How to get either a substring or a text value using awk and if?

Question

I can't figure out how to write a simple ping log. I only need either the ms value or the words "no connection".

I have myping=$(ping -c 1 10.0.10.1). I only need the value between "time=" and " ms", like 3.151 from "time=3.151 ms".

I could use awk, but then I get a lot of blank lines and I don't know how to get rid of them:

$ awk -F 'time=| ms' '{print $2}' <<< "$myping"

3.151

And then, how can I insert "no connection", when the ping result doesn't contain a ms value?

Thanks a lot!

Answer 1

If using ping from iputils / Linux, which for ping -c1 localhost outputs something like this:

PING localhost (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.026 ms

--- localhost ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.026/0.026/0.026/0.000 ms

The second line will contain ms at the end only if the destination was reachable.

So, probably not the most elegant solution, but using sed:

sed -En '2{s/.*=([0-9.]+) ms$/\1/p; t; s/.*/no connection/p}'

• -E: turn on ERE support
• -n: and don't autoprint the pattern space;
• 2{[...]}: if we're processing line #2
• s/.*=([0-9.]+) ms$/\1/p and the line matches this pattern, replace the whole line with first captured group and print the line;
• t: if a substitution was performed, start the new cycle,
• s/.*/no connection/p}: otherwise substitute the whole line with no connection.

% ping -c1 localhost | sed -En '2{s/.*=([0-9.]+) ms$/\1/p; t; s/.*/no connection/p}'  
0.022
% ping -c1 192.168.1.127 | sed -En '2{s/.*=([0-9.]+) ms$/\1/p; t; s/.*/no connection/p}'
no connection

Answer 2

Assuming you're on Linux, and your ping output looks something like this:

$ cat > ping-output.txt
PING 1.1.1.1 (1.1.1.1) 56(84) bytes of data.
64 bytes from 1.1.1.1: icmp_seq=1 ttl=59 time=1.30 ms
64 bytes from 1.1.1.1: icmp_seq=2 ttl=59 time=0.850 ms
64 bytes from 1.1.1.1: icmp_seq=3 ttl=59 time=1.25 ms

--- 1.1.1.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2027ms
rtt min/avg/max/mdev = 0.850/1.134/1.304/0.202 ms

You could make both = signs and spaces split fields and then pick the right field. And check at the end if you got a value.

On the line of an individual ping, that would be field 10.

% cat ping-output.txt | 
  awk -F"[= ]" '/time=/ { rtt=$10 } 
                END { if (rtt) print rtt; else print "no connection" }'
1.25

Alternatively, you could read the summary numbers from the last line, to e.g. pick the minimum rtt.

With / or space as field separators, the minimum rtt is field 7 on the last line.

$ cat ping-output.txt |
  awk -F"[/ ]" '/^rtt/ { rtt=$7 }
                END { if (rtt) print rtt; else print "no connection" }'
0.850

(The ping on my mac has a slightly different output, the main difference here being round-trip instead of rtt on the last line. If yours is different, you'll have to tune the patterns and field numbers accordingly.)

---

But instead of using a special string in the output to mark a remote not answering, it might be better to the command's exit status. (Which is what ping likely also does itself.)

So, add an exit 1 to an appropriate place in the script, and then you can do something like this:

remote=1.1.1.1
if rtt=$(ping -c1 "$remote" | awk -F"[/ ]" '/^rtt/ { rtt=$7 }
                END { if (rtt) print rtt; else exit 1 }'; then
    echo "'$remote' is alive, rtt=$rtt"
else
    echo "'$remote' did not answer"
fi

Answer 3

A little variant on the (right) answer by @terdon: allow you to do more than 1 ping to average it and give maybe a more accurate result:

$ PS1="$ "; PS2=""
$ cat <<EOF | awk -F 'time=| ms' '($2){k++; sum+= $2}END{ if(!k){ 
print "no connection"} else { print ( sum * 1.0 / k ) }}'
...
... time=30.5 ms
...
... time=40 ms
...
... time=20 ms
...
EOF
30.1667
# and of course: replace the : 
#  cat <<EOF
# with:
#  ping -c 3 the_ip

or even simpler: using the last line with statistics (min/avg/max/mdev) :

ping -c 3 ip | awk -F'/| = ' '/^rtt/{avg=$3} END{print (!avg) ? "KO" : avg }'

Answer 4

On my Arch system, ping results for a host that can and for a host that cannot be reached look like this:

$ ping -c1 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=118 time=39.8 ms

--- 8.8.8.8 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 39.846/39.846/39.846/0.000 ms

and

$ ping -c 1 10.0.10.1
PING 10.0.10.1 (10.0.10.1) 56(84) bytes of data.

--- 10.0.10.1 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

Assuming your output is identical, and assuming that the failed connection's output is saved in $badPing an the successful one's in $goodPing, you can do:

$ awk -F= '/time=/{k=sub(/ms/,""); l=$NF}END{print k ? l : "no connection" }' <<< "$badPing"
no connection
$ awk -F= '/time=/{k=sub(/ms/,""); l=$NF}END{print k ? l : "no connection" }' <<< "$goodPing"
39.8 

The command above uses = as the field separator. Then, on every line that contains the string time=, it replaces the first occurrence of the string ms on that line (note that this assumes only one occurrence of ms on the relevant line; if that isn't the case for you, use sub(/ms/,"",$NF) instead) which leaves us with just the numerical value as the last field, and saves the number of replacements made in k and the last field as l.

Then, after we have processed the entire input, if k is set, so if a replacement occurred, we print out the value of l and if not, we print out no connection.

Alternatively, you can set the value of l at the beginning and then just print it:

$ awk -F= -v l="no connection" '/time=/ && sub(/ms/,""){l=$NF}END{print l}' <<< "$badPing"
no connection
$ awk -F= -v l="no connection" '/time=/ && sub(/ms/,""){l=$NF}END{print l}' <<< "$goodPing"
39.8 

---

To make your original approach work, just add having a second field as a conditional and set a variable based on it. Then you can print the second field when it exist, and print no connection at the end if the variable isn't set. Like this:

$ awk -F 'time=| ms' '($2){print $2;k=1}END{ if(!k) print "no connection"}' <<< "$goodPing"
39.8

$ awk -F 'time=| ms' '($2){print $2;k=1}END{ if(!k) print "no connection"}' <<< "$badPing"
no connection