NAME

       pmOpenLog - create a log file for diagnostics and debug output

C SYNOPSIS

       #include <pcp/pmapi.h>

       FILE *pmOpenLog(const char *progname, const char *logname, FILE *oldstream, int *status);

       cc ... -lpcp

DESCRIPTION

       pmOpenLog  reassigns  the standard I/O stream oldstream (normally stderr) to be associated
       with the file logname.  If logname is not "-" and already exists, it will be  removed  and
       recreated  if  possible  (to  ensure  correct ownership and permissions from the caller to
       pmOpenLog).

       As a special case, if logname is "-" then no removal or reopening  is  performed  and  the
       function  simply  sets  status to 1 and returns oldstream.  This is useful when the caller
       wants diagnostics on oldstream stream (normally stderr) rather than a file, e.g.  pmlogger
       -l-  or  pmcd  -f  -l-.   Logging  to  stderr  is also useful for PMDAs in a containerized
       environment where it is beneficial for all PMDA logs to be written to pmcd's stderr stream
       (and  thus  to  a  single  destination),  whether  that  is a file such as pmcd.log or the
       original stream inherited from the shell.

       On return, the function value is the standard I/O stream,  possibly  replacing  oldstream.
       In  the event of an error, the return value will be oldstream unchanged and status will be
       0.

       For success, status is 1, and a standard preamble is written to logname
            Log for progname on hostname started date and time
       and an atexit(3) handler is installed to write the postscript message to logname
            Log finished date and time
       when the processes exits.

       progname is only used to annotate messages.

SEE ALSO

       atexit(3) and freopen(3).