history puzzle

history puzzle

[Ray Andrews]

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Trying to do fancier things with history I'm clearly not understanding 
something.  Doc says '^' is first word in a history entry and '$' is the 
last. But:

% history -m "^" 1                  # Shows everything
% history -m "^nosuchstring" 1      # Also shows everything
% history -m "$" 1                  # Shows nothing

... so I'm obviously missing something.

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Re: history puzzle

[Mark J. Reed]

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What's "history -m"? Doesn't that just look for items in the history
containing "-m"?

"Word" sounds like you're reading about expansions, as in:

!! - most recent command
!!:$ - last word of most recent command
!!:^ - same as :1, first argument word of most recent command
!!:0 - just the command name of most recent command

Mark J. Reed <markjreed@gmail.com>


On Tue, Jun 4, 2024 at 14:01 Ray Andrews <rayandrews@eastlink.ca> wrote:

> Trying to do fancier things with history I'm clearly not understanding
> something.  Doc says '^' is first word in a history entry and '$' is the
> last. But:
>
> % history -m "^" 1                  # Shows everything
> % history -m "^nosuchstring" 1      # Also shows everything
> % history -m "$" 1                  # Shows nothing
>
> ... so I'm obviously missing something.
>
>

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Re: history puzzle

[Kannan Varadhan]

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Aren't you basically asking zsh to show you empty strings so nothing comes back?

--
Reply to: Kannan@ieee.org
________________________________
From: Ray Andrews <rayandrews@eastlink.ca>
Sent: Tuesday, June 4, 2024 11:00 AM
To: Zsh Users
Subject: history puzzle

Trying to do fancier things with history I'm clearly not understanding something.  Doc says '^' is first word in a history entry and '$' is the last. But:

% history -m "^" 1                  # Shows everything
% history -m "^nosuchstring" 1      # Also shows everything
% history -m "$" 1                  # Shows nothing

... so I'm obviously missing something.  


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Re: history puzzle

[Lawrence Velázquez]

On Tue, Jun 4, 2024, at 2:12 PM, Mark J. Reed wrote:
> What's "history -m"? Doesn't that just look for items in the history 
> containing "-m"?

It's the same as "fc -lm": it lists history events that are within
the (explicitly or implicitly) specified range and that match the
pattern given as the option-argument to -m.

-- 
vq

Re: history puzzle

[Ray Andrews]

On 2024-06-04 11:12, Mark J. Reed wrote:
> What's "history -m"? Doesn't that just look for items in the history 
> containing "-m"?
The Devil!  Had that in my function for years, thought it meant 'pattern 
following'.  Nuts, it works:

5 /aWorking/Zsh/Source/Wk 1 % history -rn "grep*" 1
fc: event not found: grep*

5 /aWorking/Zsh/Source/Wk 1 % history -rnm "grep*" 1
grep c52f */idProduct
grep c52f
grep c349 */idProduct
...

... but I can't find it in the doc :(  A few examples would be so helpful.

Re: history puzzle

[Ray Andrews]

On 2024-06-04 12:28, Lawrence Velázquez wrote:
> On Tue, Jun 4, 2024, at 2:12 PM, Mark J. Reed wrote:
>> What's "history -m"? Doesn't that just look for items in the history
>> containing "-m"?
> It's the same as "fc -lm": it lists history events that are within
> the (explicitly or implicitly) specified range and that match the
> pattern given as the option-argument to -m.
Well that's a relief to hear.  So I'm not crazy.  My function works 
fine.  I'm now just trying to figure out this "^" thing.


>

Re: history puzzle

[Lawrence Velázquez]

On Tue, Jun 4, 2024, at 3:52 PM, Ray Andrews wrote:
> Well that's a relief to hear.  So I'm not crazy.  My function works 
> fine.  I'm now just trying to figure out this "^" thing.

Look at the "FILENAME GENERATION" section of zshexpn(1).

	% history -m "^" 1                  # Shows everything
	% history -m "^nosuchstring" 1      # Also shows everything

With EXTENDED_GLOB set, "^" matches anything except the empty string,
and "^nosuchstring" matches anything except the string "nosuchstring".

