 @@ -1,2107 +1,2358 @@
-.\"	$NetBSD: sh.1,v 1.119 2016/02/24 15:28:36 wiz Exp $
+.\"	$NetBSD: sh.1,v 1.120 2016/03/31 16:18:22 christos Exp $
 .\" Copyright (c) 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
 .\"
 .\" This code is derived from software contributed to Berkeley by
 .\" Kenneth Almquist.
 .\"
 .\" 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. 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.
 .\"
 .\"	@(#)sh.1	8.6 (Berkeley) 5/4/95
 .\"
-.Dd January 5, 2015
+.Dd March 31, 2016
 .Dt SH 1
 .ds flags abCEeFfhnuvxIimpqV
 .Os
 .Sh NAME
 .Nm sh
 .Nd command interpreter (shell)
 .Sh SYNOPSIS
 .Nm
 .Bk -words
 .Op Fl \*[flags]
 .Op Cm +\*[flags]
 .Ek
 .Bk -words
 .Op Fl o Ar option_name
 .Op Cm +o Ar option_name
 .Ek
 .Bk -words
 .Op Ar command_file Oo Ar argument ... Oc
 .Ek
 .Nm
 .Fl c
 .Bk -words
 .Op Fl \*[flags]
 .Op Cm +\*[flags]
 .Ek
 .Bk -words
 .Op Fl o Ar option_name
 .Op Cm +o Ar option_name
 .Ek
 .Bk -words
 .Ar command_string
 .Op Ar command_name Oo Ar argument ... Oc
 .Ek
 .Nm
 .Fl s
 .Bk -words
 .Op Fl \*[flags]
 .Op Cm +\*[flags]
 .Ek
 .Bk -words
 .Op Fl o Ar option_name
 .Op Cm +o Ar option_name
 .Ek
 .Bk -words
 .Op Ar argument ...
 .Ek
 .Sh DESCRIPTION
 .Nm
 is the standard command interpreter for the system.
 The current version of
 .Nm
 is in the process of being changed to conform with the
 .Tn POSIX
 .2 and 1003.2a specifications for the shell.
 This version has many
 features which make it appear similar in some respects to the Korn shell,
 but it is not a Korn shell clone (see
 .Xr ksh 1 ) .
 Only features designated by
 .Tn POSIX ,
 plus a few Berkeley extensions, are being incorporated into this shell.
 .\" We expect
 .\" .Tn POSIX
 .\" conformance by the time 4.4 BSD is released.
 This man page is not intended
 to be a tutorial or a complete specification of the shell.
 .Ss Overview
 The shell is a command that reads lines from either a file or the
 terminal, interprets them, and generally executes other commands.
 It is the program that is running when a user logs into the system
 (although a user can select a different shell with the
 .Xr chsh 1
 command).
 The shell implements a language that has flow control
 constructs, a macro facility that provides a variety of features in
 addition to data storage, along with built in history and line editing
 capabilities.
 It incorporates many features to aid interactive use and
 has the advantage that the interpretative language is common to both
 interactive and non-interactive use (shell scripts).
 That is, commands
 can be typed directly to the running shell or can be put into a file and
 the file can be executed directly by the shell.
 .Ss Invocation
 If no arguments are present and if the standard input of the shell
 is connected to a terminal (or if the
 .Fl i
 flag is set),
 and the
 .Fl c
 option is not present, the shell is considered an interactive shell.
 An interactive shell generally prompts before each command and handles
 programming and command errors differently (as described below).
 When first starting,
 the shell inspects argument 0, and if it begins with a dash
 .Sq - ,
 the shell is also considered
 a login shell.
 This is normally done automatically by the system
 when the user first logs in.
 A login shell first reads commands
 from the files
 .Pa /etc/profile
 and
 .Pa .profile
 if they exist.
 If the environment variable
 .Ev ENV
 is set on entry to a shell, or is set in the
 .Pa .profile
 of a login shell, the shell next reads
 commands from the file named in
 .Ev ENV .
 Therefore, a user should place commands that are to be executed only at
 login time in the
 .Pa .profile
 file, and commands that are executed for every shell inside the
 .Ev ENV
 file.
 To set the
 .Ev ENV
 variable to some file, place the following line in your
 .Pa .profile
 of your home directory
 .Pp
 .Dl ENV=$HOME/.shinit; export ENV
 .Pp
 substituting for
 .Dq .shinit
 any filename you wish.
 Since the
 .Ev ENV
 file is read for every invocation of the shell, including shell scripts
 and non-interactive shells, the following paradigm is useful for
 restricting commands in the
 .Ev ENV
 file to interactive invocations.
 Place commands within the
 .Dq case
 and
 .Dq esac
 below (these commands are described later):
 .Pp
 .Bl -item -compact -offset indent
 .It
 .Li case $- in *i*)
 .Bl -item -compact -offset indent
 .It
 .Li # commands for interactive use only
 .It
 .Li ...
 .El
 .It
 .Li esac
 .El
 .Pp
 If command line arguments besides the options have been specified, then
 the shell treats the first argument as the name of a file from which to
 read commands (a shell script), and the remaining arguments are set as the
 positional parameters of the shell ($1, $2, etc).
 Otherwise, the shell
 reads commands from its standard input.
 .Ss Argument List Processing
 All of the single letter options have a corresponding name that can be
 used as an argument to the
 .Fl o
 option.
 The set
 .Fl o
 name is provided next to the single letter option in
 the description below.
 Specifying a dash
 .Dq -
 turns the option on, while using a plus
 .Dq +
 disables the option.
 The following options can be set from the command line or
 with the
 .Ic set
 built-in (described later).
 .Bl -tag -width aaaallexportfoo -offset indent
 .It Fl a Em allexport
 Export all variables assigned to.
 .It Fl c
 Read commands from the
 .Ar command_string
 operand instead of from the standard input.
 Special parameter 0 will be set from the
 .Ar command_name
 operand and the positional parameters ($1, $2, etc.)
 set from the remaining argument operands.
 .Fl c
 is only available at invocation, it cannot be
 .Ic set ,
 and there is no form using
 .Dq \&+ .
 .It Fl C Em noclobber
 Don't overwrite existing files with
 .Dq \*[Gt] .
 .It Fl e Em errexit
 If not interactive, exit immediately if any untested command fails.
 The exit status of a command is considered to be
 explicitly tested if the command is used to control an
 .Ic if ,
 .Ic elif ,
 .Ic while ,
 or
 .Ic until ,
 or if the command is the left hand operand of an
 .Dq \*[Am]\*[Am]
 or
 .Dq ||
 operator,
 or if it is a pipeline (or simple command) preceded by the
 .Dq \&!
 operator.
 With pipelines, only the status of the entire pipeline
 (indicated by the last command it contains)
 is tested when
 .Fl e
 is set to determine if the shell should exit.
 .It Fl f Em noglob
 Disable pathname expansion.
 .It Fl n Em noexec
 If not interactive, read commands but do not execute them.
 This is useful for checking the syntax of shell scripts.
 .It Fl u Em nounset
 Write a message to standard error when attempting to expand a variable
 that is not set, and if the shell is not interactive, exit immediately.
 .It Fl v Em verbose
 The shell writes its input to standard error as it is read.
 Useful for debugging.
 .It Fl x Em xtrace
 Write each command to standard error (preceded by a
 .Sq +\  )
 before it is executed.
 Useful for debugging.
 .It Fl q Em quietprofile
 If the
 .Fl v
 or
 .Fl x
 options have been set, do not apply them when reading
 initialization files, these being
 .Pa /etc/profile ,
 .Pa .profile ,
 and the file specified by the
 .Ev ENV
 environment variable.
 .It Fl I Em ignoreeof
 Ignore EOFs from input when interactive.
 .It Fl i Em interactive
 Force the shell to behave interactively.
 .It Fl m Em monitor
 Turn on job control (set automatically when interactive).
 .It Fl s Em stdin
 Read commands from standard input (set automatically if no file arguments
 are present).
 This option has no effect when set or reset after the shell has
 already started running (i.e. with
 .Ic set ) .
 .It Fl V Em vi
 Enable the built-in
 .Xr vi 1
 command line editor (disables
 .Fl E
 if it has been set).
 (See the
 .Sx Command Line Editing
 section below.)
 .It Fl E Em emacs
 Enable the built-in emacs style
 command line editor (disables
 .Fl V
 if it has been set).
 (See the
 .Sx Command Line Editing
 section below.)
 .It Fl b Em notify
 Enable asynchronous notification of background job completion.
 (Not implemented.)
 .It Fl F Em fork
 Cause the shell to always use
 .Xr fork 2
 instead of attempting
 .Xr vfork 2
 when it needs to create a new process.
 This should normally have no visible effect,
 but can slow execution.
 The
 .Nm
 can be compiled to always use
 .Xr fork 2
 in which case altering the
 .Fl F
 flag has no effect.
 .It Fl h Em trackall
 Bind commands in functions to file system paths when the function is defined.
 .\" They can seek me here (that dreaded filesystem)
 When off,
 the file system is searched for commands each time the function is invoked.
