Seems simple. What's the best way (in a script) to get the IP address of an ethernet interface (in linux). For instance eth0.
I used to have (perl, but also applies as a bash solution):
$eip=`/sbin/ifconfig $int | grep 'inet addr' | awk '{print $2}' | sed -e 's/.*://'`
But the latest upgrade from F16 to F17 broke this (now the line contains "inet" but not "inet addr".
So I started thinking of finding the most standardized way that (hopefully) won't change after a future kernel upgrade :-)
It would seem that the less field parsing done, the better, as keywords and field position aren't guaranteed.
Looks like ifconfig is now deprecated (according to man ifconfig). So now I'm doing:
$eip=`ip -o -4 addr list eth0 | awk '{print $4}'`
That works now, but it still has a output format-dependent requirements.
I looked for /sys or /dev files, but can't find any that have ip4 addr. I tried to find more options to whittle ip's output to give me just the address, no joy there.
Ideas?
PS: this is important as failures like this force me to drive out onsite to headless boxes, some of which are 200km away.
my_public_ip=`curl http://ifconfig.me%60
On Sat, Mar 23, 2013 at 10:40 PM, Trevor Cordes trevor@tecnopolis.cawrote:
Seems simple. What's the best way (in a script) to get the IP address of an ethernet interface (in linux). For instance eth0.
I used to have (perl, but also applies as a bash solution):
$eip=`/sbin/ifconfig $int | grep 'inet addr' | awk '{print $2}' | sed -e 's/.*://'`
But the latest upgrade from F16 to F17 broke this (now the line contains "inet" but not "inet addr".
So I started thinking of finding the most standardized way that (hopefully) won't change after a future kernel upgrade :-)
It would seem that the less field parsing done, the better, as keywords and field position aren't guaranteed.
Looks like ifconfig is now deprecated (according to man ifconfig). So now I'm doing:
$eip=`ip -o -4 addr list eth0 | awk '{print $4}'`
That works now, but it still has a output format-dependent requirements.
I looked for /sys or /dev files, but can't find any that have ip4 addr. I tried to find more options to whittle ip's output to give me just the address, no joy there.
Ideas?
PS: this is important as failures like this force me to drive out onsite to headless boxes, some of which are 200km away. _______________________________________________ Roundtable mailing list Roundtable@muug.mb.ca http://www.muug.mb.ca/mailman/listinfo/roundtable
On 2013-03-23 Sean Walberg wrote:
my_public_ip=`curl http://ifconfig.me%60
Hehe, ya, but won't help me when I have an IP but my internet is down (dropping packets, or iptables bungled).
On 2013-03-24 Kevin McGregor wrote:
ifconfig eth0 | grep inet[^6] | awk -F"[: \t]+" '{print $4}' # Get
Doesn't fit the requirement of not relying on (now proven) changeable strings ("inet") and position ($4). :-(
On 2013-03-24 Adam Thompson wrote:
There is (AFAIK) no generic, portable, standardized solution.
Afraid of that...
- No UNIX system is guaranteed to have networking at all, never mind
TCP/IP. 2. POSIX doesn't cover networking configuration commands (that I can find, anyway)
Luckily for me I don't care at all about this working on anything other than Fedora 17 and newer. The tricky part is I want to work for as many "newer" Fedoras as possible. For instance, if there was a /sys file made by the kernel then there's a good chance Linus would never let it change. Whereas userland stuff like "ifconfig" and "ip" seem mutable at the whims of the authors :-(
Your script is good. Whittled down to just the case I care about (has ip command; ipv4 only; etc) it's pretty much what I've already written.
You'd think there'd be some other way though...
can't do it from shell. Use AF_NETLINK, which is what ip(8) does internally. Bad design, IMHO...
So if I whipped up a little C proggie I could rely on it not to change? Hmm, maybe that's the way to go, but then I have to worry about keeping compiled binaries up to date :-(
Thanks guys!
On 2013-03-24 18:06, Trevor Cordes wrote:
can't do it from shell. Use AF_NETLINK, which is what ip(8) does internally. Bad design, IMHO...
