Import macOS userland

adv_cmds-176
basic_cmds-55
bootstrap_cmds-116.100.1
developer_cmds-66
diskdev_cmds-667.40.1
doc_cmds-53.60.1
file_cmds-321.40.3
mail_cmds-35
misc_cmds-34
network_cmds-606.40.1
patch_cmds-17
remote_cmds-63
shell_cmds-216.60.1
system_cmds-880.60.2
text_cmds-106

4 files changed, 963 insertions, 0 deletions

diff --git a/file_cmds/ln/link.1 b/file_cmds/ln/link.1
new file mode 100644
index 0000000..bfb5b6e
--- /dev/null
+++ b/file_cmds/ln/link.1
@@ -0,0 +1 @@
+.so man1/ln.1
diff --git a/file_cmds/ln/ln.1 b/file_cmds/ln/ln.1
new file mode 100644
index 0000000..d9edf00
--- /dev/null
+++ b/file_cmds/ln/ln.1
@@ -0,0 +1,233 @@
+.\"-
+.\" Copyright (c) 1980, 1990, 1993
+.\"	The Regents of the University of California.  All rights reserved.
+.\"
+.\" This code is derived from software contributed to Berkeley by
+.\" the Institute of Electrical and Electronics Engineers, Inc.
+.\"
+.\" 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.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
+.\"
+.\"	@(#)ln.1	8.2 (Berkeley) 12/30/93
+.\" $FreeBSD: src/bin/ln/ln.1,v 1.31 2006/02/14 11:08:05 glebius Exp $
+.\"
+.Dd July 12, 2019
+.Dt LN 1
+.Os
+.Sh NAME
+.Nm link ,
+.Nm ln
+.Nd make links
+.Sh SYNOPSIS
+.Nm ln
+.Op Fl Ffhinsv
+.Ar source_file
+.Op Ar link_name
+.Nm ln
+.Op Fl Ffhinsv
+.Ar source_file ...
+.Ar link_dirname
+.Nm link
+.Ar source_file Ar link_name
+.Sh DESCRIPTION
+The
+.Nm ln
+utility creates a new directory entry (linked file) which has the
+same modes as the original file.
+It is useful for maintaining multiple copies of a file in many places
+at once without using up storage for the
+.Dq copies ;
+instead, a link
+.Dq points
+to the original copy.
+There are two types of links; hard links and symbolic links.
+How a link
+.Dq points
+to a file is one of the differences between a hard and symbolic link.
+.Pp
+The options are as follows:
+.Bl -tag -width flag
+.\" ==========
+.It Fl F
+If the proposed link (link_name) already exists and is a directory, then remove it
+so that the link may occur.
+The
+.Fl F
+option should be used with either
+.Fl f
+or
+.Fl i
+options.
+If none is specified,
+.Fl f
+is implied.
+The
+.Fl F
+option is a no-op unless
+.Fl s
+option is specified.
+.It Fl h
+If the
+.Ar link_name
+or
+.Ar link_dirname
+is a symbolic link, do not follow it.
+This is most useful with the
+.Fl f
+option, to replace a symlink which may point to a directory.
+.\" ==========
+.It Fl f
+If the proposed link (link_name) already exists,
+then unlink it so that the link may occur.
+(The
+.Fl f
+option overrides any previous
+.Fl i
+options.)
+.\" ==========
+.It Fl i
+Cause
+.Nm ln
+to write a prompt to standard error if the proposed link exists.
+If the response from the standard input begins with the character
+.Sq Li y
+or
+.Sq Li Y ,
+then unlink the proposed link so that the link may occur.
+Otherwise, do not attempt the link.
+(The
+.Fl i
+option overrides any previous
+.Fl f
+options.)
+.\" ==========
+.It Fl n
+Same as
+.Fl h ,
+for compatibility with other
+.Nm ln
+implementations.
+.\" ==========
+.It Fl s
+Create a symbolic link.
+.\" ==========
+.It Fl v
+Cause
+.Nm ln
+to be verbose, showing files as they are processed.
+.El
+.Pp
+By default,
+.Nm ln
+makes
+.Em hard
+links.
+A hard link to a file is indistinguishable from the original directory entry;
+any changes to a file are effectively independent of the name used to reference
+the file.
+Hard links may not normally refer to directories and may not span file systems.
+.Pp
+A symbolic link contains the name of the file to
+which it is linked.
+The referenced file is used when an
+.Xr open 2
+operation is performed on the link.
