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bsh(1)									bsh(1)

NAME    [Toc]    [Back]

     bsh, jsh -	shell, the standard/job	control	command	programming language

SYNOPSIS    [Toc]    [Back]

     bsh [ -acefhiknprstuvx ] [	args ]
     jsh [ -acefhiknprstuvx ] [	args ]

DESCRIPTION    [Toc]    [Back]

     Note: This	is the Bourne shell description. All references	to sh and
     shell pertain to bsh and all references below to /usr/lib/rsh, the
     restricted	shell, no longer apply to the Bourne shell. (See sh(1)).

     bsh is a command programming language that	executes commands read from a
     terminal or a file.

     jsh is an interface to the	shell that provides all	the functionality of
     sh	and enables Job	Control	(see Job Control below).

     See Invocation below for the meaning of arguments to the shell.

     See CAVEATS below for interaction with Korn shell builtins.

   Definitions    [Toc]    [Back]
     A blank is	a tab or a space.  A name is a sequence	of letters, digits, or
     underscores beginning with	a letter or underscore.	 A parameter is	a
     name, a digit, or any of the characters *,	@, #, ?, -, $, and ! .

   Commands    [Toc]    [Back]
     A simple-command is a sequence of non-blank words separated by blanks.
     The first word specifies the name of the command to be executed.  Except
     as	specified below, the remaining words are passed	as arguments to	the
     invoked command.  The command name	is passed as argument 0	(see exec(2)).
     The value of a simple-command is its exit status if it terminates
     normally, or (octal) 200+status if	it terminates abnormally (see
     signal(2) for a list of status values).

     A pipeline	is a sequence of one or	more commands separated	by |.  The
     standard output of	each command but the last is connected by a pipe(2) to
     the standard input	of the next command.  Each command is run as a
     separate process; the shell waits for the last command to terminate.  The
     exit status of a pipeline is the exit status of the last command.

     A list is a sequence of one or more pipelines separated by	;, &, &&, or
     ||, and optionally	terminated by ;	or &.  Of these	four symbols, ;	and &
     have equal	precedence, which is lower than	that of	&& and ||.  The
     symbols &&	and || also have equal precedence.  A semicolon	(;) causes
     sequential	execution of the preceding pipeline; an	ampersand (&) causes
     asynchronous execution of the preceding pipeline (that is,	the shell does
     not wait for that pipeline	to finish).  The symbol	&& (||)	causes the
     list following it to be executed only if the preceding pipeline returns a
     zero (nonzero) exit status.  An arbitrary number of newlines can appear
     in	a list,	instead	of semicolons, to delimit commands.

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bsh(1)									bsh(1)

     A command is either a simple-command or one of the	following.  Unless
     otherwise stated, the value returned by a command is that of the last
     simple-command executed in	the command.

     for name [	in word	... ] do list done
	       Each time a for command is executed, name is set	to the next
	       word taken from the in word list.  If in	word ...  is omitted,
	       the for command executes	the do list once for each positional
	       parameter that is set (see Parameter Substitution below).
	       Execution ends when there are no	more words in the list.

     case word in [ pattern [ |	pattern	] ...) list ;; ] ... esac
	       A case command executes the list	associated with	the first
	       pattern that matches word.  The form of the patterns is the
	       same as that used for filename generation (see Filename
	       Generation) except that a slash,	a leading dot, or a dot
	       immediately following a slash need not be matched explicitly.

     if	list then list [ elif list then	list ] ... [ else list ] fi
	       The list	following if is	executed and, if it returns a zero
	       exit status, the	list following the first then is executed.
	       Otherwise, the list following elif is executed and, if its
	       value is	zero, the list following the next then is executed.
	       Failing that, the else list is executed.	 If no else list or
	       then list is executed, the if command returns a zero exit

     while list	do list	done
	       A while command repeatedly executes the while list and, if the
	       exit status of the last command in the list is zero, executes
	       the do list; otherwise the loop terminates.  If no commands in
	       the do list are executed, the while command returns a zero exit
	       status; until can be used in place of while to negate the loop
	       termination test.

