git: 80a80b130ab1 - stable/13 - loader: create separate man pages for each of the loaders

From: Warner Losh <>
Date: Tue, 24 Jan 2023 22:09:54 UTC
The branch stable/13 has been updated by imp:


commit 80a80b130ab1f2be89a17758baab48ec04de7444
Author:     Warner Losh <>
AuthorDate: 2021-09-29 15:21:17 +0000
Commit:     Warner Losh <>
CommitDate: 2023-01-24 21:49:17 +0000

    loader: create separate man pages for each of the loaders
    Create a man page per loader. Loader(8) will have information common to
    all of them, while loader_${INTERP}(8) will have information relevant to
    that specific loader. Rewrite loader(8) to give an overview and point to
    the appropriate man page. Rewrite each of the loader_${INTER}(8) man
    pages to contain only the relevant information to that loader. Put all
    the common commands, environment variables, etc in loader_simp(8) and
    refernce that from the loader_lua or loader_4th man pages. The
    loader_lua(8) could use more details about the Lua
    integration. Additional organization may be benefitial.
    Sponsored by:           Netflix
    Differential Revision:
    (cherry picked from commit 9e1dc7bec331b4d120d4b0687cfd54692e4fddcb)
 stand/man/Makefile      |    2 +
 stand/man/loader.8      | 1083 ++---------------------------------------------
 stand/man/loader_4th.8  |  585 +++++++++++++++++++++++++
 stand/man/loader_lua.8  |  277 ++++++++++++
 stand/man/loader_simp.8 |   28 +-
 5 files changed, 911 insertions(+), 1064 deletions(-)

diff --git a/stand/man/Makefile b/stand/man/Makefile
index 5523908b6814..27370624ff62 100644
--- a/stand/man/Makefile
+++ b/stand/man/Makefile
@@ -5,6 +5,8 @@
 M.${MK_EFI}+=		boot1.efi.8
 M.yes+=			loader.8
 M.${MK_EFI}+=		loader.efi.8
+M.${MK_FORTH}+=		loader_4th.8
+M.${MK_LOADER_LUA}+=	loader_lua.8
 M.yes+=			loader_simp.8
diff --git a/stand/man/loader.8 b/stand/man/loader.8
index c606068941a7..b71ac71e16ce 100644
--- a/stand/man/loader.8
+++ b/stand/man/loader.8
@@ -1,5 +1,6 @@
 .\" Copyright (c) 1999 Daniel C. Sobral
 .\" All rights reserved.
+.\" Copyright (c) 2021 Warner Losh <>
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
@@ -24,7 +25,7 @@
 .\" $FreeBSD$
-.Dd April 7, 2021
+.Dd September 29, 2021
@@ -36,13 +37,14 @@ The program called
 is the final stage of
 .Fx Ns 's
 kernel bootstrapping process.
-On IA32 (i386) architectures, it is a
-.Pa BTX
-It is linked statically to
-.Xr libstand 3
-and usually located in the directory
-.Pa /boot .
+It is responsible for bringing the kernel, kernel modules and other files into
+It creates a set of
+.Xr sh 1
+like environment variables that are passed to the kernel.
+It executes boot scripts written in one of several interpreters.
+Together with the scripts, it controls the booting process and
+interaction with the user.
 It provides a scripting language that can be used to
 automate tasks, do pre-configuration or assist in recovery
@@ -53,10 +55,17 @@ The smaller one is a set of commands
 designed for direct use by the casual user, called "builtin
 commands" for historical reasons.
 The main drive behind these commands is user-friendliness.
-The bigger component is an
-.Tn ANS
-Forth compatible Forth interpreter based on FICL, by
+The larger component is the scripting language built into
+the boot loader.
+provides three different interpreters: Forth, Lua and Simple.
+The Forth loader is based on an ANS Forth compatible
+Forth interpreter based on FICL, by
 .An John Sadler .
