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I have a sample text:
123
456
If I delete the first line, why does
:silent! execute 'g/123/d' | execute 'g/456/d'
work while
:silent! g/123/d | g/456/d
doesn't work, unless I bring back the first line, so that both patterns are matched?
Shouldn't :silent! make it execute completely (by suppressing Neovim's Error messages) regardless of whether it succeeds in finding a match or not?
Or maybe I'm misunderstanding the mechanics of | or <Bar> aka pipe character in this context?
In your example you have a file with a single line 456. If you run:
:g/123/d | g/456/d
you get a Pattern not found message on the first command and the second one does not run. It is a message and not an error (see comments), hence that is not the reason why the second command is not running. From Neovim's :help :bar:
Note that this is confusing (inherited from Vi): With ":g" the '|' is included in the command, with ":s" it is not.
To be able to use another command anyway, use the ":execute" command.
As @D.BenKnoble pointed out, the execute is making sure that the :g does not swallow the pipe. By using execute, you are doing as instructed by the documentation.
:s/foo/bar fails, so does :execute 's/foo/bar' | echom 'hi' without echoing hi. The difference seems primarily to be that :g/123/d | g/456/d considers d | g/456/d as the on-each-line command (:help :bar). the execute prevents :g from eating the bar, so you have two separate commands.
execute does stop on error of the input command. Moreover, from the help on search-commands: 'When no match is found you get the error: E486 Pattern not found Note that for the :global command, you get a normal message "Pattern not found", for Vi compatibility.' So s throws an error but g only prints "Pattern not found". I will look into this a bit more and edit my answer.
Jun 21 at 9:16
:silent! command in my original line: :silent! g/123/d | g/456/d that you and @D.BenKnoble seem to have overlooked. This should change how the line is executed, shouldn't it? After all, errors & other messages are being suppressed, so I think | shouldn't stop execution no matter what is the outcome, whether a pattern match is found or not.
123, do] [delete, then if that succeeded, [for each line containing 456, do [delete]]]. With execute, you have [silently] [for each line containing 123, do] [delete], then if that succeeded (which it will because of [silently]), [for each line containing 456, do] [delete]. See the difference?
The difference seems primarily to be that :g/123/d | g/456/d considers d | g/456/d as the on-each-line command (:help :bar). The :execute prevents :global from eating the bar, so you have two separate commands. (Details on the structure at the end.)
This matters: in :g/123/d | g/456/d, if 123 is not found, _none of d | g/456/d runs. But in :execute 'g/123/d' | execute 'g/456/d', if 123, is not found, first d is not run, then execute 'g/456/d' is not run because the previous command errored.
Finally, by prefixing the first command with :silent! (:silent does not consume |, so only the first command is silenced), you guarantee that execute 'g/456/d' runs no matter what.
A small representation of the parsing differences:
:silent! g/123/d | g/456/d: [silently] [for each line containing 123, do] [delete, then if that succeeded, [for each line containing 456, do [delete]]]:silent! execute 'g/123/d' | execute 'g/456/d': [[silently] [for each line containing 123, do] [delete]], then if that succeeded (which it will because of [silently]), [[for each line containing 456, do] [delete]].Extract from :help :bar to justify parsing:
These commands see the '|' as their argument, and can therefore not be
followed by another Vim command:
[…]
:global
:help :bar helped me understand your statement "The difference seems primarily to be that (...)", namely the following: These commands see the '|' as their argument, and can therefore not be followed by another Vim command (a list of commands follows): (...) :global (:g) (...) Once again, RTFM does wonders!