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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 Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own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))
Making programs easy for any user to start

If you write a program in Perl, your colleague writes a program in Tcl/Tk and your company runs an open source program that's written in Python, how do your users ensure that they get the right interpretter to run the program? You certainly don't want them to have to remember to type something like:

perl bestest
tcl greatprog
python goodprice

On systems running a Microsoft Windows operating system, you can simply give the programs appropriate extensions - .pl for Perl, .tcl for Tcl and .py for Python in my examples and - provided that the registry is set up correctly - the operating system will know which language interpretter to use.

On systems running Linux or Unix based operating systems, you have two steps to take:

a) The very first line of the file should start # - ! - then the full path to the executable language - typically:
#!/usr/bin/perl
#!/usr/bin/tclsh or #!/usr/bin/wish
#!/usr/bin/python

b) The file should be marked as being executable - normally done using the chmod command. Examples:
chmod ug+x bestest
chmod a+x greatprog
chmod 550 goodprice

On all systems you might also want to update the path that the operating system looks in for executable files using the PATH environment variable. Setting of this variable depends on which (if any) command line interpretter you're using. If you don't set the path, you can still run the program by double clicking it (windows explorer) or prefixing the file name with ./ to run it on Unix or Linux. Thus:
./bestest
./greatprog
./goodprice
(written 2005-05-29, updated 2006-06-05)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
Y102 - Python - Fundamentals
  [633] Copying a reference, or cloning - (2006-03-05)
  [748] Getting rid of variables after you have finished with them - (2006-06-06)
  [956] Python security - trouble with input - (2006-11-30)
  [1430] Integer v float - Python - (2007-11-12)
  [1448] Question on division (Java) - Also Perl, PHP, Python ... - (2007-11-28)
  [1461] Python - input v raw input - (2007-12-06)
  [1878] Pascals Triangle in Python and Java - (2008-11-10)
  [2368] Python - fresh examples of all the fundamentals - (2009-08-20)
  [2442] Variable storage - Perl, Tcl and Python compared - (2009-10-08)
  [2778] Learning to program in Python 2 ... and / or in Python 3 - (2010-05-24)
  [3083] Python - fresh examples from recent courses - (2010-12-11)
  [3181] Beware - a=a+b and a+=b are different - Python - (2011-02-23)
  [3278] Do I need to initialise variables - programming in C, C++, Perl, PHP, Python, Ruby or Java. - (2011-05-05)
  [3551] Some terms used in programming (Biased towards Python) - (2011-12-12)
  [3886] Formatting output - why we need to, and first Python example - (2012-10-09)
  [3917] BODMAS - the order a computer evaluates arithmetic expressions - (2012-11-09)
  [4324] Learning to program - variables and constants - (2014-11-22)
  [4442] Mutable v Immuatble objects in Python, and the implication - (2015-02-24)
  [4712] A reminder of the key issues to consider in moving from Python 2 to Python 3 - (2016-10-30)

T202 - Tcl/Tk - Tcl Fundamentals
  [3] Looking for a donkey - (2004-08-05)
  [210] Joining lists in Tcl. Indirect variables in Tcl. - (2005-02-12)
  [349] Comments in Tcl - (2005-06-16)
  [362] The ireallyreallywanna operator - (2005-06-28)
  [782] Converting between Hex and Decimal in Tcl - (2006-06-28)
  [1136] Buffering output - why it is done and issues raised in Tcl, Perl, Python and PHP - (2007-04-06)
  [1282] Stringing together Tcl scripts - (2007-07-29)
  [1426] Buffering up in Tcl - the empty coke can comparison - (2007-11-10)
  [1469] Curley brackets v double quotes - Tcl, Tk, Expect - (2007-12-12)
  [4453] Tcl variable names - no real limits! - (2015-03-10)

P203 - More about the Perl Environment
  [743] How to debug a Perl program - (2006-06-04)
  [1865] Debugging and Data::Dumper in Perl - (2008-11-02)
  [2876] Different perl examples - some corners I rarely explore - (2010-07-18)


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How far should our support go
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The backtick operator in Python and Perl
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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