+The Lua loader is includes a full Lua interpreter from
+.Pa .
+The Simple loader only interprets a list of builtin commands
+without any control structure.
 During initialization,
@@ -73,1039 +82,36 @@ and
 are set, and
 is set to 24.
-is initialized, the builtin words are added to its vocabulary, and
-.Pa /boot/loader.4th
-is processed if it exists.
-No disk switching is possible while that file is being read.
-The inner interpreter
-will use with
-is then set to
-.Ic interpret ,
-which is
-.Tn FICL Ns 's
-After that,
-.Pa /boot/loader.rc
-is processed if available.
-These files are processed through the
-.Ic include
-command, which reads all of them into memory before processing them,
-making disk changes possible.
-At this point, if an
-.Ic autoboot
-has not been tried, and if
-.Va autoboot_delay
-is not set to
-.Dq Li NO
-(not case sensitive), then an
-.Ic autoboot
-will be tried.
-If the system gets past this point,
-.Va prompt
-will be set and
-will engage interactive mode.
-Please note that historically even when
-.Va autoboot_delay
-is set to
-.Dq Li 0
-user will be able to interrupt autoboot process by pressing some key
-on the console while kernel and modules are being loaded.
-In some
-cases such behaviour may be undesirable, to prevent it set
-.Va autoboot_delay
-.Dq Li -1 ,
-in this case
-will engage interactive mode only if
-.Ic autoboot
-has failed.
+Finally, an interpreter specific file will be executed.
-.Nm ,
-builtin commands take parameters from the command line.
-the only way to call them from a script is by using
-.Pa evaluate
-on a string.
-If an error condition occurs, an exception will be generated,
-which can be intercepted using
-.Tn ANS
-Forth exception handling
-If not intercepted, an error message will be displayed and
-the interpreter's state will be reset, emptying the stack and restoring
-interpreting mode.
-The builtin commands available are:
-.Bl -tag -width Ds -compact
-.It Ic autoboot Op Ar seconds Op Ar prompt
-Proceeds to bootstrap the system after a number of seconds, if not
-interrupted by the user.
-Displays a countdown prompt
-warning the user the system is about to be booted,
-unless interrupted by a key press.
-The kernel will be loaded first if necessary.
-Defaults to 10 seconds.
-.It Ic bcachestat
-Displays statistics about disk cache usage.
-For debugging only.
-.It Ic boot
-.It Ic boot Ar kernelname Op Cm ...
-.It Ic boot Fl flag Cm ...
-Immediately proceeds to bootstrap the system, loading the kernel
-if necessary.
-Any flags or arguments are passed to the kernel, but they
-must precede the kernel name, if a kernel name is provided.
-The behavior of this builtin is changed if
-.Xr loader.4th 8
-is loaded.
-.It Ic echo Xo
-.Op Fl n
-.Op Aq message
-Displays text on the screen.
-A new line will be printed unless
-.Fl n
-is specified.
-.It Ic heap
-Displays memory usage statistics.
-For debugging purposes only.
-.It Ic help Op topic Op subtopic
-Shows help messages read from
-.Pa /boot/ .
-The special topic
-.Em index
-will list the topics available.
-.It Ic include Ar file Op Ar
-Process script files.
-Each file, in turn, is completely read into memory,
-and then each of its lines is passed to the command line interpreter.
-If any error is returned by the interpreter, the include
-command aborts immediately, without reading any other files, and
-returns an error itself (see
-.Sx ERRORS ) .
-.It Ic load Xo
-.Op Fl t Ar type
-.Ar file Cm ...
-Loads a kernel, kernel loadable module (kld), disk image,
-or file of opaque contents tagged as being of the type
-.Ar type .
-Kernel and modules can be either in a.out or ELF format.
-Any arguments passed after the name of the file to be loaded
-will be passed as arguments to that file.
