
below) or by inspecting the headers returned by the FastCGI
application server.
Out -- See return values for out/1 below
call_fcgi_authorizer(Arg, Options) -> {allowed, Out} | {denied, Out}
Same as above, but Options overrides the defaults from the
server configuration. See call_fcgi_responder/2 above for a
description of Options.
fcgi_extract_variables(Out) -> [{Name, Value}]
Extracts the environment variables from a FastCGI authorizer
response by looking for headers of the form "Variable-Name:
Value".
Name = string() -- The name of the variable (the "Variable-" prefix
has already been removed).
Value = string() -- The value of the variable.
dir_listing(Arg)
Perform a directory listing. Can be used in special directories
when we don't want to turn on dir listings for the entire
server. Always returns ok.
RETURN VALUES from out/1
The out/1 function can return different values to control the behavior
of the server.
{html, DeepList}
This assumes that DeepList is formatted HTML code. The code
will be inserted in the page.
{ehtml|exhtml, Term}
This will transform the erlang term Term into a stream of HTML
content. The exhtml variant transforms into strict XHTML code.
The basic syntax of Term is
EHTML = [EHTML] | {Tag, Attrs, Body} | {Tag, Attrs} | {Tag} |
{Module, Fun, [Args]} | fun/0 |
binary() | character()
Tag = atom()
Attrs = [{Key, Value}]
Key = atom()
Value = string() | binary() | atom() | integer() | float() |
{Module, Fun, [Args]} | fun/0
Body = EHTML
For example, {p, [], "Howdy"} expands into "<p>Howdy</p>" and
{form, [{action, "a.yaws"}],
{input, [{type,text}]}}
expands into
<form action="a.yaws"
<input type="text">
</form>
It may be more convenient to generate erlang tuples than plain
html code.
{content, MimeType, Content}
This function will make the web server generate different con‐
tent than HTML. This return value is only allowed in a yaws file
which has only one <erl> </erl> part and no html parts at all.
{streamcontent, MimeType, FirstChunk}
This return value plays the same role as the content return
value above.
However it makes it possible to stream data to the client if the
yaws code doesn't have access to all the data in one go. (Typi‐
cally if a file is very large or if data arrives from back end
servers on the network.
{streamcontent_with_timeout, MimeType, FirstChunk, Timeout}
Similar to above, but with an explicit timeout. The default
timeout is 30 secs. I.e if the application fails to deliver data
to the Yaws process, the streaming will stop. This is often not
the desired behaviour in Comet/Ajax applications. It's possible
to provide 'infinity' as timeout.
{streamcontent_from_pid, MimeType, Pid}
This return value is similar to the streamcontent return value
above.
However it makes it possible to stream data to the client
directly from an application process to the socket. This
approach can be useful for applications that employ long-polling
(Comet) techniques, for example, and for applications wanting to
avoid buffering data or avoid HTTP chunked mode transfer for
streamed data.
{streamcontent_with_size, Sz, MimeType, FirstChunk}
This return value is similar to the streamcontent return value
above.
However it makes it possible to stream data to the client by
setting the content length of the response. As the opposite of
other ways to stream data, in this case, the response is not
chunked encoded.
{header, H}
Accumulates a HTTP header. The trailing CRNL which is supposed
to end all HTTP headers must NOT be added. It is added by the
server. The following list of headers are given special treat‐
ment.
{connection, What}
This sets the Connection: header. If What is the special value
"close", the connection will be closed once the yaws page is
delivered to the client.
{server, What}
Sets the Server: header. By setting this header, the server's
signature will be dynamically overloaded.
{location, Url}
Sets the Location: header. This header is typically combined
with the {status, 302} return value.
{cache_control, What}
Sets the Cache-Control: header.
{expires, What}
Sets the Expires: header.
{date, What}
Sets the Date: header.
{allow, What}
Sets the Allow: header.
{last_modified, What}
Sets the Last-Modified: header.
{etag, What}
Sets the Etag: header.
{set_cookie, Cookie}
Prepends a Set-Cookie: header to the list of previously set Set-
Cookie: headers.
{content_range, What}
Sets the Content-Range: header.
