exec or open "|"?

[Zhang Weiwu]

Hello. This is my discovery so far, please correct me if I am wrong:

reasons against exec:

could not output error in real time, which is a vital requirement
for my case because stderr contained progress information.

reasons against pipe:

In case of pipe, open "|xxx | yyy |& cat" could offer TCL script
real time stderr output of the last command in the pipe, but it is
the stderr outupt of the first command that I am interested in.

Plus, I am not sure how to properly escape file names that I pass
to 'open "|"', as the file name may contain single-quote ("Mum's
Lunch.odt") and double-quote (Oliver "Ollo" Twist.txt), it seems
much easier for exec.

So it seems I cannot use neither. 3rd option is to write a shell script
that contains the pipe (open "|sh -c '$cmd'" is more likely cause
trouble with file names with quote). 4th option is to handle the pipe
with TCL (low efficiency). What would you do?

Thanks for advices in advance!

[Gerald W. Lester]

On 5/9/11 9:12 AM, Zhang Weiwu wrote:
> Hello. This is my discovery so far, please correct me if I am wrong:
>
> reasons against exec:
>
> could not output error in real time, which is a vital requirement
> for my case because stderr contained progress information.
>
> reasons against pipe:
>
> In case of pipe, open "|xxx | yyy |& cat" could offer TCL script
> real time stderr output of the last command in the pipe, but it is
> the stderr outupt of the first command that I am interested in.
>
> Plus, I am not sure how to properly escape file names that I pass
> to 'open "|"', as the file name may contain single-quote ("Mum's
> Lunch.odt") and double-quote (Oliver "Ollo" Twist.txt), it seems
> much easier for exec.

Neither or a problem, just have the file names in variables and do:
set fd [open "|xxx $fn(1) $fn2" ...]

> So it seems I cannot use neither. 3rd option is to write a shell script that
> contains the pipe (open "|sh -c '$cmd'" is more likely cause trouble with
> file names with quote). 4th option is to handle the pipe with TCL (low
> efficiency). What would you do?

Reread the Endekalogue until I understand it.

--
+------------------------------------------------------------------------+
| Gerald W. Lester, President, KNG Consulting LLC |
| Email: Gerald...@kng-consulting.net |
+------------------------------------------------------------------------+

[Ralf Fassel]

* Zhang Weiwu <zhangwei...@realss.com>

| Plus, I am not sure how to properly escape file names that I pass
| to 'open "|"', as the file name may contain single-quote ("Mum's
| Lunch.odt") and double-quote (Oliver "Ollo" Twist.txt), it seems
| much easier for exec.

Create the command as a *list*

set arg1 "Mum's Lunch.odt"
set arg2 {Oliver "Ollo" Twist.txt}

set cmd [list cmd $arg1 $arg2 $arg3]
set fd [open "|$cmd" ... ]

'open' parses its first arg as a list in the case of a pipeline, so any
spaces etc are conserved if you use 'list' to construct it.

R'

[Zhang Weiwu]

Thanks all for answering the first part of my question regarding to
escape quotes in file name. I think now I should bring up the second
question in more vivid form on its own. I'll send a separate post about it.

Thanks!