-Use the
-.Li md_image
-type to make the kernel create a file-backed
-.Xr md 4
-This is useful for booting from a temporary rootfs.
-Currently, argument passing does not work for the kernel.
-.It Ic load_geli Xo
-.Op Fl n Ar keyno
-.Ar prov Ar file
-Loads a
-.Xr geli 8
-encryption keyfile for the given provider name.
-The key index can be specified via
-.Ar keyno
-or will default to zero.
-.It Ic ls Xo
-.Op Fl l
-.Op Ar path
-Displays a listing of files in the directory
-.Ar path ,
-or the root directory if
-.Ar path
-is not specified.
-.Fl l
-is specified, file sizes will be shown too.
-.It Ic lsdev Op Fl v
-Lists all of the devices from which it may be possible to load modules,
-as well as ZFS pools.
-.Fl v
-is specified, more details are printed, including ZFS pool information
-in a format that resembles
-.Nm zpool Cm status
-.It Ic lsmod Op Fl v
-Displays loaded modules.
-.Fl v
-is specified, more details are shown.
-.It Ic lszfs Ar filesystem
-A ZFS extended command that can be used to explore the ZFS filesystem
-hierarchy in a pool.
-Lists the immediate children of the
-.Ar filesystem .
-The filesystem hierarchy is rooted at a filesystem with the same name
-as the pool.
-.It Ic more Ar file Op Ar
-Display the files specified, with a pause at each
-.It Ic pnpscan Op Fl v
-Scans for Plug-and-Play devices.
-This is not functional at present.
-.It Ic read Xo
-.Op Fl t Ar seconds
-.Op Fl p Ar prompt
-.Op Va variable
-Reads a line of input from the terminal, storing it in
-.Va variable
-if specified.
-A timeout can be specified with
-.Fl t ,
-though it will be canceled at the first key pressed.
-A prompt may also be displayed through the
-.Fl p
-.It Ic reboot
-Immediately reboots the system.
-.It Ic set Ar variable
-.It Ic set Ar variable Ns = Ns Ar value
-Set loader's environment variables.
-.It Ic show Op Va variable
-Displays the specified variable's value, or all variables and their
-values if
-.Va variable
-is not specified.
-.It Ic unload
-Remove all modules from memory.
-.It Ic unset Va variable
-.Va variable
-from the environment.
-.It Ic \&?
-Lists available commands.
+The commands common to all interpreters are described in the
+.Xr loader_simp 8
-has actually two different kinds of
-.Sq environment
-There are ANS Forth's
-.Em environmental queries ,
-and a separate space of environment variables used by builtins, which
-are not directly available to Forth words.
-It is the latter type that this section covers.
-Environment variables can be set and unset through the
-.Ic set
-.Ic unset
-builtins, and can have their values interactively examined through the
-use of the
-.Ic show
-Their values can also be accessed as described in
-Notice that these environment variables are not inherited by any shell
-after the system has been booted.
-A few variables are set automatically by
-.Nm .
-Others can affect the behavior of either
-or the kernel at boot.
-Some options may require a value,
-while others define behavior just by being set.
-Both types of builtin variables are described below.
-.Bl -tag -width bootfile
-.It Va autoboot_delay
-Number of seconds
-.Ic autoboot
-will wait before booting.
-Configuration options are described in
-.Xr loader.conf 5 .
-.It Va boot_askname
-Instructs the kernel to prompt the user for the name of the root device
-when the kernel is booted.
-.It Va boot_cdrom
-Instructs the kernel to try to mount the root file system from CD-ROM.
-.It Va boot_ddb
-Instructs the kernel to start in the DDB debugger, rather than
-proceeding to initialize when booted.
-.It Va boot_dfltroot
-Instructs the kernel to mount the statically compiled-in root file system.
-.It Va boot_gdb
-Selects gdb-remote mode for the kernel debugger by default.
-.It Va boot_multicons
-Enables multiple console support in the kernel early on boot.