 (Not implemented.)
 .\" then can seek me there (the filesystem, once again)
 .It Fl p Em nopriv
 Do not attempt to reset effective uid if it does not match uid.
 This is not set by default to help avoid incorrect usage by setuid
 root programs via
 .Xr system 3
 or
 .Xr popen 3 .
 .It "\ \ " Em cdprint
 Make an interactive shell always print the new directory name when
 changed by the
 .Ic cd
 command.
 .It "\ \ " Em nolog
 Prevent the entry of function definitions into the command history (see
 .Ic fc
 in the
 .Sx Built-ins
 section.)
 (Not implemented.)
 .It "\ \ " Em posix
 Enables closer adherence to the shell standard.
 This option will default set at shell startup if the
 environment variable
 .Ev POSIXLY_CORRECT
 is present.
 That can be overridden by the
 .Fl o
 option on the command line.
 Currently this option controls whether (!posix) or not (posix)
 the file given by the
 .Ev ENV
 variable is read at startup by a non-interactive shell.
 Consequently, while it can be manipulated by the
 .Ic set
 command, doing so has no current purpose.
 .It "\ \ " Em tabcomplete
 Enables filename completion in the command line editor.
 Typing a tab character will extend the current input word to match a
 filename.
 If more than one filename matches it is only extended to be the common prefix.
 Typing a second tab character will list all the matching names.
 One of the editing modes, either
 .Fl E
 or
 .Fl V ,
 must be enabled for this to work.
 .El
 .Ss Lexical Structure
 The shell reads input in terms of lines from a file and breaks it up into
 words at whitespace (blanks and tabs), and at certain sequences of
 characters that are special to the shell called
 .Dq operators .
 There are two types of operators: control operators and redirection
 operators (their meaning is discussed later).
 Following is a list of operators:
 .Bl -ohang -offset indent
 .It "Control operators:"
 .Dl \*[Am]  \*[Am]\*[Am]  \&(  \&)  \&;  ;; | || \*[Lt]newline\*[Gt]
 .It "Redirection operators:"
 .Dl \*[Lt]  \*[Gt]  \*[Gt]|  \*[Lt]\*[Lt]  \*[Gt]\*[Gt]  \*[Lt]\*[Am]  \*[Gt]\*[Am]  \*[Lt]\*[Lt]-  \*[Lt]\*[Gt]
 .El
 .Ss Quoting
 Quoting is used to remove the special meaning of certain characters or
 words to the shell, such as operators, whitespace, or keywords.
 There are three types of quoting: matched single quotes,
 matched double quotes, and backslash.
 .Ss Backslash
 A backslash preserves the literal meaning of the following
 character, with the exception of
 .Aq newline .
 A backslash preceding a
 .Aq newline
 is treated as a line continuation.
 .Ss Single Quotes
 Enclosing characters in single quotes preserves the literal meaning of all
 the characters (except single quotes, making it impossible to put
 single quotes in a single-quoted string).
 .Ss Double Quotes
 Enclosing characters within double quotes preserves the literal
 meaning of all characters except dollar sign
 .Pq $ ,
 backquote
 .Pq ` ,
 and backslash
 .Pq \e .
 The backslash inside double quotes is historically weird, and serves to
 quote only the following characters:
 .Dl $  `  \*q  \e  \*[Lt]newline\*[Gt] .
 Otherwise it remains literal.
 .Ss Reserved Words
 Reserved words are words that have special meaning to the
 shell and are recognized at the beginning of a line and
 after a control operator.
 The following are reserved words:
 .Bl -column while while while while while -offset indent
 .It ! Ta elif Ta fi Ta while Ta case
 .It else Ta for Ta then Ta { Ta }
 .It do Ta done Ta until Ta if Ta esac
 .El
 .Pp
 Their meaning is discussed later.
 .Ss Aliases
 An alias is a name and corresponding value set using the
 .Ic alias
 built-in command.
 Whenever a reserved word may occur (see above),
 and after checking for reserved words, the shell
 checks the word to see if it matches an alias.
 If it does, it replaces it in the input stream with its value.
 For example, if there is an alias called
 .Dq lf
 with the value
 .Dq "ls -F" ,
 then the input:
 .Pp
 .Dl lf foobar Aq return
 .Pp
 would become
 .Pp
 .Dl ls -F foobar Aq return
 .Pp
 Aliases provide a convenient way for naive users to create shorthands for
 commands without having to learn how to create functions with arguments.
 They can also be used to create lexically obscure code.
 This use is discouraged.
 .Ss Commands
 The shell interprets the words it reads according to a language, the
 specification of which is outside the scope of this man page (refer to the
 BNF in the
 .Tn POSIX
 .2 document).
 Essentially though, a line is read and if the first
 word of the line (or after a control operator) is not a reserved word,
 then the shell has recognized a simple command.
 Otherwise, a complex
 command or some other special construct may have been recognized.
 .Ss Simple Commands
 If a simple command has been recognized, the shell performs
 the following actions:
 .Bl -enum -offset indent
 .It
 Leading words of the form
 .Dq name=value
 are stripped off and assigned to the environment of the simple command.
 Redirection operators and their arguments (as described below) are
 stripped off and saved for processing.
 .It
 The remaining words are expanded as described in the
 .Sx Word Expansions
 section below,
 and the first remaining word is considered the command name and the
 command is located.
 The remaining words are considered the arguments of the command.
 If no command name resulted, then the
 .Dq name=value
 variable assignments recognized in item 1 affect the current shell.
 .It
 Redirections are performed as described in the next section.
 .El
 .Ss Redirections
 Redirections are used to change where a command reads its input or sends
 its output.
 In general, redirections open, close, or duplicate an
 existing reference to a file.
 The overall format used for redirection is:
 .Pp
 .Dl [n] Va redir-op Ar file
 .Pp
 where
 .Va redir-op
 is one of the redirection operators mentioned previously.
 Following is a list of the possible redirections.
 The
 .Bq n
 is an optional number, as in
 .Sq 3
 (not
 .Sq Bq 3 ) ,
 that refers to a file descriptor.
 .Bl -tag -width aaabsfiles -offset indent
 .It [n] Ns \*[Gt] file
 Redirect standard output (or n) to file.
 .It [n] Ns \*[Gt]| file
 Same, but override the
 .Fl C
 option.
 .It [n] Ns \*[Gt]\*[Gt] file
 Append standard output (or n) to file.
 .It [n] Ns \*[Lt] file
 Redirect standard input (or n) from file.
 .It [n1] Ns \*[Lt]\*[Am] Ns n2
 Duplicate standard input (or n1) from file descriptor n2.
 .It [n] Ns \*[Lt]\*[Am]-
 Close standard input (or n).
 .It [n1] Ns \*[Gt]\*[Am] Ns n2
 Duplicate standard output (or n1) to n2.
 .It [n] Ns \*[Gt]\*[Am]-
 Close standard output (or n).
 .It [n] Ns \*[Lt]\*[Gt] file
 Open file for reading and writing on standard input (or n).
 .El
 .Pp
 The following redirection is often called a
 .Dq here-document .
 .Bl -item -offset indent
 .It
 .Li [n]\*[Lt]\*[Lt] delimiter
 .Dl here-doc-text ...
 .Li delimiter
 .El
 .Pp
-All the text on successive lines up to the delimiter, or to an EOF, is
+All the text on successive lines up to the delimiter,
 which must appear on a line by itself, with nothing other
 than an immediately following newline, is
 saved away and made available to the command on standard input, or file
 descriptor n if it is specified.
 If the delimiter as specified on the initial line is
 quoted, then the here-doc-text is treated literally; otherwise, the text is
 subjected to parameter expansion, command substitution, and arithmetic
 expansion as described in the
 .Sx Word Expansions
 section below.
 If the operator is
-.Dq \*[Lt]\*[Lt]-
+.Dq \*[Lt]\*[Lt]\(mi
 instead of
 .Dq \*[Lt]\*[Lt] ,
-then leading tabs in the here-doc-text are stripped.
+then leading tabs in all lines in the here-doc-text, including before the
 end delimiter, are stripped.
 If the delimiter is not quoted, lines in here-doc-text that end with
 an unquoted \e are joined to the following line, the \e and following
 newline are simply removed while reading the here-doc, which thus guarantees
 that neither of those lines can be the end delimiter.
 .Ss Search and Execution
 There are three types of commands: shell functions, built-in commands, and
 normal programs -- and the command is searched for (by name) in that order.
 They each are executed in a different way.
 .Pp
 When a shell function is executed, all of the shell positional parameters
 (except $0, which remains unchanged) are set to the arguments of the shell
 function.
 The variables which are explicitly placed in the environment of
 the command (by placing assignments to them before the function name) are
 made local to the function and are set to the values given.
 Then the command given in the function definition is executed.
 The positional parameters are restored to their original values
 when the command completes.
 This all occurs within the current shell.
 .Pp
 Shell built-ins are executed internally to the shell, without spawning a
 new process.
