This tries to open the given file to use as stdin, and if it fails,
for any reason, it uses /dev/null instead.
This is useful in cases where we would otherwise do either of these:
```fish
test -r /path/to/file
and string match foo < /path/to/file
cat /path/to/file 2>/dev/null | string match foo
```
This both makes it nicer and shorter, *and* helps with TOCTTOU - what if the file is removed/changed after the check?
The reason for reading /dev/null instead of a closed fd is that a closed fd will often cause an error.
In case opening /dev/null fails, it still skips the command.
That's really a last resort for when the operating system
has turned out to be a platypus and not a unix.
Fixes#4865
(cherry picked from commit df8b9b7095)
This introduces a feature flag, "test-require-arg", that removes builtin test's zero and one argument special modes.
That means:
- `test -n` returns false
- `test -z` returns true
- `test -x` with any other option errors out with "missing argument"
- `test foo` errors out as expecting an option
`test -n` returning true is a frequent source of confusion, and so we are breaking with posix in this regard.
As always the flag defaults to off and can be turned on. In future it will default to on and then eventually be made read-only.
There is a new FLOG category "deprecated-test", run `fish -d deprecated-test` and it will show any test call that would change in future.
This seems a bit better because it's what bind uses. To makes sure that
something like :kbd:`ctrl-x` looks good in HTML, remove the border from the
kbd style. Else both "ctrl" and "x" get small boxes which looks weird.
This is the last remnant of the old percent expansion.
It has the downsides of it, in that it is annoying to combine with
anything:
```fish
echo %self/foo
```
prints "%self/foo", not fish's pid.
We have introduced $fish_pid in 3.0, which is much easier to use -
just like a variable, because it is one.
If you need backwards-compatibility for < 3.0, you can use the
following shim:
```fish
set -q fish_pid
or set -g fish_pid %self
```
So we introduce a feature-flag called "remove-percent-self" to turn it
off.
"%self" will simply not be special, e.g. `echo %self` will print
"%self".
This committed the sin of introducing a concept by giving it two
names:
> An alias, or wrapper, around ``ls`` might look like this
The term "wrapper" doesn't pull its weight here. It's simpler to just
call them aliases throughout. We do use "a simple wrapping function"
in another place, but that's to define "alias", not as a separate name.
It reads nicer to not have the "see also" thing right in the first
paragraph. I'm not even done reading this, why are you sending me
elsewhere?
(of course if it's a hotlink on a specific word that's different)
I'm not sure if line continuations are covered anywhere else in the docs, but I
think the escapes section of the language page is a good place to mention them.
- Clean up the wording a little.
- Highlight the limitations of the "debugger" more clearly and don't mislead
people into thinking it's possible to really interactively set/remove
breakpoints except in select circumstances.
Sidenote: I can't believe we're using a markup language that doesn't support
nested inline markup. What a crying shame, rST!