-In a running system, console configuration can be manipulated
-by the
-.Xr conscontrol 8
-.It Va boot_mute
-All kernel console output is suppressed when console is muted.
-In a running system, the state of console muting can be manipulated by the
-.Xr conscontrol 8
-.It Va boot_pause
-During the device probe, pause after each line is printed.
-.It Va boot_serial
-Force the use of a serial console even when an internal console
-is present.
-.It Va boot_single
-Prevents the kernel from initiating a multi-user startup; instead,
-a single-user mode will be entered when the kernel has finished
-device probing.
-.It Va boot_verbose
-Setting this variable causes extra debugging information to be printed
-by the kernel during the boot phase.
-.It Va bootfile
-List of semicolon-separated search path for bootable kernels.
-The default is
-.Dq Li kernel .
-.It Va comconsole_speed
-Defines the speed of the serial console (i386 and amd64 only).
-If the previous boot stage indicated that a serial console is in use
-then this variable is initialized to the current speed of the console
-serial port.
-Otherwise it is set to 9600 unless this was overridden using the
-variable when
-was compiled.
-Changes to the
-.Va comconsole_speed
-variable take effect immediately.
-.It Va comconsole_port
-Defines the base i/o port used to access console UART
-(i386 and amd64 only).
-If the variable is not set, its assumed value is 0x3F8, which
-corresponds to PC port COM1, unless overridden by
-variable during the compilation of
-.Nm .
-Setting the
-.Va comconsole_port
-variable automatically set
-.Va hw.uart.console
-environment variable to provide a hint to kernel for location of the console.
-Loader console is changed immediately after variable
-.Va comconsole_port
-is set.
-.It Va comconsole_pcidev
-Defines the location of a PCI device of the 'simple communication'
-class to be used as the serial console UART (i386 and amd64 only).
-The syntax of the variable is
-.Li 'bus:device:function[:bar]' ,
-where all members must be numeric, with possible
-.Li 0x
-prefix to indicate a hexadecimal value.
-.Va bar
-member is optional and assumed to be 0x10 if omitted.
-The bar must decode i/o space.
-Setting the variable
-.Va comconsole_pcidev
-automatically sets the variable
-.Va comconsole_port
-to the base of the selected bar, and hint
-.Va hw.uart.console .
-Loader console is changed immediately after variable
-.Va comconsole_pcidev
-is set.
-.It Va console
-Defines the current console or consoles.
-Multiple consoles may be specified.
-In that case, the first listed console will become the default console for
-userland output (e.g.\& from
-.Xr init 8 ) .
-.It Va currdev
-Selects the default device to loader the kernel from.
-The syntax is:
-.Dl Ic loader_device:
-.Dl Ic zfs:dataset:
-.Dl Ic disk0p2:
-.Dl Ic zfs:zroot/ROOT/default:
-.It Va dumpdev
-Sets the device for kernel dumps.
-This can be used to ensure that a device is configured before the corresponding
-.Va dumpdev
-directive from
-.Xr rc.conf 5
-has been processed, allowing kernel panics that happen during the early stages
-of boot to be captured.
-.It Va init_chroot
-.Xr init 8 .
-.It Va init_exec
-.Xr init 8 .
-.It Va init_path
-Sets the list of binaries which the kernel will try to run as the initial
-The first matching binary is used.
-The default list is
-.Dq Li /sbin/init:/sbin/oinit:/sbin/init.bak:\:/rescue/init .
-.It Va init_script
-.Xr init 8 .
-.It Va init_shell
-.Xr init 8 .
-.It Va interpret
-Has the value
-.Dq Li OK
-if the Forth's current state is interpreting.
-Define the number of lines on the screen, to be used by the pager.
-.It Va module_path
-Sets the list of directories which will be searched for modules
-named in a load command or implicitly required by a dependency.
-The default value for this variable is
-.Dq Li /boot/kernel;/boot/modules .
