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Tiny Deathstars of Foulness

There’s a macOS tool called AssetCacheLocatorUtil located at /usr/bin/AssetCacheLocatorUtil. The output is in… stderr. Because stderr is so fun to work with (note that sed -i only works with stdin). So, to update the caching server(s) you are using and only print the IP address of those, you’d do the following: /usr/bin/AssetCacheLocatorUtil 2>&1 | grep guid | awk '{print$4}' | sed 's/^\(.*\):.*$/\1/' | uniq If you use Jamf Pro and would like to use this as an extension attribute, that’s posted here: https://github.com/krypted/cachecheck. I didn’t do any of the if/then there, as I’d usually just do that on the JSS.

April 17th, 2017

Posted In: Mac OS X, Mac Security, Mass Deployment, Network Infrastructure, precache

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You search for items in macOS using compound conditions in a number of ways. One way is with awk. Here, we’re going to grab the output of a simple ls command. That gets piped into an awk statement. Then we’re going to look at the expression to evaluate. Basically, we’re going to say anything that contains com. as well as apple and .plist. Because it’s ls, we’re looking for names of files that match those patterns. Each pattern is listed in brackets. And then there’s the {print} to lay out the action of printing to the files that match the pattern to the screen: ls |awk '/[com.][apple][.plist]/ {print}' Note: I know you’re not supposed to use ls in scripts. Don’t care. If it were dates and such, I’d of used stat…

March 14th, 2017

Posted In: Mac OS X, Mac OS X Server

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One of my favorite things about grabbing things with scripts is just how many ways (and sometimes how needfully or needlessly convoluted you can make them) to grab the same pieces of information. For example, something as simple as what hosts you use to resolve names on a Mac. There are a number of ways to grab what DNS server a device is using in macOS. So when you’re running a script you might choose to grab DNS information one way or another, according to what you’re after. Some of this might seem more complicated than it should be. And that’s correct…

resolv.conf

The /etc/resolv.conf file is updated automatically to look at what servers are used to resolve names used for DNS. The easiest way to see theses to simply cat it and grep for nameserver: cat /etc/resolv.conf | grep nameserver

scutil

The next way we’ll grab DNS information is using scutil. Here, we use the –dns option, which outputs a lot of DNS stuffs, including all the built-in resolvers: scutil --dns To just grab the name servers: scutil --dns | grep nameserver We can also simplify the output to just the servers with awk: scutil --dns | grep nameserver | awk '{print$3}'

networksetup

The second way is using networksetup. This command has an option to get a DNS server in (shocker) -getdnsservers. However, you have to list the interface for each. So below we’ll dump all interfaces into an array using -listallhardwareports and then read them in using a for loop and querying the name servers. interfaces=( "$(networksetup -listallhardwareports | grep Hardware | cut -c 16-900)" ) for i in "${interfaces[@]}" do networksetup -getdnsservers $i done The one tricky thing in this one is I initially forgot to quote the interfaces as they went into the array, which meant each word of the interface was an item in the array and therefore the -getdnsservers option failed. Once I quoted, it was all happy. The other thing I can point out is I used cut instead of sed because it was easier to quote; however, it seems unlikely the name can be more than 890 characters, so I think it’s fine…

dig

You can also use dig. Here, you’ll query for a name without using an @ option, but omit everything but the line with the server that responded: dig google.com | grep SERVER: The output is kinda’ fug:
;; SERVER: 4.2.2.2#53(4.2.2.2)
For simpler output, we’ll use sed to constrain the output to just what’s between the parenthesis: dig google.com | grep SERVER: | sed 's/^.*(//;s/)$//'

nslookup

nslookup is a tool similar to dig, used for querying names. We’ll basically do the same thing as above, just using awk as it’s just a standard position in a line: nslookup google.com | grep Server: | awk '{print$2}'

system_profiler

Then there’s system_profiler, the command line interface for System Profiler. Here, we can query the SPNetworkDataType. This is going to produce a lot of output, so we can limit it to just the DNS servers using grep to constrain to just the lines we want and awk for just the columns in those lines, as follows: system_profiler SPNetworkDataType | grep "Domain Name Servers:" | awk '{print$4}'

hosts

@knapjack added to use hosts. I had to use verbose mode to pull the local name server as follows: host -v -t ns google.com | grep Received | awk '{print $5}'

ipconfig

Thanks to the lovely Allister (@sacrilicious), we also have ipconfig to add to the list: /usr/sbin/ipconfig getpacket en0 2> /dev/null | grep name_ | cut -d' ' -f3- There are tons of ways to find things in macOS. Do you have a way to find a DNS server that I didn’t think of here?