     (list)    Execute list in a subshell.

     {list;}   list is executed	in the current (that is, parent) shell.	 The {
	       must be followed	by a space.

     name () {list;}
	       Define a	function that is referenced by name.  The body of the
	       function	is the list of commands	between	{ and }.  The list can
	       appear on the same line as the {.  If it	does, the { and	list
	       must be separated by a space.  The } cannot be on the same line
	       as list;	it must	be on a	newline.  Execution of functions is
	       described below (see Execution).	 The { and } are unnecessary
	       if the body of the function is a	command	as defined above,
	       under Commands.

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bsh(1)									bsh(1)

     The following words are only recognized as	the first word of a command
     and when not quoted:

	  if then else elif fi case esac for while until do done { }

   Comments    [Toc]    [Back]
     A word beginning with # causes that word and all the following characters
     up	to a newline to	be ignored.

   Command Substitution    [Toc]    [Back]
     The shell reads commands from the string between two grave	accents	(``)
     and the standard output from these	commands can be	used as	all or part of
     a word.  Trailing newlines	from the standard output are removed.

     No	interpretation is done on the string before the	string is read,	except
     to	remove backslashes (\) used to escape other characters.	 Backslashes
     can be used to escape a grave accent (`) or another backslash (\) and are
     removed before the	command	string is read.	 Escaping grave	accents	allows
     nested command substitution.  If the command substitution lies within a
     pair of double quotes (" ... `...`	... "),	a backslash used to escape a
     double quote (\") is removed; otherwise, it is left intact.

     If	a backslash is used to escape a	newline	character (\newline), both the
     backslash and the newline are removed (see	the later section on
     "Quoting").  In addition, backslashes used	to escape dollar signs (\$)
     are removed.  Since no interpretation is done on the command string
     before it is read,	inserting a backslash to escape	a dollar sign has no
     effect.  Backslashes that precede characters other	than \,	`, ", newline,
     and $ are left intact when	the command string is read.

   Parameter Substitution    [Toc]    [Back]
     The character $ is	used to	introduce substitutable	parameters.  There are
     two types of parameters, positional and keyword.  If parameter is a
     digit, it is a positional parameter.  Positional parameters can be
     assigned values by	set.  Keyword parameters (also known as	variables) can
     be	assigned values	by writing:

	  name = value [ name =	value ]	...

     Pattern-matching is not performed on value.  There	cannot be a function
     and a variable with the same name.

     ${parameter}	 The value, if any, of the parameter is	substituted.
			 The braces are	required only when parameter is
			 followed by a letter, digit, or underscore that is
			 not to	be interpreted as part of its name.  If
			 parameter is *	or @, all the positional parameters,
			 starting with $1, are substituted (separated by
			 spaces).  Parameter $0	is set from argument zero when
			 the shell is invoked.

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bsh(1)									bsh(1)

     ${parameter:-word}	 If parameter is set and is non-null, substitute its
			 value;	otherwise substitute word.

     ${parameter:=word}	 If parameter is not set or is null set	it to word;
			 the value of the parameter is substituted.
			 Positional parameters cannot be assigned to in	this

     ${parameter:?word}	 If parameter is set and is non-null, substitute its
			 value;	otherwise, print word and exit from the	shell.
			 If word is omitted, the message "parameter null or
			 not set" is printed.

     ${parameter:+word}	 If parameter is set and is non-null, substitute word;
			 otherwise substitute nothing.

     In	the above, word	is not evaluated unless	it is to be used as the
     substituted string, so that, in the following example, pwd	is executed
     only if d is not set or is	null:

	  echo ${d:-`pwd`}

     If	the colon (:) is omitted from the above	expressions, the shell only
     checks whether parameter is set or	not.

     The following parameters are automatically	set by the shell:

     *	  Expands to the positional parameters,	beginning with 1.

     @	  Expands to the positional parameters beginning with 1, except	when
	  expanded within double quotes, in which case each positional
	  parameter expands as a separate field.

     #	  The number of	positional parameters in decimal.

     -	  Flags	supplied to the	shell on invocation or by the set command.

