Provided by: libpcp3-dev_6.3.0-1_amd64 
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 the file already exists, it will be renamed to logname.prev else removed. Due
to permissions restrictions, the rename or removal may not succeed, but in the common use cases
logname.prev remains with the contents of the previous version of logname. Then logname is recreated if
possible (to ensure correct ownership and permissions from the caller to pmOpenLog).
As a special case, if logname is "-" then no renaming, 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).