lua - 使用 Lua 将一些文本附加到文件的第一行

Question

如何使用 Lua 将一些文本添加到文件的第一行？

out = io.open('file.txt}','a')
out:write('Hello world. ')
out:write('This is different')
io.close(out)

我只知道如何使用上面的代码将内容附加到文件。

Answer 1

您可以像这样将文本添加到文件的第一行。

-- Open the file in r mode (don't modify file, just read)
local out = io.open('file.txt', 'r')

-- Fetch all lines and add them to a table
local lines = {}
for line in f:lines() do
    table.insert(lines, line)
end

-- Close the file so that we can open it in a different mode
out:close()

-- Insert what we want to write to the first line into the table
table.insert(lines, 1, "<what you want to write to the first line>\n")

-- Open temporary file in w mode (write data)
-- Iterate through the lines table and write each line to the file
local out = io.open('file.tmp.txt', 'w')
for _, line in ipairs(lines) do
    out:write(line)
end
out:close()

-- At this point, we should have successfully written the data to the temporary file

-- Delete the old file
os.remove('file.txt')

-- Rename the new file
os.rename('file.tmp.txt', 'file.txt')

我希望这被证明是有用的!如果它不能如您所愿地工作，请告诉我。

这里有一个关于 IO 库的很好的文档以供进一步引用。 http://lua-users.org/wiki/IoLibraryTutorial