Add pidfile() from NetBSD/OpenBSD, missing in GLIBC.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Makefile

@@ -56,7 +56,7 @@ endif
 DISTFILES   = README LICENSE
 HEADERS     = lite.h
 OBJS       := chomp.o copyfile.o dir.o fexist.o fisdir.o fmode.o fsendfile.o
-OBJS       += makepath.o rsync.o strlcpy.o strlcat.o strtonum.o tempfile.o
+OBJS       += makepath.o pidfile.o rsync.o strlcpy.o strlcat.o strtonum.o tempfile.o
 DEPS       := $(OBJS:.o=.d)
 JUNK        = *~ *.bak *.map .*.d *.d DEADJOE semantic.cache *.gdb *.elf core core.*
 

README.md

@@ -100,6 +100,22 @@ Generic Functions
   with the `dst` name.  On successful operation the source is removed
   and the function returns POSIX OK (0).
 
+- `pidfile(basename)`
+
+  Write a daemon pid file.  Creates a pidfile in `_PATH_VARRUN` using
+  either `basename` or, if `basename` is `NULL`, `__progname`.  The
+  file name has the form `/var/run/basename.pid`.
+
+  Use this function to create a pid file for your daemon when it is
+  ready to receive signals.  A client application may poll for the
+  existence of this file, so make sure to have your signal handlers
+  properly setup before calling this function.
+  
+  The pidfile is removed when the program exits, using an `atexit()`
+  handler.  However, depending on how the program terminates the file
+  may still exist even though the program is no longer running.  This
+  is only a problem for clients.
+
 - `rsync(src, dst, delete, *filter())`
 
   Very simple `rsync()` to copy files files and directories

lite.h

@@ -51,6 +51,8 @@ int     makepath   (char *dir);
 int     dir        (const char *dir, const char *type, int (*filter) (const char *file), char ***list, int strip);
 int     rsync      (char *src, char *dst, int delete, int (*filter) (const char *file));
 
+int     pidfile    (const char *basename);
+
 #ifndef strlcpy
 size_t  strlcpy    (char *dst, const char *src, size_t siz);
 #endif

pidfile.c

@@ -0,0 +1,107 @@
+/*	$OpenBSD: pidfile.c,v 1.10 2014/06/30 00:26:22 deraadt Exp $	*/
+/*	$NetBSD: pidfile.c,v 1.4 2001/02/19 22:43:42 cgd Exp $	*/
+
+/*-
+ * Copyright (c) 1999 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Jason R. Thorpe.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <errno.h>
+#include <paths.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+static char *pidfile_path;
+static pid_t pidfile_pid;
+
+static void pidfile_cleanup(void);
+
+extern char *__progname;
+
+int
+pidfile(const char *basename)
+{
+	int save_errno, result;
+	pid_t pid;
+	FILE *f;
+
+	if (basename == NULL)
+		basename = __progname;
+
+	if (pidfile_path != NULL) {
+		free(pidfile_path);
+		pidfile_path = NULL;
+	}
+
+	/* _PATH_VARRUN includes trailing / */
+	result = asprintf(&pidfile_path, "%s%s.pid", _PATH_VARRUN, basename);
+	if (result == -1 || pidfile_path == NULL)
+		return (-1);
+
+	if ((f = fopen(pidfile_path, "w")) == NULL) {
+		save_errno = errno;
+		free(pidfile_path);
+		pidfile_path = NULL;
+		errno = save_errno;
+		return (-1);
+	}
+
+	pid = getpid();
+	if (fprintf(f, "%ld\n", (long)pid) <= 0 || fflush(f) != 0) {
+		save_errno = errno;
+		(void) fclose(f);
+		(void) unlink(pidfile_path);
+		free(pidfile_path);
+		pidfile_path = NULL;
+		errno = save_errno;
+		return (-1);
+	}
+	(void) fclose(f);
+
+	pidfile_pid = pid;
+	if (atexit(pidfile_cleanup) < 0) {
+		save_errno = errno;
+		(void) unlink(pidfile_path);
+		free(pidfile_path);
+		pidfile_path = NULL;
+		pidfile_pid = 0;
+		errno = save_errno;
+		return (-1);
+	}
+
+	return (0);
+}
+
+static void
+pidfile_cleanup(void)
+{
+
+	if (pidfile_path != NULL && pidfile_pid == getpid())
+		(void) unlink(pidfile_path);
+}