[SOLVED] need help matching string variables in a bash script

slockna · 10-26-2015, 04:38 AM

Hi, can't figure out how to best evaluate if a variable is an IP address or not.

the below example does not work, can someone help ?

Code:

MYIP=$(/usr/bin/wget -qO - http://ipecho.net/plain)
echo "$MYIP" |od -x
if [ $MYIP == [0-9]* ]; 
        then        TEXTEN="Connected, IP : $MYIP"
        else

            TEXTEN="No Internet connection"
        fi


echo "$TEXTEN"

pan64 · 10-26-2015, 04:49 AM

use the regexp match feature of bash: http://www.linuxjournal.com/content/...ar-expressions

slockna · 10-26-2015, 05:00 AM

Quote:

Originally Posted by pan64

use the regexp match feature of bash: http://www.linuxjournal.com/content/...ar-expressions

i am trying, but i do not get a hang of the syntax; i am thinking i only need to test if the first character is a digit ^[0-9] then it is a match...

Code:

pi@plutten ~ $ cat test.bash
MYIP=$(/usr/bin/wget -qO - http://ipecho.net/plain)
echo "$MYIP" |od -x
if [ $MYIP =~ ^[0-9] ];
then        TEXTEN="Connected, IP : $MYIP"
    else
            TEXTEN="No internet connection"
    fi
echo "<p> $TEXTEN </p>"

pi@plutten ~ $ bash -x test.bash
++ /usr/bin/wget -qO - http://ipecho.net/plain
+ MYIP=95.192xxxxxx
+ echo 95.192xxxxxx
+ od -x
0000000 3539 312e 3239 32a
0000017
+ '[' 95.192xxxxxx '=~' '^[0-9]' ']'
test.bash: line 3: [: =~: binary operator expected
+ TEXTEN='No internet connection'
+ echo '<p> No internet connection </p>'
<p> No internet connection </p>

pan64 · 10-26-2015, 05:10 AM

you can use an online regexp checker to understand how regexp works: http://www.myezapp.com/apps/dev/regexp/show.ws
You will see ^[0-9] will match only a single number, nothing else. To make it properly you need to use double brackets [[ ]] as it was used on the link I posted.

slockna · 10-26-2015, 05:34 AM

Thanks,

i still haven't a single clue what i did, but it works now !

Code:

MYIP=$(/usr/bin/wget -qO - http://ipecho.net/plain)

if [[ $MYIP =~ ^[0-9].* ]];
then        TEXTEN="Connected, IP : $MYIP"
    else
            TEXTEN="No internet connection"
    fi
echo "<p> $TEXTEN </p>"

pan64 · 10-26-2015, 05:47 AM

have you checked it on the link I gave? That is: one digit and after that any number of anything - from the beginning of the line.
a bit better: https://regex101.com/r/sZ9lF4/2

slockna · 10-26-2015, 05:48 AM

I think i get it now :P

background info: this is part of a web page ( yes , i am using sudoed bash scripts for CGI for system management ) don't try this at home kids ! unless you know what you're doing, which would per se keep you from doing it in the first place.

Obviously i don't know what i'm doing, which is why i am doing it....