Re: Set verbose Flag Inside if-block

[alex xmb ratchev]

On Sun, Apr 16, 2023, 23:10 Chet Ramey <chet.ramey@case.edu> wrote:

> On 4/16/23 4:46 PM, Sysadmin Lists wrote:
>
> >>> That's not what's happening. Breaking up that command line into
> newlines shows
> >>> the bug.  The first version should echo everything inside the
> if-statement after the
> >>>    'set -ve' but doesn't.
> >>
> >> It should not.
> >
> > It should. It'd be useful to only echo commands inside the if-block if
> we get there.
>
> It's simply not how the shell works. I'm not sure if you really understand
> the difference between the shell's reading input, parsing that input into
> commands, and executing those commands. The shell is not a read-and-
> execute-on-the-fly engine. Let me see if I can explain that below.
>
>
> >>> It's treating the entire if-block as a single command.
> >>
> >> The if command is a single compound command that is read and parsed in
> its
> >> entirety before any of it is executed.
> >
> > Why can't the same logic used for the -x flag apply to the -v flag here?
> It'd make sense.
>
> OK. `if' is a compound command. A compound command is a single syntactic
> unit in terms of parsing and execution. This means that the entire `if'
> command, from `if' to `fi', is read and parsed before the compound command
> is executed. (How else would you deal with syntax errors?) You can see
> where this is going: the entire body of the `if' command is read and parsed
> before even the condition is executed.
>
> The `-v' option affects behavior as a command is read. Since compound
> commands are read and parsed in their entirety before any execution, a
> `set -v' in the body of a compound command cannot affect the behavior of
> that command: by the time the verbose option is enabled, the entire `if'
> compound command has already been read and parsed.
>

you could use current .c mem runtime addr of the read , maybe supported
with slight meta data structure
or fill data structures
.. i mean , if u d care about such functionality ..
.. logic errs everywhere ..

The `-x' option, on the other hand, affects behavior as a command is
> executed. As soon as it's enabled, the shell enables execution tracing for
> subsequently-executed commands. Since it takes effect as a command is
> executing, even a compound command, it can affect commands following the
> `set -x' in the body of the compound command.
>
> --
> ``The lyf so short, the craft so long to lerne.'' - Chaucer
>                  ``Ars longa, vita brevis'' - Hippocrates
> Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/
>
>
>