How to find patterns across multiple lines in Linux? - linux

Question

i'm trying to get some specific lines of this command:
ifconfig
here is the output of the command:
eth0 Link encap:Ethernet HWaddr 00:10:E0:3F:6F:BC
inet addr:10.71.1.30 Bcast:10.71.1.255 Mask:255.255.255.0
inet6 addr: fe80::210:e0ff:fe3f:6fbc/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3059275068 errors:0 dropped:1378 overruns:0 frame:0
TX packets:2094779962 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:6566542892239 (5.9 TiB) TX bytes:202791652910 (188.8 GiB)
eth1 Link encap:Ethernet HWaddr 00:10:E0:3F:6F:BD
UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
RX packets:1417584931 errors:0 dropped:32908 overruns:0 frame:0
TX packets:1284691038 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2256566826674 (2.0 TiB) TX bytes:182643225952 (170.0 GiB)
I just want lines that contains "Link" and "bytes" words, for example:
eth0 Link encap:Ethernet HWaddr 00:10:E0:3F:6F:BC
RX bytes:6566542892239 (5.9 TiB) TX bytes:202791652910 (188.8 GiB)
eth1 Link encap:Ethernet HWaddr 00:10:E0:3F:6F:BD
RX bytes:2256566826674 (2.0 TiB) TX bytes:182643225952 (170.0 GiB)

Answer 1

Te best approach must be to use grep to filter the lines. For example, use:
ifconfig | egrep " Link|bytes"
Note I added a space before Link to avoid matching the line ending with Scope:Link.
You can also use:
ifconfig | awk '/ Link/ || /bytes/'
or
ifconfig | grep " Link\|bytes"

Answer 2

Of course grep is the best tool for this. But, there are some other ways are available to do the same. That is,
ifconfig | sed -n '/Link \|bytes/p'
and
ifconfig | awk '/Link |bytes/'

Answer 3

ifcofig|perl -lne 'print if(/Link/||/bytes/)'

Answer 4

Here's a couple of useful patterns that most people I've met don't seem to know about. The first is particularly relevant to your problem.
grep -e is your best new-found friend
ifconfig | grep -e Link -e bytes
You can do a similar thing with sed, which has an additional bonus of also printing out the first line (which might contain a heading). In this example, I'm printing out the heading line and any lines contain LISTEN or 'bar' (The second expression is just there to reinforce the fact that you're not limited to one.) Here, the 1p is addressing the first line, (origin-1), with the operation to 'p'rint
lsof -Pni | sed -n -e 1p -e '/LISTEN/p' -e '/bar/p'