 .Pp
 Otherwise, if the command name doesn't match a function or built-in, the
 command is searched for as a normal program in the file system (as
 described in the next section).
 .\" But the damned elusive filesystem shall never be defeated!
 When a normal program is executed, the shell runs the program,
 passing the arguments and the environment to the program.
 If the program is not a normal executable file (i.e., if it does
 not begin with the "magic number" whose
 .Tn ASCII
 representation is "#!", so
 .Xr execve 2
 returns
 .Er ENOEXEC
 then) the shell will interpret the program in a subshell.
 The child shell will reinitialize itself in this case,
 so that the effect will be as if a
 new shell had been invoked to handle the ad-hoc shell script, except that
 the location of hashed commands located in the parent shell will be
 remembered by the child.
 .Pp
 Note that previous versions of this document and the source code itself
 misleadingly and sporadically refer to a shell script without a magic
 number as a "shell procedure".
 .Ss Path Search
 When locating a command, the shell first looks to see if it has a shell
 function by that name.
 Then it looks for a built-in command by that name.
 If a built-in command is not found, one of two things happen:
 .Bl -enum
 .It
 Command names containing a slash are simply executed without performing
 any searches.
 .It
 The shell searches each entry in
 .Ev PATH
 in turn for the command.
 The value of the
 .Ev PATH
 variable should be a series of entries separated by colons.
 Each entry consists of a directory name.
 The current directory may be indicated
 implicitly by an empty directory name, or explicitly by a single period.
 .El
 .Ss Command Exit Status
 Each command has an exit status that can influence the behavior
 of other shell commands.
 The paradigm is that a command exits
 with zero for normal or success, and non-zero for failure,
 error, or a false indication.
 The man page for each command
 should indicate the various exit codes and what they mean.
 Additionally, the built-in commands return exit codes, as does
 an executed shell function.
 .Pp
 If a command consists entirely of variable assignments then the
 exit status of the command is that of the last command substitution
 if any, otherwise 0.
 .Ss Complex Commands
 Complex commands are combinations of simple commands with control
 operators or reserved words, together creating a larger complex command.
 More generally, a command is one of the following:
 .Bl -bullet
 .It
 simple command
 .It
 pipeline
 .It
 list or compound-list
 .It
 compound command
 .It
 function definition
 .El
 .Pp
 Unless otherwise stated, the exit status of a command is that of the last
 simple command executed by the command.
 .Ss Pipelines
 A pipeline is a sequence of one or more commands separated
 by the control operator |.
 The standard output of all but
 the last command is connected to the standard input
 of the next command.
 The standard output of the last
 command is inherited from the shell, as usual.
 .Pp
 The format for a pipeline is:
 .Pp
 .Dl [!] command1 [ | command2 ...]
 .Pp
 The standard output of command1 is connected to the standard input of
 command2.
 The standard input, standard output, or both of a command is
 considered to be assigned by the pipeline before any redirection specified
 by redirection operators that are part of the command.
 .Pp
 If the pipeline is not in the background (discussed later), the shell
 waits for all commands to complete.
 .Pp
 If the reserved word ! does not precede the pipeline, the exit status is
 the exit status of the last command specified in the pipeline.
 Otherwise, the exit status is the logical NOT of the exit status of the
 last command.
 That is, if the last command returns zero, the exit status
 is 1; if the last command returns greater than zero, the exit status is
 zero.
 .Pp
 Because pipeline assignment of standard input or standard output or both
 takes place before redirection, it can be modified by redirection.
 For example:
 .Pp
 .Dl $ command1 2\*[Gt]\*[Am]1 | command2
 .Pp
 sends both the standard output and standard error of command1
 to the standard input of command2.
 .Pp
 A ; or
 .Aq newline
 terminator causes the preceding AND-OR-list (described
 next) to be executed sequentially; a \*[Am] causes asynchronous execution of
 the preceding AND-OR-list.
 .Pp
 Note that unlike some other shells, each process in the pipeline is a
 child of the invoking shell (unless it is a shell built-in, in which case
 it executes in the current shell -- but any effect it has on the
 environment is wiped).
 .Ss Background Commands -- \*[Am]
 If a command is terminated by the control operator ampersand (\*[Am]), the
 shell executes the command asynchronously -- that is, the shell does not
 wait for the command to finish before executing the next command.
 .Pp
 The format for running a command in background is:
 .Pp
 .Dl command1 \*[Am] [command2 \*[Am] ...]
 .Pp
 If the shell is not interactive, the standard input of an asynchronous
 command is set to
 .Pa /dev/null .
 The process identifier of the most recent command started in the
 background can be obtained from the value of the special parameter
 .Dq \&!
 (see
 .Sx Special Parameters ) .
 .Ss Lists -- Generally Speaking
 A list is a sequence of zero or more commands separated by newlines,
 semicolons, or ampersands, and optionally terminated by one of these three
 characters.
 The commands in a list are executed in the order they are written.
 If command is followed by an ampersand, the shell starts the
-command and immediately proceed onto the next command; otherwise it waits
+command and immediately proceeds to the next command; otherwise it waits
 for the command to terminate before proceeding to the next one.
 .Ss Short-Circuit List Operators
 .Dq \*[Am]\*[Am]
 and
 .Dq ||
 are AND-OR list operators.
 .Dq \*[Am]\*[Am]
 executes the first command, and then executes the second command if and only
 if the exit status of the first command is zero.
 .Dq ||
 is similar, but executes the second command if and only if the exit status
 of the first command is nonzero.
 .Dq \*[Am]\*[Am]
 and
 .Dq ||
 both have the same priority.
 Note that these operators are left-associative, so
 .Dq true || echo bar \*[Am]\*[Am] echo baz
 writes
 .Dq baz
 and nothing else.
 This is not the way it works in C.
 Also, if you forget the left-hand side (for example when continuing lines but
 forgetting to use a backslash) it defaults to a true statement.
 This behavior is not useful and should not be relied upon.
 Similarly, if input to the
 .Nm
 reaches end of file immediately after one of these operators,
 it is assumed that a true statement follows.
 This behavior is also not useful and should not be relied upon.
 .Ss Flow-Control Constructs -- if, while, for, case
 The syntax of the if command is
 .Bd -literal -offset indent
 if list
 then list
 [ elif list
 then    list ] ...
 [ else list ]
 fi
 .Ed
 .Pp
 The syntax of the while command is
 .Bd -literal -offset indent
 while list
 do   list
 done
 .Ed
 .Pp
 The two lists are executed repeatedly while the exit status of the
 first list is zero.
 The until command is similar, but has the word
 until in place of while, which causes it to
 repeat until the exit status of the first list is zero.
 .Pp
 The syntax of the for command is
 .Bd -literal -offset indent
-for variable in word ...
+for variable [ in word ... ]
 do   list
 done
 .Ed
 .Pp
-The words are expanded, and then the list is executed repeatedly with the
+The words are expanded, or "$@" if no words are given,
 and then the list is executed repeatedly with the
 variable set to each word in turn.
 do and done may be replaced with
 .Dq {
 and
-.Dq } .
+.Dq } ,
 but doing so is non-standard and not recommended.
 .Pp
 The syntax of the break and continue command is
 .Bd -literal -offset indent
 break [ num ]
 continue [ num ]
 .Ed
 .Pp
 Break terminates the num innermost for or while loops.
 Continue continues with the next iteration of the innermost loop.
 These are implemented as built-in commands.
 .Pp
 The syntax of the case command is
 .Bd -literal -offset indent
 case word in
 pattern) list ;;
 \&...
 esac
 .Ed
 .Pp
 The pattern can actually be one or more patterns (see
 .Sx Shell Patterns
 described later), separated by
 .Dq \*(Ba
 characters.
 .Ss Grouping Commands Together
 Commands may be grouped by writing either
 .Pp
 .Dl (list)
 .Pp
 or
 .Pp
 .Dl { list; }
 .Pp
 The first of these executes the commands in a subshell.
 Built-in commands grouped into a (list) will not affect the current shell.
 The second form does not fork another shell so is slightly more efficient.
 Grouping commands together this way allows you to redirect
 their output as though they were one program:
 .Bd -literal -offset indent
 { echo -n \*q hello \*q ; echo \*q world" ; } \*[Gt] greeting
 .Ed
 .Pp
 Note that
 .Dq }
 must follow a control operator (here,
 .Dq \&; )
 so that it is recognized as a reserved word and not as another command argument.
 .Ss Functions
 The syntax of a function definition is
 .Pp
-.Dl name ( ) command
+.Dl name ( ) command [ redirect... ]
 .Pp
 A function definition is an executable statement; when executed it
 installs a function named name and returns an exit status of zero.
 The command is normally a list enclosed between
 .Dq {
 and
 .Dq } .
 The standard syntax also allows the command to be any of the other
 compound commands, or a sub-shell, all of which are supported.
 As an extension, this shell also allows a simple command to be
 used, though users should be aware this is non-standard syntax.
 This means that
 .Dl l() ls "$@"
 works to make
 .Dq l
 an alternative name for the
 .Ic ls
 command.
