我将所有 tex 文件保存在 Dropbox 目录中，但不同的计算机（所有基于 Windows 的计算机）都有不同的用户名，因此我想在模板中定义一个命令，即 Dropbox 路径，我可以将以下命令的路径附加到该路径中，例如
\includegraphics{\Dropbox/Figures/fig1}
\input{\Dropbox/Macros/math_commands}
从Dropbox 网站我发现 Dropbox 路径可以从 JSON 文件中读取
%LOCALAPPDATA%\Dropbox\info.json
所以我想解析该文件（我的文件只包含一个个人账户，但如果 .json 文件包含其他账户，则可能需要指定这一点）并定义一个新命令
\newcommand{\Dropbox}{%path from the json%}
关于在 LaTeX 中解析 JSON 的先前问题是关于打印内容，我不知道如何使其适应我的用例。
如果有必要，我会通过 latexmk 使用 lualatex。
答案1
可以使用 Lua 来完成。准备一个名为 的文件，dropboxpath.lua其中包含以下代码：
json = dofile("json.lua")
function get_dropbox_folder(filename)
-- The folder is different in windows and unix/osx
if filename == nil then
filename = os.getenv("LOCALAPPDATA")
end
if filename == nil then
filename = os.getenv("HOME") .. "/.dropbox/info.json"
else
filename = filename .. "/Dropbox/info.json"
end
jsonfile = io.open(filename)
config = jsonfile:read("*all")
return (json.parse(config)["personal"]["path"])
end
在同一文件夹中下载代码https://gist.github.com/tylerneylon/59f4bcf316be525b30ab（为了方便起见，我在这个答案的末尾重现了它），文件名为json.lua。
然后，您可以按照以下示例使用所有这些：
\documentclass{article}
\directlua{dofile("dropboxpath.lua")}
\edef\Dropbox{\directlua{tex.print(get_dropbox_folder())}}
\begin{document}
The Dropbox folder in this machine is \Dropbox.
\end{document}
结果：
免责声明我在 Linux 和 OSX 上测试了此代码，在这两种情况下都可以正常工作。我没有在 Windows 上测试过，我不确定在这种情况下路径是否应该使用\而不是。/
附件. 代碼json.lua：
--[[ json.lua
A compact pure-Lua JSON library.
The main functions are: json.stringify, json.parse.
## json.stringify:
This expects the following to be true of any tables being encoded:
* They only have string or number keys. Number keys must be represented as
strings in json; this is part of the json spec.
* They are not recursive. Such a structure cannot be specified in json.
A Lua table is considered to be an array if and only if its set of keys is a
consecutive sequence of positive integers starting at 1. Arrays are encoded like
so: `[2, 3, false, "hi"]`. Any other type of Lua table is encoded as a json
object, encoded like so: `{"key1": 2, "key2": false}`.
Because the Lua nil value cannot be a key, and as a table value is considerd
equivalent to a missing key, there is no way to express the json "null" value in
a Lua table. The only way this will output "null" is if your entire input obj is
nil itself.
An empty Lua table, {}, could be considered either a json object or array -
it's an ambiguous edge case. We choose to treat this as an object as it is the
more general type.
To be clear, none of the above considerations is a limitation of this code.
Rather, it is what we get when we completely observe the json specification for
as arbitrary a Lua object as json is capable of expressing.
## json.parse:
This function parses json, with the exception that it does not pay attention to
\u-escaped unicode code points in strings.
It is difficult for Lua to return null as a value. In order to prevent the loss
of keys with a null value in a json string, this function uses the one-off
table value json.null (which is just an empty table) to indicate null values.
This way you can check if a value is null with the conditional
`val == json.null`.
If you have control over the data and are using Lua, I would recommend just
avoiding null values in your data to begin with.
--]]
local json = {}
-- Internal functions.
local function kind_of(obj)
if type(obj) ~= 'table' then return type(obj) end
local i = 1
for _ in pairs(obj) do
if obj[i] ~= nil then i = i + 1 else return 'table' end
end
if i == 1 then return 'table' else return 'array' end
end
local function escape_str(s)
local in_char = {'\\', '"', '/', '\b', '\f', '\n', '\r', '\t'}
local out_char = {'\\', '"', '/', 'b', 'f', 'n', 'r', 't'}
for i, c in ipairs(in_char) do
s = s:gsub(c, '\\' .. out_char[i])
end
return s
end
-- Returns pos, did_find; there are two cases:
-- 1. Delimiter found: pos = pos after leading space + delim; did_find = true.
-- 2. Delimiter not found: pos = pos after leading space; did_find = false.
-- This throws an error if err_if_missing is true and the delim is not found.
local function skip_delim(str, pos, delim, err_if_missing)
pos = pos + #str:match('^%s*', pos)
if str:sub(pos, pos) ~= delim then
if err_if_missing then
error('Expected ' .. delim .. ' near position ' .. pos)
end
return pos, false
end
return pos + 1, true
end
-- Expects the given pos to be the first character after the opening quote.
