.TH ERROR 3 local
.DA 8 May 1984
.SH NAME
error, warning \- print error messages
.SH SYNOPSIS
.nf
.B error(s1, s2)
.B char *s1;
.B char *s2;

.B warning(s1, s2)
.B char *s1;
.B char *s2;

.B extern char *progname;
.B extern int errno;

.B progname = argv[0];
.SH DESCRIPTION
.I Warning
prints an error message, with suitable embellishments,
and clears
.IR errno .
.I Error
does likewise and then exits.
The
.I s1
argument should be a
.I printf
format string (without a trailing newline), with
.I s2
available as an argument.
.PP
If there is an environment variable
.BR CMDNAME
with non-null value,
its contents are printed first, followed by a colon.
Following this,
any non-null value of
.I progname
is printed, followed by a colon and a space.
Following this,
.IR fprintf (3)
is invoked with
.I s1
as the format string and
.I s2
as the argument.
If the value of
.I errno
is within the normal range,
a standard elaborating message is printed (see
.IR intro (2)).
.PP
.B CMDNAME
should be set by shellfiles that expect subordinate programs to
issue error message in the shellfile's name.
.I Progname
should be set by all programs;
.I argv[0]
is usually a suitable thing to set it to.
.I Errno
is set by system calls and various other routines,
although its use is not universal;
note that it is not reset by successful system calls following an
unsuccessful one.
.SH SEE ALSO
intro(2), intro(3), printf(3), exit(2), getopt(3)
.SH DIAGNOSTICS
.IR Error 's
exit status is 1.
.SH HISTORY
Local products, modelled on the
.I error
in Kernighan&Pike.
.SH BUGS
Be nice if they could take a full
.IR printf -style
argument list.