 .Pp
 If the optional redirect, (see
 .Sx Redirections ) ,
 which may be of any of the normal forms,
 is given, it is applied each time the
 function is called.
 This means that a simple
 .Dq "Hello World
 function might be written (in the extended syntax) as:
 .Dl hello() cat <<EOF
 .Dl Hello World!
 .Dl EOF
 To be correctly standards conforming this should be re-written as:
 .Dl hello() { cat; } <<EOF
 .Dl Hello World!
 .Dl EOF
 Note the distinction between those forms, and
 .Dl hello() { cat <<EOF
 .Dl Hello World!
 .Dl EOF
 .Dl \&}
 which reads and processes the
 .Ic "here document
 each time the shell executes the function, and which applies
 that input only to the cat command, not to any other commands
 that might appear in the function.
 .Pp
 Variables may be declared to be local to a function by using a local
 command.
 This should appear as the first statement of a function, and the syntax is
 .Pp
 .Dl local [ variable | - ] ...
 .Pp
-.Dq Local
+.Dq Ic local
 is implemented as a built-in command.
 .Pp
-When a variable is made local, it inherits the initial value and exported
+When a variable is made local, it inherits the initial value and exported,
 unexportable,
 and read-only flags from the variable with the same name in the surrounding
 scope, if there is one.
 Otherwise, the variable is initially unset.
 Making a read-only variable local is possible, but pointless.
 If the
 .Ic readonly
 command is applied to a variable that has been declared local,
 the variable cannot be (further) modified within the function,
 or any other functions it calls, however when the function returns,
 the previous status (and value) of the variable is returned.
 .Pp
 Values may be given to local variables on the
 .Ic local
 command line in a similar fashion as used for
 .Ic export
 and
 .Ic readonly .
 .Pp
 The shell uses dynamic scoping, so that if you make the variable x local to
 function f, which then calls function g, references to the variable x made
 inside g will refer to the variable x declared inside f, not to the global
 variable named x.
 .Pp
 Note that the parameters $1, $2, ... (see
 .Sx Positional Parameters ) ,
 and $#, $* and $@ (see
 .Sx Special Parameters ) ,
 are always made local in all functions, and are reset inside the
 function to represent the options and arguments passed to the function.
 Note that $0 however retains the value it had outside the function,
 as do all the other special parameters.
 .Pp
 The only special parameter that can be made local is
 .Dq - .
 Making
 .Dq -
 local causes any shell options that are changed via the set command inside the
 function to be restored to their original values when the function
 returns.
 .Pp
 It is a syntax error to use
 .Ic local
 outside the scope of a function definition.
 When used inside a function, it exits with status 0.
 .Pp
 The syntax of the return command is
 .Pp
 .Dl return [ exitstatus ]
 .Pp
-It terminates the currently executing function.
+It terminates the currently executing function or
 .Dq \&.
 script.
 Return is implemented as a built-in command.
 The exit status of the function (or
 .Dl \&.
 command) is either that given on the
 .Ic return
 command line, or the value of the special parameter
 .Dq $?
 immediately before the return was executed.
 .Ss Variables and Parameters
 The shell maintains a set of parameters.
 A parameter denoted by a name is called a variable.
 When starting up, the shell turns all the environment
 variables into shell variables.
 New variables can be set using the form
 .Pp
 .Dl name=value
 .Pp
 Variables set by the user must have a name consisting solely of
 alphabetics, numerics, and underscores - the first of which must not be
 numeric.
 A parameter can also be denoted by a number or a special
 character as explained below.
 .Ss Positional Parameters
 A positional parameter is a parameter denoted by a number (n \*[Gt] 0).
 The shell sets these initially to the values of its command line arguments
 that follow the name of the shell script.
 The
 .Ic set
-built-in can also be used to set or reset them.
+built-in can also be used to set or reset them, and
 .Ic shift
 can be used to manipulate the list.
 .Pp
 To refer to the 10th (and later) positional parameters,
 the form ${n} must be used.
 Without the braces, a digit following
 .Dq $
 can only refer to one of the first 9 positional parameters,
 or the special parameter
 .Dq 0 .
 The word
 .Dq $10
 is treated identically to
 .Dq ${1}0 .
 .Ss Special Parameters
 A special parameter is a parameter denoted by one of the following special
 characters.
 The value of the parameter is listed next to its character.
 .Bl -tag -width thinhyphena
 .It *
 Expands to the positional parameters, starting from one.
 When the
 expansion occurs within a double-quoted string it expands to a single
 field with the value of each parameter separated by the first character of
 the
 .Ev IFS
 variable, or by a
 .Aq space
 if
 .Ev IFS
 is unset.
 .It @
 Expands to the positional parameters, starting from one.
 When the expansion occurs within double quotes, each positional
 parameter expands as a separate argument.
 If there are no positional parameters, the
 expansion of @ generates zero arguments, even when @ is
 double-quoted.
 What this basically means, for example, is
 if $1 is
 .Dq abc
 and $2 is
 .Dq def ghi ,
 then
 .Qq $@
 expands to
 the two arguments:
 .Pp
 .Sm off
 .Dl \*q abc \*q \  \*q def\ ghi \*q
 .Sm on
 .It #
 Expands to the number of positional parameters.
 .It \&?
 Expands to the exit status of the most recent pipeline.
 .It - (Hyphen.)
 Expands to the current option flags (the single-letter
 option names concatenated into a string) as specified on
 invocation, by the set built-in command, or implicitly
 by the shell.
 .It $
 Expands to the process ID of the invoked shell.
 A subshell retains the same value of $ as its parent.
 .It \&!
 Expands to the process ID of the most recent background
 command executed from the current shell.
 For a pipeline, the process ID is that of the last command in the pipeline.
 If no background commands have yet been started by the shell, then
 .Dq \&!
 will be unset.
 Once set, the value of
 .Dq \&!
 will be retained until another background command is started.
 .It 0 (Zero.)
 Expands to the name of the shell or shell script.
 .El
 .Ss Word Expansions
 This section describes the various expansions that are performed on words.
 Not all expansions are performed on every word, as explained later.
 .Pp
 Tilde expansions, parameter expansions, command substitutions, arithmetic
 expansions, and quote removals that occur within a single word expand to a
 single field.
 It is only field splitting or pathname expansion that can
 create multiple fields from a single word.
 The single exception to this
 rule is the expansion of the special parameter @ within double quotes, as
 was described above.
 .Pp
 The order of word expansion is:
 .Bl -enum
 .It
 Tilde Expansion, Parameter Expansion, Command Substitution,
 Arithmetic Expansion (these all occur at the same time).
 .It
 Field Splitting is performed on fields
 generated by step (1) unless the
 .Ev IFS
 variable is null.
 .It
 Pathname Expansion (unless set
 .Fl f
 is in effect).
 .It
 Quote Removal.
 .El
 .Pp
 The $ character is used to introduce parameter expansion, command
 substitution, or arithmetic evaluation.
 .Ss Tilde Expansion (substituting a user's home directory)
 A word beginning with an unquoted tilde character (~) is
 subjected to tilde expansion.
 All the characters up to
 a slash (/) or the end of the word are treated as a username
 and are replaced with the user's home directory.
 If the username is missing (as in
 .Pa ~/foobar ) ,
 the tilde is replaced with the value of the
 .Va HOME
 variable (the current user's home directory).
 .Ss Parameter Expansion
 The format for parameter expansion is as follows:
 .Pp
 .Dl ${expression}
 .Pp
 where expression consists of all characters until the matching
 .Dq } .
 Any
 .Dq }
 escaped by a backslash or within a quoted string, and characters in
 embedded arithmetic expansions, command substitutions, and variable
 expansions, are not examined in determining the matching
 .Dq } .
 .Pp
 The simplest form for parameter expansion is:
 .Pp
 .Dl ${parameter}
 .Pp
 The value, if any, of parameter is substituted.
 .Pp
 The parameter name or symbol can be enclosed in braces, which are
 optional except for positional parameters with more than one digit or
 when parameter is followed by a character that could be interpreted as
 part of the name.
 If a parameter expansion occurs inside double quotes:
 .Bl -enum
 .It
 Pathname expansion is not performed on the results of the expansion.
 .It
 Field splitting is not performed on the results of the
 expansion, with the exception of the special rules for @.
 .El
 .Pp
 In addition, a parameter expansion can be modified by using one of the
 following formats.
 If the
 .Dq Dv \&:
 is omitted in the following modifiers, then the expansion is applied only
 to unset parameters, not null ones.
 .Bl -tag -width aaparameterwordaaaaa
-.It ${parameter:-word}
+.It ${parameter:\(miword}
 Use Default Values.
 If parameter is unset or null, the expansion of word
 is substituted; otherwise, the value of parameter is substituted.
 .It ${parameter:=word}
 Assign Default Values.
 If parameter is unset or null, the expansion of
 word is assigned to parameter.
 In all cases, the final value of parameter is substituted.
 Only variables, not positional parameters or special
 parameters, can be assigned in this way.
 .It ${parameter:?[word]}
 Indicate Error if Null or Unset.
