Implement $_ , the last argument to the previous command run

[jyn514]

bash treats $_ as 'the last argument to the previous command run`. I think it's unset for the first command. osh treats this as the name it was invoked with.

Expected behaviour:

$ ls INSTALL.txt 
INSTALL.txt
$ echo $_
INSTALL.txt

Actual behaviour:

$ ls INSTALL.txt
INSTALL.txt
$ echo $_
bin/osh

[andychu]

OK it looks like OSH does nothing, but it's inherited from the parent bash process! bash actually exports it for some reason.

Thanks for the report, keep them coming!

(Although personally I've never used $_, I always use !$ i.e. history expansion)

[Crestwave]

(Although personally I've never used $_, I always use !$ i.e. history expansion)

$_ is usually used as a temporary variable for parameter expansion in scripts. For example, to print the effective username, you could run the following:

: '\u'
printf '%s\n' "${_@P}"

[andychu]

OK I just wrote some tests, and this is implemented in both bash and zsh. For some reason I thought it was only an interactive thing but it's not.

#679 depends on it

[andychu]

FWIW after looking at the neofetch diff, I'm going to concentrate on the word eval quoting problems over this one...

There were only 2 usages -- it seems like the first was definitely questionable since you can use $1, and the second was also questionable since you can just have os= in every case clause.

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An ulterior motivation for not doing this is that I wanted to make $_ mean something else, e.g. maybe something like what it means in Perl.

In other words, I'm sort of biased against this feature, since I think it makes programs harder to read, and the 10K lines of neofetch didn't dissuade me of that...

Still if anyone wants to submit a patch, there are already test cases for it...

[Crestwave]

It is true that its uses are totally replaceable. However, the thing is that it is used (it's used several times in the pure bash bible, so even others might use it) and scripts will have to manually support Oil. I suppose it could be fine if @dylanaraps agrees not to use it, though.