	% history -m "$" 1                  # Shows nothing

The character "$" is not special in patterns, so this only matches
the string "$".

-- 
vq

Re: history puzzle

[Lawrence Velázquez]

On Tue, Jun 4, 2024, at 3:49 PM, Ray Andrews wrote:
> On 2024-06-04 11:12, Mark J. Reed wrote:
>> What's "history -m"? Doesn't that just look for items in the history 
>> containing "-m"?
> The Devil!  Had that in my function for years, thought it meant 'pattern 
> following'.  Nuts, it works:
>
> 5 /aWorking/Zsh/Source/Wk 1 % history -rn "grep*" 1
> fc: event not found: grep*
>
> 5 /aWorking/Zsh/Source/Wk 1 % history -rnm "grep*" 1
> grep c52f */idProduct
> grep c52f
> grep c349 */idProduct
> ...
>
> ... but I can't find it in the doc :(  A few examples would be so helpful.

See the description of "fc" in zshbuiltins(1).  No examples, though.

-- 
vq

Re: history puzzle

[Mark J. Reed]

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What the . . . oh, I had *history* aliased for some reason, to *history -t
%FT%T 0*. Convenient when I type it by itself, but too late for *-m* by the
end of it; I so rarely use the command that I didn't notice I'd restricted
myself that way. Sorry for the added confusion.

(I replaced it with a function that only adds those arguments if I didn't
supply any already.)

I still think from Ray's mention of "words" that he was reading
documentation about history expansion rather than pattern-matching.

So, OK, *-m* option restricts the list of history entries printed out to
those matching the pattern. The argument is a glob pattern of the sort used
to match files, not a regular expression. Even if it were a regular
expression, though, *^ * and *$* would still match everything, since every
string has a beginning and an end. So I'm not clear what your goal was.

If you have *extendedglob* turned on, then *^ *is negation; *^foo* matches
anything that doesn't match *foo*, so *^* again matches everything. If you
don't have *extendedglob* turned on, it's not special at all, and *^* looks
for an entry exactly equal to nothing but "*^*".  And *$* is not special
either way, so that is again looking for an entry consisting of nothing but
a single dollar sign, and not surprisingly failing to find one.



On Tue, Jun 4, 2024 at 4:21 PM Lawrence Velázquez <larryv@zsh.org> wrote:

> On Tue, Jun 4, 2024, at 3:49 PM, Ray Andrews wrote:
> > On 2024-06-04 11:12, Mark J. Reed wrote:
> >> What's "history -m"? Doesn't that just look for items in the history
> >> containing "-m"?
> > The Devil!  Had that in my function for years, thought it meant 'pattern
> > following'.  Nuts, it works:
> >
> > 5 /aWorking/Zsh/Source/Wk 1 % history -rn "grep*" 1
> > fc: event not found: grep*
> >
> > 5 /aWorking/Zsh/Source/Wk 1 % history -rnm "grep*" 1
> > grep c52f */idProduct
> > grep c52f
> > grep c349 */idProduct
> > ...
> >
> > ... but I can't find it in the doc :(  A few examples would be so
> helpful.
>
> See the description of "fc" in zshbuiltins(1).  No examples, though.
>
> --
> vq
>
>

-- 
Mark J. Reed <markjreed@gmail.com>

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Re: history puzzle

[Ray Andrews]

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On 2024-06-04 13:19, Lawrence Velázquez wrote:
> See the description of "fc" in zshbuiltins(1). No examples, though.

I was reading 'info zsh history' ... definitely says '^' is first word 
and '$' is last word, so I seem to have the wrong doc.  Come to think of 
it, I couldn't make sense of very much of it, so maybe that's the reason.

So the pattern matching follows globbing rules?  Ok, that makes sense.  
Now that I know where to look it should go more smoothly. Tx.




