Add err_set_file() and err_set_exit() functions to make it possible for

programs which use err(3) to work nicely in a wider range of environments
(e.g., dialog).

include/err.h

@@ -55,6 +55,8 @@ void		warn __P((const char *, ...));
 void		vwarn __P((const char *, _BSD_VA_LIST_));
 void		warnx __P((const char *, ...));
 void		vwarnx __P((const char *, _BSD_VA_LIST_));
+void		err_set_file __P((void *));
+void		err_set_exit __P((void (*)__P((int))));
 __END_DECLS
 
 #endif /* !_ERR_H_ */

lib/libc/gen/err.3

@@ -29,9 +29,10 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"	@(#)err.3	8.1 (Berkeley) 6/9/93
+.\"	From: @(#)err.3	8.1 (Berkeley) 6/9/93
+.\"	$Id$
 .\"
-.Dd "June 9, 1993"
+.Dd April 13, 1995
 .Dt ERR 3
 .Os BSD 4
 .Sh NAME
@@ -42,7 +43,9 @@
 .Nm warn ,
 .Nm vwarn ,
 .Nm warnx ,
-.Nm vwarnx
+.Nm vwarnx ,
+.Nm err_set_file ,
+.Nm err_set_exit
 .Nd formatted error messages
 .Sh SYNOPSIS
 .Fd #include <err.h>
@@ -62,13 +65,19 @@
 .Fn warnx "const char *fmt" "..."
 .Ft void
 .Fn vwarnx "const char *fmt" "va_list args"
+.Ft void
+.Fn err_set_file "void *fp"
+.Ft void
+.Fn err_set_exit "void (*exitf)(int)"
 .Sh DESCRIPTION
 The
 .Fn err
 and
 .Fn warn
 family of functions display a formatted error message on the standard
-error output.
+error output, or on another file specified using the
+.Fn err_set_file
+function.
 In all cases, the last component of the program name, a colon character,
 and a space are output.
 If the
@@ -95,6 +104,13 @@ and
 .Fn verrx
 functions do not return, but exit with the value of the argument
 .Fa eval .
+The
+.Fn err_set_exit
+function can be used to specify a function which is called before
+.Xr exit 2
+to perform any necessary cleanup; passing a null function pointer for
+.Va exitf
+resets the hook to do nothing.
 .Sh EXAMPLES
 Display the current errno information string and exit:
 .Bd -literal -offset indent

lib/libc/gen/err.c

@@ -49,6 +49,24 @@ static char sccsid[] = "@(#)err.c	8.1 (Berkeley) 6/4/93";
 
 extern char *__progname;		/* Program name, from crt0. */
 
+static FILE *err_file; /* file to use for error output */
+static void (*err_exit)(int);
+
+void
+err_set_file(void *fp)
+{
+	if (fp)
+		err_file = fp;
+	else
+		err_file = stderr;
+}
+
+void
+err_set_exit(void (*ef)(int))
+{
+	err_exit = ef;
+}
+
 __dead void
 #ifdef __STDC__
 err(int eval, const char *fmt, ...)
@@ -78,12 +96,16 @@ verr(eval, fmt, ap)
 	int sverrno;
 
 	sverrno = errno;
-	(void)fprintf(stderr, "%s: ", __progname);
+	if (! err_file)
+		err_set_file((FILE *)0);
+	(void)fprintf(err_file, "%s: ", __progname);
 	if (fmt != NULL) {
-		(void)vfprintf(stderr, fmt, ap);
-		(void)fprintf(stderr, ": ");
+		(void)vfprintf(err_file, fmt, ap);
+		(void)fprintf(err_file, ": ");
 	}
-	(void)fprintf(stderr, "%s\n", strerror(sverrno));
+	(void)fprintf(err_file, "%s\n", strerror(sverrno));
+	if(err_exit)
+		err_exit(eval);
 	exit(eval);
 }
 
@@ -113,10 +135,14 @@ verrx(eval, fmt, ap)
 	const char *fmt;
 	va_list ap;
 {
-	(void)fprintf(stderr, "%s: ", __progname);
+	if (! err_file)
+		err_set_file((FILE *)0);
+	(void)fprintf(err_file, "%s: ", __progname);
 	if (fmt != NULL)
-		(void)vfprintf(stderr, fmt, ap);
-	(void)fprintf(stderr, "\n");
+		(void)vfprintf(err_file, fmt, ap);
+	(void)fprintf(err_file, "\n");
+	if (err_exit)
+		err_exit(eval);
 	exit(eval);
 }
 
@@ -147,12 +173,14 @@ vwarn(fmt, ap)
 	int sverrno;
 
 	sverrno = errno;
-	(void)fprintf(stderr, "%s: ", __progname);
+	if (! err_file)
+		err_set_file((FILE *)0);
+	(void)fprintf(err_file, "%s: ", __progname);
 	if (fmt != NULL) {
-		(void)vfprintf(stderr, fmt, ap);
-		(void)fprintf(stderr, ": ");
+		(void)vfprintf(err_file, fmt, ap);
+		(void)fprintf(err_file, ": ");
 	}
-	(void)fprintf(stderr, "%s\n", strerror(sverrno));
+	(void)fprintf(err_file, "%s\n", strerror(sverrno));
 }
 
 void
@@ -179,8 +207,10 @@ vwarnx(fmt, ap)
 	const char *fmt;
 	va_list ap;
 {
-	(void)fprintf(stderr, "%s: ", __progname);
+	if (! err_file)
+		err_set_file((FILE *)0);
+	(void)fprintf(err_file, "%s: ", __progname);
 	if (fmt != NULL)
-		(void)vfprintf(stderr, fmt, ap);
-	(void)fprintf(stderr, "\n");
+		(void)vfprintf(err_file, fmt, ap);
+	(void)fprintf(err_file, "\n");
 }