+A
+.Xr stat 2
+on a symbolic link will return the linked-to file; an
+.Xr lstat 2
+must be done to obtain information about the link.
+The
+.Xr readlink 2
+call may be used to read the contents of a symbolic link.
+Symbolic links may span file systems and may refer to directories.
+.Pp
+Given one or two arguments,
+.Nm ln
+creates a link to an existing file
+.Ar source_file .
+If
+.Ar link_name
+is given, the link has that name;
+.Ar link_name
+may also be a directory in which to place the link;
+otherwise it is placed in the current directory.
+If only the directory is specified, the link will be made
+to the last component of
+.Ar source_file .
+.Pp
+Given more than two arguments,
+.Nm ln
+makes links in
+.Ar link_dirname
+to all the named source files.
+The links made will have the same name as the files being linked to.
+.Pp
+When the utility is called as
+.Nm link ,
+exactly two arguments must be supplied,
+neither of which may specify a directory.
+No options may be supplied in this simple mode of operation,
+which performs a
+.Xr link 2
+operation using the two passed arguments.
+.Sh COMPATIBILITY
+The
+.Fl h ,
+.Fl i ,
+.Fl n
+and
+.Fl v
+options are non-standard and their use in scripts is not recommended.
+They are provided solely for compatibility with other
+.Nm ln
+implementations.
+.Pp
+The
+.Fl F
+option is
+.Fx
+extention and should not be used in portable scripts.
+.Sh SEE ALSO
+.Xr link 2 ,
+.Xr lstat 2 ,
+.Xr readlink 2 ,
+.Xr stat 2 ,
+.Xr symlink 2 ,
+.Xr symlink 7
+.Sh STANDARDS
+The
+.Nm ln
+utility conforms to
+.St -p1003.2-92 .
+.Pp
+The simplified
+.Nm link
+command conforms to
+.St -susv2 .
+.Sh HISTORY
+An
+.Nm ln
+command appeared in
+.At v1 .
diff --git a/file_cmds/ln/ln.c b/file_cmds/ln/ln.c
new file mode 100644
index 0000000..0455dce
--- /dev/null
+++ b/file_cmds/ln/ln.c
@@ -0,0 +1,272 @@
+/*-
+ * Copyright (c) 1987, 1993, 1994
+ *	The Regents of the University of California.  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.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
+ */
+
+#if 0
+#ifndef lint
+static char const copyright[] =
+"@(#) Copyright (c) 1987, 1993, 1994\n\
+	The Regents of the University of California.  All rights reserved.\n";
+#endif /* not lint */
+
+#ifndef lint
+static char sccsid[] = "@(#)ln.c	8.2 (Berkeley) 3/31/94";
+#endif /* not lint */
+#endif
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD: src/bin/ln/ln.c,v 1.34 2006/02/14 11:08:05 glebius Exp $");
+
+#include <sys/param.h>
+#include <sys/stat.h>
+
+#include <err.h>
+#include <errno.h>
+#include <libgen.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+int	fflag;				/* Unlink existing files. */
+int	Fflag;				/* Remove empty directories also. */
+int	hflag;				/* Check new name for symlink first. */
+int	iflag;				/* Interactive mode. */
+int	sflag;				/* Symbolic, not hard, link. */
+int	vflag;				/* Verbose output. */
+					/* System link call. */
+int (*linkf)(const char *, const char *);
+char	linkch;
+
+int	linkit(const char *, const char *, int);
+void	usage(void);
+
+int
+main(int argc, char *argv[])
+{
+	struct stat sb;
+	char *p, *sourcedir;
+	int ch, exitval;
+
+	if (argc < 1)
+		usage();
+	/*
+	 * Test for the special case where the utility is called as
+	 * "link", for which the functionality provided is greatly
+	 * simplified.
