NAME

       com_err - common error display routine

SYNOPSIS

        #include <et/com_err.h>
       void (*proc) (const char *, long, const char *, va_list);

       void com_err (const char *whoami, long code, const char *format, ...);

       proc = set_com_err_hook (proc);

       proc = reset_com_err_hook ();

       void initialize_XXXX_error_table ();

DESCRIPTION

       Com_err  displays  an  error  message  on the standard error stream stderr (see stdio(3S))
       composed of the whoami string, which should specify the program name or some subportion of
       a  program,  followed  by  an  error  message  generated from the code value (derived from
       compile_et(1)), and a string produced using the format string and any following arguments,
       in the same style as fprintf(3).

       The  behavior  of com_err can be modified using set_com_err_hook; this defines a procedure
       which is called with the arguments passed to com_err,  instead  of  the  default  internal
       procedure  which sends the formatted text to error output.  Thus the error messages from a
       program can all easily be  diverted  to  another  form  of  diagnostic  logging,  such  as
       syslog(3).   Reset_com_err_hook  may  be  used  to  restore the behavior of com_err to its
       default form.  Both  procedures  return  the  previous  ``hook''  value.   These  ``hook''
       procedures must have the declaration given for proc above in the synopsis.

       The  initialize_XXXX_error_table routine is generated mechanically by compile_et(1) from a
       source file containing names and associated strings.  Each table has a name of up to  four
       characters, which is used in place of the XXXX in the name of the routine.  These routines
       should be called before any of the corresponding error codes are used, so that the com_err
       library will recognize error codes from these tables when they are used.

       The  com_err.h  header  file should be included in any source file that uses routines from
       the com_err library; executable files must be linked using ``-lcom_err'' in order to cause
       the com_err library to be included.

SEE ALSO

       compile_et (1), syslog (3).

       Ken Raeburn, "A Common Error Description Library for UNIX".