 If parameter is unset or null, the
 expansion of word (or a message indicating it is unset if word is omitted)
 is written to standard error and the shell exits with a nonzero exit status.
 Otherwise, the value of parameter is substituted.
 An interactive shell need not exit.
 .It ${parameter:+word}
 Use Alternative Value.
 If parameter is unset or null, null is
 substituted; otherwise, the expansion of word is substituted.
 .It ${#parameter}
 String Length.
 The length in characters of the value of parameter.
 .El
 .Pp
 The following four varieties of parameter expansion provide for substring
 processing.
 In each case, pattern matching notation (see
 .Sx Shell Patterns ) ,
 rather than regular expression notation, is used to evaluate the patterns.
 If parameter is * or @, the result of the expansion is unspecified.
 Enclosing the full parameter expansion string in double quotes does not
 cause the following four varieties of pattern characters to be quoted,
 whereas quoting characters within the braces has this effect.
 .Bl -tag -width aaparameterwordaaaaa
 .It ${parameter%word}
 Remove Smallest Suffix Pattern.
 The word is expanded to produce a pattern.
 The parameter expansion then results in parameter, with the
 smallest portion of the suffix matched by the pattern deleted.
 .It ${parameter%%word}
 Remove Largest Suffix Pattern.
 The word is expanded to produce a pattern.
 The parameter expansion then results in parameter, with the largest
 portion of the suffix matched by the pattern deleted.
 .It ${parameter#word}
 Remove Smallest Prefix Pattern.
 The word is expanded to produce a pattern.
 The parameter expansion then results in parameter, with the
 smallest portion of the prefix matched by the pattern deleted.
 .It ${parameter##word}
 Remove Largest Prefix Pattern.
 The word is expanded to produce a pattern.
 The parameter expansion then results in parameter, with the largest
 portion of the prefix matched by the pattern deleted.
 .El
 .Ss Command Substitution
 Command substitution allows the output of a command to be substituted in
 place of the command name itself.
 Command substitution occurs when the command is enclosed as follows:
 .Pp
 .Dl $(command)
 .Pp
 or
 .Po
 .Dq backquoted
 version
 .Pc :
 .Pp
 .Dl `command`
 .Pp
 The shell expands the command substitution by executing command in a
 subshell environment and replacing the command substitution with the
 standard output of the command, removing sequences of one or more
 .Ao newline Ac Ns s
 at the end of the substitution.
 (Embedded
 .Ao newline Ac Ns s
 before
 the end of the output are not removed; however, during field splitting,
 they may be translated into
 .Ao space Ac Ns s ,
 depending on the value of
 .Ev IFS
 and quoting that is in effect.)
 .Ss Arithmetic Expansion
 Arithmetic expansion provides a mechanism for evaluating an arithmetic
 expression and substituting its value.
 The format for arithmetic expansion is as follows:
 .Pp
 .Dl $((expression))
 .Pp
 The expression is treated as if it were in double quotes, except
 that a double quote inside the expression is not treated specially.
 The shell expands all tokens in the expression for parameter expansion,
 command substitution, and quote removal.
 .Pp
 Next, the shell treats this as an arithmetic expression and
 substitutes the value of the expression.
 .Pp
 Arithmetic expressions use a syntax similar to that
 of the C language, and are evaluated using the
 .Ql intmax_t
 data type (this is an extension to
 .Tn POSIX ,
 which requires only
 .Ql long
 arithmetic).
 Shell variables may be referenced by name inside an arithmetic
 expression, without needing a
 .Dq \&$
 sign.
 .Ss White Space Splitting (Field Splitting)
 After parameter expansion, command substitution, and
 arithmetic expansion the shell scans the results of
-expansions and substitutions that did not occur in double quotes for
+expansions and substitutions that did not occur in double quotes,
-field splitting and multiple fields can result.
+and
 .Dq $@
 even if it did,
 for field splitting and multiple fields can result.
 .Pp
 The shell treats each character of the
 .Ev IFS
-as a delimiter and use the delimiters to split the results of parameter
+as a delimiter and uses the delimiters to split the results of parameter
 expansion and command substitution into fields.
 .Pp
 Non-whitespace characters in
 .Ev IFS
-are treated strictly as parameter terminators.
+are treated strictly as parameter separators.
 So adjacent non-whitespace
 .Ev IFS
 characters will produce empty parameters.
 On the other hand, any sequence of whitespace
 characters that occur in
 .Ev IFS
 (known as
 .Ev IFS
 whitespace)
 can occur, leading and trailing
 .Ev IFS
 whitespace, and
 .Ev IFS
 whitespace surrounding a non whitespace
 .Ev IFS
 delimiter, is removed.
 Any sequence of
 .Ev IFS
 whitespace characters without a non-whitespace
 .Ev IFS
 delimiter acts as a field separator.
 .Pp
 If
 .Ev IFS
-is unset it is assumed to contain space, tab, and newline.
+is unset it is assumed to contain space, tab, and newline,
 all of which are
 .Ev IFS
 whitespace characters.
 If
 .Ev IFS
 is set to a null string, there are no delimiters,
 and no field splitting occurs.
 .Ss Pathname Expansion (File Name Generation)
 Unless the
 .Fl f
 flag is set, file name generation is performed after word splitting is
 complete.
 Each word is viewed as a series of patterns, separated by slashes.
 The process of expansion replaces the word with the names of all
 existing files whose names can be formed by replacing each pattern with a
 string that matches the specified pattern.
 There are two restrictions on
 this: first, a pattern cannot match a string containing a slash, and
 second, a pattern cannot match a string starting with a period unless the
 first character of the pattern is a period.
 The next section describes the
 patterns used for both Pathname Expansion and the
 .Ic case
 command.
 .Ss Shell Patterns
 A pattern consists of normal characters, which match themselves,
 and meta-characters.
 The meta-characters are
 .Dq \&! ,
 .Dq * ,
 .Dq \&? ,
 and
 .Dq \&[ .
 These characters lose their special meanings if they are quoted.
 When command or variable substitution is performed
 and the dollar sign or backquotes are not double-quoted,
 the value of the variable or the output of
 the command is scanned for these characters and they are turned into
 meta-characters.
 .Pp
 An asterisk
 .Pq Dq *
 matches any string of characters.
 A question mark
 .Pq Dq \&?
 matches any single character.
 A left bracket
 .Pq Dq \&[
 introduces a character class.
 The end of the character class is indicated by a right bracket
 .Pq Dq \&] ;
 if this
 .Dq \&]
 is missing then the
 .Dq \&[
 matches a
 .Dq \&[
 rather than introducing a character class.
 A character class matches any of the characters between the square brackets.
 A named class of characters (see
 .Xr wctype 3 )
 may be specified by surrounding the name with
 .Pq Dq [:
 and
 .Pq Dq :] .
 For example,
 .Pq Dq [[:alpha:]]
 is a shell pattern that matches a single letter.
 A range of characters may be specified using a minus sign
-.Pq Dq - .
+.Pq Dq \(mi .
 The character class may be complemented
 by making an exclamation mark
 .Pq Dq \&!
 the first character of the character class.
 .Pp
 To include a
 .Dq \&]
 in a character class, make it the first character listed (after the
 .Dq \&! ,
 if any).
 To include a
-.Dq - ,
+.Dq \(mi ,
 make it the first or last character listed.
 .Ss Built-ins
 This section lists the built-in commands which are built-in because they
 need to perform some operation that can't be performed by a separate
 process.
 In addition to these, there are several other commands that may
 be built in for efficiency (e.g.
 .Xr printf 1 ,
 .Xr echo 1 ,
 .Xr test 1 ,
 etc).
 .Bl -tag -width 5n
 .It : [ Ar arg ... ]
 A null command that returns a 0 (true) exit value.
-Any arguments are ignored.
+Any arguments or redirects are evaluated, then ignored.
 .It \&. file
 The dot command reads and executes the commands from the specified
 .Ar file
 in the current shell environment.
 The file does not need to be executable and is looked up from the directories
 listed in the
 .Ev PATH
-variable if it does not contain a directory separator
+variable if its name does not contain a directory separator
 .Pq Sq / .
 The return command can be used for a premature return from the sourced file.
 .Pp
-The POSIX standard is unclear on how loop control keywords (break
+The POSIX standard has been unclear on how loop control keywords (break
 and continue) behave across a dot command boundary.
 This implementation allows them to control loops surrounding the dot command,
 but obviously such behavior should not be relied on.
 It is now permitted by the standard, but not required.
 .It alias Op Ar name Ns Op Ar "=string ..."
 If
 .Ar name=string
 is specified, the shell defines the alias
 .Ar name
 with value
 .Ar string .
 If just
 .Ar name
 is specified, the value of the alias
 .Ar name
 is printed.
 With no arguments, the
 .Ic alias
 built-in prints the
 names and values of all defined aliases (see
 .Ic unalias ) .
 .It bg [ Ar job ] ...
 Continue the specified jobs (or the current job if no
 jobs are given) in the background.