+	 */
+	if ((p = rindex(argv[0], '/')) == NULL)
+		p = argv[0];
+	else
+		++p;
+	if (strcmp(p, "link") == 0) {
+		while (getopt(argc, argv, "") != -1)
+			usage();
+		argc -= optind;
+		argv += optind;
+		if (argc != 2)
+			usage();
+		linkf = link;
+		/* UNIX conformance requires that both operands be NOT a dir */
+		for (int i = 0; i < 2; i++) {
+			if (stat(argv[i], &sb) == 0 && S_ISDIR(sb.st_mode)){
+				errno = EISDIR;
+				warn("%s", argv[0]);
+				return 1;
+			}
+		}
+
+		exit(linkit(argv[0], argv[1], 0));
+	}
+
+	while ((ch = getopt(argc, argv, "Ffhinsv")) != -1)
+		switch (ch) {
+		case 'F':
+			Fflag = 1;
+			break;
+		case 'f':
+			fflag = 1;
+			iflag = 0;
+			break;
+		case 'h':
+		case 'n':
+			hflag = 1;
+			break;
+		case 'i':
+			iflag = 1;
+			fflag = 0;
+			break;
+		case 's':
+			sflag = 1;
+			break;
+		case 'v':
+			vflag = 1;
+			break;
+		case '?':
+		default:
+			usage();
+		}
+
+	argv += optind;
+	argc -= optind;
+
+	linkf = sflag ? symlink : link;
+	linkch = sflag ? '-' : '=';
+	if (sflag == 0)
+		Fflag = 0;
+	if (Fflag == 1 && iflag == 0)
+		fflag = 1;
+
+	switch(argc) {
+	case 0:
+		usage();
+		/* NOTREACHED */
+	case 1:				/* ln target */
+		exit(linkit(argv[0], ".", 1));
+	case 2:				/* ln target source */
+		exit(linkit(argv[0], argv[1], 0));
+	default:
+		;
+	}
+					/* ln target1 target2 directory */
+	sourcedir = argv[argc - 1];
+	if (hflag && lstat(sourcedir, &sb) == 0 && S_ISLNK(sb.st_mode)) {
+		/*
+		 * We were asked not to follow symlinks, but found one at
+		 * the target--simulate "not a directory" error
+		 */
+		errno = ENOTDIR;
+		err(1, "%s", sourcedir);
+	}
+	if (stat(sourcedir, &sb))
+		err(1, "%s", sourcedir);
+	if (!S_ISDIR(sb.st_mode))
+		usage();
+	for (exitval = 0; *argv != sourcedir; ++argv)
+		exitval |= linkit(*argv, sourcedir, 1);
+	exit(exitval);
+}
+
+int
+linkit(const char *target, const char *source, int isdir)
+{
+	struct stat sb;
+	const char *p;
+	int ch, exists, first;
+	char path[PATH_MAX];
+	char bbuf[PATH_MAX];
+
+	if (!sflag) {
+		/* If target doesn't exist, quit now. */
+		if (stat(target, &sb)) {
+			warn("%s", target);
+			return (1);
+		}
+		/* Only symbolic links to directories. */
+		if (S_ISDIR(sb.st_mode)) {
+			errno = EISDIR;
+			warn("%s", target);
+			return (1);
+		}
+	}
+
+	/*
+	 * If the source is a directory (and not a symlink if hflag),
+	 * append the target's name.
+	 */
+	if (isdir ||
+	    (lstat(source, &sb) == 0 && S_ISDIR(sb.st_mode)) ||
+	    (!hflag && stat(source, &sb) == 0 && S_ISDIR(sb.st_mode))) {
+		if (strlcpy(bbuf, target, sizeof(bbuf)) >= sizeof(bbuf) ||
+		    (p = basename(bbuf)) == NULL ||
+		    snprintf(path, sizeof(path), "%s/%s", source, p) >=
+		    (ssize_t)sizeof(path)) {
+			errno = ENAMETOOLONG;
+			warn("%s", target);
+			return (1);
+		}
+		source = path;
+	}
+
+	exists = !lstat(source, &sb);
+	/*
+	 * If the file exists, then unlink it forcibly if -f was specified
+	 * and interactively if -i was specified.
