Bash Script – How to Read URLs from .txt File and Ping Each One

bashcommand linescripts

I have a .txt file with 5 urls in it. I want to read it line by line, and perform 4 ping requests for each site, and extract the time. The code I wrote is below, but it isn't working.

Can anyone give me a hint? 

#!/bin/bash

cat /home/akis/Desktop/sites.txt
declare -i var=1
while read -r line
do
    while $var <= 5 
    do
        var2=$((var2+1)) 
        name="$line" | ping -c 4 $name > $var.txt | awk '{ print $8 }' < $var.txt | awk '/time/' > $var2.txt | tr '=' '\t' < $var2.txt | awk '{ print $2 }' > $var2.txt
    done

    var=$((var+1))  
done

Best Answer

This as well as Sergiy's answer came from Loop over text file with URLs and execute ping on each.

Assuming the file urls resides in the current directory and contains your urls only, one per line:

#!/bin/bash
while IFS='' read -r l || [ -n "$l" ]; do
  avg=$(ping -q -w 10 "$l" | sed '$!d;s_.*=[^/]*/\([^/]*\)/.*_\1_')
  echo "Average respond time for $l: $avg ms" >> avg_time
done < "urls"

Example run

Above script was named avg here. 

$ cat urls
askubuntu.com
unix.stackexchange.com
stackoverflow.com
$ ./avg
$ cat avg_time 
Average respond time for askubuntu.com: 37.742 ms
Average respond time for unix.stackexchange.com: 35.966 ms
Average respond time for stackoverflow.com: 38.982 ms

Explanations

  • #!/bin/bash
    this so-called shebang defines which shell your script has to be started with, here it's bash
  • while IFS='' read -r l || [ -n "$l" ]; do stuff; done < "urls"
    read the file named urls line by line, assigning the content of the currently processed line to variable l and doing stuff with it
  • ping -q -w 10 "$l" (= ping -qw10 "$l")
    call ping with the content of variable l as the argument and the options -quiet (less output we don't need) and -w 10 (timeout in seconds), so that the currently processed URL is pinged for exactly 10 seconds – you may adjust this value to your needs as well as specify other options (see man ping) for the list)

  • avg=$(ping … | sed …)
    pipe the output of ping to sed which cuts out the average respond time and save this value in variable avg

    • sed '$!d;s_.*=[^/]*/\([^/]*\)/.*_\1_'
    • sed '$!d
      don't (!) delete the last line ($), but the whole rest
    • sed 's/a/b/'
      substitute a by b – can also be written as e.g. sed 's_a_b_' if useful, this way we don't need to escape literal slash characters in the strings
      • .* – take everything
      • = and / – a literal “=” and “/”
      • [^/]* – take everything that's not (^) a slash
      • \([^/]*\) – take everything that's not (^) a slash and save it in a group
      • \1 – the first group saved with \(…\) before
    • the same work could also be done with awk -F/ '/^rtt/{print$5}':
      • -F/ – define / as the Field delimiter
      • /^rtt/{…} – select the line beginning (^) with “rtt” and do … with it
      • print$5 – print only field no. 5

  • echo "Average respond time for $l: $avg ms" >> avg_time
    print the text inserting the content of the variables l and avg and redirect this output to the file avg_time appending to its content

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