Add nohup tool (approved by Ben)

commands/simple/Makefile

@@ -133,6 +133,7 @@ ALL	= \
 	mt \
 	nm \
 	newroot \
+	nohup \
 	nonamed \
 	nice \
 	od \
@@ -591,6 +592,10 @@ nice:	nice.c
 	$(CCLD) -o $@ $<
 	@install -S 8kw $@
 
+nohup:	nohup.c
+	$(CCLD) -o $@ $<
+	@install -S 4kw $@
+
 nonamed:	nonamed.c
 	$(CCLD) -o $@ $<
 	@install -S 8kw $@
@@ -1022,6 +1027,7 @@ install:	\
 	/usr/bin/newroot \
 	/usr/bin/nm \
 	/usr/bin/nice \
+	/usr/bin/nohup \
 	/usr/bin/nonamed \
 	/usr/bin/od \
 	/usr/bin/passwd \
@@ -1443,6 +1449,9 @@ install:	\
 /usr/bin/nice:	nice
 	install -cs -o bin $< $@
 
+/usr/bin/nohup:	nohup
+	install -cs -o bin $< $@
+
 /usr/bin/nonamed:	nonamed
 	install -cs -o bin $< $@
 

commands/simple/nohup.c

@@ -0,0 +1,141 @@
+/*
+ * Copyright (c) 2009, Erik van der Kouwe
+ * All rights reserved.
+ *
+ * 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. 
+ * 3. The name of the author may not be used to endorse or promote products 
+ *    derived from this software without specific prior written permission. 
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
+ */
+ 
+/*
+ * Functionality implemented according to this specification:
+ * http://www.opengroup.org/onlinepubs/000095399/utilities/nohup.html
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#define NOHUP_OUT_FILENAME "nohup.out"
+
+static void print_usage(const char *argv0)
+{
+	printf("Usage: %s command [arg...]\n", argv0);
+}
+
+static int redirect_tty(void)
+{
+	int fd;
+	char buffer[PATH_MAX + 1], *home;
+
+	/* redirect stdout to a file if needed */
+	if (isatty(STDOUT_FILENO))
+	{
+		/* first try: current directory */
+		fd = open(NOHUP_OUT_FILENAME, O_WRONLY | O_APPEND | O_CREAT, S_IRUSR | S_IWUSR);
+		if (fd < 0)
+		{
+			/* alternative: home directory */
+			home = getenv("HOME");
+			if (home)
+			{
+				snprintf(buffer, sizeof(buffer), "%s/%s", home, NOHUP_OUT_FILENAME);
+				buffer[sizeof(buffer) - 1] = 0;
+				fd = open(buffer, O_WRONLY | O_APPEND | O_CREAT, S_IRUSR | S_IWUSR);
+			}
+		}
+				
+		if (fd < 0)
+		{
+			perror("cannot create " NOHUP_OUT_FILENAME " and $HOME/" NOHUP_OUT_FILENAME);
+			return -1;
+		}
+		
+		/* move the fd to stdout */
+		if (dup2(fd, STDOUT_FILENO) < 0 || close(fd) < 0)
+		{
+			perror("cannot redirect stdout");
+			return -1;
+		}
+	}
+	
+	/* redirect stderr to stdout if needed */
+	if (isatty(STDERR_FILENO))
+	{
+		if (dup2(STDOUT_FILENO, STDERR_FILENO) < 0)
+		{
+			perror("cannot redirect stderr");
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	struct sigaction sa;
+
+	/* check parameters */
+	if (argc < 2)
+	{
+		print_usage(argv[0]);
+		return 127;
+	}
+
+	/* ignore SIGHUP */
+	sa.sa_handler = SIG_IGN;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = 0;
+	if (sigaction(SIGHUP, &sa, NULL) < 0)
+	{
+		perror("cannot ignore SIGHUP");
+		return 127;
+	}
+
+	/* redirect TTY input and output */
+	if (redirect_tty() < 0)
+		return 127;
+
+	/* run the command */
+	execvp(argv[1], argv + 1);
+	perror("cannot execute");
+
+	/* exit code depends on whether the utility was found */
+	switch (errno)
+	{
+		case ELOOP:
+		case ENAMETOOLONG:
+		case ENOENT:
+		case ENOTDIR:
+			/* utility not found */
+			return 127;
+
+		default:
+			/* exec failed for other reason */
+			return 126;
+	}
+}

man/man1/nohup.1

@@ -0,0 +1,19 @@
+.TH NOHUP 1
+.SH NAME
+nohup \- ignore hangup signal
+.SH SYNOPSIS
+\fBnohup\fP \fIutility\fP [\fIargument\fP...]
+.SH DESCRIPTION
+The
+.B nohup
+utility runs \fIutility\fP while ignoring the SIGHUP signal. This 
+allows the process to continue running after the current terminal
+exits, for example when logging off a telnet session. 
+
+Unless output is explicitly redirected when invoking nohup, output is 
+appended to a file named nohup.out. This file is created in the current
+directory or, if this is not possible, in $HOME. If the standard error 
+stream is not explicitly redirected, it is sent to the standard output.
+.SH AUTHOR
+This manual page and the utility were written by Erik van der Kouwe 
+<vdkouwe@cs.vu.nl>.