这就是我到目前为止所拥有的。这不是您所需要的一切吗？我不断收到错误“错误：未绑定模块标准”
let r file =
let chan = open_in file in
Std.input_list (chan)
仅使用标准库的命令式解决方案：
let read_file filename =
let lines = ref [] in
let chan = open_in filename in
try
while true; do
lines := input_line chan :: !lines
done; !lines
with End_of_file ->
close_in chan;
List.rev !lines ;;
如果您有 Batteries-included 库，您可以将文件读入 Enum.t 并按如下方式迭代它：
let filelines = File.lines_of filename in
Enum.iter ( fun line -> (*Do something with line here*) ) filelines
如果您安装了 OCaml Core 库，那么就很简单：
open Core.Std
let r file = In_channel.read_lines file
如果您安装了
corebuildcorebuild filename.byte
如果您的代码位于名为
filename.ml如果您没有 OCaml Core，或者不想安装它，或者其他一些标准库实现，那么，当然，您可以使用普通 OCaml 的标准库来实现它。在
input_linePervasivesin_channellet read_lines name : string list =
let ic = open_in name in
let try_read () =
try Some (input_line ic) with End_of_file -> None in
let rec loop acc = match try_read () with
| Some s -> loop (s :: acc)
| None -> close_in ic; List.rev acc in
loop []
此实现使用递归，对于 OCaml 编程来说更加自然。
这是一个简单的递归解决方案，它不会累积行或使用外部库，而是让您读取一行，使用函数处理它，递归读取下一行直到完成，然后干净地退出。 exit 函数关闭打开的文件句柄并向调用程序发出成功信号。
let read_lines file process =
let in_ch = open_in file in
let rec read_line () =
let line = try input_line in_ch with End_of_file -> exit 0
in (* process line in this block, then read the next line *)
process line;
read_line ();
in read_line ();;
read_lines some_file print_endline;;
这将读取文件的行并打印每一行：
open Core.Std
let handle_line line =
printf "Your line: %s \n" line
let () =
let file_to_read = "./file_to_read.txt" in
let lines = In_channel.read_lines file_to_read in
List.iter ~f: handle_line lines
这是使用 Scanf 的递归解决方案：
let read_all_lines file_name =
let in_channel = open_in file_name in
let rec read_recursive lines =
try
Scanf.fscanf in_channel "%[^\r\n]\n" (fun x -> read_recursive (x :: lines))
with
End_of_file ->
lines in
let lines = read_recursive [] in
let _ = close_in_noerr in_channel in
List.rev (lines);;
用途：
let all_lines = read_all_lines "input.txt";;
但是，我更喜欢逐行流式传输：
let make_reader file_name =
let in_channel = open_in file_name in
let closed = ref false in
let read_next_line = fun () ->
if !closed then
None
else
try
Some (Scanf.fscanf in_channel "%[^\r\n]\n" (fun x -> x))
with
End_of_file ->
let _ = close_in_noerr in_channel in
let _ = closed := true in
None in
read_next_line;;
用途：
let read_next = make_reader "input.txt";;
let next_line = read_next ();;
并且可能有点锦上添花：
type reader = {read_next : unit -> string option};;
let make_reader file_name =
let in_channel = open_in file_name in
let closed = ref false in
let read_next_line = fun () ->
if !closed then
None
else
try
Some (Scanf.fscanf in_channel "%[^\r\n]\n" (fun x -> x))
with
End_of_file ->
let _ = close_in_noerr in_channel in
let _ = closed := true in
None in
{read_next = read_next_line};;
用途：
let r = make_reader "input.txt";;
let next_line = r.read_next ();;
希望这有帮助！
使用 Scanf“字符串指示”和零宽度字符从文件中读取行的另一种样式。这就像传统的命令式风格。
open Scanf
open Printf
(* little helper functions *)
let id x = x
let const x = fun _ -> x
let read_line file = fscanf file "%s@\n" id
let is_eof file = try fscanf file "%0c" (const false) with End_of_file -> true
let _ =
let file = open_in "/path/to/file" in
while not (is_eof file) do
let s = read_line file in
(* do something with s *)
printf "%s\n" s
done;
close_in file
注意：
这只是将整个文件加载到一个大字符串中，但稍后您可以随时将其拆分为一个列表。
let read_file path =
let channel = open_in path in
let buffer = Buffer.create 1024 in
let rec go () =
try
Buffer.add_channel buffer channel 1024; go ()
with End_of_file ->
Buffer.contents buffer in
go ();;
我知道这是一个老问题，但是还有另一个有趣的递归变体（至少在我看来），没有库或逆转：
let read_lines filename =
let f = open_in filename in
let rec loop () =
try
let next = input_line f in
next :: loop ()
with End_of_file ->
close_in f;
[]
in loop ()
请注意，
let next = ...2022年3月28日发布的OCaml版本4.14.0的标准库中有新模块
In_channelOut_channel现在，我们可以轻松地从文件中读取内容，如下所示：
# let conx = In_channel.with_open_text "example.dat" In_channel.input_all;;
val conx : string = "hey!\nworld"
说，
example.dathey!
world
要基于 @alwaysday1 的解决方案，您可以创建一个简单的函数，使用 OCaml 4.14.0 中的
In_channelStrlet read_lines file =
In_channel.with_open_text file In_channel.input_all
|> Str.(split (regexp "\n"))
这将生成文件中所有行的列表。
回复晚了，不过好在OCaml标准库正在不断完善。从 OCaml 5.1 开始，人们可以执行以下操作：
let read_lines (file_name : string) : string list =
In_channel.with_open_text file_name (In_channel.input_lines)
In_channel