     ?	  The decimal value returned by	the last synchronously executed

     $	  The process number of	this shell.  $ reports the process ID of the
	  parent shell in all shell constructs,	including pipelines, and in
	  parenthesized	subshells.

     !	  The process number of	the last background command invoked.

     The following parameters are used by the shell:

     HOME      The default argument (home directory) for the cd	command, set
	       to the user's login directory by	login(1) from the password
	       file (see passwd(4)).

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bsh(1)									bsh(1)

     PATH      The search path for commands (see Execution below).  The	user
	       cannot change PATH if executing under rsh.

     CDPATH    The search path for the cd command.

     MAIL      If this parameter is set	to the name of a mail file and the
	       MAILPATH	parameter is not set, the shell	informs	the user of
	       the arrival of mail in the specified file.

     MAILCHECK This parameter specifies	how often (in seconds) the shell
	       checks for the arrival of mail in the files specified by	the
	       MAILPATH	or MAIL	parameters.  The default value is 600 seconds
	       (10 minutes).  If set to	0, the shell checks before each

     MAILPATH  A colon (:)  separated list of filenames.  If this parameter is
	       set, the	shell informs the user of the arrival of mail in any
	       of the specified	files.	Each filename can be followed by % and
	       a message to be printed when the	modification time changes.
	       The default message is "you have	mail".

     PS1       Primary prompt string, by default ``$ ''.

     PS2       Secondary prompt	string,	by default ``> ''.

     IFS       Internal	field separators, normally space, tab, and newline.

     SHACCT    If this parameter is set	to the name of a file writable by the
	       user, the shell writes an accounting record in the file for
	       each shell procedure executed.

     SHELL     When the	shell is invoked, it scans the environment (see
	       Environment below) for this name.  If it	is found and 'rsh' is
	       the filename part of its	value, the shell becomes a restricted

     The shell gives default values to PATH, PS1, PS2, MAILCHECK, and IFS.
     HOME and MAIL are set by login(1).

   Blank Interpretation    [Toc]    [Back]
     After parameter and command substitution, the results of substitution are
     scanned for internal field	separator characters (those found in IFS) and
     split into	distinct arguments where such characters are found.  Explicit
     null arguments (""	or '') are retained.  Implicit null arguments (those
     resulting from parameters that have no values) are	removed.  The original
     whitespace	characters (space, tab,	and newline) are always	considered
     internal field separators.

     A command's input and output can be redirected using a special notation
     interpreted by the	shell.	The following can appear anywhere in a
     simple-command or can precede or follow a command and are not passed on

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bsh(1)									bsh(1)

     as	arguments to the invoked command.  Note	that parameter and command
     substitution occurs before	word or	digit is used.

     <word     Use file	word as	standard input (file descriptor	0).

     >word     Use file	word as	standard output	(file descriptor 1).  If the
	       file does not exist it is created; otherwise, it	is truncated
	       to zero length.

     >>word    Use file	word as	standard output.  If the file exists output is
	       appended	to it (by first	seeking	to the end-of-file);
	       otherwise, the file is created.

     <<[-]word After parameter and command substitution	is done	on word, the
	       shell input is read up to the first line	that literally matches
	       the resulting word, or to an end-of-file.  If, however, - is
	       appended	to <<:

	       1.  Leading tabs	are stripped from word before the shell	input
		   is read (but	after parameter	and command substitution is
		   done	on word).

	       2.  Leading tabs	are stripped from the shell input as it	is
		   read	and before each	line is	compared with word.

	       3.  Shell input is read up to the first line that literally
		   matches the resulting word, or to an	end-of-file.

	       If any character	of word	is quoted (see Quoting,	later),	no
	       additional processing is	done to	the shell input.  If no
	       characters of word are quoted:

	       1.  Parameter and command substitution occurs.

	       2.  (Escaped) \newline is ignored.

	       3.  \ must be used to quote the characters \, $,	and `.

	       The resulting document becomes the standard input.

     <&digit   Use the file associated with file descriptor digit as standard
	       input.  Similarly for the standard output using >&digit.

