On 01/26/15 23:18, Laurent Bercot wrote:
- execline: I'd like the addition of a new command, e.g. readvar, that
would allow to read the content/first line of a file into a variable.
IOW, something similar to importas (including an optional default
value), only instead of specifying an environment variable one would
give a file name to load the value from (in a similar manner as to what
s6-envdir does, only for one var/file and w/out actually using
environment variable).
How about
backtick -n SOMETHING { redirfd -r 0 FILE cat } import -U SOMETHING ?
Sure it's longer, but it's exactly what the readvar command would do.
You can even program the readvar command in execline. ;)
That looks good, except that I need a default value, in case the file
doesn't exist. If there's a way to work a default value in that case
then that'd be fine, yes.
...is there a way to add a default value if FILE doesn't exist?
If for some reason it's inconvenient for you, I can envision writing
something similar to readvar, but it *is* going to use the environment:
I've been trying to reduce the number of commands that perform
substitution themselves, so that passing state via the environment is
prioritized over rewriting the argv, and import is kind of the
one-stop-shop when you need substitution. I don't want to go back on
that intent and add another substituting command. Is it a problem for
you to use the environment ?
No it's not, it just felt unneeded when thinking of readvar, is all. But
i could combine it with import, as I said what I really want is to have
a default value if the file doesn't exist, instead of nothing/empty
string, skipping/not using the environment was/is not a requirement at all.
- s6-log: I think a new action to write to a file could be useful.
The problem with that is the whole design of s6-log revolves around
controlling the size of your logging space: no uncontrolled file
growth. Writing to a file would forfeit that.
What I'm considering, though, is to add a spawn a given program
action, like a !processor but every time a line is selected and triggers
that action. It would answer your need, and it would also answer
Patrick's need without fswatch. However, it would be dangerous: a
misconfiguration could uncontrollably spawn children. I'll do that when
I find a safe way to proceed.
Yeah that would work for me... I thought the writing to file action
was maybe more generic, but I get your point re: controlling the
logging size.
Running an external program would work for me just as well, yes. Looking
forward to this nice little addition.
(re: misconfiguration, in what way though? It could lead to the program
being triggered for each new line, but that doesn't mean uncontrollably
spawning children?
It might be a lot, but with a rotation every 4096 bytes one might
already have frequent calls to the processor, no?)
-j
