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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Solution for Delphi – post-build event with multiple if/copy combinations only execute if first file does not exist – Stack Overflow

Posted by jpluimers on 2018/11/15

My solution in [WayBack] delphi – post-build event with multiple if/copy combinations only execute if first file does not exist – Stack Overflow is an addendum to my 2014 post Delphi prebuild/prelink/postbuild events.

Here we go:

Q

Given the bin\ directory inside the Delphi project contains the files Cert.pem and Key.pem, the below Delphi post-build event only copies both files if C:\Binaries\Cert.pem does not exist:

if not exist $(OUTPUTDIR)Cert.pem (copy bin\Cert.pem $(OUTPUTDIR))
if not exist $(OUTPUTDIR)Key.pem (copy bin\Key.pem $(OUTPUTDIR))

As soon as C:\Binaries\Cert.pem exists, the Key.pem file is never copied.

How can I solve this in the post-build event?

Edit: unlike my 2014 post, this is indeed possible using parentheses. See my answer below.

A

The problem with Delphi post-build events is that they are not batch files.

It means that statements that look like lines are being concatenated by the Delphi IDE into one big & ampersand separated statement. This ensures the commands are executed in sequence, as per Command Redirection, Pipes – Windows CMD – SS64.com:

commandA &  commandB      Run commandA and then run commandB

So this is the actual statement that gets executed:

if not exist $(OUTPUTDIR)Cert.pem (copy bin\Cert.pem $(OUTPUTDIR))&if not exist $(OUTPUTDIR)Key.pem (copy bin\Key.pem $(OUTPUTDIR))

The problem here is that now the second if is seen as a continuation of the “then” part of the first if statement: the second if never executes when the $(OUTPUTDIR)Cert.pem exists.

What helps is a little known feature that you can wrap each command inside parentheses. Normally this is to allow one command to span multiple lines (especially for if, and for..do loops), but it also works on one line.

Wrapping each line having an if statement inside parentheses ensures they become standalone statements not affecting the other lines, even if they are being concatenated with & ampersand separators.

In the dialog it looks like this:

(if not exist $(OUTPUTDIR)Cert.pem (copy bin\Cert.pem $(OUTPUTDIR)))
(if not exist $(OUTPUTDIR)Key.pem (copy bin\Key.pem $(OUTPUTDIR)))

That way, the IDE translates it into one statement:

(if not exist $(OUTPUTDIR)Cert.pem (copy bin\Cert.pem $(OUTPUTDIR)))&(if not exist $(OUTPUTDIR)Key.pem (copy bin\Key.pem $(OUTPUTDIR)))

Now it works as intended:

  • When $(OUTPUTDIR)Cert.pem exists but $(OUTPUTDIR)Key.pem does not, only $(OUTPUTDIR)Cert.pem is copied
  • When $(OUTPUTDIR)Cert.pem does exists but $(OUTPUTDIR)Key.pem does, only $(OUTPUTDIR)Key.pem is copied
  • when neither exist, both are copied
  • when both exist, neither are copied

I did not know this “trick” when writing my 2014 post Delphi prebuild/prelink/postbuild events, so I need to write an update for it.

Searching for batch file parentheses site:microsoft.com -site:social.technet.microsoft.com -site:answers.microsoft.com did not reveal it in the official documentation, but I am not surprised as it grew hysterically, instead of being designed. Or like the Old New Thing attributes h2g2:

Much like the universe, if anyone ever does fully come to understand Batch then the language will instantly be replaced by an infinitely weirder and more complex version of itself. This has obviously happened at least once before ;)

The best documentation I could find was at Parenthesis/Brackets – Windows CMD – SS64.com:

Parenthesis can be used to split commands across multiple lines. This can make code more readable. Variables will be evaluated for the code block just as if the command was a single line.