-.It Va num_ide_disks
-Sets the number of IDE disks as a workaround for some problems in
-finding the root disk at boot.
-This has been deprecated in favor of
-.Va root_disk_unit .
-.It Va prompt
-Value of
-.Nm Ns 's
-Defaults to
-.Dq Li "${interpret}" .
-If variable
-.Va prompt
-is unset, the default prompt is
-.Ql > .
-.It Va root_disk_unit
-If the code which detects the disk unit number for the root disk is
-confused, e.g.\& by a mix of SCSI and IDE disks, or IDE disks with
-gaps in the sequence (e.g.\& no primary slave), the unit number can
-be forced by setting this variable.
-.It Va rootdev
-By default the value of
-.Va currdev
-is used to set the root file system
-when the kernel is booted.
-This can be overridden by setting
-.Va rootdev
-Other variables are used to override kernel tunable parameters.
-The following tunables are available:
-.Bl -tag -width Va
-.It Va efi.rt.disabled
-Disable UEFI runtime services in the kernel, if applicable.
-Runtime services are only available and used if the kernel is booted in a UEFI
-.It Va hw.physmem
-Limit the amount of physical memory the system will use.
-By default the size is in bytes, but the
-.Cm k , K , m , M , g
-.Cm G
-are also accepted and indicate kilobytes, megabytes and gigabytes
-An invalid suffix will result in the variable being ignored by the
-.It Va hw.pci.host_start_mem , hw.acpi.host_start_mem
-When not otherwise constrained, this limits the memory start
-The default is 0x80000000 and should be set to at least size of the
-memory and not conflict with other resources.
-Typically, only systems without PCI bridges need to set this variable
-since PCI bridges typically constrain the memory starting address
-(and the variable is only used when bridges do not constrain this
-.It Va hw.pci.enable_io_modes
-Enable PCI resources which are left off by some BIOSes or are not
-enabled correctly by the device driver.
-Tunable value set to ON (1) by default, but this may cause problems
-with some peripherals.
-.It Va kern.maxusers
-Set the size of a number of statically allocated system tables; see
-.Xr tuning 7
-for a description of how to select an appropriate value for this
-When set, this tunable replaces the value declared in the kernel
-compile-time configuration file.
-.It Va kern.ipc.nmbclusters
-Set the number of mbuf clusters to be allocated.
-The value cannot be set below the default
-determined when the kernel was compiled.
-.It Va kern.ipc.nsfbufs
-Set the number of
-.Xr sendfile 2
-buffers to be allocated.
-Not all architectures use such buffers; see
-.Xr sendfile 2
-for details.
-.It Va kern.maxswzone
-Limits the amount of KVM to be used to hold swap
-metadata, which directly governs the
-maximum amount of swap the system can support,
-at the rate of approximately 200 MB of swap space
-per 1 MB of metadata.
-This value is specified in bytes of KVA space.
-If no value is provided, the system allocates
-enough memory to handle an amount of swap
-that corresponds to eight times the amount of
-physical memory present in the system.
-Note that swap metadata can be fragmented,
-which means that the system can run out of
-space before it reaches the theoretical limit.
-Therefore, care should be taken to not configure
-more swap than approximately half of the
-theoretical maximum.
-Running out of space for swap metadata can leave
-the system in an unrecoverable state.
-Therefore, you should only change
-this parameter if you need to greatly extend the
-KVM reservation for other resources such as the
-buffer cache or
-.Va kern.ipc.nmbclusters .
-Modifies kernel option
-.It Va kern.maxbcache
-Limits the amount of KVM reserved for use by the
-buffer cache, specified in bytes.
-The default maximum is 200MB on i386,
-and 400MB on amd64.
-This parameter is used to
-prevent the buffer cache from eating too much
-KVM in large-memory machine configurations.
-Only mess around with this parameter if you need to
-greatly extend the KVM reservation for other resources
-such as the swap zone or
-.Va kern.ipc.nmbclusters .
