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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-13 13:44:03 +0000 |
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| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-13 13:44:03 +0000 |
| commit | 293913568e6a7a86fd1479e1cff8e2ecb58d6568 (patch) | |
| tree | fc3b469a3ec5ab71b36ea97cc7aaddb838423a0c /doc/src/sgml/html/pltcl-overview.html | |
| parent | Initial commit. (diff) | |
| download | postgresql-16-293913568e6a7a86fd1479e1cff8e2ecb58d6568.tar.xz postgresql-16-293913568e6a7a86fd1479e1cff8e2ecb58d6568.zip | |
Adding upstream version 16.2.upstream/16.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'doc/src/sgml/html/pltcl-overview.html')
| -rw-r--r-- | doc/src/sgml/html/pltcl-overview.html | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/doc/src/sgml/html/pltcl-overview.html b/doc/src/sgml/html/pltcl-overview.html new file mode 100644 index 0000000..a10cdd9 --- /dev/null +++ b/doc/src/sgml/html/pltcl-overview.html @@ -0,0 +1,43 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>44.1. Overview</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="pltcl.html" title="Chapter 44. PL/Tcl — Tcl Procedural Language" /><link rel="next" href="pltcl-functions.html" title="44.2. PL/Tcl Functions and Arguments" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">44.1. Overview</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pltcl.html" title="Chapter 44. PL/Tcl — Tcl Procedural Language">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="pltcl.html" title="Chapter 44. PL/Tcl — Tcl Procedural Language">Up</a></td><th width="60%" align="center">Chapter 44. PL/Tcl — Tcl Procedural Language</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.2 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="pltcl-functions.html" title="44.2. PL/Tcl Functions and Arguments">Next</a></td></tr></table><hr /></div><div class="sect1" id="PLTCL-OVERVIEW"><div class="titlepage"><div><div><h2 class="title" style="clear: both">44.1. Overview <a href="#PLTCL-OVERVIEW" class="id_link">#</a></h2></div></div></div><p> + PL/Tcl offers most of the capabilities a function writer has in + the C language, with a few restrictions, and with the addition of + the powerful string processing libraries that are available for + Tcl. + </p><p> + One compelling <span class="emphasis"><em>good</em></span> restriction is that + everything is executed from within the safety of the context of a + Tcl interpreter. In addition to the limited command set of safe + Tcl, only a few commands are available to access the database via + SPI and to raise messages via <code class="function">elog()</code>. PL/Tcl + provides no way to access internals of the database server or to + gain OS-level access under the permissions of the + <span class="productname">PostgreSQL</span> server process, as a C + function can do. Thus, unprivileged database users can be trusted + to use this language; it does not give them unlimited authority. + </p><p> + The other notable implementation restriction is that Tcl functions + cannot be used to create input/output functions for new data + types. + </p><p> + Sometimes it is desirable to write Tcl functions that are not restricted + to safe Tcl. For example, one might want a Tcl function that sends + email. To handle these cases, there is a variant of <span class="application">PL/Tcl</span> called <code class="literal">PL/TclU</code> + (for untrusted Tcl). This is exactly the same language except that a full + Tcl interpreter is used. <span class="emphasis"><em>If <span class="application">PL/TclU</span> is used, it must be + installed as an untrusted procedural language</em></span> so that only + database superusers can create functions in it. The writer of a <span class="application">PL/TclU</span> + function must take care that the function cannot be used to do anything + unwanted, since it will be able to do anything that could be done by + a user logged in as the database administrator. + </p><p> + The shared object code for the <span class="application">PL/Tcl</span> and + <span class="application">PL/TclU</span> call handlers is automatically built and + installed in the <span class="productname">PostgreSQL</span> library + directory if Tcl support is specified in the configuration step of + the installation procedure. To install <span class="application">PL/Tcl</span> + and/or <span class="application">PL/TclU</span> in a particular database, use the + <code class="command">CREATE EXTENSION</code> command, for example + <code class="literal">CREATE EXTENSION pltcl</code> or + <code class="literal">CREATE EXTENSION pltclu</code>. + </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pltcl.html" title="Chapter 44. PL/Tcl — Tcl Procedural Language">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pltcl.html" title="Chapter 44. PL/Tcl — Tcl Procedural Language">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="pltcl-functions.html" title="44.2. PL/Tcl Functions and Arguments">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 44. PL/Tcl — Tcl Procedural Language </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.2 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 44.2. PL/Tcl Functions and Arguments</td></tr></table></div></body></html>
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