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For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Network (TCP) client in Tcl

Posted by admin (Graham Ellis), 21 November 2002
I had a request on this week's course for a demo program in Tcl that visits a web site, picks up a page from that web site,  and analyses what it gets back.

OK ... here's a program that connects to www.ecb.int (which I have manually resolved to 193.96.201.13), grabs a page that contains a daily table of exchange rates between the Euro and about 30 other currencies, extracts the rate between the pound an Euro, and prints out the result:

Code:
#!/usr/bin/tcl

set sock [socket 193.96.201.13 80]

puts $sock "GET /home/eurofxref.htm HTTP/1.0\n"
flush $sock

while {[gets $sock line] >= 0} {
       append page $line
       }

regexp {>GBP<.*?>\s*<.*?>(.*?)<.*?>\s*<.*?>(.*?)<} $page all name rate

puts "Exchange rate to GBP ($name) from Euros is $rate"


Yep, it's that short!  And run, we get ....

Code:
$ ./exrate.tcl
Exchange rate to GBP (Pound sterling) from Euros is 0.63640
$


Footnote - the European Central Bank updates its exchange rates tables each afternoon, and declares on its website that this information is being placed in the public domain so you're free to use it too.  If you're going to use it many times per day, do the ECB the courtesty of grabbing a copy just once each time they update it, and cache the HTML on your local machine!






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