So if I whipped up a little C proggie I could rely on it not to change? Hmm, maybe that's the way to go, but then I have to worry about keeping compiled binaries up to date :-(
Well, if it's a statically-linked binary (use uLibc if necessary to keep the size reasonable) and you follow the LSB guidelines, it should remain portable pretty much forever. At least until AF_NETLINK is deprecated, which I would expect to be a very very very long time from now. You still have to take into account multi-homed systems, but at least you can get the device names out of /proc/net/dev or 'netstat -i'. -Adam
Does this work?
ifconfig eth0 | grep inet[^6] | awk -F"[: \t]+" '{print $4}' # Get your IPv4 IP address from ifconfig. This is the Linux version.
From climagic.
Sent from my iPhone
On 2013-03-23, at 10:40 PM, Trevor Cordes trevor@tecnopolis.ca wrote:
Seems simple. What's the best way (in a script) to get the IP address of an ethernet interface (in linux). For instance eth0.
I used to have (perl, but also applies as a bash solution):
$eip=`/sbin/ifconfig $int | grep 'inet addr' | awk '{print $2}' | sed -e 's/.*://'`
But the latest upgrade from F16 to F17 broke this (now the line contains "inet" but not "inet addr".
So I started thinking of finding the most standardized way that (hopefully) won't change after a future kernel upgrade :-)
It would seem that the less field parsing done, the better, as keywords and field position aren't guaranteed.
Looks like ifconfig is now deprecated (according to man ifconfig). So now I'm doing:
$eip=`ip -o -4 addr list eth0 | awk '{print $4}'`
That works now, but it still has a output format-dependent requirements.
I looked for /sys or /dev files, but can't find any that have ip4 addr. I tried to find more options to whittle ip's output to give me just the address, no joy there.
Ideas?
PS: this is important as failures like this force me to drive out onsite to headless boxes, some of which are 200km away. _______________________________________________ Roundtable mailing list Roundtable@muug.mb.ca http://www.muug.mb.ca/mailman/listinfo/roundtable
There is (AFAIK) no generic, portable, standardized solution. Reasons: 1. No UNIX system is guaranteed to have networking at all, never mind TCP/IP. 2. POSIX doesn't cover networking configuration commands (that I can find, anyway) 3. LSB doesn't cover networking configuration commands (that I can find)
To be portable across multiple versions, you have to check for various things: 1. existence of 'ip' command from iproute/iproute2 (and acceptable output) 2. if not, then existence of ifconfig (and at least two forms of output) isn't guaranteed either
There *is* one standardized way to get the info on any Linux kernel from the last ~10 years, but you can't do it from shell. Use AF_NETLINK, which is what ip(8) does internally. Bad design, IMHO... should have been exported via /proc or /sys to conform to the "everything is a file" paradigm.
See attached for how you would portably handle the four cases I'm aware of in bash. Note that there are some bash-specific constructs in there. It's probably runnable under ksh, but the new-style conditionals definitely don't run in dash(1).
Obviously, the script could be made a LOT more compact.
-Adam
On 2013-03-23 22:40, Trevor Cordes wrote:
Seems simple. What's the best way (in a script) to get the IP address of an ethernet interface (in linux). For instance eth0.
I used to have (perl, but also applies as a bash solution):
$eip=`/sbin/ifconfig $int | grep 'inet addr' | awk '{print $2}' | sed -e 's/.*://'`
But the latest upgrade from F16 to F17 broke this (now the line contains "inet" but not "inet addr".
So I started thinking of finding the most standardized way that (hopefully) won't change after a future kernel upgrade :-)
It would seem that the less field parsing done, the better, as keywords and field position aren't guaranteed.
Looks like ifconfig is now deprecated (according to man ifconfig). So now I'm doing:
$eip=`ip -o -4 addr list eth0 | awk '{print $4}'`
That works now, but it still has a output format-dependent requirements.
I looked for /sys or /dev files, but can't find any that have ip4 addr. I tried to find more options to whittle ip's output to give me just the address, no joy there.
Ideas?
PS: this is important as failures like this force me to drive out onsite to headless boxes, some of which are 200km away. _______________________________________________ Roundtable mailing list Roundtable@muug.mb.ca http://www.muug.mb.ca/mailman/listinfo/roundtable
-
Adam Thompson -
Kevin McGregor -
Sean Walberg -
Trevor Cordes