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Check for valid hostnames

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Top Forums Shell Programming and Scripting Check for valid hostnames
# 8  
Old 06-03-2016
Hello RudiC,

The following points also needs to be satisfied by the script for a valid hostname naming convention :

1) The hostname cannot start or end with a hyphen.

In the below example output should be bad :

Code:
$ ./hostchk.sh
Enter hostname
deda23-
good

$ ./hostchk.sh
Enter hostname
-dwedr
good


2) Hostnames are composed of series of labels concatenated with dots. Each label must be between 1 and 63 characters long. Hence we cannot have two dots together in the hostname ( ".." ) .Also we cannot have a dot in the beginning ( since each label must be between 1-63 characters).

In the below example output should be bad :

Code:
$ ./hostchk.sh
Enter hostname
deda1x..
good

$ ./hostchk_rudic.sh
Enter hostname
.deda
good

Last edited by rahul2662; 06-03-2016 at 03:41 AM..
# 9  
Old 06-03-2016
Hello rahul2662,

Could you please try following.
Code:
echo "Please enter the name:"
read NAME
ONE=1
VALUE=`echo $NAME | awk '{if($0 !~ /^\./ &&  $0 !~ /\.$/ && $0 !~ /^[[:digit:]]/ && $0 !~ /^-/ && $0 !~ /-$/ && $0 !~ /[[:space:]]/ && $0 !~ /[[:cntrl:]]/){num=split($0, A,".");if(num<=3){for(i=1;i<=num;i++){if(length(A[i])>63){exit};Q=Q?Q+length(A[i]):length(A[i])};if(length(Q)<=189){print 1}}}}'`
 if [[ $VALUE == $ONE ]]
then
        echo "You have entered correct name as " $NAME
else
        echo "Please enter correct name as it is NOT matching the standards."
fi

Following are few tests which I ran for above code too.
Code:
##### Digit starting TEST.
./script.ksh
Please enter the name:
12334ewfwfwffw.defwfwwfw
Please enter correct name as it is NOT matching the standards.
  
##### DOT ending TEST.
./script.ksh
Please enter the name:
dwqfwfweffwfe.
Please enter correct name as it is NOT matching the standards.
  
##### Length of a field is more than 63 TEST.
./script.ksh
Please enter the name:
qdqeewfweffew.fwefwfewf.fweffwfwfwfwfwfwfwfwfwfwfwfwqcwdcwcwvwfwcwdvfdwgfeqseqrwqfw
Please enter correct name as it is NOT matching the standards.
  
##### Ending entry with an hyphen TEST.
./script.ksh
Please enter the name:
fefewfwefd-
Please enter correct name as it is NOT matching the standards.
  
##### starting with hyphen of entry TEST.
./script.ksh
Please enter the name:
-dwqwfwffwwv2131241.sqcwdwdcw
Please enter correct name as it is NOT matching the standards.

EDIT: Adding a non-one liner form of solution too now.
Code:
 echo "Please enter the name:"
read NAME
ONE=1
 VALUE=`echo $NAME | awk '{if($0 !~ /^\./ &&  $0 !~ /\.$/ && $0 !~ /^[[:digit:]]/ && $0 !~ /^-/ && $0 !~ /-$/ && $0 !~ /[[:space:]]/ && $0 !~ /[[:cntrl:]]/){
                          num=split($0, A,".");
                          if(num<=3){
                                        for(i=1;i<=num;i++){
                                                                if(length(A[i])>63){exit}
                                                                Q=Q?Q+length(A[i]):length(A[i])
                                                           };
                                        if(length(Q)<=189) {
                                                                print 1
                                                           }
                                    }
                                                                                                                                           }
                          }'`
 if [[ $VALUE == $ONE ]]
then
        echo "You have entered correct name as " $NAME
else
        echo "Please enter corect name as it is NOT matching the standards."
fi

Also adding a working example too following.
Code:
 ./script.ksh
Please enter the name:
dqdqfdq.213124.wrgfrewge
You have entered correct name as  dqdqfdq.213124.wrgfrewge

Thanks,
R. Singh
Last edited by RavinderSingh13; 06-03-2016 at 05:21 AM.. Reason: Added a non-one liner form of solution now. Added input shouldn't sart from a DOT too now.
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