Include LEVEL into SysLog log file

Question

Is it possibile to show the level (LOG_INFO, LOG_ERROR, ...) information passed to the "syslog" function into each log line?

Thank you! Antonio

Answer 1

You can write a wrapper function like this

#include <stdarg.h>
#include <stdio.h>
#include <syslog.h>
#include <string.h>
#include <stdlib.h>

int
mysyslog(int __level, const char *const syslogformat, ...)
{
    va_list args;
    char *format;
    size_t length;
    char *level;
    ssize_t result;

    va_start(args,syslogformat);

    level = "?";
    switch (__level)
    {
        case LOG_ALERT:
            level = "LOG_ALERT";
            break;
        case LOG_INFO:
            level = "LOG_INFO";
            break;
       case LOG_EMERG:
            level = "LOG_EMERG";
            break;
       case LOG_CRIT:
            level = "LOG_CRIT";
            break;
       case LOG_ERR:
            level = "LOG_ERR";
            break;
       case LOG_WARNING:
            level = "LOG_WARNING";
            break;
       case LOG_NOTICE:
            level = "LOG_NOTICE";
            break;
       case LOG_DEBUG:
            level = "LOG_DEBUG";
            break;
    }

    length = strlen(syslogformat) + strlen(level) + 2;
    format = malloc(length + 1);
    result = snprintf(format, length + 1, "%s: %s", level, syslogformat);
    if ((result < 0) || (result >= length + 1))
        return -1;
    vsyslog(__level, format, args);
    va_end(args);

    return 0;
}

int main(void) 
{
    mysyslog(LOG_NOTICE, "This is a log message `%d' with an integer as parameter\n", 100);
    return 0;
}

Answer 2

Just use a template for your destination file in which you specifie how your log message will be displayed/written; something like this shows only syslog level and message:

template t_example { template("${LEVEL}" "${MSG}"); };

destination d_example { file("/var/log/example.log" template(t_example) ); };