 .It command Oo Fl p Oc Oo Fl v Oc Oo Fl V Oc Ar command Oo Ar arg ... Oc
 Execute the specified command but ignore shell functions when searching
 for it.
 (This is useful when you
-have a shell function with the same name as a built-in command.)
+have a shell function with the same name as a command.)
 .Bl -tag -width 5n
 .It Fl p
 search for command using a
 .Ev PATH
 that guarantees to find all the standard utilities.
 .It Fl V
 Do not execute the command but
 search for the command and print the resolution of the
 command search.
 This is the same as the
 .Ic type
 built-in.
 .It Fl v
 Do not execute the command but
 search for the command and print the absolute pathname
 of utilities, the name for built-ins or the expansion of aliases.
 .El
 .It cd Oo Fl P Oc Op Ar directory Op Ar replace
 Switch to the specified directory (default
 .Ev $HOME ) .
 If
 .Ar replace
 is specified, then the new directory name is generated by replacing
 the first occurrence of
 .Ar directory
 in the current directory name with
 .Ar replace .
 If
 .Ar directory
 is
 .Sq - ,
 then the current working directory is changed to the previous current
 working directory as set in
 .Ev OLDPWD .
 Otherwise if an entry for
 .Ev CDPATH
 appears in the environment of the
 .Ic cd
 command or the shell variable
 .Ev CDPATH
 is set and the directory name does not begin with a slash,
 or its first (or only) component isn't dot or dot dot,
 then the directories listed in
 .Ev CDPATH
 will be searched for the specified directory.
 The format of
 .Ev CDPATH
 is the same as that of
 .Ev PATH .
 .Pp
 The
 .Fl P
 option instructs the shell to update
 .Ev PWD
 with the specified physical directory path and change to that directory.
 This is the default.
 .Pp
 When the directory changes, the variable
 .Ev OLDPWD
 is set to the working directory before the change.
 .Pp
 Some shells also support a
 .Fl L
 option, which instructs the shell to update
 .Ev PWD
 with the logical path and to change the current directory
 accordingly.
 This is not supported.
 .Pp
 In an interactive shell, the
 .Ic cd
 command will print out the name of the
 directory that it actually switched to if this is different from the name
 that the user gave.
 These may be different either because the
 .Ev CDPATH
 mechanism was used or because a symbolic link was crossed.
 .It eval Ar string ...
 Concatenate all the arguments with spaces.
 Then re-parse and execute the command.
 .It exec Op Ar command arg ...
 Unless command is omitted, the shell process is replaced with the
 specified program (which must be a real program, not a shell built-in or
 function).
 Any redirections on the
 .Ic exec
 command are marked as permanent, so that they are not undone when the
 .Ic exec
 command finishes.
 File descriptors created via such redirections are marked close-on-exec
 (see
 .Xr open 2
 .Dv O_CLOEXEC
 or
 .Xr fcntl 2
 .Dv F_SETFD /
 .Dv FD_CLOEXEC ) ,
 unless the descriptors they point to refer to the standard input,
 output, or error (file descriptors 0, 1, 2).
 Traditionally Bourne-like shells
 (except
 .Xr ksh 1 ) ,
 made those file descriptors available to exec'ed processes.
 .It exit Op Ar exitstatus
 Terminate the shell process.
 If
 .Ar exitstatus
 is given it is used as the exit status of the shell; otherwise the
 exit status of the preceding command is used.
-.It export Ar name ...
+.It export Oo Fl npx Oc Ar name ...
-.It export Fl p
+.It export Fl p Oo Fl x Oc
-The specified names are exported so that they will appear in the
+With no options,
 the specified names are exported so that they will appear in the
 environment of subsequent commands.
-The only way to un-export a variable is to unset it.
+With
 .Fl n
 the specified names are un-exported.
 Variables can also be un-exported using the unset builtin command.
 With
 .Fl x
 (exclude) the specified names are marked not to be exported,
 and any that had been exported, will be un-exported.
 Later attempts to export the variable will be refused.
 Note this does not prevent explicitly exporting a variable
 to a single command, script or function by preceding that
 command invocation by a variable assignment to that variable,
 provided the variable is not also readonly.
 That is
 .Dl	export -x FOO ; # FOO will now not be exported by default
 .Dl	FOO=some_value my_command
 still passes the value (FOO=some_value) to
 .Ic my_command
 through the environment.
 .Pp
 The shell allows the value of a variable to be set at the
 same time it is exported by writing
 .Pp
 .Dl export name=value
 .Pp
-With no arguments the export command lists the names of all exported variables.
+With no arguments the export command lists the names of all exported variables,
 or if
 .Fl x
 was given, all variables marked not for export.
 With the
 .Fl p
 option specified the output will be formatted suitably for non-interactive use.
 .Pp
 The
 .Ic export
 built-in exits with status 0,
 unless an invalid option, or option combination, is given,
 or unless an attempt is made to export a variable which has
 been marked as unavailable for export,
 in which cases it exits with status 1.
 .Pp
 Note that there is no restriction upon exporting,
 or un-exporting, readonly variables.
 The no-export flag can be reset by unsetting the variable
 and creating it again \(en provided it is not also readonly.
 .It fc Oo Fl e Ar editor Oc Oo Ar first Oo Ar last Oc Oc
 .It fc Fl l Oo Fl nr Oc Oo Ar first Oo Ar last Oc Oc
 .It fc Fl s Oo Ar old=new Oc Oo Ar first Oc
 The
 .Ic fc
 built-in lists, or edits and re-executes, commands previously entered
 to an interactive shell.
 .Bl -tag -width 5n
 .It Fl e No editor
 Use the editor named by editor to edit the commands.
 The editor string is a command name, subject to search via the
 .Ev PATH
 variable.
 The value in the
 .Ev FCEDIT
 variable is used as a default when
 .Fl e
 is not specified.
 If
 .Ev FCEDIT
 is null or unset, the value of the
 .Ev EDITOR
 variable is used.
 If
 .Ev EDITOR
 is null or unset,
 .Xr ed 1
 is used as the editor.
 .It Fl l No (ell)
 List the commands rather than invoking an editor on them.
 The commands are written in the sequence indicated by
 the first and last operands, as affected by
 .Fl r ,
 with each command preceded by the command number.
 .It Fl n
 Suppress command numbers when listing with -l.
 .It Fl r
 Reverse the order of the commands listed (with
 .Fl l )
 or edited (with neither
 .Fl l
 nor
 .Fl s ) .
 .It Fl s
 Re-execute the command without invoking an editor.
 .It first
 .It last
 Select the commands to list or edit.
 The number of previous commands that
 can be accessed are determined by the value of the
 .Ev HISTSIZE
 variable.
 The value of first or last or both are one of the following:
 .Bl -tag -width 5n
 .It [+]number
 A positive number representing a command number; command numbers can be
 displayed with the
 .Fl l
 option.
 .It Fl number
 A negative decimal number representing the command that was executed
 number of commands previously.
 For example, \-1 is the immediately previous command.
 .El
 .It string
 A string indicating the most recently entered command that begins with
 that string.
 If the old=new operand is not also specified with
 .Fl s ,
 the string form of the first operand cannot contain an embedded equal sign.
 .El
 .Pp
 The following environment variables affect the execution of fc:
 .Bl -tag -width HISTSIZE
 .It Ev FCEDIT
 Name of the editor to use.
 .It Ev HISTSIZE
 The number of previous commands that are accessible.
 .El
 .It fg Op Ar job
 Move the specified job or the current job to the foreground.
 .It getopts Ar optstring var
 The
 .Tn POSIX
 .Ic getopts
 command, not to be confused with the
 .Em Bell Labs
 -derived
 .Xr getopt 1 .
 .Pp
 The first argument should be a series of letters, each of which may be
 optionally followed by a colon to indicate that the option requires an
 argument.
 The variable specified is set to the parsed option.
 .Pp
 The
 .Ic getopts
 command deprecates the older
 .Xr getopt 1
 utility due to its handling of arguments containing whitespace.
 .Pp
 The
 .Ic getopts
 built-in may be used to obtain options and their arguments
 from a list of parameters.
 When invoked,
 .Ic getopts
 places the value of the next option from the option string in the list in
 the shell variable specified by
 .Va var
 and its index in the shell variable
 .Ev OPTIND .
 When the shell is invoked,
 .Ev OPTIND
 is initialized to 1.
 For each option that requires an argument, the
 .Ic getopts
 built-in will place it in the shell variable
 .Ev OPTARG .
 If an option is not allowed for in the
 .Va optstring ,
 then
 .Ev OPTARG
 will be unset.
 .Pp
 .Va optstring
 is a string of recognized option letters (see
 .Xr getopt 3 ) .
 If a letter is followed by a colon, the option is expected to have an
 argument which may or may not be separated from it by whitespace.
 If an option character is not found where expected,
 .Ic getopts
 will set the variable
 .Va var
 to a
 .Dq \&? ;
 .Ic getopts
 will then unset
 .Ev OPTARG
 and write output to standard error.
