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(* Example from the documentation, this code is in public domain. *)
(* Implementation of the command, we just print the args. *)
type loc = bool * int
type verb = Verbose | Quiet
type follow = Name | Descriptor
let str = Printf.sprintf
let opt_str sv = function None -> "None" | Some v -> str "Some(%s)" (sv v)
let loc_str (rev, k) = if rev then str "%d" k else str "+%d" k
let follow_str = function Name -> "name" | Descriptor -> "descriptor"
let verb_str = function Verbose -> "verbose" | Quiet -> "quiet"
let tail lines follow verb pid files =
Printf.printf
"lines = %s\nfollow = %s\nverb = %s\npid = %s\nfiles = %s\n"
(loc_str lines) (opt_str follow_str follow) (verb_str verb)
(opt_str string_of_int pid) (String.concat ", " files)
(* Command line interface *)
open Cmdliner
let loc_arg =
let parse s =
try
if s <> "" && s.[0] <> '+'
then Ok (true, int_of_string s)
else Ok (false, int_of_string (String.sub s 1 (String.length s - 1)))
with Failure _ -> Error (`Msg "unable to parse integer")
in
let print ppf p = Format.fprintf ppf "%s" (loc_str p) in
Arg.conv ~docv:"N" (parse, print)
let lines =
let doc = "Output the last $(docv) lines or use $(i,+)$(docv) to start \
output after the $(i,N)-1th line."
in
Arg.(value & opt loc_arg (true, 10) & info ["n"; "lines"] ~docv:"N" ~doc)
let follow =
let doc = "Output appended data as the file grows. $(docv) specifies how \
the file should be tracked, by its $(b,name) or by its \
$(b,descriptor)."
in
let follow = Arg.enum ["name", Name; "descriptor", Descriptor] in
Arg.(value & opt (some follow) ~vopt:(Some Descriptor) None &
info ["f"; "follow"] ~docv:"ID" ~doc)
let verb =
let quiet =
let doc = "Never output headers giving file names." in
Quiet, Arg.info ["q"; "quiet"; "silent"] ~doc
in
let verbose =
let doc = "Always output headers giving file names." in
Verbose, Arg.info ["v"; "verbose"] ~doc
in
Arg.(last & vflag_all [Quiet] [quiet; verbose])
let pid =
let doc = "With -f, terminate after process $(docv) dies." in
Arg.(value & opt (some int) None & info ["pid"] ~docv:"PID" ~doc)
let files = Arg.(value & (pos_all non_dir_file []) & info [] ~docv:"FILE")
let cmd =
let doc = "Display the last part of a file" in
let man = [
`S Manpage.s_description;
`P "$(tname) prints the last lines of each $(i,FILE) to standard output. If
no file is specified reads standard input. The number of printed
lines can be specified with the $(b,-n) option.";
`S Manpage.s_bugs;
`P "Report them to <bugs@example.org>.";
`S Manpage.s_see_also;
`P "$(b,cat)(1), $(b,head)(1)" ]
in
let info = Cmd.info "tail" ~version:"v1.3.0" ~doc ~man in
Cmd.v info Term.(const tail $ lines $ follow $ verb $ pid $ files)
let main () = exit (Cmd.eval cmd)
let () = main ()
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