     <&-       The standard input is closed.  Similarly	for the	standard
	       output using >&-.

     If	any of the above is preceded by	a digit, the file descriptor that will
     be	associated with	the file is that specified by the digit	(instead of
     the default 0 or 1).  For example:

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bsh(1)									bsh(1)

	  ... 2>&1

     associates	file descriptor	2 with the file	currently associated with file
     descriptor	1.

     The order in which	redirections are specified is significant.  The	shell
     evaluates redirections left-to-right.  For	example:

	  ... 1>xxx <b>2>&1

     first associates file descriptor 1	with file xxx.	It associates file
     descriptor	2 with the file	associated with	file descriptor	1 (that	is,
     xxx).  If the order of redirections were reversed,	file descriptor	2
     would be associated with the terminal (assuming file descriptor 1 had
     been) and file descriptor 1 would be associated with file xxx.

     Using the terminology introduced on the first page, under Commands, if a
     command is	composed of several simple commands, redirection is evaluated
     for the entire command before it is evaluated for each simple command.
     That is, the shell	evaluates redirection for the entire list, then	each
     pipeline within the list, then each command within	each pipeline, then
     each list within each command.

     If	a command is followed by & the default standard	input for the command
     is	the empty file /dev/null.  Otherwise, the environment for the
     execution of a command contains the file descriptors of the invoking
     shell as modified by input/output specifications.

     Redirection of output is not allowed in the restricted shell.

   Filename Generation    [Toc]    [Back]
     Before a command is executed, each	command	word is	scanned	for the
     characters	*, ?, and [.  If one of	these characters appears the word is
     regarded as a pattern.  The word is replaced with alphabetically sorted
     filenames that match the pattern.	If no filename is found	that matches
     the pattern, the word is left unchanged.  The character . at the start of
     a filename	or immediately following a /, as well as the character /
     itself, must be matched explicitly.

     *	  Matches any string, including	the null string.

     ?	  Matches any single character.

	  Matches any one of the enclosed characters.  A pair of characters
	  separated by - matches any character lexically between the pair,
	  inclusive.  If the first character following the opening [ is	a !,
	  any character	not enclosed is	matched.

   Quoting    [Toc]    [Back]
     The following characters have a special meaning to	the shell and cause
     termination of a word unless quoted:

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bsh(1)									bsh(1)

	  ;  &	(  )  |	 ^  <  >  newline  space  tab

     A character can be	quoted that is,	made to	stand for itself) by preceding
     it	with a backslash (\) or	inserting it between a pair of quote marks (''
     or	"").  During processing, the shell can quote certain characters	to
     prevent them from taking on a special meaning.  Backslashes used to quote
     a single character	are removed from the word before the command is
     executed.	The pair \newline is removed from a word before	command	and
     parameter substitution.

     All characters enclosed between a pair of single quote marks (''),	except
     a single quote, are quoted	by the shell.  Backslash has no	special
     meaning inside a pair of single quotes.  A	single quote can be quoted
     inside a pair of double quote marks (for example, "'").

     Inside a pair of double quote marks (""), parameter and command
     substitution occurs and the shell quotes the results to avoid blank
     interpretation and	filename generation.  If $* is within a	pair of	double
     quotes, the positional parameters are substituted and quoted, separated
     by	quoted spaces ("$1 $2 ..."); however, if $@ is within a	pair of	double
     quotes, the positional parameters are substituted and quoted, separated
     by	unquoted spaces	("$1" "$2" ...).  \ quotes the characters \, `,	", and
     $.	 The pair \newline is removed before parameter and command
     substitution.  If a backslash precedes characters other than \, `,	", $,
     and newline, then the backslash itself is quoted by the shell.

   Prompting    [Toc]    [Back]
     When used interactively, the shell	prompts	with the value of PS1 before
     reading a command.	 If at any time	a newline is typed and further input
     is	needed to complete a command, the secondary prompt that	is, the	value
     of	PS2) is	issued.