 (command)

 (
  command
  command )

Things that break inside parenthesis The CMD shell does not use any great intelligence when evaluating parenthesis, so for example the command below will fail:

IF EXIST MyFile.txt (ECHO Some(more)Potatoes)

–jeroen

Posted in Delphi, Development, Software Development | Leave a Comment »

dig: getting the list of root servers

Posted by jpluimers on 2018/11/15

For many dig queries, it helps to get the current list of root DNS servers.

Though the list is pretty static, occasionally it changes. While writing there were 13 of them and the most recent history report was in “RSSAC023: History of the Root Server System” at [WayBackwww.icann.org/en/system/files/files/rssac-023-04nov16-en.pdf.

So below are the steps to get an accurate list based on

First find out what the root servers are:

$  dig +noall +answer . ns | sort
.           106156  IN  NS  a.root-servers.net.
.           106156  IN  NS  b.root-servers.net.
.           106156  IN  NS  c.root-servers.net.
.           106156  IN  NS  d.root-servers.net.
.           106156  IN  NS  e.root-servers.net.
.           106156  IN  NS  f.root-servers.net.
.           106156  IN  NS  g.root-servers.net.
.           106156  IN  NS  h.root-servers.net.
.           106156  IN  NS  i.root-servers.net.
.           106156  IN  NS  j.root-servers.net.
.           106156  IN  NS  k.root-servers.net.
.           106156  IN  NS  l.root-servers.net.
.           106156  IN  NS  m.root-servers.net.

You should shorten this to $ dig +noall +answer . ns but that will not give you the TTL (how long the information will be cached before your DNS server refreshes it).

Now query at least 3 of these to get the actual list of root servers (I list only one statement, the rest is similar):

$ dig +noall +answer . ns @j.root-servers.net. | sort
.           518400  IN  NS  a.root-servers.net.
.           518400  IN  NS  b.root-servers.net.
.           518400  IN  NS  c.root-servers.net.
.           518400  IN  NS  d.root-servers.net.
.           518400  IN  NS  e.root-servers.net.
.           518400  IN  NS  f.root-servers.net.
.           518400  IN  NS  g.root-servers.net.
.           518400  IN  NS  h.root-servers.net.
.           518400  IN  NS  i.root-servers.net.
.           518400  IN  NS  j.root-servers.net.
.           518400  IN  NS  k.root-servers.net.
.           518400  IN  NS  l.root-servers.net.
.           518400  IN  NS  m.root-servers.net.

Compare the lists. If they are equal, then you’re done.

If not, then the internet is in trouble (:

When you want the A and AAAA records with IP addresses in addition to the NS records with names, then add +additional to your query:

dig +noall +answer +additional @j.root-servers.net. | sort
.           518400  IN  NS  a.root-servers.net.
.           518400  IN  NS  b.root-servers.net.
.           518400  IN  NS  c.root-servers.net.
.           518400  IN  NS  d.root-servers.net.
.           518400  IN  NS  e.root-servers.net.
.           518400  IN  NS  f.root-servers.net.
.           518400  IN  NS  g.root-servers.net.
.           518400  IN  NS  h.root-servers.net.
.           518400  IN  NS  i.root-servers.net.
.           518400  IN  NS  j.root-servers.net.
.           518400  IN  NS  k.root-servers.net.
.           518400  IN  NS  l.root-servers.net.
.           518400  IN  NS  m.root-servers.net.
a.root-servers.net. 518400  IN  A   198.41.0.4
a.root-servers.net. 518400  IN  AAAA    2001:503:ba3e::2:30
b.root-servers.net. 518400  IN  A   192.228.79.201
b.root-servers.net. 518400  IN  AAAA    2001:500:200::b
c.root-servers.net. 518400  IN  A   192.33.4.12
d.root-servers.net. 518400  IN  A   199.7.91.13
e.root-servers.net. 518400  IN  A   192.203.230.10
f.root-servers.net. 518400  IN  A   192.5.5.241
g.root-servers.net. 518400  IN  A   192.112.36.4
h.root-servers.net. 518400  IN  A   198.97.190.53
i.root-servers.net. 518400  IN  A   192.36.148.17
j.root-servers.net. 518400  IN  A   192.58.128.30
k.root-servers.net. 518400  IN  A   193.0.14.129
l.root-servers.net. 518400  IN  A   199.7.83.42
m.root-servers.net. 518400  IN  A   202.12.27.33

–jeroen

Posted in DNS, Internet, Power User | 1 Comment »

Find the TTL for a domain and subdomain by getting to the authoritative nameserver first

Posted by jpluimers on 2018/11/15

Lets find the authoritative name server and TTL (time to live) for the example.org domain and www.example.org subdomain.