+	 */
+	if (fflag && exists) {
+		if (Fflag && S_ISDIR(sb.st_mode)) {
+			if (rmdir(source)) {
+				warn("%s", source);
+				return (1);
+			}
+		} else if (unlink(source)) {
+			warn("%s", source);
+			return (1);
+		}
+	} else if (iflag && exists) {
+		fflush(stdout);
+		fprintf(stderr, "replace %s? ", source);
+
+		first = ch = getchar();
+		while(ch != '\n' && ch != EOF)
+			ch = getchar();
+		if (first != 'y' && first != 'Y') {
+			fprintf(stderr, "not replaced\n");
+			return (1);
+		}
+
+		if (Fflag && S_ISDIR(sb.st_mode)) {
+			if (rmdir(source)) {
+				warn("%s", source);
+				return (1);
+			}
+		} else if (unlink(source)) {
+			warn("%s", source);
+			return (1);
+		}
+	}
+
+	/* Attempt the link. */
+	if ((*linkf)(target, source)) {
+		warn("%s", source);
+		return (1);
+	}
+	if (vflag)
+		(void)printf("%s %c> %s\n", source, linkch, target);
+	return (0);
+}
+
+void
+usage(void)
+{
+	(void)fprintf(stderr, "%s\n%s\n%s\n",
+	    "usage: ln [-Ffhinsv] source_file [link_name]",
+	    "       ln [-Ffhinsv] source_file ... linkname_dir",
+	    "       link source_file link_name");
+	exit(1);
+}
diff --git a/file_cmds/ln/symlink.7 b/file_cmds/ln/symlink.7
new file mode 100644
index 0000000..7c6c757
--- /dev/null
+++ b/file_cmds/ln/symlink.7
@@ -0,0 +1,457 @@
+.\"-
+.\" Copyright (c) 1992, 1993, 1994
+.\"	The Regents of the University of California.  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.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
+.\"
+.\"	@(#)symlink.7	8.3 (Berkeley) 3/31/94
+.\" $FreeBSD: src/bin/ln/symlink.7,v 1.30 2005/02/13 22:25:09 ru Exp $
+.\"
+.Dd March 31, 1994
+.Dt SYMLINK 7
+.Os
+.Sh NAME
+.Nm symlink
+.Nd symbolic link handling
+.Sh SYMBOLIC LINK HANDLING
+Symbolic links are files that act as pointers to other files.
+To understand their behavior, you must first understand how hard links
+work.
+A hard link to a file is indistinguishable from the original file because
+it is a reference to the object underlying the original file name.
+Changes to a file are independent of the name used to reference the
+file.
+Hard links may not refer to directories and may not reference files
+on different file systems.
+A symbolic link contains the name of the file to which it is linked,
+i.e., it is a pointer to another name, and not to an underlying object.
+For this reason, symbolic links may reference directories and may span
+file systems.
+.Pp
+Because a symbolic link and its referenced object coexist in the file system
+name space, confusion can arise in distinguishing between the link itself
+and the referenced object.
+Historically, commands and system calls have adopted their own link
+following conventions in a somewhat ad-hoc fashion.
+Rules for more a uniform approach, as they are implemented in this system,
+are outlined here.
+It is important that local applications conform to these rules, too,
+so that the user interface can be as consistent as possible.
+.Pp
+Symbolic links are handled either by operating on the link itself,
+or by operating on the object referenced by the link.
+In the latter case,
+an application or system call is said to
+.Dq follow
+the link.
+Symbolic links may reference other symbolic links,
+in which case the links are dereferenced until an object that is
+not a symbolic link is found,
+a symbolic link which references a file which does not exist is found,
+or a loop is detected.
+(Loop detection is done by placing an upper limit on the number of
+links that may be followed, and an error results if this limit is
+exceeded.)
+.Pp
+There are three separate areas that need to be discussed.
+They are as follows:
+.Pp
+.Bl -enum -compact -offset indent
+.It
+Symbolic links used as file name arguments for system calls.
+.It
+Symbolic links specified as command line arguments to utilities that
+are not traversing a file tree.
+.It
+Symbolic links encountered by utilities that are traversing a file tree
+(either specified on the command line or encountered as part of the
+file hierarchy walk).
+.El
+.Ss System calls.
+The first area is symbolic links used as file name arguments for
+system calls.
+.Pp
+Except as noted below, all system calls follow symbolic links.
+For example, if there were a symbolic link
+.Dq Li slink
+which pointed to a file named
+.Dq Li afile ,
+the system call
+.Dq Li open("slink" ...\&)
+would return a file descriptor to the file
+.Dq afile .
+.Pp
+There are nine system calls that do not follow links, and which operate
+on the symbolic link itself.
+They are:
+.Xr lchflags 2 ,
+.Xr lchmod 2 ,
+.Xr lchown 2 ,
+.Xr lstat 2 ,
+.Xr lutimes 3 ,
+.Xr readlink 2 ,
+.Xr rename 2 ,
+.Xr rmdir 2 ,
+and
+.Xr unlink 2 .
+Because
+.Xr remove 3
+is an alias for
+.Xr unlink 2 ,
+it also does not follow symbolic links.
+When
+.Xr rmdir 2
+is applied to a symbolic link, it fails with the error
+.Er ENOTDIR .
