Date: Thu, 02 Jan 2003 12:18:55 -0800 From: Tim Kientzle <kientzle@acm.org> To: Terry Lambert <tlambert2@mindspring.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Reading rc.conf from C programs? Message-ID: <3E149EAF.9040100@acm.org> References: <3E1362FD.6070001@acm.org> <3E13CCF1.FA78AD5D@mindspring.com>
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Terry Lambert wrote: > Tim Kientzle wrote: >>I'm trying to figure out how to read and use >>/etc/rc.conf configuration variables from within >>a C program. > > #!/bin/sh > # Throw all of rc.conf into the environemnet so a C program > # named "fred" can read any of them with "getenv". > . /etc/rc.conf > fred This doesn't work. /etc/rc.conf does not export its variables to the environment. It only sets them in the local shell. Try the above where 'fred' is #!/bin/sh printenv and you'll see what I mean. >>Has anyone done anything like this before? >> > > Yeah. fopen(3), for(;;) { fgets(3), strtok(3) } fclose(3). This is what 'thefish' and 'sysinstall' both do, more or less. Of course, this doesn't work in all cases. (Witness the last 20 lines or so of /etc/defaults/rc.conf to understand why this doesn't work.) rc.conf is _not_ a list of variable=value pairs. It is a shell script that sets a number of shell variables. Nothing less than a full-fledged implementation of /bin/sh is gauranteed to work in all cases. Which comes back to the question in my original posting: does anyone have sample code for manipulating a slave /bin/sh using popen? or, alternatively, has anyone modified /bin/sh to operate as an embedded interpreter? Tim Kientzle To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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