Notes:

1a: get parents of name servers

First start with a root server (dig: getting the list of root servers) to get parents of the name servers for example.org (don’t you love indirection!):

$ dig +norecurse +noall +authority @f.root-servers.net. example.org.
org.            172800  IN  NS  a0.org.afilias-nst.info.
org.            172800  IN  NS  a2.org.afilias-nst.info.
org.            172800  IN  NS  b0.org.afilias-nst.org.
org.            172800  IN  NS  b2.org.afilias-nst.org.
org.            172800  IN  NS  c0.org.afilias-nst.info.
org.            172800  IN  NS  d0.org.afilias-nst.org.

You can repeat this query for 2 more root servers to ensure they are in sync.

1b: get authoritative name servers from the parents

Now repeat with at least 3 of these to ensure they give matching results for the name servers for example.org:

$ dig +norecurse +noall +authority @b0.org.afilias-nst.info. example.org.
example.org.        86400   IN  NS  b.iana-servers.net.
example.org.        86400   IN  NS  a.iana-servers.net.
$ dig +norecurse +noall +authority @c0.org.afilias-nst.info. example.org.
example.org.        86400   IN  NS  a.iana-servers.net.
example.org.        86400   IN  NS  b.iana-servers.net.
$ dig +norecurse +noall +authority @a0.org.afilias-nst.info. example.org.
example.org.        86400   IN  NS  a.iana-servers.net.
example.org.        86400   IN  NS  b.iana-servers.net.

2a: getting the domain name servers from a public name server

A query to a public DNS server will also return a name server list, but then you would need to know that name server first. In addition, you can not ask for +authority; you have to ask for +answer NS in stead:

$ dig +norecurse +noall +answer NS @8.8.8.8 example.org.
example.org.        55312   IN  NS  a.iana-servers.net.
example.org.        55312   IN  NS  b.iana-servers.net.

The name servers on the list are not guaranteed to be authoritative, as this query returns an empty result:

$ dig +norecurse +noall +authority @8.8.8.8 example.org.

2b. ensuring the name servers are authoritative name servers

From the name servers returned, you can now check if the servers themselves return the same name servers. If so, then you are sure they are authoritative:

$ dig +norecurse +noall +authority @a.iana-servers.net. example.org.
example.org.        86400   IN  NS  a.iana-servers.net.
example.org.        86400   IN  NS  b.iana-servers.net.
$ dig +norecurse +noall +authority @b.iana-servers.net. example.org.
example.org.        86400   IN  NS  b.iana-servers.net.
example.org.        86400   IN  NS  a.iana-servers.net.

3: get the actual TTL

With the authoritative name servers, you can get the actual TTL:

$ dig +norecurse +noall +answer SOA @a.iana-servers.net. example.org.
example.org.        3600    IN  SOA sns.dns.icann.org. noc.dns.icann.org. 2017042729 7200 3600 1209600 3600
$ dig +norecurse +noall +multiline +answer SOA @a.iana-servers.net. example.org.
example.org.        3600 IN SOA sns.dns.icann.org. noc.dns.icann.org. (
                2017042729 ; serial
                7200       ; refresh (2 hours)
                3600       ; retry (1 hour)
                1209600    ; expire (2 weeks)
                3600       ; minimum (1 hour)
                )

I got the +multiline trick from [WayBackHOWTO: Using dig(1) to Find DNS Time to Live (TTL) Values – A-Team Systems.

