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Full Discussion: Passing a file descriptor
Top Forums Shell Programming and Scripting Passing a file descriptor Post 302202391 by robotball on Wednesday 4th of June 2008 05:48:35 PM
Old 06-04-2008
Question Passing a file descriptor
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
 

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LEARN ABOUT OPENSOLARIS

dirfd

dirfd(3C)						   Standard C Library Functions 						 dirfd(3C)

NAME

       dirfd - get directory stream file descriptor

SYNOPSIS

       #include <dirent.h>

       int dirfd(DIR *dir);

DESCRIPTION

       The dirfd() function returns the file descriptor associated with the directory stream dir.

       This  file  descriptor  is  the one used internally by the directory stream operations. See opendir(3C), closedir(3C), readdir(3C), rewind-
       dir(3C), seekdir(3C), telldir(3C).  The file descriptor is automatically closed when closedir() is called for the directory stream  dir	or
       when one of the exec functions is called.  See exec(2).

       The  file descriptor can safely be used only by functions that do not depend on or alter the file position, such as fstat(2) and fchdir(2).
       Closing the file descriptor with close(2) or modifying the file position by means other than the directory stream operations  listed  above
       causes undefined behavior to occur when one of the directory stream operations is subsequently called with the directory stream dir.

RETURN VALUES

       Upon  successful  completion,  the  dirfd() function returns an open file descriptor for the directory associated with the directory stream
       dir.

ERRORS

       There are no defined error returns.  Passing an invalid directory stream as an argument to the dirfd() function results in undefined behav-
       ior.

USAGE

       The dirfd() function is intended to be used to obtain a file descriptor for use with the fchdir() function.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       close(2), exec(2), fchdir(2), fstat(2), closedir(3C), opendir(3C), readdir(3C), rewinddir(3C), seekdir(3C), telldir(3C), attributes(5)

SunOS 5.11							    24 Oct 2007 							 dirfd(3C)
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