by
Anonymous Coward
on 2019年11月08日 8時26分
(#3712646)
スラドの法則：英語の記事はリンクを張っても誰も読まない
Toby Thain wrote: > "Dennis Ritchie" wrote
>> Spurious. dd was always named after JCL dd cards. > > Alright, I'll bite: What did *that* "dd" stand for? I hesitate to leap in front of Dennis Ritchie, but ...
On IBM mainframes, programs are started by "submitting" them in JCL ("Job Control language") to JES, the Job Entry System.
One of the most important statements in JCL is the DD statement. DD stands for "Data Definition". It is used to define the data (duh ;-) that is used when the job is run - input files, output files etc.
JCL has a "unique" flavour; it is utterly unlike normal programming languages and is archane, cryptic, obscure, complex and rude. It is also ugly and stupid. However there is so much JCL in the world that, hell, we still have to live with it - even after thirty years of Unix ;-).
The Unix dd command copies data from one place to another, rather like a typical DD card in a JCL stack.
The "if=", "of=", "bs=", etc, parameters to the Unix dd command retain some of the characteristic syntactic idioms of JCL (not to say that the dd command is as ugly as JCL - it just has a faint echo of the JCL syntax).
For a mainframe guy, the dd command on Unix gives a nice homely touch.
>> Spurious. dd was always named after JCL dd cards.
>
> Alright, I'll bite: What did *that* "dd" stand for?
I hesitate to leap in front of Dennis Ritchie, but ...
Dennis Ritchieが「（cc由来説は）大嘘。JCLのdd文に由来する」と書いた記事に、
Toby Thainが「分かった。じゃあ『dd』ってのは何に由来するの？」と問う記事を書き、
それに対して、Andrew McLarenがJCLの説明を書いている記事だぞ。
disk direct？ (スコア:0)
disk directとかdirect diskとかdirect driveとか勝手に考えてた
Re:disk direct？ (スコア:2)
direct duplicate辺りかと思っていた。
Re:disk direct？ (スコア:1)
たぶん、外部記憶と関係するから device がからんでそう。でも、まず mt が来るだろうから disk は遠いと思うんだが。
Re: (スコア:0)
よく考えたことなかったけど、わしゃdirect dumpかな？と思ってた。でもたしかにマニュアルにはcopy and convertって書いてあるなあ。conv=noerrorばかり指定してて、本当のconvert目的で使ったことがないのだが…
Re: (スコア:0)
Sun-3 リアルタイム世代ですけど
device dumpの略あたりかな?と勝手に思ってましたわー
Re: (スコア:0)
JCLのDDが由来という説もあるらしいけど、じゃあJCLのDDはどこから来たのか？とやっぱり思うよね。
私の知ってるMVS互換OSではDDはファイル記述子と実際のデータセットを結びつける指示だった。
元をだとればdeviceなんちゃらだったと思われる。
だいたいあってるような気がする。
Re:disk direct？ (スコア:2, 参考になる)
スラドの法則：英語の記事はリンクを張っても誰も読まない
Toby Thain wrote:
> "Dennis Ritchie" wrote
>> Spurious. dd was always named after JCL dd cards.
>
> Alright, I'll bite: What did *that* "dd" stand for?
I hesitate to leap in front of Dennis Ritchie, but ...
On IBM mainframes, programs are started by "submitting" them in JCL ("Job
Control language") to JES, the Job Entry System.
One of the most important statements in JCL is the DD statement. DD stands
for "Data Definition". It is used to define the data (duh ;-) that is used
when the job is run - input files, output files etc.
JCL has a "unique" flavour; it is utterly unlike normal programming
languages and is archane, cryptic, obscure, complex and rude. It is also
ugly and stupid. However there is so much JCL in the world that, hell, we
still have to live with it - even after thirty years of Unix ;-).
The Unix dd command copies data from one place to another, rather like a
typical DD card in a JCL stack.
The "if=", "of=", "bs=", etc, parameters to the Unix dd command retain some
of the characteristic syntactic idioms of JCL (not to say that the dd
command is as ugly as JCL - it just has a faint echo of the JCL syntax).
For a mainframe guy, the dd command on Unix gives a nice homely touch.
Cheers
Andrew
Re:disk direct？ (スコア:5, 参考になる)
Toby Thain wrote:
> "Dennis Ritchie" wrote
>> Spurious. dd was always named after JCL dd cards.
>
> Alright, I'll bite: What did *that* "dd" stand for?
I hesitate to leap in front of Dennis Ritchie, but ...
Dennis Ritchieが「（cc由来説は）大嘘。JCLのdd文に由来する」と書いた記事に、
Toby Thainが「分かった。じゃあ『dd』ってのは何に由来するの？」と問う記事を書き、
それに対して、Andrew McLarenがJCLの説明を書いている記事だぞ。
Re: (スコア:0)
disk deathtroyerの略
Re:disk direct？ (スコア:1)
Re: (スコア:0)
destroyerじゃないのか……？
Re: (スコア:0)
Winユーザーの俺がFF外から失礼します。
UNIX/Linux には DD (Disk Dump) という便利なツールがありまして、それを Windows に移植したのが・・・
っていうお話を信じていた俺がFF外から失礼しました。