Re: Command Languages Versus Programming Languages

On 30.03.2024 00:51, Lawrence D'Oliveiro wrote:

On Sat, 30 Mar 2024 00:14:42 +0100, Janis Papanagnou wrote:
 

So what is  'for i in a ; do ... ; done'  then in your world?

 
“for” is just the name of a command, like any other. In POSIX, this one
happens to be built into the shell; it might not in other shells.

'for' is a "reserved word" and part of a "compound command". It's
part of the _shell syntax_! - You get syntax errors like

  $ for ; do : ; done
  ksh: syntax error: `;' unexpected

And, specifically, "i in a" are *not* arguments of a 'for' command
but also part of the control construct syntax.

But, okay, I see where you're coming from.

Besides the naming, keep in mind that there's a semantical differences
between a "command", a "built-in command", and "shell construct". An
example where you can observe operational differences is:
  '/bin/test' and '/bin/['
  'test' and '['
  '[['
where (for example) the latter does not need quoting.

 $ x="Hello world" ; [[ $x == "Hello world" ]] ; echo $?
 0
 $ x="Hello world" ; [ $x == "Hello world" ] ; echo $?
 ksh: [: world: unknown operator
 2
 $ x="Hello world" ; [ "$x" == "Hello world" ] ; echo $?
 0

The distinction is important since there's operational differences
associated with these forms. The same holds for other control constructs
("built-in compound commands"), like 'case', or even simple assignments.

Janis