Shell Programming and Scripting

I am trying to right a function which uses a file descriptor to write to a log file. The problem is that the on the print statement the file descriptor is called bad. Now when I first open the file and print to it in the f_open function by passing the descriptor to f_print_log all works well, however when I returned the file descriptor to logtest.sh and then try to pass it to f_print_log I get bad file descriptor. Any help would be appreciated. Here are my functions and calling script:

********* THESE FUNCTIONS ARE IN f_log.sh
function f_open_log
{
next_fh=$LOG_FH_COUNTER
eval "exec $next_fh>$1"

f_print_log $next_fh "Log file opened"
(( LOG_FH_COUNTER=LOG_FH_COUNTER + 1 ))

echo ${next_fh}
return 0
}

function f_print_log
{
print -u$1 $2
return 0
}
***************************************************

logtest.sh -->

#!/bin/ksh

. f_log.sh

typeset -i LOG_FH_COUNTER=3

LOG=$(f_open_log bigfile)
f_print_log $LOG "This is a test"

exit

Which particular version of ksh are you using? ksh88, phksh or ksh93?

Thanks for responding. I am running ksh88.

I found what is causing the bad file descriptor, however I do not know how to get the funcitonallity I want to work. I left a line out out of the f_print_log function as I was trying not to make my post to long. The function should be

function f_print_log
{
[[ $VERBOSE == 0 ]] && print $2
print -u$1 $2
return 0
}

So if I set the VERBOSE option in logtest.sh, output would be written to the screen and the file, however when f_open_log is called and it writes the "Log file open" using the f_print_log subroutine both the file descriptor and that line are sent back to logtest.sh which generates the bad descriptor.

Any suggestions. I would like to keep the Log file opened line if I can. Thanks.

I don't think the descriptor will persist in the parent shell when you run it from inside backticks. At least that's the case here, with Bash.

Found a solution. I added an additional argument to the f_print_log routine to turn verbose off. I use this in the f_open_log routine and everything works fine.

The problem is with the following line of code

Code:

LOG=$(f_open_log bigfile)

This causes the file descriptor to be closed. One workaround is to use a global variable as in the following example

Code:

#!/bin/ksh88

typeset -i fh

function open_log
{
    next=${LOG_FH_COUNTER}
    eval "exec ${next}>$1"
    fh=${next}

    print_log ${next} "Log file opened"
    ((LOG_FH_COUNTER=LOG_FH_COUNTER+1))

    echo ${next}
}

function print_log
{
    print -u$1 $2
}

typeset -i LOG_FH_COUNTER=3
open_log bigfile
print_log ${fh} "This is a test"

exit 0