I have a script that creates a KSH co-process for Oracle sqlplus and I am presently interacting with it via print -p and read -p.
I also need to interact with another Oracle database what isn't permitted to have any direct connection to the first. Presently, I simply disconnect from the first database, connect to the second database, and reconnect to the first database when I am finished, again using print -p and read -p.
I would like to enhance this a bit using a second co-process. I know how to create the second sqlplus co-process by first redirecting stdout and stdin for the first co-process using exec fd>&p and exec fd<&p. Then I can create the second co-process and interact with both.
My desire is to write a db_connect function that is capable of determining that a co-process has already been started and a new co-process with new file descriptors needs to be started. Along with this, I would like to dynamically determine which co-process to communicate to using generalized functions.
Any thoughts? Can the open file descriptors be tested? The version of KSH is KSH-88 I believe.
The only thing I can think of is to create a global variable and increment it for each co-process. The test on a fd that I know of is
[ -t $fd ]
which checks for being a tty.
Thanks for the suggestion with regards to using a global variable. I am not opposed to doing this. I hope that it doesn't get lost on the poor DBAs here who will have to maintain these scripts when I eventually have to move on.
I started working on a proof of concept and hit an unexpected snag using eval. My thought is that I would pass a handle (just a string really) to my database functions and build variables based on the handle. When I try to redirect stdout and stdin to some open file descriptors, I get an error.
eval exec ${TESTVAR_stdout}>&p <==== results in "t[13]: 3: not found"
The previous lines work fine, I am scratching my head on why TESTVAR_stdout isn't expanding properly.
What is more perplexing is If I manually execute the lines with numeric literals, it works. If I manually execute the lines using variable and no "eval", KSH indicates that I have running jobs for stdout and closes my session for stdin.
If I can get past this hurdle, I can implement the concept easily.
Sorry, I am not trying to bump up my post but I wanted to retract my previous post as the solution only works when I name my variables. I realized that I wasn't referencing my dynamic variable "x". I am still scratching my head...
Sorry, again, I am not trying to bump anything up, I have a core issue, that I am trying to narrow this thread's scope to focus on, using "eval" that is eluding me so if I can get past this, my problem is solved.
Essentially my "x" variable should be able to translate into another variable containing my file descriptor. If I can get "x" to expand into TEXTVAR2_stdout and then expand this so that "4" can be assigned to a local function variable, I am golden.
Code:
#!/usr/bin/ksh
sqlplus -s /nolog |&
x=TESTVAR2
eval export "${x}_stdout=3"
eval export "${x}_stdin=4"
# Print using named variables
print $TESTVAR2_stdout
print $TESTVAR2_stdin
# Same thing attempting expansion of my "x" variable;
# results in print TESTVAR2_stdout but no 4
eval "print ${x}_stdout"
# results in print $TESTVAR2_stdout
print $(expr $"${x}_stdout")
I get down to something that looks like $TESTVAR2_stdout but I cannot get the shell to treat it as a variable.
Hi, I'm playing with KSH
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:)
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Multiple co-processor file descriptors
I think I may have it
