Section files

Section file (or secfile) is the standard format of text files Freeciv stores its data. Rulesets, tilesets, savegames and some other files are stored in this INI-like format, sometimes (particulary, the savegames) archived for saving disk space. In the source code, the main frontend for secfile reading is located in utility/registry_ini.[ch], from comments whereof this manual is mostly copied.
== Secfile format ==
* Whitespace lines are ignored, as are lines where the first non-whitespace character is ';' (comment lines). Optionally '#' can also be used for comments.
* A line of the form
 *include "filename"
includes the named file at that point. (The '*' must be the first character on the line.) The file is found by looking in FREECIV_DATA_PATH. Non-infinite recursive includes are allowed.
* A line with [name] labels the start of a section with that name; one of these must be the first non-comment line in the file. Any spaces within the brackets are included in the name, but this feature (?) should probably not be used... You can break sections in parts and restart under the same name mostly freely unless the file is loaded by a function specially hunting for this section and throwing the rest of the code away if it encounters another one after it (this is known to restrict only [scenario] sections yet).
* Within a section, lines have one of the following forms:
 subname = "stringvalue"
 subname = -digits
 subname = digits
 subname = ([+-])?digits.(digits)?
 subname = TRUE
 sunname = FALSE
for a value with given name and string, negative integer, positive integer, real, Boolean true and false values, respectively. These entries are referenced in the following functions as "sectionname.subname".
The section name should not contain any dots ('.'); the subname
can, but they have no particular significance. Formally, section and entry names should consist of alphanumeric characters or any among _.,-[], but consider the information below and to avoid confusion use in most cases only letters and underscores unless you know better. There can be optional whitespace before and/or after the equals sign.
You can put a newline after (but not before) the equals sign.
Backslash is an escape character in strings (double-quoted strings only, not names); recognised escapes are \n, \\, and \".
Any other \<char> is just treated as <char>. Backslash at line end removes the new line character (even in $...$-strings or *...*-files).
There is an alternative syntax for strings $something$ that is often used for Lua scripts in script.code entry because you don't need to escape "quotes" in them and Lua deals with \'s itself. 
* Gettext markings: You can surround strings like so:
 foo = _("stringvalue")
:The registry just ignores these extra markings, but this is useful for marking strings for translations (see Internationalization for details) via gettext tools.
* Multiline strings: Strings can have embeded newlines, eg:
 foo = _("
 This is a string
 over multiple lines
 ")
:This is equivalent to:
 foo = _("\nThis is a string\nover multiple lines\n")
:Note that if you misplace the trailing doublequote you can easily end up with strange errors reading the file...
* Strings read from a file: A file can be read as a string value:
 foo = *filename.txt*
* Vector format: An entry can have multiple values separated by commas, eg:
 foo = 10, 11, "x"
These are accessed by names "foo", "foo,1" and "foo,2"
(with section prefix as above). So the above is equivalent to:
 foo = 10
 foo,1 = 11
 foo,2 = "x"
As in the example, in principle you can mix integers and strings,
but the calling program will probably require elements to be the
same type. Note that the first element of a vector is not "foo,0",
in order that the name of the first element is the same whether or
not there are subsequent elements. However as a convenience, if
you try to lookup "foo,0" then you get back "foo". (So you should
never have "foo,0" as a real name in the datafile.)
* Tabular format: The lines:
 foo = { "bar", "baz", "bax"
 "wow", 10, -5
 "cool", "str"
 "hmm", 314, 99, 33, 11
 }
:are equivalent to the following:
 foo0.bar = "wow"
 foo0.baz = 10
 foo0.bax = -5
 foo1.bar = "cool"
 foo1.baz = "str"
 foo2.bar = "hmm"
 foo2.baz = 314
 foo2.bax = 99
 foo2.bax,1 = 33
 foo2.bax,2 = 11
The first line specifies the base name and the column names (must be strings in ""), and the
subsequent lines have data. Again it is possible to mix string and
integer values in a column, and have either more or less values
in a row than there are column headings, but the code which uses
this information (via the registry) may set more stringent conditions.
If a row has more entries than column headings, the last column is
treated as a vector (as above). You can optionally put a newline
after '=' and/or after '{'. FYI, the length of sectionname.entryname path may not exceed 1024. 
The equivalence above between the new and old formats is fairly
direct: internally, data is converted to the old format.
In principle it could be a good idea to represent the data
as a table (2-d array) internally, but the current method
seems sufficient and relatively simple...
There is a limited ability to save data in tabular:
So long as the section_file is constructed in an expected way,
tabular data (with no missing or extra values) can be saved
in tabular form. (See section_file_save().)
* Multiline vectors: if the last non-comment non-whitespace character in a line is a comma, the line is considered to continue on to the next line. Eg:
 foo = 10,
 11,
 "x"
This is equivalent to the original "vector format" example above.
Such multi-lines can occur for column headings, vectors, or
table rows, again with some potential for strange errors...
Category:Technical docs