March 6th, 2017

Posted In: bash, Mac OS X, Mac OS X Server, Mac Security, Ubuntu

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Namespace conflicts can be interesting. Especially with multiple local domains. To grab the path of a directory domain of a currently logged in user (when running as the user) using a script, you can run the following: dscl . -read /Users/`whoami` | grep AppleMetaNodeLocation | awk '{print $2}' You can then replace the string we’re using with grep if you’d like to pull a different attribute from the user record, you’d use the following: dscl . -read /Users/`whoami` | grep UniqueID | awk '{print $2}'

August 22nd, 2016

Posted In: Mac OS X, Mac OS X Server, Mac Security

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Just a quick one-liner. Enjoy. profiles -Cv | grep Enrollment | awk '{ s = ""; for (i = 5; i <= NF; i++) s = s $i " "; print s }'

August 20th, 2016

Posted In: Mac OS X, Mac OS X Server, Mac Security, Mass Deployment

Tags: ,

You see a lot of entries for various things in log files. Here, we’re going to print out the number of entries with backupd in them: awk '/backupd/{print NR}' /var/log/system.log

July 11th, 2015

Posted In: Mac OS X, Ubuntu, Unix

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Recently I was working on a project where we were isolating IP addresses by country. In the process, I found an easy little tool built right into OS X called ip2cc. Using ip2cc, you can lookup what country an IP is in. To do so, simply run ip2cc followed by a name or ip address. For example, to lookup apple.com you might run: ip2cc apple.com Or to lookup Much Music, you might run: ip2cc muchmusic.ca The output would be: IP::Country modules (v2.28) Copyright (c) 2002-13 Nigel Wetters Gourlay Database updated Wed May 15 15:29:48 2013 Name: muchmusic.com Address: 199.85.71.88 Country: CA (Canada) You can just get the country line: ip2cc apple.com | grep Country: To just get the country code: ip2cc apple.com | grep Country: | awk '{ print $2 }' Finally, ip2cc is located at /usr/bin/ip2cc so we’ll complicate things just a tad by replacing the hostname with the current IP (note that private IPs can’t be looked up, so this would only work if you’re rocking on a wan ip or feeding it what a curl from a service like whatismyip brings back): ip2cc `ipconfig getifaddr en0` | grep Country: | awk '{ print $2 }'

December 13th, 2014

Posted In: Mac OS X, Mac OS X Server

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The number of characters n a line of text can be a difficult thing to calculate in a given app. If you have data in a text file, you can use awk to view the number of characters in a given line of the file. This is very helpful, for example, if you have code that you’ve put into documentation that exceeds the character maximum and therefore wraps. When going to print, you need to split these lines up. Here, we’re going to use the awk command to review all lines that exceed 56 characters: awk 'length($0) > 56' ~/Repo/Chapter1.xml

October 15th, 2013

Posted In: Mac OS X, Mac OS X Server, Mac Security, Unix

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Yesterday I showed a way to get the serial number from a Mac OS X machine. However, as a couple of people pointed out, Apple will soon be adding another character to the serial number. This means that rather than use cut I should have used awk to allow for either serial number length. To grab the serial this way:
ioreg -l | grep IOPlatformSerialNumber | awk ‘{print $4}’
Or without the quotes:
ioreg -l | grep IOPlatformSerialNumber | awk ‘{print $4}’ | sed ‘s/”//g’

May 13th, 2010

Posted In: Mac OS X, Mac OS X Server, Mass Deployment

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A number of commands available for finding positions that you want in a line and extracting only a certain amount of text can be pretty cumbersome in terms of learning curve. This isn’t to say that once you get the hang of them that they’re terribly complicated but it can take a little while to get the hang of them. And when you need something fast, you might want an easy command for extracting text from lines. In these cases, consider cut. The cut command doesn’t do regular expressions (I guess you could argue that its ability to use a delimiter can be used as a regular expression) and so it’s really easy to use. Basically, you feed cut some data and then tell it which characters in the line that you want to keep. It then gets rid of the rest. The easiest use of this is to look at a list of data. For example, let’s saw we have a file called test.txt with the following contents:
abc123 abc124 abc134 abc234 abd234 acd234
Now we’re going to cat the file (which just reads the file contents) and then pipe the output of reading that file into a cut command (which is done by simply adding a pipe character at the end of the first part of the command. Then we’re going to use the -c option of cut (which looks at character positions) to simply grab the first three positions (1-3) of the lines. The command would end up looking as follows:
cat test.txt | cut -c 1-3
And the output would look as follows (this output could then be redirected into a new file btw):
abc abc abc abc abd acd
You can also specify multiple ranges of characters (or single characters for that matter). For example, to see only characters 1-2 and 5-6:
cat test.txt | cut -c 1-2,5-6
Overall, cut is a very easy to use tool, with a limitation that your pattern that you are looking to maintain must be consistent in terms of the character position that you are using in each line. It also uses every line in a file; however, to go another step and look for all positions in a line only if the line has a pattern that it can match you could simply add a grep in the middle. For example, if you’re looking for each line of our sample text file that has the number 4 then you could do:
cat test.txt | grep 4
This would show you only the last five lines of the file since those are the only lines that have that number in them. You could then pipe the output of that file into your cut and, let’s say, look for characters 1-3 and 6 in the output:
cat test.txt | grep 4 | cut -c 1-3,6
Your result would then be the following:
abc4 abc4 abc4 abd4 acd4
Finally, there are going to be times when you’re not looking for a specific character position in a line but instead a character position or a pattern that begins with another pattern. For this you’re going to end up needing to use a more advanced tool, such as awk or if you’re feelin’ frisky (maybe I’m speaking for myself there) regex. These tools will have a steeper learning curve, but ultimately be far more useful.

January 17th, 2010

Posted In: Mac OS X, Mac OS X Server, Mac Security, Unix

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