+.Pp
+The owner and group of an existing symbolic link can be changed by
+means of the
+.Xr lchown 2
+system call.
+The flags, access permissions, owner/group and modification time of
+an existing symbolic link can be changed by means of the
+.Xr lchflags 2 ,
+.Xr lchmod 2 ,
+.Xr lchown 2 ,
+and
+.Xr lutimes 3
+system calls, respectively.
+Of these, only the flags are used by the system;
+the access permissions and ownership are ignored.
+.Pp
+The
+.Bx 4.4
+system differs from historical
+.Bx 4
+systems in that the system call
+.Xr chown 2
+has been changed to follow symbolic links.
+The
+.Xr lchown 2
+system call was added later when the limitations of the new
+.Xr chown 2
+became apparent.
+.Ss Commands not traversing a file tree.
+The second area is symbolic links, specified as command line file
+name arguments, to commands which are not traversing a file tree.
+.Pp
+Except as noted below, commands follow symbolic links named as command
+line arguments.
+For example, if there were a symbolic link
+.Dq Li slink
+which pointed to a file named
+.Dq Li afile ,
+the command
+.Dq Li cat slink
+would display the contents of the file
+.Dq Li afile .
+.Pp
+It is important to realize that this rule includes commands which may
+optionally traverse file trees, e.g.\& the command
+.Dq Li "chown file"
+is included in this rule, while the command
+.Dq Li "chown -R file"
+is not.
+(The latter is described in the third area, below.)
+.Pp
+If it is explicitly intended that the command operate on the symbolic
+link instead of following the symbolic link, e.g., it is desired that
+.Dq Li "chown slink"
+change the ownership of the file that
+.Dq Li slink
+is, whether it is a symbolic link or not, the
+.Fl h
+option should be used.
+In the above example,
+.Dq Li "chown root slink"
+would change the ownership of the file referenced by
+.Dq Li slink ,
+while
+.Dq Li "chown -h root slink"
+would change the ownership of
+.Dq Li slink
+itself.
+.Pp
+There are four exceptions to this rule.
+The
+.Xr mv 1
+and
+.Xr rm 1
+commands do not follow symbolic links named as arguments,
+but respectively attempt to rename and delete them.
+(Note, if the symbolic link references a file via a relative path,
+moving it to another directory may very well cause it to stop working,
+since the path may no longer be correct.)
+.Pp
+The
+.Xr ls 1
+command is also an exception to this rule.
+For compatibility with historic systems (when
+.Nm ls
+is not doing a tree walk, i.e., the
+.Fl R
+option is not specified),
+the
+.Nm ls
+command follows symbolic links named as arguments if the
+.Fl H
+or
+.Fl L
+option is specified,
+or if the
+.Fl F ,
+.Fl d
+or
+.Fl l
+options are not specified.
+(The
+.Nm ls
+command is the only command where the
+.Fl H
+and
+.Fl L
+options affect its behavior even though it is not doing a walk of
+a file tree.)
+.Pp
+The
+.Xr file 1
+command is also an exception to this rule.
+The
+.Xr file 1
+command does not follow symbolic links named as argument by default.
+The
+.Xr file 1
+command does follow symbolic links named as argument if
+.Fl L
+option is specified.
+.Pp
+The
+.Bx 4.4
+system differs from historical
+.Bx 4
+systems in that the
+.Nm chown
+and
+.Nm chgrp
+commands follow symbolic links specified on the command line.
+.Ss Commands traversing a file tree.
+The following commands either optionally or always traverse file trees:
+.Xr chflags 1 ,
+.Xr chgrp 1 ,
+.Xr chmod 1 ,
+.Xr cp 1 ,
+.Xr du 1 ,
+.Xr find 1 ,
+.Xr ls 1 ,
+.Xr pax 1 ,
+.Xr rm 1 ,
+.Xr tar 1
+and
+.Xr chown 8 .
+.Pp
+It is important to realize that the following rules apply equally to
+symbolic links encountered during the file tree traversal and symbolic
+links listed as command line arguments.
+.Pp
+The first rule applies to symbolic links that reference files that are
+not of type directory.
+Operations that apply to symbolic links are performed on the links
+themselves, but otherwise the links are ignored.
+.Pp
+The command
+.Dq Li "rm -r slink directory"
+will remove
+.Dq Li slink ,
+as well as any symbolic links encountered in the tree traversal of
+.Dq Li directory ,
+because symbolic links may be removed.
+In no case will
+.Nm rm
+affect the file which
+.Dq Li slink
+references in any way.