-Note that
-the NBUF parameter will override this limit.
-.It Va kern.msgbufsize
-Sets the size of the kernel message buffer.
-The default limit of 96KB is usually sufficient unless
-large amounts of trace data need to be collected
-between opportunities to examine the buffer or
-dump it to a file.
-Overrides kernel option
-.It Va machdep.disable_mtrrs
-Disable the use of i686 MTRRs (x86 only).
-.It Va net.inet.tcp.tcbhashsize
-Overrides the compile-time set value of
-or the preset default of 512.
-Must be a power of 2.
-.It Va twiddle_divisor
-Throttles the output of the
-.Sq twiddle
-I/O progress indicator displayed while loading the kernel and modules.
-This is useful on slow serial consoles where the time spent waiting for
-these characters to be written can add up to many seconds.
-The default is 16; a value of 32 spins half as fast,
-while a value of 8 spins twice as fast.
-.It Va vm.kmem_size
-Sets the size of kernel memory (bytes).
-This overrides the value determined when the kernel was compiled.
-.It Va vm.kmem_size_min
-.It Va vm.kmem_size_max
-Sets the minimum and maximum (respectively) amount of kernel memory
-that will be automatically allocated by the kernel.
-These override the values determined when the kernel was compiled.
-supports the following format for specifying ZFS filesystems which
-can be used wherever
-.Xr loader 8
-refers to a device specification:
-.Ar zfs:pool/filesystem:
-.Pa pool/filesystem
-is a ZFS filesystem name as described in
-.Xr zfs 8 .
-.Pa /etc/fstab
-does not have an entry for the root filesystem and
-.Va vfs.root.mountfrom
-is not set, but
-.Va currdev
-refers to a ZFS filesystem, then
-will instruct kernel to use that filesystem as the root filesystem.
-When a builtin command is executed, the rest of the line is taken
-by it as arguments, and it is processed by a special parser which
-is not used for regular Forth commands.
-This special parser applies the following rules to the parsed text:
-.Bl -enum
-All backslash characters are preprocessed.
-.Bl -bullet
-\eb , \ef , \er , \en and \et are processed as in C.
-\es is converted to a space.
-\ev is converted to
-\ez is just skipped.
-Useful for things like
-.Dq \e0xf\ez\e0xf .
-\e0xN and \e0xNN are replaced by the hex N or NN.
-\eNNN is replaced by the octal NNN
-\e" , \e' and \e$ will escape these characters, preventing them from
-receiving special treatment in Step 2, described below.
-\e\e will be replaced with a single \e .
-In any other occurrence, backslash will just be removed.
-Every string between non-escaped quotes or double-quotes will be treated
-as a single word for the purposes of the remaining steps.
-Replace any
-with the value of the environment variable
-Space-delimited arguments are passed to the called builtin command.
-Spaces can also be escaped through the use of \e\e .
-An exception to this parsing rule exists, and is described in
-All builtin words are state-smart, immediate words.
-If interpreted, they behave exactly as described previously.
-If they are compiled, though,
-they extract their arguments from the stack instead of the command line.
-If compiled, the builtin words expect to find, at execution time, the
-following parameters on the stack:
-.D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
-.Ar addrX lenX
-are strings which will compose the command line that will be parsed
-into the builtin's arguments.
-Internally, these strings are concatenated in from 1 to N,
-with a space put between each one.
-If no arguments are passed, a 0
-.Em must
-be passed, even if the builtin accepts no arguments.
-While this behavior has benefits, it has its trade-offs.
-If the execution token of a builtin is acquired (through
-.Ic '
-.Ic ['] ) ,
-and then passed to
-.Ic catch
-.Ic execute ,
-the builtin behavior will depend on the system state
-.Bf Em
-at the time
-.Ic catch
-.Ic execute
-is processed!
