I am learning BASH scripting and I would appreciate any help with a small problem I am having...
I am writing a script that builds a simple hosts file for DNS reasons related to a piece of software called netdb by parsing another application's config files for IP's and their hostnames.
The script works correctly for all hosts except a relatively small group. What ends up happening is the string my script finds for a hostname ends up overwriting everything on the line that it is currently located on. I've narrowed my script down to only parse the config file that produces these problem strings after my script runs.
The erroneous output is as follows:
here is my script code
Like I said above this works with all my other cfg files but this one. This cfg file is in the same format as all the other.
Last edited by jim mcnamara; 06-13-2012 at 12:01 AM..
Reason: code tags also for data...
i doubt that this works. correct should be (notice the spaces):
If i read the script source correctly the variables in question are both integers. You could also use integer comparation then (see man test for a complete description of available options)
I am not sure if this works or not, but in any case this will definitely be correct (again, notice the spaces, they are necessary):
A further tip: do NOT USE BACKTICKS! Backticks are an ancient device, which has some (quite intricate) shortcomings and are supported only for backwards compatibility. You use something like:
and want the output of "command" to become the variables content. Use
for this purpose, which has none of the shortcomings and all of the features of the above syntax.
One last tip: before using *any* variable, declare it at the beginning of your script. This offers the opportunity to document the variables contents, which helps greatly in maintaining your scripts, as well as to make sure all necessary variables are initialized with sensible values:
Thanks for the help. Your pointers certainly have helped made my code run better.
But the real problem I am having is with this part of code
Instead of outputting to the terminal on the echo command what is intended I get the following:
I have over 600 addresses and host names and it only does this weird output for 8 of them. I want to say its an overflow but I can't convince my self that is what is happening.
Thanks for the help. Your pointers certainly have helped made my code run better.
Well, probably they have helped some parts of your script run at all. In the meantime i have found some other syntactical errors and probable logic errors:
Quote:
Originally Posted by Wesley545
The script works correctly for all hosts except a relatively small group.
Sorry to say that, but more likely is the script produces the expected result out of pure chance with many hosts and isn't so lucky on the others.
First, have a look at these three lines:
Variable names are case sensitive, therefore "$TotalAdrFOUND" will always be empty because it is never used nor given any value before. I suppose this to be a typing error, but this check (whatever it is for) can never have worked in the expected way.
Now for the probable cause of your visible problems:
To be honest this is by far the ....ahem.... most creatively phrased piece of code i ever saw. I needed several passes to even understand what it does.
If i get you correctly you have one or several IP addresses in $args. Now you want to take them one at a time in $IP and get the corresponding host names from a list stored in a file, reading it one by one, yes?
First, do not use a normal variable to store tabular data. This is what arrays are for. Now bash treats all variables in a pipeline local to this pipeline, so the following looks a little more clumsy than in ksh, but anyway:
This replaces the "$args" variable with an array with IP values. Test if they are correctly stored with the following:
Do the same with the host names. You just replace "address" with "A longer name" in the awk statement and replace the array name (like, say "DNS"). The logic stays the same.
Instead of this:
you just use:
The construct "${#arrayname[*]}" is the number of elements stored in the array.
Now, instead of writing the DNS names into a temporary file first, then reading them back from there again, you simply do the following:
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