+.Pp
+The second rule applies to symbolic links that reference files of type
+directory.
+Symbolic links which reference files of type directory are never
+.Dq followed
+by default.
+This is often referred to as a
+.Dq physical
+walk, as opposed to a
+.Dq logical
+walk (where symbolic links referencing directories are followed).
+.Pp
+As consistently as possible, you can make commands doing a file tree
+walk follow any symbolic links named on the command line, regardless
+of the type of file they reference, by specifying the
+.Fl H
+(for
+.Dq half\-logical )
+flag.
+This flag is intended to make the command line name space look
+like the logical name space.
+(Note, for commands that do not always do file tree traversals, the
+.Fl H
+flag will be ignored if the
+.Fl R
+flag is not also specified.)
+.Pp
+For example, the command
+.Dq Li "chown -HR user slink"
+will traverse the file hierarchy rooted in the file pointed to by
+.Dq Li slink .
+Note, the
+.Fl H
+is not the same as the previously discussed
+.Fl h
+flag.
+The
+.Fl H
+flag causes symbolic links specified on the command line to be
+dereferenced both for the purposes of the action to be performed
+and the tree walk, and it is as if the user had specified the
+name of the file to which the symbolic link pointed.
+.Pp
+As consistently as possible, you can make commands doing a file tree
+walk follow any symbolic links named on the command line, as well as
+any symbolic links encountered during the traversal, regardless of
+the type of file they reference, by specifying the
+.Fl L
+(for
+.Dq logical )
+flag.
+This flag is intended to make the entire name space look like
+the logical name space.
+(Note, for commands that do not always do file tree traversals, the
+.Fl L
+flag will be ignored if the
+.Fl R
+flag is not also specified.)
+.Pp
+For example, the command
+.Dq Li "chown -LR user slink"
+will change the owner of the file referenced by
+.Dq Li slink .
+If
+.Dq Li slink
+references a directory,
+.Nm chown
+will traverse the file hierarchy rooted in the directory that it
+references.
+In addition, if any symbolic links are encountered in any file tree that
+.Nm chown
+traverses, they will be treated in the same fashion as
+.Dq Li slink .
+.Pp
+As consistently as possible, you can specify the default behavior by
+specifying the
+.Fl P
+(for
+.Dq physical )
+flag.
+This flag is intended to make the entire name space look like the
+physical name space.
+.Pp
+For commands that do not by default do file tree traversals, the
+.Fl H ,
+.Fl L
+and
+.Fl P
+flags are ignored if the
+.Fl R
+flag is not also specified.
+In addition, you may specify the
+.Fl H ,
+.Fl L
+and
+.Fl P
+options more than once; the last one specified determines the
+command's behavior.
+This is intended to permit you to alias commands to behave one way
+or the other, and then override that behavior on the command line.
+.Pp
+The
+.Xr ls 1
+and
+.Xr rm 1
+commands have exceptions to these rules.
+The
+.Nm rm
+command operates on the symbolic link, and not the file it references,
+and therefore never follows a symbolic link.
+The
+.Nm rm
+command does not support the
+.Fl H ,
+.Fl L
+or
+.Fl P
+options.
+.Pp
+To maintain compatibility with historic systems,
+the
+.Nm ls
+command acts a little differently.
+If you do not specify the
+.Fl F ,
+.Fl d
+or
+.Fl l
+options,
+.Nm ls
+will follow symbolic links specified on the command line.
+If the
+.Fl L
+flag is specified,
+.Nm ls
+follows all symbolic links,
+regardless of their type,
+whether specified on the command line or encountered in the tree walk.
+.Sh SEE ALSO
+.Xr chflags 1 ,
+.Xr chgrp 1 ,
+.Xr chmod 1 ,
+.Xr cp 1 ,
+.Xr du 1 ,
+.Xr find 1 ,
+.Xr ln 1 ,
+.Xr ls 1 ,
+.Xr mv 1 ,
+.Xr pax 1 ,
+.Xr rm 1 ,
+.Xr tar 1 ,
+.Xr lchflags 2 ,
+.Xr lchmod 2 ,
+.Xr lchown 2 ,
+.Xr lstat 2 ,
+.Xr lutimes 3 ,
+.Xr readlink 2 ,
+.Xr rename 2 ,
+.Xr symlink 2 ,
+.Xr unlink 2 ,
+.Xr fts 3 ,
+.Xr remove 3 ,
+.Xr chown 8