 By specifying a colon as the first character of
 .Va optstring
 all errors will be ignored.
 .Pp
 A nonzero value is returned when the last option is reached.
 If there are no remaining arguments,
 .Ic getopts
 will set
 .Va var
 to the special option,
 .Dq -- ,
 otherwise, it will set
 .Va var
 to
 .Dq \&? .
 .Pp
 The following code fragment shows how one might process the arguments
 for a command that can take the options
 .Op a
 and
 .Op b ,
 and the option
 .Op c ,
 which requires an argument.
 .Bd -literal -offset indent
 while getopts abc: f
 do
 	case $f in
 	a | b)	flag=$f;;
 	c)	carg=$OPTARG;;
 	\e?)	echo $USAGE; exit 1;;
 	esac
 done
 shift $(expr $OPTIND - 1)
 .Ed
 .Pp
 This code will accept any of the following as equivalent:
 .Bd -literal -offset indent
 cmd \-acarg file file
 cmd \-a \-c arg file file
 cmd \-carg -a file file
 cmd \-a \-carg \-\- file file
 .Ed
 .It hash Fl rv Ar command ...
 The shell maintains a hash table which remembers the
 locations of commands.
 With no arguments whatsoever,
 the
 .Ic hash
 command prints out the contents of this table.
 Entries which have not been looked at since the last
 .Ic cd
 command are marked with an asterisk; it is possible for these entries
 to be invalid.
 .Pp
 With arguments, the
 .Ic hash
 command removes the specified commands from the hash table (unless
 they are functions) and then locates them.
 With the
 .Fl v
 option, hash prints the locations of the commands as it finds them.
 The
 .Fl r
 option causes the hash command to delete all the entries in the hash table
 except for functions.
 .It inputrc Ar file
 Read the
 .Va file
 to set key bindings as defined by
 .Xr editrc 5 .
 .It jobid Op Ar job
 Print the process id's of the processes in the job.
 If the
 .Ar job
 argument is omitted, the current job is used.
 .It jobs
 This command lists out all the background processes
 which are children of the current shell process.
 .It pwd Op Fl \&LP
 Print the current directory.
 If
 .Fl L
 is specified the cached value (initially set from
 .Ev PWD )
 is checked to see if it refers to the current directory; if it does
 the value is printed.
 Otherwise the current directory name is found using
 .Xr getcwd 3 .
 The environment variable
 .Ev PWD
 is set to the printed value.
 .Pp
 The default is
 .Ic pwd
 .Fl L ,
 but note that the built-in
 .Ic cd
 command doesn't currently support the
 .Fl L
 option and will cache (almost) the absolute path.
 If
 .Ic cd
 is changed,
 .Ic pwd
 may be changed to default to
 .Ic pwd
 .Fl P .
 .Pp
 If the current directory is renamed and replaced by a symlink to the
 same directory, or the initial
 .Ev PWD
 value followed a symbolic link, then the cached value may not
 be the absolute path.
 .Pp
 The built-in command may differ from the program of the same name because
 the program will use
 .Ev PWD
 and the built-in uses a separately cached value.
 .It read Oo Fl p Ar prompt Oc Oo Fl r Oc Ar variable Oo Ar ... Oc
 The prompt is printed if the
 .Fl p
 option is specified and the standard input is a terminal.
 Then a line is read from the standard input.
 The trailing newline is deleted from the
 line and the line is split as described in the
 .Sx Word Expansions
 section above, and the pieces are assigned to the variables in order.
 If there are more pieces than variables, the remaining pieces
 (along with the characters in
 .Ev IFS
 that separated them) are assigned to the last variable.
 If there are more variables than pieces,
 the remaining variables are assigned the null string.
 The
 .Ic read
 built-in will indicate success unless EOF is encountered on input, in
 which case failure is returned.
 .Pp
 By default, unless the
 .Fl r
 option is specified, the backslash
 .Dq \e
 acts as an escape character, causing the following character to be treated
 literally.
 If a backslash is followed by a newline, the backslash and the
 newline will be deleted.
 .It readonly Ar name ...
 .It readonly Fl p
 The specified names are marked as read only, so that they cannot be
 subsequently modified or unset.
 The shell allows the value of a variable
 to be set at the same time it is marked read only by writing
 .Pp
 .Dl readonly name=value
 .Pp
 With no arguments the readonly command lists the names of all read only
 variables.
 With the
 .Fl p
 option specified the output will be formatted suitably for non-interactive use.
 .Pp
 .It return [ Ar n ]
 Stop executing the current function or a dot command with return value of
 .Ar n
 or the value of the last executed command, if not specified.
 For portability,
 .Ar n
 should be in the range from 0 to 255.
 .Pp
 The POSIX standard says that the results of
 .Sq return
 outside a function or a dot command are unspecified.
 This implementation treats such a return as a no-op with a return value of 0
 (success, true).
 Use the exit command instead, if you want to return from a script or exit
 your shell.
 .It set Oo { Fl options | Cm +options | Cm \-- } Oc Ar arg ...
 The
 .Ic set
 command performs three different functions.
 .Pp
 With no arguments, it lists the values of all shell variables.
 .Pp
 If options are given, it sets the specified option
 flags, or clears them as described in the
 .Sx Argument List Processing
 section.
 .Pp
 The third use of the set command is to set the values of the shell's
 positional parameters to the specified arguments.
 To change the positional
 parameters without changing any options, use
 .Dq --
 as the first argument to set.
 If no arguments are present, the set command
 will clear all the positional parameters (equivalent to executing
 .Dq shift $# . )
 .It setvar Ar variable Ar value
 Assigns value to variable.
 (In general it is better to write
 variable=value rather than using
 .Ic setvar .
 .Ic setvar
 is intended to be used in
 functions that assign values to variables whose names are passed as
 parameters.)
 .It shift Op Ar n
 Shift the positional parameters n times.
 If n is omitted, 1 is assumed.
 Each
 .Ic shift
 sets the value of
 .Va $1
-to the value of
+to the previous value of
 .Va $2 ,
 the value of
 .Va $2
-to the value of
+to the previous value of
 .Va $3 ,
 and so on, decreasing
 the value of
 .Va $#
 by one.
-If there are zero positional parameters,
+The shift count must be less than or equal to the number of
-.Ic shift
+positional parameters (
-does nothing.
+.Dq $# )
 before the shift.
 .It trap Oo Fl l Oc
 .It trap Oo Ar action Oc Ar signal ...
 Cause the shell to parse and execute action when any of the specified
 signals are received.
 The signals are specified by signal number or as the name of the signal.
 If
 .Ar signal
 is
 .Li 0
 or its equivalent, EXIT,
 the action is executed when the shell exits.
 .Ar action
 may be null, which cause the specified signals to be ignored.
 With
 .Ar action
 omitted or set to
 .Sq -
 the specified signals are set to their default action.
 When the shell forks off a subshell, it resets trapped (but not ignored)
 signals to the default action.
 On non-interactive shells, the
 .Ic trap
 command has no effect on signals that were
 ignored on entry to the shell.
 On interactive shells, the
 .Ic trap
 command will catch or reset signals ignored on entry.
 Issuing
 .Ic trap
 with option
 .Ar -l
 will print a list of valid signal names.
 .Ic trap
 without any arguments cause it to write a list of signals and their
 associated action to the standard output in a format that is suitable
 as an input to the shell that achieves the same trapping results.
 .Pp
 Examples:
 .Pp
 .Dl trap
 .Pp
 List trapped signals and their corresponding action
 .Pp
 .Dl trap -l
 .Pp
 Print a list of valid signals
 .Pp
 .Dl trap '' INT QUIT tstp 30
 .Pp
 Ignore signals INT QUIT TSTP USR1
 .Pp
 .Dl trap date INT
 .Pp
-Print date upon receiving signal INT
+Run the
 .Dq date
 command (print the date) upon receiving signal INT
 .It type Op Ar name ...
 Interpret each name as a command and print the resolution of the command
 search.
 Possible resolutions are:
 shell keyword, alias, shell built-in,
 command, tracked alias and not found.
 For aliases the alias expansion is
 printed; for commands and tracked aliases the complete pathname of the
 command is printed.
 .It ulimit Oo Fl H \*(Ba Fl S Oc Oo Fl a \*(Ba Fl btfdscmlrpnv Oo Ar value Oc Oc
 Inquire about or set the hard or soft limits on processes or set new
 limits.
 The choice between hard limit (which no process is allowed to
 violate, and which may not be raised once it has been lowered) and soft
 limit (which causes processes to be signaled but not necessarily killed,
 and which may be raised) is made with these flags:
 .Bl -tag -width Fl
 .It Fl H
 set or inquire about hard limits
 .It Fl S
 set or inquire about soft limits.
 If neither
 .Fl H
 nor
 .Fl S
 is specified, the soft limit is displayed or both limits are set.
 If both are specified, the last one wins.
