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* Use more auxiliary functions, showing the record being passed in as an argument and out as a return * Returning a number from `return main()` does not do what one would expect (it's not equivalent to `os.exit`) * Do not reference snippets of the code itself in the markdown, makes it harder to maintain in sync * Uppercase-convert the input as a trivial example of data transformation between input and output * Use more descriptive variable/field names instead of comments * Do not use `""` as a sentinel value, as it is less idiomatic for Lua
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,68 +1,99 @@ | ||
| -- files/src/main.tl | ||
| -- Read content from STDIN or file; write content to STDOUT or file. | ||
| -- | ||
| -- build: cyan build | ||
| -- | ||
| -- usage: lua files.lua [-i <file>] [-o <file>] | ||
| -- | ||
| -- Reads content from STDIN or file; | ||
| -- writes content in uppercase to STDOUT or file. | ||
| ------------------------------------------------------------------------------- | ||
|
|
||
| -- record to hold file handles | ||
| local type Handles = record | ||
| i: FILE -- input | ||
| o: FILE -- output | ||
| local record Handles | ||
| input: FILE | ||
| output: FILE | ||
| end | ||
|
|
||
| -- a simple command-line parser | ||
| local function parse_arguments(args: {string}): string, string | ||
| local i_name, o_name: string, string | ||
| local err: string | ||
| local i = 1 | ||
| while i <= #args do | ||
| local a, b = args[i], args[i+1] | ||
| if a == "-i" then | ||
| if not b then | ||
| err = "-i name?" | ||
| else | ||
| i_name = b | ||
| i = i + 2 | ||
| end | ||
| elseif a == "-o" then | ||
| if not b then | ||
| err = "-o name?" | ||
| else | ||
| o_name = b | ||
| i = i + 2 | ||
| end | ||
| else | ||
| err = "unknown arg: " .. a | ||
| end | ||
| if err then | ||
| -- exit, giving a hint on the way out | ||
| error(err) | ||
| end | ||
| end | ||
| return i_name, o_name | ||
| end | ||
|
|
||
| -- create or return file handles | ||
| local function get_fd(name: string, mode: string, default: FILE): FILE, string | ||
| if not name then | ||
| return default | ||
| end | ||
|
|
||
| local fd, err = io.open(name, mode) | ||
| if not fd then | ||
| return nil, err | ||
| end | ||
|
|
||
| -- main ----------------------------------------------------------------------- | ||
| local function main(f: Handles): integer | ||
| local lines = f.i:read("a") | ||
| -- do work on input, then write it out -- | ||
| f.o:write(lines) | ||
| return 0 | ||
| return fd | ||
| end | ||
|
|
||
| -- get handles record | ||
| local function get_handles(input_name: string, output_name: string): Handles | ||
| local handles: Handles = {} | ||
| local err: string | ||
|
|
||
| -- command line --------------------------------------------------------------- | ||
| local fin, fout = "", "" -- input and output file names | ||
| local errstr = "" | ||
| local i = 1 | ||
| while i <= #arg do | ||
| local a, b = arg[i], arg[i+1] | ||
| if a == "-i" then | ||
| if not b then | ||
| errstr = "-i filename?" | ||
| else | ||
| fin = b | ||
| i = i + 2 | ||
| end | ||
| elseif a == "-o" then | ||
| if not b then | ||
| errstr = "-o filename?" | ||
| else | ||
| fout = b | ||
| i = i + 2 | ||
| end | ||
| else | ||
| errstr = "unknown arg: " .. a | ||
| end | ||
| if errstr ~= "" then -- exit, giving a hint on the way out | ||
| error(errstr) | ||
| end | ||
| handles.input, err = get_fd(input_name, "r", io.stdin) | ||
| if err then | ||
| error(err) | ||
| end | ||
|
|
||
| handles.output, err = get_fd(output_name, "w", io.stdout) | ||
| if err then | ||
| error(err) | ||
| end | ||
|
|
||
| return handles | ||
| end | ||
|
|
||
| -- create file handles, as needed | ||
| local handle: Handles = {} | ||
| if fin == "" then | ||
| handle.i = io.stdin | ||
| else | ||
| handle.i = assert(io.open(fin, "r")) | ||
| -- do some work using the file handles | ||
| local function process_handles(h: Handles) | ||
| local lines = h.input:read("*a") | ||
| h.input:close() | ||
|
|
||
| -- simple example of doing work on the input: | ||
| -- convert it to ASCII uppercase | ||
| lines = lines:upper() | ||
|
|
||
| h.output:write(lines) | ||
| h.output:close() | ||
| end | ||
| if fout == "" then | ||
| handle.o = io.stdout | ||
| else | ||
| handle.o = assert(io.open(fout, "w")) | ||
|
|
||
| local function main(args: {string}): integer | ||
| local input_name, output_name = parse_arguments(args) | ||
|
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||
| local h = get_handles(input_name, output_name) | ||
|
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| process_handles(h) | ||
|
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||
| os.exit(0) | ||
| end | ||
|
|
||
| -- launch the main function | ||
| return main(handle) | ||
| main(arg) |