Rewrite. Map can be used with several keywords, to use text files (txt: ), hashfiles (dbm: ), randomized text (rnd: ) or external mapping scripts ( this one is the prg: keyword ). In this mode the external script is launched when apache start. Then for every incoming request, when mod- rewrite is calling the prg: mapping, apache sends input to that script and reads the output stream to get the value. External Rewriting Program MapType: prg. External rewriting programs are not started if they're defined in a context that does not have RewriteEngine set to on. Hi, currently, the External Rewriting Program (RewriteMap 'prg:') is run as root. I would like to change it but I see three ways how to do it: 1. Execute it right after drop. This looks like best way, but I. Any experienced users of the external program 'prg' mechanism of Rewritemap who use a compiled binary file as opposed to interpreted language? Is there an appreciable performance difference on a high volume site, even when the. IIS Mod-Rewrite examples: Overview Documentation Download Purchase FAQ . To implement this database driven url rewriting. Using an external Programm do do rewriting – in fact it can do anything depending on the request. First a non-mentioned fact: if you use an external rewriting program apache will spawn it as a child process. Prg: External Rewriting Program. When a MapType of prg is used. For each mapping-function use one RewriteMap directive to declare its rewriting mapfile. While you cannot declare a map in per-directory context. External Rewriting Program MapType: prg, MapSource: Unix filesystem path to valid regular file. For each mapping-function use one RewriteMap directive to declare its rewriting mapfile. Rewrite. Lock must be used in that case to prevent parallel requests (so parallel inputs to that external process) to mix answers on this process standard output. It's a locking mechanism (a file, the given path, which is a classical token, only one user) to enforce serialization of the calls to this external mapping script. IMHO it should be transparently applied by mod- rewrite when using prg: as I never found a prg case where this locking thing is not mandatory. Edit: Well in fact you could use an external prg: without the rewrite. Lock if randomization of the output is not a problem, i. Configuration Directives RewriteEngine Syntax. The RewriteMap directive defines an external Rewriting Map which can be used inside rule substitution strings by the mapping-functions to. I am trying to set up an external rewriting map to do the job on my server and. It cannot be in a Location, a Directory or a . So chances are this will never work in a . Now @puk asked for an example of Rewrite. Damned cool voodoo, but still. It supports an unlimited number of rules and an. URL manipulation. The URL manipulations can depend on various tests. HTTP. headers, time stamps and even external database lookups in. URL. matching. This module operates on the full URLs (including the. The rewritten result can lead to internal. But all this functionality and flexibility has its. So don't expect to understand this. This module was invented and originally written in April. The Apache Group in July 1. Ralf S. A hook for each of these. Apache API. A few. In both situations mod. This is a usage. of the API which was not intended to be this way when the API. Apache 1. x this is the only way. To make this point more clear. Although mod. In Apache. But this point has no drawbacks for. Apache does more in the URL- to- filename hook than the API. It has to be this way because. In other. words: According to the API phases at this time it is too. URL manipulations. To overcome this chicken. This restarts processing of. API phases. But on the other hand this is the only way. Then the URL rewriting. The operation of the. URL rewriting engine itself is exactly the same for both. Only the final result processing is. The order of rules in the ruleset is important because the. The rule is this: The rewriting engine loops. Rewrite. Rule directives) and. Rewrite. Cond. directives). For historical reasons the conditions are given. See. Figure 1 for more details. Figure 1: The control flow through the rewriting ruleset. As you can see, first the URL is matched against the. Pattern of each rule. If the Pattern matches, mod. If none are present, it. URL with a new value which is. Substitution and goes on. But if conditions exist, it starts an. For conditions the logic is different: we don't match. URL. Instead we first create a. Test. String by expanding variables. If the pattern. doesn't match, the complete set of conditions and the. If the pattern matches, then the. If all conditions match, processing is continued. URL with. Substitution. As of Apache 1. 3. Test. String and Substitution strings can be. In other words, you can include an actual. Substitution string by. These are available for creating. Substitution and Test. String. But you will benefit from this knowledge when. This module keeps track of two additional (non- standard). CGI/SSI environment variables named SCRIPT. These contain the. Web- view to the current resource, while the. CGI/SSI variables SCRIPT. Notice: These variables hold the URI/URL as they were. This is important because the rewriting process is. URLs to physical. Example. SCRIPT. There you can. As you will see. below, Rewrite. Rule. can be used in per- directory config files. There it will act locally. At the end it is automatically added back to the. The default setting is; Rewrite. Basephysical- directory- path. When a substitution occurs for a new URL, this module has. URL into the server processing. To be able. to do this it needs to know what the corresponding URL- prefix. URL- base is. By default this prefix is the corresponding. But at most websites URLs are NOT. There you have to. Rewrite. Base directive to specify the. URL- prefix. If your webserver's URLs are not directly. Rewrite. Base in every . Rewrite. Rule directives. So, when it occurs the (rewritten) request. Apache kernel! BUT. While this seems like a serious overhead, it really. Apache server and the same. Apache. So, you can be sure the design and. Description. Defines a condition under which rewriting will take place. Rewrite. Cond. Test. String. Cond. Pattern. Default. None. Context. Override. File. Info. Status. Extension. Module. mod. Precede a Rewrite. Rule directive with one. Rewrite. Cond directives. The following. rewriting rule is only used if its pattern matches the current. URI and if these additional. Test. String is a string which can contains the. Rewrite. Rule backreferences: These are. N < = 9) which provide access to the grouped. Rewrite. Rule directive (the one. Rewrite. Cond. directives). Those that are special to. Sub- requests may be generated. URIs in order to complete their tasks. API. The module API version. Apache in use (in. Apache 1. 