.TH PERROR 2
.SH NAME
perror, syslog \- system error messages
.SH SYNOPSIS
.B
void perror(char *s)
.PP
.B
void syslog(int cons, char *logname, char *fmt, ...)
.SH DESCRIPTION
.I Perror
produces a short error message
on the standard error file
describing the last error encountered during a call
to the system.
First the argument string
.I s
is printed, then a colon, then the message and a new-line.
If
.I s
is 0, only the error message and new-line are printed.
.PP
.I Syslog
logs messages in the file named by
.I logname
in the directory
.BR /sys/log ;
the file must already exist and should be append-only.
.I Logname
must contain no slashes.
The message is a line with up to five fields:
the current time;
the program name (if
.I argv0
is set; see
.IR ARG (2));
the user name;
the message specified by the
.IR print (2)
format
.I fmt
and any following arguments;
and a final newline.
If
.I cons
is set or the log file cannot be opened, the message is also printed
on the system console.
.I Syslog
can be used safely in multi-threaded programs.
.SH "SEE ALSO"
.IR intro (2),
.IR errstr (2)