Linux bash script to extract IP address

Question

I want to make big script on my Debian 7 3   something like translated and much more new user friendly enviroment    I have a problem  I want to use only some of the informations that commands give me  For example my ifconfig looks like   eth0      Link encap Ethernet  HWaddr 08 00 27 a3 e3 b0             inet addr 192 168 1 103  Bcast 192 168 1 255  Mask 255 255 255 0           inet6 addr  fe80  a00 27ff fea3 e3b0 64 Scope Link           UP BROADCAST RUNNING MULTICAST  MTU 1500  Metric 1           RX packets 1904 errors 0 dropped 0 overruns 0 frame 0           TX packets 2002 errors 0 dropped 0 overruns 0 carrier 0           collisions 0 txqueuelen 1000            RX bytes 1309425  1 2 MiB   T   I want to display only the IP address in line  echo  Your IP address is   IP ADDRESS     Is there any command that allow me to do such a thing  to search in stream for informations I want to get   I know about grep and sed but I am not really good with them   Edit  Firstly to say thank you for helping me with this problem  now I know much more  Secondly to say project is in progress  If anyone would be interested in it just pm me

User · Answer

ip -4 addr show eth0   grep -oP     lt  inet

User · Answer

If You want to use only sed to extract IP address  ifconfig eth0 2 gt  dev null sed -n  s      space        digit      digit         digit      digit         digit      digit         digit      digit          1 p

User · Answer

Just a note  since I just spent some time trouble-shooting a botched upgrade on a server  Turned out  that  years ago  I had implemented a test to see if dynamically added interfaces  e g  eth0 1  were present  and if so  I would bind certain proggis to the  main  IP on eth0  Basically it was a variation on the  ifconfig grep    sed      solution  plus checking for  eth0   presence   The upgrade brought new net-tools  and with it the output has changed slightly   old ifconfig   eth0      Link encap Ethernet  HWaddr 42 01 0A F0 B0 1D           inet addr 10 240 176 29  Bcast 10 240 176 29  Mask 255 255 255 255           UP BROADCAST RUNNING MULTICAST  MTU 1460  Metric 1               lt SNIP gt    whereas the new version will display this   eth0  flags 4163 lt UP BROADCAST RUNNING MULTICAST gt   mtu 1460       inet 10 240 212 165  netmask 255 255 255 255  broadcast 10 240 212 165           lt SNIP gt    rendering the hunt for  eth0   as well as  inet addr   search busted  never mind interfaces called  em0   br0  or  wlan0       Sure you could check for  inet    or  inet6    and make the addr  part optional  but looking closer  you ll see that more or less everything has changed   Mask  is now  netmask       The  ip route      suggestion s pretty nifty - so maybe    MyIP     ip route get 8 8 8 8   awk  NR  1  print  NF      if    A  MyIP      A    then      MyIPs     hostname -I        for  MyIP in    MyIPs      do         echo  Found IP      MyIP        done else     echo  Found IP    MyIP  fi   Well  something of that sort anyway  Since all proposed solutions seem to have circumstances where they fail  check for possible edge cases - no eth  multiple eth s  amp  lo s  when would  hostname -i  fail     and then decide on best solution  check it worked  otherwise 2nd best   Cheers  n  beers

User · Answer

May be not for all cases  especially if you have several NIC s   this will help   hostname -I   awk    print  1

User · Answer

ip route get 8 8 8 8  grep src  sed  s   src          1 g  cut -f1 -d

User · Answer

A slight modification to one of the previous ip route     solutions  which eliminates the need for a grep   ip route get 8 8 8 8   sed -n  s    src          1 gp

User · Answer

If you want to get a space separated list of your IPs  you can use the hostname command with the --all-ip-addresses  short -I  flag  hostname -I   as described here  Putting IP Address into bash variable  Is there a better way

User · Answer

If the goal is to find the IP address connected in direction of internet  then this should be a good solution        UPDATE    With new version of linux you get more information on the line    ip route get 8 8 8 8 8 8 8 8 via 10 36 15 1 dev ens160 src 10 36 15 150 uid 1002     cache   so to get IP you need to find the IP after src  ip route get 8 8 8 8   awk -F src    NR  1 split  2 a      print a 1    10 36 15 150   and if you like the interface name  ip route get 8 8 8 8   awk -F dev    NR  1 split  2 a      print a 1    ens192   ip route does not open any connection out  it just shows the route needed to get to 8 8 8 8  8 8 8 8 is Google s DNS   If you like to store this into a variable  do   my ip   ip route get 8 8 8 8   awk -F src    NR  1 split  2 a      print a 1      my interface   ip route get 8 8 8 8   awk -F dev    NR  1 split  2 a      print a 1         Why other solution may fail   ifconfig eth0   If the interface you have has another name  eno1  wifi  venet0 etc  If you have more than one interface IP connecting direction is not the first in a list of more than one IF    Hostname -I   May get only the 127 0 1 1 Does not work on all systems

User · Answer

awk   inet addr   gsub     5       2   print  2   file 192 168 1 103

User · Answer

sbin ifconfig eth0   grep  inet addr     cut -d  -f2   awk    print  1

User · Answer

In my opinion the simplest and most elegant way to achieve what you need is this   ip route get 8 8 8 8   tr -s       cut -d    -f7     ip route get  host  - gives you the gateway used to reach a remote host e g    8 8 8 8 via 192 168 0 1 dev enp0s3  src 192 168 0 109     tr -s     - removes any extra spaces  now you have uniformity e g    8 8 8 8 via 192 168 0 1 dev enp0s3 src 192 168 0 109     cut -d    -f7 - truncates the string into    space separated fields  then selects the field  7 from it e g    192 168 0 109

User · Answer

Take your pick     cat file eth0      Link encap Ethernet  HWaddr 08 00 27 a3 e3 b0           inet addr 192 168 1 103  Bcast 192 168 1 255  Mask 255 255 255 0           inet6 addr  fe80  a00 27ff fea3 e3b0 64 Scope Link           UP BROADCAST RUNNING MULTICAST  MTU 1500  Metric 1           RX packets 1904 errors 0 dropped 0 overruns 0 frame 0           TX packets 2002 errors 0 dropped 0 overruns 0 carrier 0           collisions 0 txqueuelen 1000           RX bytes 1309425  1 2 MiB   T    awk  sub  inet addr       print  1   file 192 168 1 103    awk -F          inet addr  print  4   file 192 168 1 103

User · Answer

To just get your IP address   echo  ifconfig eth0 2 gt  dev null awk   inet addr    print  2   sed  s addr        This will give you the IP address of eth0   Edit  Due to name changes of interfaces in recent versions of Ubuntu  this doesn t work anymore  Instead  you could just use this   hostname --all-ip-addresses or hostname -I  which does the same thing  gives you ALL IP addresses of the host

[linux] Linux bash script to extract IP address

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