{content_type, MimeType}
Sets the Content-Type: header.
{content_encoding, What}
Sets the Content-Encoding: header. If this header is defined, no
deflate is performed by Yaws, allowing you to compress data
yourself if you wish to do so.
{content_length, Len}
Normally yaws will ship Yaws pages using Transfer-Encoding:
chunked. This is because we generally can't know how long a yaws
page will be. If we for some reason want to force a Content-
Length: header (and we actually do know the length of the con‐
tent, we can force Yaws to not ship the page chunked.
{transfer_encoding, What}
Sets the Transfer-Encoding: header.
{www_authenticate, What}
Sets the WWW-Authenticate: header.
{vary, What}
Sets the Vary: header.
All other headers must be added using the normal HTTP syntax.
Example:
{header, {"My-X-Header", "gadong"}} or {header, "My-X-Header:
gadong"}
{header, {HeaderName, erase}}
Clears the header named HeaderName from the accumulated headers.
{allheaders, HeaderList}
Will clear all previously accumulated headers and replace them.
{status, Code}
Will set another HTTP status code than 200.
break Will stop processing of any consecutive chunks of erl or html
code in the yaws file.
ok Do nothing.
flush Flush remaining data sent by the client.
{redirect, Url}
Erase all previous headers and accumulate a single Location
header. Set the status code.
{redirect_local, Path}
Does a redirect to the same Scheme://Host:Port/Path as we cur‐
rently are executing in.
{get_more, Cont, State}
When we are receiving large POSTs we can return this value and
be invoked again when more Data arrives.
{page, Page}
Make Yaws returns a different page than the one being requested.
Page is a Request-URI, so it must be url-encoded and can contain
a query-string.
{page, {Options, Page}}
Like the above, but supplying an additional deep list of
options. Supported option types are:
{status, C} - Set the HTTP response status code C for page Page.
{header, H} - Accumulate the HTTP header H for page Page.
{disable_cache, Bool} - if set to true, disable the cache of
Page for this call.
{websocket, CallbackModule, Options}
Tell Yaws to use CallbackModule as a WebSocket Protocol handler
for traffic on the client socket. See the Yaws websocket docu‐
mentation for more details.
{ssi, File, Delimiter, Bindings}
Server side include File and macro expansion in File. Each
occurrence of a string, say "xyz", inside File that's within a
Delimiter pair is replaced with the corresponding value in Bind‐
ings.
Example: Delimiter = %%
File contains the string .... %%xyz%% .....
Bindings contain the tuple {"xyz", "Dingbat"}
The occurrence of %%xyz%% in File will be replaced with "Ding‐
bat" in the Server side included output.
The {ssi, File, Delimiter, Bindings} statement can also occur
within a deep ehtml structure.
{bindings, [{Key1, Value2}, {Key2, Value2} .....]}
Establish variable bindings that can be used in the page.
All bindings can then be used in the rest of yaws code (in HTML
source and within erl tags). In HTML source %%Key%% is expanded
to Value and within erl tags yaws_api:binding(Key) can be used
to extract Value and yaws_api:binding_exists(Key) can be used to
check for the existence of a binding.
{yssi, YawsFile}
Include a yaws file. Compile it and expand as if it had occured
inline.
#arg{} Return an instance of an #arg{} record. This can be useful when
used as part of a [ListOfValues] return value, so that any sub‐
sequent elements in the return list that require an #arg{} get
the returned instance rather than the original. For example, an
out/1 function might set the state field of an #arg{}, then
return both it and {yssi, YawsFile} in a list, in which case
Yaws will pass the returned #arg{}, rather than the original
instance, to the yaws file out/1 function.
[ListOfValues]
It is possible to return a deep list of the above defined return
values. Any occurrence of streamcontent, streamcon‐
tent_with_timeout, streamcontent_with_size, streamcon‐
tent_from_pid, get_more, page or break in this list is legal
only if it is the last position of the list. If not, remaining
values in the list are ignored.
AUTHOR
Written by Claes Wikstrom
SEE ALSO
yaws.conf(5) erl(1)
YAWS_API(5)
