Bash script $variable content echoing empty

Question

$RESPONSE variable does not being displayed in if block. In my code i have commented exactly where

#!/bin/bash

TIME=`date +%d-%m-%Y:%H:%M:%S`
cat sites.txt | while read site
do
    URL="http://$site"
    RESPONSE=`curl -I $URL | head -n1`
    echo $RESPONSE #echo works
    if echo $RESPONSE | grep -E '200 OK|302 Moved|302 Found' > /dev/null;then
        echo "$URL is up"
    else
        #$RESPONSE variable empty. Returns [TIME] [URL] is DOWN. Status:
        echo "[$TIME] $URL is DOWN. Status:$RESPONSE" | bash slackpost.sh
    fi  
done

Any ideas how to pipe $RESPONSE text with? $RESPONSE holds string like curl: (6) Could not resolvehost ..... or HTTP.1.1 200 OK

See also superuser.com/q/272265

Jeff Schaller
– Jeff Schaller ♦

2017-03-10 20:07:25 +00:00
Commented Mar 10, 2017 at 20:07 — Jeff Schaller
– Jeff Schaller ♦, Commented Mar 10, 2017 at 20:07

terdon · Accepted Answer · 2017-03-10 19:15:03Z

Your script actually works. Are you sure your sites.txt is correct? For example, I tried with:

$ cat sites.txt 
google.com
unix.stackexchange.com
yahoo.com

I saved your script as foo.sh, and running it on the file above gives:

$ foo.sh 2>/dev/null
HTTP/1.1 302 Found
http://google.com is up
HTTP/1.1 200 OK
http://unix.stackexchange.com is up
HTTP/1.1 301 Redirect
[10-03-2017:20:49:29] http://yahoo.com is DOWN. Status:HTTP/1.1 301 Redirect

By the way, as you can see above, it fails for yahoo.com which is redirecting. Perhaps a better way would be to use ping to check. Something like this (including some other general improvements):

while read site
do
    if ping -c1 -q "$site" &>/dev/null; then
        echo "$site is up"
    else
        echo "[$(date +%d-%m-%Y:%H:%M:%S)] $site is not reachable."
    fi  
done < sites.txt

If you really do need the status, use:

#!/bin/bash

## No need for cat, while can take a file as input
while read site
do
    ## Try not to use UPPER CASE variables to avoid conflicts
    ## with the default environmental variable names. 
    site="http://$site";
    response=$(curl -I "$site" 2>/dev/null | head -n1)
    ## grep -q is silent
    if grep -qE '200 OK|302 Moved|302 Found|301 Redirect' <<<"$response"; then
        echo "$site is up"
    else
        ## better to run 'date' on the fly, if you do it once
        ## at the beginning, the time shown might be very different.
        echo "[$(date +%d-%m-%Y:%H:%M:%S)] $site is DOWN. Status:$response" 
    fi  
done < sites.txt

Hmmm strange.Can it be then rasberry pi issue? maybe bash does not read it somehow? — Mindau
– Mindau, Commented Mar 10, 2017 at 19:18
anyway your solution is way better with ping at it works as expected — Mindau
– Mindau, Commented Mar 10, 2017 at 19:25
@Mindau are you 100% sure you're actually using bash? You didn't mention anything about raspberry. Are you sure you aren't using sh instead of bash, or even some sort of busybox shell? — terdon
– terdon ♦, Commented Mar 10, 2017 at 19:28

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