From: krewat@kilonet.net (Arthur Krewat)
Subject: [TUHS] dmr note on BSD's sins
Date: Wed, 3 May 2017 09:09:52 -0400 [thread overview]
Message-ID: <58cf42d9-b153-7831-5012-16e5544faf2f@kilonet.net> (raw)
In-Reply-To: <CAEoi9W5hz74awSWhR5Mi3pgKKkFxo4OGOS8hGzbxSC6Sq2XMXg@mail.gmail.com>
Not to mention, you can cat multiple files - as in concatenate :)
On 5/3/2017 8:54 AM, Dan Cross wrote:
> On Tue, May 2, 2017 at 8:59 PM, Dave Horsfall <dave at horsfall.org
> <mailto:dave at horsfall.org>> wrote:
>
> On Tue, 2 May 2017, Doug McIlroy wrote:
> > With Steve's eloquent grump and cat -v on the table, I can't help
> > re-citing the peerless cardinal sin of
> > less --help | wc
>
> Speaking of "cat", what really drives me nuts is "cat file | cmd"...
>
> What's wrong with "cmd < file" (or to really confuse newbies, "< file
> cmd")?
>
>
> Ooo! Ooo! Ooo! I've actually got something for this....
>
> First of all, there's nothing strictly speaking *wrong* with 'cmd <
> file' and cat 'cat file | cmd' is definitely overused, often
> unintentionally and out of ignorance.
>
> However, 'cmd <file' requires 'file' as a literal string in the
> command; `cat` can be useful when the file parameter may be optional.
> E.g., 'cat "$@" | ...'. Now some folks will immediately respond by
> saying, "many commands will read from stdin if a filename is not
> presented on the command line, so why not, 'cmd "$@"'?" And that's
> certainly a valid question, to which I would answer that the semantics
> of a command sometimes subtly change when presented with one or more
> filenames as argument (e.g. 'grep'), so using `cat` may suppress that
> behavior if desired. "But `grep` has the `-h` option to tell it not to
> print the filename!" Yes, but `grep` is just *one command* and not
> *all* of them do. The point being that 'cat' in a pipeline has it's
> place, even if that place is rarely the place we see it.
>
> Another, related use to cover up one of the more odious of recent
> design decisions in Unix-like systems is to use `cat` at the *end* of
> the pipeline. Some programs change behavior if they know that they are
> writing into a tty; one can suppress that if one terminates the
> pipeline in `cat`. This is surely a case of mis-using a feature to
> mask a bug, but it's often useful regardless.
>
> - Dan C.
>
next prev parent reply other threads:[~2017-05-03 13:09 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-03 0:52 Doug McIlroy
2017-05-03 0:59 ` Dave Horsfall
2017-05-03 12:54 ` Dan Cross
2017-05-03 13:09 ` Arthur Krewat [this message]
2017-05-03 13:46 ` Michael Kjörling
2017-05-03 14:57 ` Clem Cole
2017-05-03 15:34 ` arnold
2017-05-03 15:44 ` Clem Cole
-- strict thread matches above, loose matches on Subject: below --
2017-05-03 13:41 Nemo
2017-05-03 22:18 ` Dave Horsfall
2017-05-04 14:59 ` Tim Bradshaw
2017-05-04 23:14 ` Larry McVoy
2017-05-05 14:01 ` Random832
2017-05-05 18:56 ` A. P. Garcia
2017-05-05 17:33 ` Tim Bradshaw
2017-05-01 17:25 ron minnich
2017-05-01 18:09 ` Toby Thain
2017-05-02 16:11 ` Steve Johnson
2017-05-02 16:39 ` Erik E. Fair
2017-05-02 16:43 ` ron minnich
2017-05-02 20:28 ` Diomidis Spinellis
[not found] ` <CAM4FNStH7KH6+ab0o_fYKfzutvPQ__0w0Zq5_6hk4AFP=+aSAw@mail.gmail.com>
2017-05-02 20:34 ` Daniel Camolês
2017-05-02 20:34 ` Steve Johnson
2017-05-02 21:22 ` Andy Kosela
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