Capture output of a bash command, parse it and store into different bash variables
Solution 1
Got the answer:
$ read IPETH0 IPLO <<< $(ifconfig | awk '/inet[[:space:]]/ { print $2 }' | cut -d ':' -f 2)
$ echo "${IPETH0}"
192.168.23.2
$ echo "${IPLO}"
127.0.0.1
This assumes the order of the eth0
and lo
interfaces, but it shows the basic idea.
Pure awk
You can do this exclusively in awk
using the split
function:
$ read IPETH0 IPLO <<< $(ifconfig | awk '/inet[[:space:]]/ { split($2,a,":"); print a[2]}')
Solution 2
I presume that you know for each of your commands which part of the command's return you want to store.
In your example this would be words number 7 and 47.
Do it like this (note the back ticks around your command ifconfig
):
array=(`ifconfig`)
Show all elements of this array:
echo ${array[@]}
eth0 Link encap:Ethernet HWaddr 30:F7:0D:6D:34:CA inet addr:10.106.145.12 Bcast:10.106.145.255 Mask:255.255.255.0 inet6 addr: fe80::32f7:dff:fe6d:34ca/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1104666 errors:0 dropped:0 overruns:0 frame:0 TX packets:2171 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:444437904 (423.8 MiB) TX bytes:238380 (232.7 KiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.255.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:15900 errors:0 dropped:0 overruns:0 frame:0 TX packets:15900 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:467306 (456.3 KiB) TX bytes:467306 (456.3 KiB)
Show specific words:
echo ${array[6]} ${array[46]}
addr:10.106.145.12 addr:127.0.0.1
Pipe the result into sed to extract only your IP addresses:
echo ${array[6]} ${array[46]} | sed 's/addr://g'
10.106.145.12 127.0.0.1
Using Arpith's nifty approach with 'read' here is the flexible answer.
read IPETH0 IPLO <<< $(echo ${array[6]} ${array[46]} |\
sed 's/addr://g')
echo $IPETH0 $IPLO
10.106.145.12 127.0.0.1
Please note that array elements are being counted from 0. Therefore your word number 7 would be referred to as "${array[6]}".
The array indexes are positive integers. So you can do all sorts of calculations in your shell script to pick specific words (like ranges or for-loops) ...
To write a portable script you would need to keep a kind of table with these numbers. On my system (BSD) the IP addresses would be numbers 17 and 49 instead of your Linux numbers 7 and 47. Also the resulting strings look different (disregarding my local and Arpith's global ID address):
echo ${array2[16]}
192.168.0.103
echo ${array2[48]}
127.0.0.1
slm's "pure awk" approach (see below) would fail on my BSD system. The split function into an array would not work as my 'ifconfig' command prints "127.0.0.1" and Arpith's "addr:127.0.0.1"...
read IPETH0 IPLO <<< $(ifconfig |\
awk '/inet[[:space:]]/ { split($2,a,":"); print a[2]}')
HTH
bernie
Solution 3
AWK :
/sbin/ifconfig | awk -F':' 'NR==2{split($2,a," "); print a[1]}'
SED :
ip -f inet addr show dev eth0 | sed -n 's/^ *inet *\([.0-9]*\).*/\1/p'
OR
ifconfig eth0 | sed -n 's/^ *inet addr:*\([.0-9]*\).*/\1/p'
GREP :
ifconfig eth0|grep -Po 't addr:\K[\d.]+'
Thanks to @Stephane Chazelas
Solution 4
A usual way to do that is to have for instance awk
generate some bash
code and have it interpreted by bash
.
Like:
eval "$(
ifconfig | awk -F '[: ]+' '
/^[^[:blank:]]/ {iface=$1}
/inet addr:/ {ip[iface]=$4}
END {for (i in ip) print "IP" toupper(i) "=" ip[i]}')"
Arpith
Senior Software Engineer with MobileIron, Inc. Previously, Software Developer with Cisco Systems, Inc. and Frog Design, Inc.
Updated on September 18, 2022Comments
-
Arpith over 1 year
Explanation:
I have a small bash script which simply runs any Linux command (e.g. say
ifconfig
)The typical output of ifconfig is something like this:
eth0 Link encap:Ethernet HWaddr 30:F7:0D:6D:34:CA inet addr:10.106.145.12 Bcast:10.106.145.255 Mask:255.255.255.0 inet6 addr: fe80::32f7:dff:fe6d:34ca/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1104666 errors:0 dropped:0 overruns:0 frame:0 TX packets:2171 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:444437904 (423.8 MiB) TX bytes:238380 (232.7 KiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.255.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:15900 errors:0 dropped:0 overruns:0 frame:0 TX packets:15900 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:467306 (456.3 KiB) TX bytes:467306 (456.3 KiB)
Now what most people usually do is store the entire output into a file/variable and parse based on that. I however want to know if there is anyway that I could put specific parts of the output in more than one variable (say a bash variable called
${IPETH0}
to carry the IP address10.106.145.12
from eth0 and${IPLO}
to carry the IP address127.0.0.1
from lo in the above example without running ifconfig command twice).Something like what tee command does with the input but I want to do this for the output and store the output into 2 or more variables in one go. Any ideas?
-
slm over 10 yearsSee this Q&A: unix.stackexchange.com/questions/87468/…
-
Arpith over 10 years@slm: I am not trying to obtain the IP address. I wanna know how I can store broken-down output of a command into more than one bash variable. The example you pointed out still stores output in a single variable.
-
slm over 10 years@Arpith - yeah that was just to get you started, not show you exactly your solution.
-
Bananguin about 6 years
-
terdon about 6 years@Bananguin true, but this is 4 and a half years old. Not much point in doing anything about it anymore, I'm afraid.
-
Bananguin about 6 years@terdon I suppose. But maybe others get the hint.
-
-
jordanm over 10 yearsYou shouldn't use
awk
andcut
together. You only needawk
. -
Arpith over 10 yearsI know. I know very minimal awk. Hence the cacophony. :-p
-
slm over 10 years@jordanm - i added a awk only method.