4: get the count down TTL from a local name server

You can repeat the above process with a non-authoritative name server a few times to see the TTL decrease:

$ dig +norecurse +noall +answer SOA example.org.
example.org.        322 IN  SOA sns.dns.icann.org. noc.dns.icann.org. 2017042729 7200 3600 1209600 3600
$ dig +norecurse +noall +answer SOA example.org.
example.org.        321 IN  SOA sns.dns.icann.org. noc.dns.icann.org. 2017042729 7200 3600 1209600 3600

This is for instance what is returned by [WayBackexample.org DNS information – who.is example.org DNS information. DNS records such SOA, TTL, MX, TXT and more.

Public DNS servers having multiple servers per IP can even run disperse TTL numbers, for instance Google DNS at 8.8.8.8 does this:

$ dig +norecurse +noall +answer SOA @8.8.8.8 example.org.
example.org.        13  IN  SOA sns.dns.icann.org. noc.dns.icann.org. 2017042729 7200 3600 1209600 3600
$ dig +norecurse +noall +answer SOA @8.8.8.8 example.org.
example.org.        1388    IN  SOA sns.dns.icann.org. noc.dns.icann.org. 2017042729 7200 3600 1209600 3600
$ dig +norecurse +noall +answer SOA @8.8.8.8 example.org.
example.org.        10  IN  SOA sns.dns.icann.org. noc.dns.icann.org. 2017042729 7200 3600 1209600 3600

Note that +nssearch does not work for me

Using +nssearch as per [WayBackHow to find what Authoritative Name Server provided the answer using dig? – Server Fault fails for me:

$ dig +nssearch example.org
SOA sns.dns.icann.org. noc.dns.icann.org. 2017042729 7200 3600 1209600 3600 from server 199.43.135.53 in 83 ms.
SOA sns.dns.icann.org. noc.dns.icann.org. 2017042729 7200 3600 1209600 3600 from server 199.43.133.53 in 144 ms.
;; connection timed out; no servers could be reached

This reveals this in the bold values:

  • The authoritative nameserver sns.dns.icann.org is not publicly accessible.
  • TTL 7200 (7200 seconds is 2 hours).

Future research

Authoritative answers might not be present in dig queries on some platforms. I need to dig deeper into [WayBackterminal – Dig not returning authority section? – Ask Different to see why.

Glue records are always tricky to get right: [WayBackHow to check domain NS glue records using dig « Admins eHow

–jeroen

Posted in *nix, *nix-tools, bash, Development, dig, DNS, Internet, Power User, Scripting, Software Development | Leave a Comment »

Setting the sound volume through NirCmd – Windows command line tool

Posted by jpluimers on 2018/11/14

I needed this during logon on Windows machines to set the sound volume: [WayBackNirCmd – Windows command line tool set-soundvolume-25-percent.bat:

:: requires https://www.nirsoft.net/utils/nircmd.html
:: 100% = 65535
nircmd setsysvolume 16000

Works on all Windows versions (7-10) I tested so far.

Via

There are way sexier ways to do this, but they were all too convoluted for the time I had to get this to work.

For the future:

–jeroen

Posted in Batch-Files, Development, Power User, Scripting, Software Development, Windows | Leave a Comment »

How to automatically choose a label color to contrast with background | TrendCT

Posted by jpluimers on 2018/11/14

Choosing label colours other than black or white is like making a dynamic mouse cursor that inverts the colours underneath it: it fails horribly in the low contrast regions, and looks very strange on pink-noise backgrounds.

This approach is uses black and white depending on the perceived brightness:

[WayBack] How to automatically choose a label color to contrast with background | TrendCT:

What would data viz be without labels? Just viz, that’s what. This guide aimed at web designers discusses how to choose a label text color with enough contrast.

Via: [WayBack] For all those people incapable of choosing the right color combinations. – Thomas Mueller (dummzeuch) – Google+

–jeroen

Posted in Algorithms, Development, Software Development, Usability, User Experience | Leave a Comment »

 
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