HP OpenVMS Systems

C stdout and log files? message logging?

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The Question is:

 
Hi...
   I've got an alpha running custom applications written in C (DEC C
V5.7-004 on OpenVMS Alpha V7.1)(by myself and other developers).
The applications are critical and run 7*24.  Informational messages and
alarms are written to log files via stdout.
The way these detached process are run, it allows me to look/edit the log
files while the programs are running, but alas,
the files get large over a few weeks, and the editor takes a while to bring
the files up or simply fails to bring them up.
 
I would like to be able tell my program to close the log file (stdout) and
re-open a new one.  Alas, my attempts so far have
ended up in a myriad of trials in file protections, none of which have
clearly duplicated the implicit open that VMS or the CRTL
stuffs into my code at link time.
 
 
 
any thoughts?
 
Thanks in advance
Mike
 

The Answer is :

 
  The OpenVMS Wizard would tend to use an I/O channel specifically
  for the log file, rather than stdout.  This allows you to have
  full control over the behaviour of the log file.  (Short of a
  process rundown and restart, there is no readily available way
  to switch a process log file.)
 
  For best control over file operations, the Wizard would tend to use
  RMS cakks directly.  (Obviously, C can also certainly be directly
  used for file access.  Native RMS calls provide much more direct
  control over the file-related activities, however.)
 
  To allow file sharing within C code, use options such as "shr=get"
  on the open -- see the documentation of creat for details -- and
  also remember to use the fsync and fflush calls at periodic intervals,
  as appropriate.
 
  A somewhat more unusual potential solution for your present
  application design -- one requiring fewer source modifications to
  your main applications -- would involve specifying the output device
  for the detached process as a mailbox, and creating a process that
  starts up before other applications, creates the necessary mailbox(es),
  and then reads the mailbox(es) and writes the contents of the messages
  to the file.
 
  In the longer term, the OpenVMS Wizard would tend to recommend the
  creation of a logging subsystem within the application, and writing
  binary (or binary and text format) messages into the logging subsystem
  for processing.  Processing could include generating alarms when
  specific conditions arise, or simply formatting and writing various
  of the message to a log file.
 
  There are a variety of C programming examples -- including examples
  using mailboxes and RMS calls -- available on the OpenVMS Freeware
  V4.0 CD-ROM.  Specifically, see the DISK$FREEWAREV4_2:[SRH_EXAMPLES]
  directory, among other directories.
 

  

     

     
answer written or last revised on ( 26-FEB-1999 )
     
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