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regex inside if comparison

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# 1  
Old 09-03-2008
regex inside if comparison
I'm trying to compare the last octet of an IP to a regex:

Code:
IP=$(ifconfig eth0 | grep inet | awk -F: '{print $2}' | awk -F. '{print $4}' | awk '{print $1}')
 
            if [ $IP -eq ^1[1-3][0-9] ]; then
                echo "GOOD: Correct IP range for server"
            else
                echo "ERROR: Incorrect IP range for server"
            fi

It looks like it is literally comparing the regex.

'[' 121 -eq '^1[1-3][0-9]' ']'
./temp.sh: line 23: [: ^1[1-3][0-9]: integer expression expected
+ echo 'ERROR: Incorrect IP range for server'
ERROR: Incorrect IP range for server

Any ideas how to fix this?
# 2  
Old 09-03-2008
-eq is a numeric comparison, you want to do a string comparison:

Code:
if [[ $IP = 1[1-3][0-9] ]]; then

Note also that it is not a regular expression as such, [[ uses the simpler filename matching type syntax (as you would use for file specifications).

Note also that there's no need for so many awks and greps, this should be enough to pull out that last octet:

Code:
ifconfig eth0 | awk -F '[ :.]+' '/inet/ {print $7}'

# 3  
Old 09-03-2008
Although personally I would do the comparison numerically anyway:

Code:
if [[ "$IP" -ge 110 && "$IP" -le 139 ]]; then

# 4  
Old 09-03-2008
Quote:
Originally Posted by Annihilannic
-eq is a numeric comparison, you want to do a string comparison:

Code:
if [[ $IP = 1[1-3][0-9] ]]; then

Note also that it is not a regular expression as such, [[ uses the simpler filename matching type syntax (as you would use for file specifications).
Awesome, thanks for that and the other snippets. To be clear, why is this not a regex?
# 5  
Old 09-03-2008
Just because... it isn't. Smilie It wasn't implemented that way. You can use expr string : regex if you wish to match against a Basic Regular Expression.
# 6  
Old 09-03-2008
Quote:
Originally Posted by Annihilannic
Just because... it isn't. Smilie It wasn't implemented that way. You can use expr string : regex if you wish to match against a Basic Regular Expression.

Fair enough, thanks again.
# 7  
Old 09-04-2008
Don't forget case which does support a constrained form of regular expression (but shell wildcards are not real regular expressions).

Code:
case $IP in 1[1-3][0-9]*) echo good;; esac

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