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

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Archive for February 18th, 2020

linux – Bash: Command grouping (&&, ||, …) – Stack Overflow

Posted by jpluimers on 2020/02/18

Excellent answer at [WayBack] linux – Bash: Command grouping (&&, ||, …) – Stack Overflow by Charles Duffy:

Operator precedence for && and || is strictly left-to-right.

Thus:

pwd; (ls) || { cd .. && ls student/; }  && cd student || cd / && cd ;

…is equivalent to…

pwd; { { { (ls) || { cd .. && ls student/; }; } && cd student; } || cd /; } && cd ; }

…breaking that down graphically:

pwd; {                                      # 1
       {                                    # 2
         { (ls) ||                          # 3
                   { cd .. &&               # 4
                              ls student/;  # 5
                   };                       # 6
         } && cd student;                   # 7
       } || cd /;                           # 8
     } && cd ;                              # 9
  1. pwd happens unconditionally
  2. (Grouping only)
  3. ls happens (in a subshell) unconditionally.
  4. cd .. happens if (3) failed.
  5. ls student/ happens if (3) failed and (4) succeeded
  6. (Grouping only)
  7. cd student happens if either (3) succeeded or both (4) and (5) succeeded.
  8. cd / happens if either [both (3) and one of (4) or (5) failed], or [(7) failed].
  9. cd happens if (7) occurred and succeeded, or (7) occurred and succeeded.

Using explicit grouping operators is wise to avoid confusing yourself. Avoiding writing code as hard to read as this is even wiser.

–jeroen

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

Some interesting Delphi MVVM posts…

Posted by jpluimers on 2020/02/18

Via [WayBack] We kick off a week of MVVM with an introduction of the Model-View-ViewModel pattern and how data binding is used to realize it. – Erik van Bilsen – Google+:

I wrote (and gave a few conference talks) about DSharp before, so the above is very interesting.

–jeroen

References:

Posted in Delphi, Development, Software Development | 2 Comments »

Scott Hanselman on Twitter: Learn C# in your browser, no install! Practice your .NET skills on an ChromeBook if you like! Your choice!

Posted by jpluimers on 2020/02/18

This is indeed an interesting live way to learn about C# even if you think you know most of it:

[WayBack] Scott Hanselman on Twitter: Learn C# in your browser, no install! Practice your .NET skills on an ChromeBook if you like! Your choice!

Here you go:

–jeroen

Read the rest of this entry »

Posted in .NET, C#, Development, Software Development | Leave a Comment »