3. 1. 4, for. THE. This does not. REQUEST. This is looked- up via internal. Apache structures and (if not found there) via. Apache server process. There is the special format. This is looked- up from the HTTP. Use this when you want to use a. API phase and thus is not available at the current stage. On the other hand, because mod. Most of the time this is the same as. LA- U above. Cond. Pattern is the condition pattern. Test. String, i. e.. Test. String is evaluated and then matched against. Cond. Pattern. Remember: Cond. Pattern is a. standard Extended Regular Expression with some. You can prefix the pattern string with a. True if. Test. String is lexically lower than. Cond. Pattern.'> Cond. Pattern' (is lexically. Treats the Cond. Pattern as a plain string and. Test. String. True if. Test. String is lexically greater than. Cond. Pattern.'=Cond. Pattern' (is lexically. Treats the Cond. Pattern as a plain string and. Test. String. True if. Test. String is lexically equal to. Cond. Pattern, i. If Cond. Pattern. This uses an internal. U' (is existing URL via. Checks if Test. String is a valid URL and. This uses an internal. Notice. All of these tests can. Flags is a comma- separated list of the. It has no. effect on filesystem and subrequest checks. Typical example. Rewrite. Cond %. If you use any other browser you get. The Rewrite. Engine directive enables or. If it is set to. off this module does no runtime processing at. It does not even update the SCRIPT. This means that you need to have a. Rewrite. Engine on directive for each virtual host. This directive sets the filename for a synchronization. Set this lockfile to a local path (not on a. NFS- mounted device) when you want to use a rewriting. It is not required for other types of rewriting. Description. Sets the name of the file used for logging rewrite engine. Syntax. Rewrite. Log file- path. Context. server config, virtual host. Status. Extension. Module. mod. If the name does not begin with a slash. Server Root. The directive should occur only once per. To disable logging either. Rewrite. Log. directive or use Rewrite. Log. Level 0! The default level 0. To disable the logging of rewriting actions simply set. Level to 0. This disables all rewrite action. Using a high value for. Level will slow down your Apache server. Use the rewriting logfile at a. Level greater than 2 only for debugging! The source of. this lookup can be of various types. The is. the name of the map and will be used to specify a. If the. key is found, the map- function construct is substituted by. Subst. Value. If the key is not found then it is. Default. Value or by the empty string. Default. Value was specified. The following combinations for Map. Type and. Map. Source can be used: Standard Plain Text. Map. Type: txt, Map. Source: Unix filesystem. This is the standard rewriting map feature where the. Map. Source is a plain ASCII file containing. Matching. Key. Subst. Value. Example. ## map. Ralf. S. Engelschall rse # Bastard Operator From Hell. Mr. Joe. Average joe # Mr. Average. Rewrite. Map real- to- user txt: /path/to/file/map. Randomized Plain Text. Map. Type: rnd, Map. Source: Unix filesystem. This is identical to the Standard Plain Text variant. After. looking up a value it is parsed according to contained. In other words they indicate a set of. Although this sounds crazy and useless. Example. ## map. txt - - rewriting map. You can create such a. NDBM tool or with the following Perl. This program is started once at startup of the Apache. For each map- function lookup it will. It then has to give back the. NULL'' if it fails (i. A trivial. program which will implement a 1: 1 map (i. This will cause a deadloop! Hence. the ``$. By default no such. The Rewrite. Map directive can occur more than. For each mapping- function use one. Rewrite. Map directive to declare its rewriting. While you cannot declare a map in. Note For plain text and DBM format files the. This way you can have. The Option strings can be one of the. This forces the current configuration to inherit the. In per- virtual- server context. In per- directory context this means. The Rewrite. Rule directive is the real. The directive can occur more than once. The. definition order of these rules is. Here. ``current'' means the value of the URL when this rule gets. This may not be the originally requested URL. Some hints about the syntax of regular expressions: Text. If you are interested in more detailed. POSIX regex, Perl regex, etc.) have a look at the. Mastering Regular Expressions. Jeffrey E. F. Friedl. Nutshell Handbook Series. O'Reilly & Associates, Inc. ISBN 1- 5. 65. 92- 2. Additionally in mod. This gives. you the ability to negate a pattern; to say, for instance. URL does NOT match this. This can be used for exceptional cases, where. Notice. When using the NOT character. This is impossible because when the. NOT match, there are no contents for the. In consequence, if negated patterns are used, you. N in the substitution. Beside plain text you can useback- references $N to the Rewrite. Rule. patternback- references %N to the last matched. Rewrite. Cond patternserver- variables as in rule condition test- strings. The server- variables are the same. Test. String of a Rewrite. Cond. directive. The mapping- functions come from the. Rewrite. Map directive and are explained there. As already mentioned above, all the rewriting rules are. Substitution (in the order of. The URL is completely. Substitution and the. L flag - see below. There is a special substitution string named. NO. substitution! No, it is useful to. URLs but do no substitution, e. C (chain) flag to be. One more note: You can even create URLs in the. Just use. a question mark inside the substitution string to indicate. QUERY. When you want to erase an existing query. Note. There is a special feature. When you prefix a substitution field with. This auto- reduction on implicit external redirect. URLs is a useful and important feature when used in.
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