Convert hex to decimal inside script with awk

philipz · 12-14-2010, 07:03 AM

All,

I have a script that creates a textfile with ip addresses and ports, but the ports are in hex format so they need to be converted.
Currently I have this code:

Code:

myscript.sh 10.10.10.10 | awk '{print $$2,$6,$4}'

10.11.12.13 06DF 10.13.18.20
10.10.10.11 0600 10.14.15.16
10.12.13.14 06DF 10.16.17.81

I'd like to have the second column in decimal instead of hex, like this:

Code:

10.11.12.13 1759 10.13.18.20
10.10.10.11 1536 10.14.15.16
10.12.13.14 1759 10.16.17.81

Is there any way to do that with awk, preferably in a oneliner? Would printf be an option?

Thanks!

catkin · 12-14-2010, 07:19 AM

If you want to convert in myscript.sh then http://tldp.org/LDP/abs/html/mathc.html#HEXCONVERT shows a technique. bc is another option. If you want to convert in the awk then prefix the second column string with 0x or 0X and use the strtonum function on it.

philipz · 12-14-2010, 07:45 AM

Quote:

Originally Posted by catkin

If you want to convert in myscript.sh then http://tldp.org/LDP/abs/html/mathc.html#HEXCONVERT shows a technique. bc is another option. If you want to convert in the awk then prefix the second column string with 0x or 0X and use the strtonum function on it.

I am not very familiar with functions and string operations i awk, but this gives an error:
myscript.sh 10.10.10.10 | awk '{print $2,strtonum(0x$6),$4}'
awk: calling undefined function strtonum

Any clue?

catkin · 12-14-2010, 08:06 AM

Which awk version are you using? Works here:

Code:

c@CW8:~$ echo | awk '{print strtonum( 0xa )}'
10
c@CW8:~$ awk --version
GNU Awk 3.1.8
[snip]

philipz · 12-14-2010, 08:35 AM

Quote:

Originally Posted by catkin

Which awk version are you using?

Mine states awk version 20050424 (FreeBSD) so I guess that function was not available at that time.
Rather than upgrading awk (I have quite some scripts relying on it so I don't want to break anything) I tried to use gawk (v3.1.5):

Code:

./myscript.sh 10.10.10.10 | gawk '{print $2,$7,$4}'
10.11.12.13 08BA  10.12.14.16
13.14.15.16 07FA 10.2.3.4
10.20.30.40 01BD  10.15.16.17

./myscript.sh 10.10.10.10 | gawk '{print $2,strtonum( 0x$7 ),$4}'
10.11.12.13 8 10.12.14.16
13.14.15.16 7 10.2.3.4
10.20.30.40 1 10.15.16.17

It recognizes the function but the conversion is wrong... 08BA is 2234 and not 8

catkin · 12-14-2010, 08:45 AM

0x$7 does not concatenate string 0x onto the value of $7 (I do not know awk well enough to know what it does do). You need to make 0x a string; the default operation is concatenation:

Code:

c@CW8:~$ echo 08BA | awk '{print strtonum( "0x" $1 )}'
2234

grail · 12-14-2010, 08:50 AM

Well personally I think you should be looking inside your myscript and doing the conversion there, however, try:

Code:

gawk '{print $2,strtonum( "0x"$7 ),$4}'

philipz · 12-14-2010, 09:16 AM

Quote:

Originally Posted by catkin

0x$7 does not concatenate string 0x onto the value of $7 (I do not know awk well enough to know what it does do). You need to make 0x a string; the default operation is concatenation:

Code:

c@CW8:~$ echo 08BA | awk '{print strtonum( "0x" $1 )}'
2234

That did the trick... Many thanks for the help, appreciated!

catkin · 12-14-2010, 09:18 AM

Ah grail

How you doing? Good you've dropped in. What does 0x$7 become that strtonum converts it to 8?

grail · 12-14-2010, 09:53 AM

Quote:

What does 0x$7 become that strtonum converts it to 8?

The thing to remember about strtonum is that it ignores all strings that are not numbers as well as the fact that all variables are auto set to 0 when used.
So

Code:

0 = 0
x = 0
$7 = 08BA

strtonum(00"08BA")

# BA is ignored
strtonum(00"08")

8

catkin · 12-14-2010, 12:06 PM

Thanks grail

It's so simple now you have explained it.

theNbomr · 12-14-2010, 08:19 PM

One-liner requested; Perl to the rescue.

Code:

perl -e 'while($rec=<>){@fields=split /\s+/,$rec; printf( "%s %d %s\n", $fields[0],hex($fields[1]),$fields[2]);}' filename.dat

Of course, you could make it into a proper, readable, script...

--- rod.