-This is particularly annoying for programs that want or need to
-handle exceptions.
-In this case, the use of a proxy is recommended.
-For example:
-.Dl : (boot) boot ;
-is a Forth interpreter written in C, in the form of a forth
-virtual machine library that can be called by C functions and vice
-.Nm ,
-each line read interactively is then fed to
-.Tn FICL ,
-which may call
-back to execute the builtin words.
-The builtin
-.Ic include
-will also feed
-.Tn FICL ,
-one line at a time.
-The words available to
-can be classified into four groups.
-.Tn ANS
-Forth standard words, extra
-words, extra
-words, and the builtin commands;
-the latter were already described.
-.Tn ANS
-Forth standard words are listed in the
+The environment variables common to all interpreters are described in the
+.Xr loader_simp 8
-The words falling in the two other groups are described in the
-following subsections.
-.Bl -tag -width wid-set-super
-.It Ic .env
-.It Ic .ver
-.It Ic -roll
-.It Ic 2constant
-.It Ic >name
-.It Ic body>
-.It Ic compare
-This is the STRING word set's
-.Ic compare .
-.It Ic compile-only
-.It Ic endif
-.It Ic forget-wid
-.It Ic parse-word
-.It Ic sliteral
-This is the STRING word set's
-.Ic sliteral .
-.It Ic wid-set-super
-.It Ic w@
-.It Ic w!
-.It Ic x.
-.It Ic empty
-.It Ic cell-
-.It Ic -rot
-.Bl -tag -width XXXXXXXX
-.It Ic \&$ Pq --
-Evaluates the remainder of the input buffer, after having printed it first.
-.It Ic \&% Pq --
-Evaluates the remainder of the input buffer under a
-.Ic catch
-exception guard.
-.It Ic .#
-Works like
-.Ic "."
-but without outputting a trailing space.
-.It Ic fclose Pq Ar fd --
-Closes a file.
-.It Ic fkey Pq Ar fd -- char
-Reads a single character from a file.
-.It Ic fload Pq Ar fd --
-Processes a file
-.Em fd .
-.It Ic fopen Pq Ar addr len mode Li -- Ar fd
-Opens a file.
-Returns a file descriptor, or \-1 in case of failure.
-.Ar mode
-parameter selects whether the file is to be opened for read access, write
-access, or both.
-The constants
-are defined in
-.Pa /boot/support.4th ,
-indicating read only, write only, and read-write access, respectively.
-.It Xo
-.Ic fread
-.Pq Ar fd addr len -- len'
-Tries to read
-.Em len
-bytes from file
-.Em fd
-into buffer
-.Em addr .
-Returns the actual number of bytes read, or -1 in case of error or end of
-.It Ic heap? Pq -- Ar cells
-Return the space remaining in the dictionary heap, in cells.
-This is not related to the heap used by dynamic memory allocation words.
-.It Ic inb Pq Ar port -- char
-Reads a byte from a port.
-.It Ic key Pq -- Ar char
-Reads a single character from the console.
-.It Ic key? Pq -- Ar flag
-.Ic true
-if there is a character available to be read from the console.
-.It Ic ms Pq Ar u --
-.Em u
-.It Ic outb Pq Ar port char --
-Writes a byte to a port.
-.It Ic seconds Pq -- Ar u
-Returns the number of seconds since midnight.
-.It Ic tib> Pq -- Ar addr len
-Returns the remainder of the input buffer as a string on the stack.
-.It Ic trace! Pq Ar flag --
-Activates or deactivates tracing.
-Does not work with
-.Ic catch .
-.Bl -tag -width Ds
-.It arch-i386
-if the architecture is IA32.
-.It FreeBSD_version
-version at compile time.
-.It loader_version
-Access to the
-command line provides several ways of compromising system security,
-including, but not limited to:
-.Bl -bullet
-Booting from removable storage, by setting the
-.Va currdev
-.Va loaddev
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