Re: Reading rc.conf from C programs?

[Jordan K Hubbard]

There's no canned code for doing this, though sysinstall has some very basic parsing routines for reading/writing rc.conf variables you could certain crib from. It sounds like that "thefish" utility someone else mentioned has an even more exotic parser, though I haven't compared the two implementations. The readConfigFile() routine in sysinstall simply reads the configuration data into a fixed-size array, so it's pretty braindead.

- Jordan

On Wednesday, January 1, 2003, at 01:51 PM, Tim Kientzle wrote:

I'm trying to figure out how to read and use
/etc/rc.conf configuration variables from within
a C program.  The standard technique, of course,
is to use a shell-script wrapper and pass the
extracted values to the C program on the command
line.  But I want access to _all_ of the rc.conf
variables, not just a couple of them, and I don't
see any reasonable way to accomplish that with a
shell wrapper.

One approach would embed /bin/sh and drive that
from my program.  (E.g., tell the embedded interpreter
to read and interpret the config file, then
programmatically query the config variables.)
It's not clear to me how simple it would be to
build an embeddable /bin/sh.

Alternatively, I suppose I could fire up /bin/sh via
popen and drive it from my program (passing 'echo $var'
to query variables, etc.).  But I'm not entirely
convinced this would work; what if a variable value has
a newline in it, for example?

Has anyone done anything like this before?

Thanks,

Tim Kientzle


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--
Jordan K. Hubbard
Engineering Manager, BSD technology group
Apple Computer


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