Very Computer

I'm have the following problem that I need a resolution to.  If anyone
can help out I would greatly appreciate it.

Problem:  I need to make a Korn Shell function that will log the run
               time output to a file PLUS the screen.  Also, I need
               it to log all the errors to a separate error log file
               PLUS the screen AND the run time output file.

I'm aware of the exec command and file descriptors but I only know how
to get them to redirect the output to just the file or the screen and
not both.  (Ex:  exec 1>sysout.log   -> for system output
                        exec 2>error.log      -> for error messages)

Any help or assistance would be great!

Jeff Dobies

| I'm have the following problem that I need a resolution to.  If anyone
| can help out I would greatly appreciate it.
|
| Problem:  I need to make a Korn Shell function that will log the run
|                time output to a file PLUS the screen.  Also, I need
|                it to log all the errors to a separate error log file
|                PLUS the screen AND the run time output file.

This isn't strictly a Korn shell issue, any Bourne class shell can do
this.  You're talking about copying output, and the solution to that
is a UNIX command tee(1).  The difficult part is that you want 3 copies
of the diagnostic output.

Here's how I did it - there could be other solutions.  Units 1 and 2 are
output and error output, respectively.  Unit 3 is created here for my
convenience.  The notation 2>&1 means redirect 2 into the stream already
open on 1.  Pipes involve unit 1.

$ (ls -li nosuchfile .kshrc 2>&1 1>&3 | tee /tmp/eele) 3>&1 | tee /tmp/eelo
nosuchfile not found
35208 -rw-r--r--   1 donn     user        1579 May  6 13:29 .kshrc
$ cat /tmp/eelo
nosuchfile not found
35208 -rw-r--r--   1 donn     user        1579 May  6 13:29 .kshrc
$ cat /tmp/eele
nosuchfile not found

To analyze this, start at the "outermost" level, the pipe to the final
tee.  It's copying 3 and 1 into the output log, and to the screen.
The subshell pipe is copying only 2 into the error log, because I
redirected 1 to 3, bypassing the pipe - the output from that tee is
unit 1 for the outer pipe, the output from ls is unit 3.

If you really need to set these units up during execution, as you'd
do with "exec", that's so much funkier that it would really be worth
looking at design alternatives.  You could use co-processes, first
the output tee and then the error tee, subsequently redirecting the
appropriate descriptor into the coprocess, like 2>&p.  Use the same
3>&1 technique to force output from the tees, which would normally
go back through the coprocess pipe pair.  For a more general approach
(coprocesses are ksh-specific), you could use named pipes (man mknod).

        Donn Cave, University Computing Services, University of Washington

Example Korn Shell Script:

more nosuchfile
more .kshrc
ls -las

Is there any commands that I can stick before these commands to
capture the desired results?  Or is there a way to enclose the series
of commands so that it will be logged as described originally?  Again,
thanks for your help...worse case senario, I'll have to have an extra
script for each execution - 1 for the logging process and the 2nd for
the actual execution of the script.  Obviously, it would be great if I
could reduce this down to one process/script.  

Jeff P. Dobies

: I'm have the following problem that I need a resolution to.  If anyone
: can help out I would greatly appreciate it.

: Problem:  I need to make a Korn Shell function that will log the run
:                time output to a file PLUS the screen.  Also, I need
:                it to log all the errors to a separate error log file
:                PLUS the screen AND the run time output file.

: I'm aware of the exec command and file descriptors but I only know how
: to get them to redirect the output to just the file or the screen and
: not both.  (Ex:  exec 1>sysout.log   -> for system output
:                         exec 2>error.log      -> for error messages)

: Any help or assistance would be great!

: Jeff Dobies

You use a coprocess piping the output to tee:

tee -a $logfile  >/dev/tty |&     # start the coprocess
exec 2>&p                         # dup stderr as input to coprocess

--
Dan Mercer

Opinions expressed herein are my own and may not represent those of my employer.