 .El
 .Pp
 The limit to be interrogated or set, then, is chosen by specifying
 any one of these flags:
 .Bl -tag -width Fl
 .It Fl a
 show all the current limits
 .It Fl b
 show or set the limit on the socket buffer size of a process (in bytes)
 .It Fl t
 show or set the limit on CPU time (in seconds)
 .It Fl f
 show or set the limit on the largest file that can be created
 (in 512-byte blocks)
 .It Fl d
 show or set the limit on the data segment size of a process (in kilobytes)
 .It Fl s
 show or set the limit on the stack size of a process (in kilobytes)
 .It Fl c
 show or set the limit on the largest core dump size that can be produced
 (in 512-byte blocks)
 .It Fl m
 show or set the limit on the total physical memory that can be
 in use by a process (in kilobytes)
 .It Fl l
 show or set the limit on how much memory a process can lock with
 .Xr mlock 2
 (in kilobytes)
 .It Fl r
 show or set the limit on the number of threads this user can
 have at one time
 .It Fl p
 show or set the limit on the number of processes this user can
 have at one time
 .It Fl n
 show or set the limit on the number of files a process can have open at once
 .It Fl v
 show or set the limit on how large a process address space can be
 .El
 .Pp
 If none of these is specified, it is the limit on file size that is shown
 or set.
 If value is specified, the limit is set to that number; otherwise
 the current limit is displayed.
 .Pp
 Limits of an arbitrary process can be displayed or set using the
 .Xr sysctl 8
 utility.
 .Pp
 .It umask Op Ar mask
 Set the value of umask (see
 .Xr umask 2 )
 to the specified octal value.
 If the argument is omitted, the umask value is printed.
 .It unalias Oo Fl a Oc Oo Ar name Oc
 If
 .Ar name
 is specified, the shell removes that alias.
 If
 .Fl a
 is specified, all aliases are removed.
-.It unset Ar name ...
+.It unset Oo Fl efv Oc Ar name ...
-The specified variables and functions are unset and unexported.
+If
-If a given name corresponds to both a variable and a function, both
+.Fl v
-the variable and the function are unset.
+is specified, the specified variables are unset and unexported.
 Readonly variables cannot be unset.
 If
 .Fl f
 is specified, the specified functions are undefined.
 If
 .Fl e
 is given, the specified variables are unexported, but otherwise unchanged.
 .Pp
 If no flags are provided
 .Fl v
 is assumed.
 If
 .Fl f
 is given with one (or both) of
 .Fl v
 or
 .Fl e ,
 then the named variables will be unset, or unexported, and functions
 of the same names will be undefined.
 It makes no sense to give both
 .Fl v
 and
 .Fl e
 as unsetting a variable unexports it as well.
 However doing so is not an error, the last specified is used.
 The exit status is 0, unless an attempt was made to unset
 a readonly variable, in which case the exit status is 1.
 It is not an error to unset (or undefine) a variable (or function)
 that is not currently set (or defined.)
 .It wait Op Ar job
 Wait for the specified job to complete and return the exit status of the
-last process in the job.
+last process in the job, or 127 if the job is not a current child of
 the shell.
 If the argument is omitted, wait for all jobs to
 complete and then return an exit status of zero.
 If the wait is interrupted by a signal,
 its exit status will be greater than 128.
 .Pp
 Once waited upon, by specific process number or job-id,
 or by a
 .Ic wait
 with no argumentss,
 knowledge of the child is removed from the system,
 and it cannot be waited upon again.
 .El
 .Ss Command Line Editing
 When
 .Nm
 is being used interactively from a terminal, the current command
 and the command history (see
 .Ic fc
 in the
 .Sx Built-ins
 section)
 can be edited using emacs-mode or vi-mode command-line editing.
 The command
 .Ql set -o emacs
 enables emacs-mode editing.
 The command
 .Ql set -o vi
 enables vi-mode editing and places the current shell process into
 .Ar vi
 insert mode.
 (See the
 .Sx Argument List Processing
 section above.)
 .Pp
 The
 .Ar vi
 mode uses commands similar to a subset of those described in the
 .Xr vi 1
 man page.
 With vi-mode
 enabled,
 .Nm sh
 can be switched between insert mode and command mode.
 It's similar to
 .Xr vi 1 :
 pressing the
 .Aq ESC
 key will throw you into command VI command mode.
 Pressing the
 .Aq return
 key while in command mode will pass the line to the shell.
 .Pp
 The
 .Ar emacs
 mode uses commands similar to a subset available in
 the
 .Xr emacs 1
 editor.
 With emacs-mode enabled, special keys can be used to modify the text
 in the buffer using the control key.
 .Pp
 .Nm
 uses the
 .Xr editline 3
 library.
 .Sh ENVIRONMENT
 .Bl -tag -width MAILCHECK
 .It Ev CDPATH
 The search path used with the
 .Ic cd
 built-in.
 .It Ev HISTSIZE
 The number of lines in the history buffer for the shell.
 .It Ev HOME
 Set automatically by
 .Xr login 1
 from the user's login directory in the password file
 .Pq Xr passwd 5 .
 This environment variable also functions as the default argument for the
 .Ic cd
 built-in.
-.It Ev PATH
+.It Ev IFS
-The default search path for executables.
+Input Field Separators.
 This is normally set to
 .Aq space ,
 .Aq tab ,
 and
 .Aq newline .
 See the
-.Sx Path Search
+.Sx White Space Splitting
-section above.
+section for more details.
 .It Ev CDPATH
 The search path used with the
 .Ic cd
 built-in.
 .It Ev LINENO
 The current line number in the script or function.
 .It Ev LANG
 The string used to specify localization information that allows users
 to work with different culture-specific and language conventions.
 See
 .Xr nls 7 .
 .It Ev LINENO
 The current line number in the script or function.
 .It Ev MAIL
 The name of a mail file, that will be checked for the arrival of new mail.
 Overridden by
 .Ev MAILPATH .
 .It Ev MAILCHECK
 The frequency in seconds that the shell checks for the arrival of mail
 in the files specified by the
 .Ev MAILPATH
 or the
 .Ev MAIL
 file.
 If set to 0, the check will occur at each prompt.
 .It Ev MAILPATH
 A colon
 .Dq \&:
 separated list of file names, for the shell to check for incoming mail.
 This environment setting overrides the
 .Ev MAIL
 setting.
 There is a maximum of 10 mailboxes that can be monitored at once.
 .It Ev PATH
 The default search path for executables.
 See the
 .Sx Path Search
 section above.
 .It Ev PS1
 The primary prompt string, which defaults to
 .Dq $ \  ,
 unless you are the superuser, in which case it defaults to
 .Dq # \  .
 .It Ev PS2
 The secondary prompt string, which defaults to
 .Dq \*[Gt] \  .
 .It Ev PS4
 Output before each line when execution trace (set -x) is enabled,
 defaults to
 .Dq + \  .
 .It Ev IFS
 Input Field Separators.
 This is normally set to
 .Aq space ,
 .Aq tab ,
 and
 .Aq newline .
 See the
 .Sx White Space Splitting
 section for more details.
 .It Ev TERM
 The default terminal setting for the shell.
 This is inherited by
 children of the shell, and is used in the history editing modes.
-.It Ev HISTSIZE
+.\" This is explicitly last, not in sort order - please leave!
-The number of lines in the history buffer for the shell.
+.It Ev NETBSD_SHELL
 Unlike the variables mentioned above,
 this variable is somewhat strange,
 in that it cannot be set,
 inherited from the environment,
 modified, or exported from the shell.
 If set, it indicates that the shell is the
 .Ic sh
 defined by this manual page, and gives its version information.
 It behaves like any other variable that has the read-only
 and un-exportable attributes set.
 .El
 .Sh FILES
 .Bl -item
 .It
 .Pa $HOME/.profile
 .It
 .Pa /etc/profile
 .El
 .Sh EXIT STATUS
 Errors that are detected by the shell, such as a syntax error, will cause the
 shell to exit with a non-zero exit status.
 If the shell is not an
 interactive shell, the execution of the shell file will be aborted.
 Otherwise
 the shell will return the exit status of the last command executed, or
 if the exit built-in is used with a numeric argument, it will return the
 argument.
 .Sh SEE ALSO
 .Xr csh 1 ,
 .Xr echo 1 ,
 .Xr getopt 1 ,
 .Xr ksh 1 ,
 .Xr login 1 ,
 .Xr printf 1 ,
 .Xr test 1 ,
 .Xr editline 3 ,
 .Xr getopt 3 ,
 .\" .Xr profile 4 ,
 .Xr editrc 5 ,
 .Xr passwd 5 ,
 .Xr environ 7 ,
 .Xr nls 7 ,
 .Xr sysctl 8
 .Sh HISTORY
+A
 .Nm
 command appeared in
 .At v1 .
 It was, however, unmaintainable so we wrote this one.
 .Sh BUGS
 Setuid shell scripts should be avoided at all costs, as they are a
 significant security risk.
 .Pp
 PS1, PS2, and PS4 should be subject to parameter expansion before
 being displayed.
 .Pp
 The characters generated by filename completion should probably be quoted
 to ensure that the filename is still valid after the input line has been
 processed.
 .Pp
 Many, many, more.