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digitalmars.D.learn - Basic question about stderr

reply chaseratx <test test.com> writes:
I'm learning D and I have a basic question.

I'm trying to write stderr to a file using open() (rather than 
shell piping/redirection).  It works for stdout but doesn't seem 
to work with stderr.

http://pastebin.com/KgzR9wAF

stdout is written to the file, but stderr is not and outputs to 
the shell.  I'm not sure why.  I Googled but couldn't find an 
answer.  Any hints?
May 21 2016
parent reply Era Scarecrow <rtcvb32 yahoo.com> writes:
On Saturday, 21 May 2016 at 21:21:31 UTC, chaseratx wrote:

 I'm learning D and I have a basic question.

 I'm trying to write stderr to a file using open() (rather than 
 shell piping/redirection).  It works for stdout but doesn't 
 seem to work with stderr.

 http://pastebin.com/KgzR9wAF

 stdout is written to the file, but stderr is not and outputs to 
 the shell.  I'm not sure why.  I Googled but couldn't find an 
 answer.  Any hints?


   // <= causes range violation, might use foreach instead
   while (i < numbers.length) {
     write(numbers[i], " ");
     stderr.write(numbers[i]*10); //force stderr, 10x to 
differentiate output

     with (stderr) {              //also force stderr
       write(" ");
     }
May 21 2016
parent reply chaseratx <test test.com> writes:
On Saturday, 21 May 2016 at 21:40:36 UTC, Era Scarecrow wrote:

 On Saturday, 21 May 2016 at 21:21:31 UTC, chaseratx wrote:

 I'm learning D and I have a basic question.

 I'm trying to write stderr to a file using open() (rather than 
 shell piping/redirection).  It works for stdout but doesn't 
 seem to work with stderr.

 http://pastebin.com/KgzR9wAF

 stdout is written to the file, but stderr is not and outputs 
 to the shell.  I'm not sure why.  I Googled but couldn't find 
 an answer.  Any hints?


   // <= causes range violation, might use foreach instead
   while (i < numbers.length) {
     write(numbers[i], " ");
     stderr.write(numbers[i]*10); //force stderr, 10x to 
 differentiate output

     with (stderr) {              //also force stderr
       write(" ");
     }


Thanks Era, but I am not trying to fix the range error.  That was 
put there intentionally to create stderr output.  I'm trying to 
figure out how to get ALL stderr output directed to a file the 
same as if I had used a "2>error.log" redirect from the command 
line.
May 21 2016
parent reply Era Scarecrow <rtcvb32 yahoo.com> writes:
On Saturday, 21 May 2016 at 21:47:20 UTC, chaseratx wrote:

 Thanks Era, but I am not trying to fix the range error.  That 
 was put there intentionally to create stderr output.  I'm 
 trying to figure out how to get ALL stderr output directed to a 
 file the same as if I had used a "2>error.log" redirect from 
 the command line.


  Ahh, I didn't realize you were intentionally trying to use the 
exception for the error output.

  I wonder, this sounds like a TLS (Thread Local Storage) issue 
where the local thread's stderr was updated but the global 
(shared?) one wasn't.

https://dlang.org/phobos/std_stdio.html#.stderr

The stderr is defined as "File stderr", not shared. I'm convinced 
TLS is the likely culprit. Unless you can affect the original 
instantiation it probably isn't going to work. I just tried using 
a static this() and it has a similar effect but doesn't affect 
stderr. :(
May 21 2016
next sibling parent reply Era Scarecrow <rtcvb32 yahoo.com> writes:
On Saturday, 21 May 2016 at 21:54:43 UTC, Era Scarecrow wrote:

 On Saturday, 21 May 2016 at 21:47:20 UTC, chaseratx wrote:

 Thanks Era, but I am not trying to fix the range error.  That 
 was put there intentionally to create stderr output.





  I wonder, this sounds like a TLS (Thread Local Storage) issue 
 where the local thread's stderr was updated but the global 
 (shared?) one wasn't.


  Well found a quick solution. gotta close the original handle 
first! :)

   stderr.close();
   stderr.open("error.log", "a");
   stdout.open("output.log", "a");
May 21 2016
parent reply chaseratx <test test.com> writes:
On Saturday, 21 May 2016 at 22:08:15 UTC, Era Scarecrow wrote:

 On Saturday, 21 May 2016 at 21:54:43 UTC, Era Scarecrow wrote:

 On Saturday, 21 May 2016 at 21:47:20 UTC, chaseratx wrote:

 Thanks Era, but I am not trying to fix the range error.  That 
 was put there intentionally to create stderr output.





  I wonder, this sounds like a TLS (Thread Local Storage) issue 
 where the local thread's stderr was updated but the global 
 (shared?) one wasn't.


  Well found a quick solution. gotta close the original handle 
 first! :)

   stderr.close();
   stderr.open("error.log", "a");
   stdout.open("output.log", "a");


Oh, excellent!  I will try that now. :)
May 21 2016
parent Mike Parker <aldacron gmail.com> writes:
On Saturday, 21 May 2016 at 22:11:30 UTC, chaseratx wrote:

 On Saturday, 21 May 2016 at 22:08:15 UTC, Era Scarecrow wrote:

 On Saturday, 21 May 2016 at 21:54:43 UTC, Era Scarecrow wrote:

 On Saturday, 21 May 2016 at 21:47:20 UTC, chaseratx wrote:

 Thanks Era, but I am not trying to fix the range error.  
 That was put there intentionally to create stderr output.





  I wonder, this sounds like a TLS (Thread Local Storage) 
 issue where the local thread's stderr was updated but the 
 global (shared?) one wasn't.


  Well found a quick solution. gotta close the original handle 
 first! :)

   stderr.close();
   stderr.open("error.log", "a");
   stdout.open("output.log", "a");


 Oh, excellent!  I will try that now. :)


This should also work:

stderr = File("error.log", "a");
stdout = File("output.log", "a");
May 21 2016
prev sibling parent chaseratx <test test.com> writes:
On Saturday, 21 May 2016 at 21:54:43 UTC, Era Scarecrow wrote:

 On Saturday, 21 May 2016 at 21:47:20 UTC, chaseratx wrote:

 Thanks Era, but I am not trying to fix the range error.  That 
 was put there intentionally to create stderr output.  I'm 
 trying to figure out how to get ALL stderr output directed to 
 a file the same as if I had used a "2>error.log" redirect from 
 the command line.


  Ahh, I didn't realize you were intentionally trying to use the 
 exception for the error output.

  I wonder, this sounds like a TLS (Thread Local Storage) issue 
 where the local thread's stderr was updated but the global 
 (shared?) one wasn't.

 https://dlang.org/phobos/std_stdio.html#.stderr

 The stderr is defined as "File stderr", not shared. I'm 
 convinced TLS is the likely culprit. Unless you can affect the 
 original instantiation it probably isn't going to work. I just 
 tried using a static this() and it has a similar effect but 
 doesn't affect stderr. :(


Ok, thanks for looking into it.  It does seem like it should work 
(to me) since there is no apparent difference between stdout and 
stderr in the docs, and using open() works for stdout.  Not 
something I could intuit.

Appreciate the help.
May 21 2016