-- Returns val, pos; the returned pos is after the closing quote character.
local function parse_str_val(str, pos, val)
val = val or ''
local early_end_error = 'End of input found while parsing string.'
if pos > #str then error(early_end_error) end
local c = str:sub(pos, pos)
if c == '"' then return val, pos + 1 end
if c ~= '\\' then return parse_str_val(str, pos + 1, val .. c) end
-- We must have a \ character.
local esc_map = {b = '\b', f = '\f', n = '\n', r = '\r', t = '\t'}
local nextc = str:sub(pos + 1, pos + 1)
if not nextc then error(early_end_error) end
return parse_str_val(str, pos + 2, val .. (esc_map[nextc] or nextc))
end
-- Returns val, pos; the returned pos is after the number's final character.
local function parse_num_val(str, pos)
local num_str = str:match('^-?%d+%.?%d*[eE]?[+-]?%d*', pos)
local val = tonumber(num_str)
if not val then error('Error parsing number at position ' .. pos .. '.') end
return val, pos + #num_str
end
-- Public values and functions.
function json.stringify(obj, as_key)
local s = {} -- We'll build the string as an array of strings to be concatenated.
local kind = kind_of(obj) -- This is 'array' if it's an array or type(obj) otherwise.
if kind == 'array' then
if as_key then error('Can\'t encode array as key.') end
s[#s + 1] = '['
for i, val in ipairs(obj) do
if i > 1 then s[#s + 1] = ', ' end
s[#s + 1] = json.stringify(val)
end
s[#s + 1] = ']'
elseif kind == 'table' then
if as_key then error('Can\'t encode table as key.') end
s[#s + 1] = '{'
for k, v in pairs(obj) do
if #s > 1 then s[#s + 1] = ', ' end
s[#s + 1] = json.stringify(k, true)
s[#s + 1] = ':'
s[#s + 1] = json.stringify(v)
end
s[#s + 1] = '}'
elseif kind == 'string' then
return '"' .. escape_str(obj) .. '"'
elseif kind == 'number' then
if as_key then return '"' .. tostring(obj) .. '"' end
return tostring(obj)
elseif kind == 'boolean' then
return tostring(obj)
elseif kind == 'nil' then
return 'null'
else
error('Unjsonifiable type: ' .. kind .. '.')
end
return table.concat(s)
end
json.null = {} -- This is a one-off table to represent the null value.
function json.parse(str, pos, end_delim)
pos = pos or 1
if pos > #str then error('Reached unexpected end of input.') end
local pos = pos + #str:match('^%s*', pos) -- Skip whitespace.
local first = str:sub(pos, pos)
if first == '{' then -- Parse an object.
local obj, key, delim_found = {}, true, true
pos = pos + 1
while true do
key, pos = json.parse(str, pos, '}')
if key == nil then return obj, pos end
if not delim_found then error('Comma missing between object items.') end
pos = skip_delim(str, pos, ':', true) -- true -> error if missing.
obj[key], pos = json.parse(str, pos)
pos, delim_found = skip_delim(str, pos, ',')
end
elseif first == '[' then -- Parse an array.
local arr, val, delim_found = {}, true, true
pos = pos + 1
while true do
val, pos = json.parse(str, pos, ']')
if val == nil then return arr, pos end
if not delim_found then error('Comma missing between array items.') end
arr[#arr + 1] = val
pos, delim_found = skip_delim(str, pos, ',')
end
elseif first == '"' then -- Parse a string.
return parse_str_val(str, pos + 1)
elseif first == '-' or first:match('%d') then -- Parse a number.
return parse_num_val(str, pos)
elseif first == end_delim then -- End of an object or array.
return nil, pos + 1
else -- Parse true, false, or null.
local literals = {['true'] = true, ['false'] = false, ['null'] = json.null}
for lit_str, lit_val in pairs(literals) do
local lit_end = pos + #lit_str - 1
if str:sub(pos, lit_end) == lit_str then return lit_val, lit_end + 1 end
end
local pos_info_str = 'position ' .. pos .. ': ' .. str:sub(pos, pos + 10)
error('Invalid json syntax starting at ' .. pos_info_str)
end
end
return json
更新
根据OP，上述代码需要修改才能在Windows下工作（将文件夹分隔符更改为\）。
.lua此外，如果文件没有与主文档存储在同一个文件夹中，它就不起作用。
以下代码解决了这两个问题：
-- This is dropboxpath.lua
json = dofile(kpse.find_file("json.lua"))
function get_dropbox_folder(filename)
if filename == nil then
filename = os.getenv("LOCALAPPDATA")
end
if filename == nil then
filename = os.getenv("HOME") .. "/.dropbox/info.json"
else
filename = filename .. "/Dropbox/info.json"
end
jsonfile = io.open(filename)
config = jsonfile:read("*all")
path = json.parse(config)["personal"]["path"]
path = string.gsub(path, "\\", "/")
return (path)
end
将lua的加载和\Dropbox命令的定义隐藏在单独的.sty文件中：
% This is dropboxpath.sty
\directlua{dofile(kpse.find_file('dropboxpath.lua'))}
\edef\Dropbox{\directlua{tex.print(get_dropbox_folder())}}
新的“main.tex”更简单：
% This is dropboxtest.tex
\documentclass{article}
\usepackage{dropboxpath}
\begin{document}
The Dropbox folder in this machine is \Dropbox.
\end{document}