commit 295d1e9853ee4dfee799b7cc81d57e0e3dbfdf93
parent 5545d19d7f59964144254095c0d82ea257eba4e5
Author: Christian Grothoff <christian@grothoff.org>
Date: Fri, 25 Aug 2023 13:02:05 +0200
document environment variable substitution (#7013)
Diffstat:
1 file changed, 30 insertions(+), 32 deletions(-)
diff --git a/frags/common-conf-syntax.rst b/frags/common-conf-syntax.rst
@@ -1,27 +1,18 @@
-The configuration file is line-oriented.
-Blank lines and whitespace at the beginning and end of a line are ignored.
-Comments start with ``#`` or ``%`` in the first column
-(after any beginning-of-line whitespace) and go to the end of the line.
-
-The file is split into sections.
-Every section begins with “[SECTIONNAME]” and
-contains a number of options of the form “OPTION=VALUE”.
-There may be whitespace around the ``=`` (equal sign).
-Section names and options are *case-insensitive*.
-
-The values, however, are *case-sensitive*.
-In particular, boolean values are one of ``YES`` or ``NO``.
-Values can include whitespace by surrounding
-the entire value with ``"`` (double quote).
-Note, however, that there are no escape characters in such strings;
-all characters between the double quotes (including other double quotes)
-are taken verbatim.
-
-Values that represent filenames can begin with a ``/bin/sh``-like
-variable reference.
-This can be simple, such as ``$TMPDIR/foo``, or complex,
-such as ``${TMPDIR:-${TMP:-/tmp}}/foo``.
-See ``[PATHS]`` (below).
+The configuration file is line-oriented. Blank lines and whitespace at the
+beginning and end of a line are ignored. Comments start with ``#`` or ``%``
+in the first column (after any beginning-of-line whitespace) and go to the end
+of the line.
+
+The file is split into sections. Every section begins with ``[SECTIONNAME]``
+and contains a number of options of the form ``OPTION=VALUE``. There may be
+whitespace around the ``=`` (equal sign). Section names and options are
+*case-insensitive*.
+
+The values, however, are *case-sensitive*. In particular, boolean values are
+one of ``YES`` or ``NO``. Values can include whitespace by surrounding the
+entire value with ``"`` (double quote). Note, however, that there are no
+escape characters in such strings; all characters between the double quotes
+(including other double quotes) are taken verbatim.
Values that represent a time duration are represented as a series
of one or more ``NUMBER UNIT`` pairs, e.g. ``60 s``, ``4 weeks 1 day``,
@@ -31,17 +22,24 @@ Values that represent an amount are in the usual amount syntax:
``CURRENCY:VALUE.FRACTION``, e.g. ``EUR:1.50``.
The ``FRACTION`` portion may extend up to 8 places.
+Values that represent filenames can begin with a ``/bin/sh``-like variable
+reference. This can be simple, such as ``$TMPDIR/foo``, or complex, such as
+``${TMPDIR:-${TMP:-/tmp}}/foo``. The variables are expanded either using
+key-values from the ``[PATHS]`` section (see below) or from the environment
+(``getenv()``). The values from ``[PATHS]`` take precedence over those from
+the environment.
-The “[PATHS]” section is special in that it contains paths that can be
-referenced using “$” in other configuration values that specify
+The ``[PATHS]`` section is special in that it contains paths that can be
+referenced using ``$`` in other configuration values that specify
*filenames*. Note that configuration options that are not specifically
retrieved by the application as *filenames* will not see “$”-expressions
-expanded. To expand “$”-expressions when using ``taler-config``, you must pass
+expanded. To expand ``$``-expressions when using ``taler-config``, you must pass
the ``-f`` command-line option.
-The system automatically pre-populates the “[PATHS]” section with a few values
-at run-time in addition to the values that are in the actual configuration
-file. These automatically generated values refer to installation properties
+The system automatically pre-populates the ``[PATHS]`` section with a few values
+at run-time (in addition to the values that are in the actual configuration
+file and automatically overwriting those values if they are present).
+These automatically generated values refer to installation properties
from `GNU autoconf
<https://www.gnu.org/prep/standards/html_node/Directory-Variables.html>`_. The
values are usually dependent on an ``INSTALL_PREFIX`` which is determined by
@@ -58,5 +56,5 @@ the ``--prefix`` option given to configure. The canonical values are:
Note that on some platforms, the given paths may differ depending
on how the system was compiled or installed, the above are just the
-canonical locations of the various resources.
-
+canonical locations of the various resources. These
+automatically generated values are never written to disk.
