mod_substitute - Apache HTTP Server Version 2.4









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Apache HTTP Server Version 2.4



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Apache Module mod_substitute

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Description:Perform search and replace operations on response bodies
Status:Extension
Module Identifier:substitute_module
Source File:mod_substitute.c
Compatibility:Available in Apache HTTP Server 2.2.7 and later
Summary

    mod_substitute provides a mechanism to perform
    both regular expression and fixed string substitutions on
    response bodies.

Directives

 Substitute
 SubstituteInheritBefore
 SubstituteMaxLineLength

Bugfix checklisthttpd changelogKnown issuesReport a bugSee also

Comments


Substitute Directive

Description:Pattern to filter the response content
Syntax:Substitute s/pattern/substitution/[infq]
Context:directory, .htaccess
Override:FileInfo
Status:Extension
Module:mod_substitute

    The Substitute directive specifies a
    search and replace pattern to apply to the response body.

    The meaning of the pattern can be modified by using any
    combination of these flags:

    
        i
        Perform a case-insensitive match.
        n
        By default the pattern is treated as a regular expression.
        Using the n flag forces the pattern to be treated
        as a fixed string.
        f
        The f flag causes mod_substitute to flatten the
        result of a substitution allowing for later substitutions to
        take place on the boundary of this one. This is the default.
        q
        The q flag causes mod_substitute to not
        flatten the buckets after each substitution. This can
        result in much faster response and a decrease in memory
        utilization, but should only be used if there is no possibility
        that the result of one substitution will ever match a pattern
        or regex of a subsequent one.
    

    The substitution may contain literal text and regular
    expression backreferences

    Example<Location "/">
    AddOutputFilterByType SUBSTITUTE text/html
    Substitute "s/foo/bar/ni"
</Location>


    The character which is used to separate (or "delimit") the
    various parts of the substitution string is referred to as the
    "delimiter", and it is most common to use a slash for this
    purpose.

    If either the pattern or the substitution contain a slash
    character then an alternative delimiter may be used to make the
    directive more readable:

    Example of using an alternate delimiter<Location "/">
    AddOutputFilterByType SUBSTITUTE text/html
    Substitute "s|<BR */?>|<br />|i"
</Location>


    Backreferences can be used in the comparison and in the substitution,
    when regular expressions are used, as illustrated in the following example: 
    Example of using backreferences and captures<Location "/">
    AddOutputFilterByType SUBSTITUTE text/html
    # "foo=k,bar=k" -> "foo/bar=k"
    Substitute "s|foo=(\w+),bar=\1|foo/bar=$1|"
</Location>


    A common use scenario for mod_substitute is the
    situation in which a front-end server proxies requests to a back-end
    server which returns HTML with hard-coded embedded URLs that refer
    to the back-end server. These URLs don't work for the end-user,
    since the back-end server is unreachable.

    In this case, mod_substitute can be used to rewrite
    those URLs into something that will work from the front end:

    Rewriting URLs embedded in proxied contentProxyPass        "/blog/" "http://internal.blog.example.com/"
ProxyPassReverse "/blog/" "http://internal.blog.example.com/"

Substitute "s|http://internal.blog.example.com/|http://www.example.com/blog/|i"


    ProxyPassReverse
    modifies any Location (redirect) headers that are sent
    by the back-end server, and, in this example,
    Substitute takes care of the rest of the problem by
    fixing up the HTML response as well.




SubstituteInheritBefore Directive

Description:Change the merge order of inherited patterns
Syntax:SubstituteInheritBefore on|off
Default:SubstituteInheritBefore off
Context:directory, .htaccess
Override:FileInfo
Status:Extension
Module:mod_substitute
Compatibility:Available in httpd 2.4.17 and later

    Whether to apply the inherited Substitute
    patterns first (on), or after the ones of the current
    context (off).
    SubstituteInheritBefore is itself inherited,
    hence contexts that inherit it (those that don't specify their own
    SubstituteInheritBefore value) will apply the
    closest defined merge order.



SubstituteMaxLineLength Directive

Description:Set the maximum line size
Syntax:SubstituteMaxLineLength bytes(b|B|k|K|m|M|g|G)
Default:SubstituteMaxLineLength 1m
Context:directory, .htaccess
Override:FileInfo
Status:Extension
Module:mod_substitute
Compatibility:Available in httpd 2.4.11 and later

    The maximum line size handled by mod_substitute
    is limited to restrict memory use. The limit can be configured
    using SubstituteMaxLineLength.
    The value can be given as the number of bytes and can be suffixed
    with a single letter b, B, k,
    K, m, M, g,
    G to provide the size in bytes, kilobytes, megabytes
    or gigabytes respectively.

    Example<Location "/">
    AddOutputFilterByType SUBSTITUTE text/html
    SubstituteMaxLineLength 10m
    Substitute "s/foo/bar/ni"
</Location>






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