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Re: history puzzle

[Ray Andrews]

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On 2024-06-04 13:37, Mark J. Reed wrote:
> What the . . . oh, I had *history* aliased for some reason, to 
> *history -t %FT%T 0*. Convenient when I type it by itself, but too 
> late for *-m* by the end of it; I so rarely use the command that I 
> didn't notice I'd restricted myself that way. Sorry for the added 
> confusion.
Lawrence caught it before I went and killed myself.  Seriously you 
haven't lead me astray very often.
>
> (I replaced it with a function that only adds those arguments if I 
> didn't supply any already.)
>
> I still think from Ray's mention of "words" that he was reading 
> documentation about history expansion rather than pattern-matching.

I think that's what's happening.  'history' refers to the 'topic' and 
not the command.


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Re: history puzzle

[Lawrence Velázquez]

On Tue, Jun 4, 2024, at 7:48 PM, Ray Andrews wrote:
> On 2024-06-04 13:19, Lawrence Velázquez wrote:
>> See the description of "fc" in zshbuiltins(1). No examples, though. 
> I was reading 'info zsh history'

That shows the "History Expansion" section of the manual, which
does not mention the "history" builtin at all.

-- 
vq

Re: history puzzle

[Ray Andrews]

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On 2024-06-04 17:33, Lawrence Velázquez wrote:
> I was reading 'info zsh history'
> That shows the "History Expansion" section of the manual, which
> does not mention the "history" builtin at all.
>
Ok, at least that's clear.  I should be using 'info zshbuiltins'. 
'History Expansion' ... I'm taking that to be what the history command 
does so ... actually now that I look closely, it's obviously the wrong 
place.  And 'run-help history' goes somewhere else entirely.

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Re: history puzzle

[Mark J. Reed]

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On Tue, Jun 4, 2024 at 10:01 PM Ray Andrews <rayandrews@eastlink.ca> wrote:

>
>
> On 2024-06-04 17:33, Lawrence Velázquez wrote:
>
> I was reading 'info zsh history'
>
> That shows the "History Expansion" section of the manual, which
> does not mention the "history" builtin at all.
>
>
> Ok, at least that's clear.  I should be using 'info zshbuiltins'.
> 'History Expansion' ... I'm taking that to be what the history command does
> so ... actually now that I look closely, it's obviously the wrong place.
> And 'run-help history' goes somewhere else entirely.
>

The term "history expansion" refers to the expansion of references into the
command history. Those start with *!, *for example:

*zsh% vi path/to/some/file*
*zsh% gcc !$ # compile the file I just edited*

In general, the *!* is followed by a selector that determines which item
from the history you want to copy from. This can be an item number (which
matches the one shown by *history*/*fc -l*), another *! *(which means the
most recent command), or a prefix string (which refers to the most recent
command starting with that prefix, e.g. *!ls* to refer to the most recent
*ls* command). The selector can be followed by modifiers to restrict the
expansion to just part of the command: *:0 *for the command name, *:** for
the arguments without the command name, *:$* for just the last argument,
etc. The *!!:$* expression (last word of the last command) is so common
that it got its own shortcut, the *!$* I used above.

History expansion is purely an interactive command-line feature; it doesn't
work in scripts. If you need to access the history programmatically, use
the *fc* command (or *history*, which is equivalent to *fc -l*).

Anyway, that's what you were reading about. :)
--
Mark J. Reed <markjreed@gmail.com>

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Re: history puzzle

[Ray Andrews]

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On 2024-06-05 08:53, Mark J. Reed wrote:
>
> History expansion is purely an interactive command-line feature; it 
> doesn't work in scripts. If you need to access the history 
> programmatically, use the *fc* command (or *history*, which is 
> equivalent to *fc -l*).
>
> Anyway, that's what you were reading about. :)

I wish I could kill the whole thread, it was a misunderstanding from the 
getgo.  Not the first time I've ended up barking up entirely the wrong 
tree.  And with hindsight it is obvious I wasn't looking at a command -- 
but I'm so used to being baffled by the manual that I took it as normal ;-)


> --
> Mark J. Reed <markjreed@gmail.com>

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