ref: 1717368f640180cab63a870a19d650276172cbfd
dir: /sys/src/libc/9sys/syslog.c/
#include <u.h> #include <libc.h> static struct { int fd; int consfd; char *name; Dir *d; Dir *consd; Lock; } sl = { -1, -1, }; static void _syslogopen(void) { char buf[1024]; if(sl.fd >= 0) close(sl.fd); snprint(buf, sizeof(buf), "/sys/log/%s", sl.name); sl.fd = open(buf, OWRITE|OCEXEC); } static int eqdirdev(Dir *a, Dir *b) { return a != nil && b != nil && a->dev == b->dev && a->type == b->type && a->qid.path == b->qid.path; } /* * Print * sysname: time: mesg * on /sys/log/logname. * If cons or log file can't be opened, print on the system console, too. */ void syslog(int cons, char *logname, char *fmt, ...) { char buf[1024]; char *ctim, *p; va_list arg; int n; Dir *d; char err[ERRMAX]; err[0] = '\0'; errstr(err, sizeof err); lock(&sl); /* * paranoia makes us stat to make sure a fork+close * hasn't broken our fd's */ d = dirfstat(sl.fd); if(sl.fd < 0 || sl.name == nil || strcmp(sl.name, logname) != 0 || !eqdirdev(d, sl.d)){ free(sl.name); sl.name = strdup(logname); if(sl.name == nil) cons = 1; else{ free(sl.d); sl.d = nil; _syslogopen(); if(sl.fd < 0) cons = 1; else sl.d = dirfstat(sl.fd); } } free(d); if(cons){ d = dirfstat(sl.consfd); if(sl.consfd < 0 || !eqdirdev(d, sl.consd)){ free(sl.consd); sl.consd = nil; sl.consfd = open("#c/cons", OWRITE|OCEXEC); if(sl.consfd >= 0) sl.consd = dirfstat(sl.consfd); } free(d); } if(fmt == nil){ unlock(&sl); return; } ctim = ctime(time(0)); p = buf + snprint(buf, sizeof(buf)-1, "%s ", sysname()); strncpy(p, ctim+4, 15); p += 15; *p++ = ' '; errstr(err, sizeof err); va_start(arg, fmt); p = vseprint(p, buf+sizeof(buf)-1, fmt, arg); va_end(arg); *p++ = '\n'; n = p - buf; if(sl.fd >= 0){ seek(sl.fd, 0, 2); write(sl.fd, buf, n); } if(cons && sl.consfd >=0) write(sl.consfd, buf, n); unlock(&sl); }