   Environment    [Toc]    [Back]
     The environment (see environ(5)) is a list	of name-value pairs that is
     passed to an executed program in the same way as a	normal argument	list.
     The shell interacts with the environment in several ways.	On invocation,
     the shell scans the environment and creates a parameter for each name
     found, giving it the corresponding	value.	If the user modifies the value
     of	any of these parameters	or creates new parameters, none	of these
     affects the environment unless the	export command is used to bind the
     shell's parameter to the environment (see also set	-a).  A	parameter can
     be	removed	from the environment with the unset command.  The environment
     seen by any executed command is thus composed of any unmodified namevalue
 pairs originally inherited by the shell, minus any pairs removed by
     unset, plus any modifications or additions, all of	which must be noted in
     export commands.

     The environment for any simple-command can	be augmented by	prefixing it
     with one or more assignments to parameters.  Thus these two commands are
     equivalent	(as far	as the execution of cmd	is concerned if	cmd is not a
     Special Command):

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bsh(1)									bsh(1)

	  TERM=450 cmd
	  (export TERM;	TERM=450; cmd)

     If	cmd is a Special Command, then

	  TERM=45 cmd

     modifies the TERM variable	in the current shell.

     If	the -k flag is set, all	keyword	arguments are placed in	the
     environment, even if they occur after the command name.  The following
     first prints a=b c	and c:

	  echo a=b c
	  set -k
	  echo a=b c

   Signals    [Toc]    [Back]
     When a command is run in the background (cmd <b>&) under sh, it can receive
     INTERRUPT and QUIT	signals	but ignores them by default.  (A background
     process can override this default behavior	via trap or signal.  For
     details, see the description of trap, below, or signal(2).)  When a
     command is	run in the background under jsh, however, it does not receive
     INTERRUPT or QUIT signals.

     Otherwise signals have the	values inherited by the	shell from its parent,
     with the exception	of signal 11 (SIGSEGV).	 See also the trap command

   Execution    [Toc]    [Back]
     Each time a command is executed, the command substitution,	parameter
     substitution, blank interpretation, input/output redirection, and
     filename generation listed	above are carried out.	If the command name
     matches the name of a defined function, the function is executed in the
     shell process (note how this differs from the execution of	shell
     procedures).  If the command name does not	match the name of a defined
     function, but matches one of the Special Commands listed below, it	is
     executed in the shell process.  The positional parameters $1, $2, and so
     on	are set	to the arguments of the	function.  If the command name matches
     neither a Special Command nor the name of a defined function, a new
     process is	created	and an attempt is made to execute the command via

     The shell parameter PATH defines the search path for the directory
     containing	the command.  Alternative directory names are separated	by a
     colon (:).	 The default path is:


     specifying	the current directory, /usr/sbin, /usr/bsd, /bin, /usr/bin,
     and /usr/bin/X11, in that order.  Note that the current directory is

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bsh(1)									bsh(1)

     specified by a null pathname.  It can appear immediately after the	equal
     sign, between two colon delimiters	anywhere in the	path list, or at the
     end of the	path list.  If the command name	contains a / the search	path
     is	not used; such commands	are not	executed by the	restricted shell.
     Otherwise,	each directory in the path is searched for an executable file.
     If	the file has execute permission	but is not an a.out file, it is
     assumed to	be a file containing shell commands.  A	subshell is spawned to
     read it.  A parenthesized command is also executed	in a subshell.

     The location in the search	path where a command was found is remembered
     by	the shell (to help avoid unnecessary execs later).  If the command was
     found in a	relative directory, its	location must be re-determined
     whenever the current directory changes.  The shell	forgets	all remembered
     locations whenever	the PATH variable is changed or	the hash -r command is
     executed (see below).

   Special Commands    [Toc]    [Back]
     Input/output redirection is now permitted for these commands.  File
     descriptor	1 is the default output	location.  When	Job Control is
     enabled, additional Special Commands are added to the shell's environment
     (see Job Control).

     :			 No effect; the	command	does nothing.  A zero exit
			 code is returned.

     . file		 Read and execute commands from	file and return.  The
			 search	path specified by PATH is used to find the
			 directory containing file.

     break [ n ]	 Exit from the enclosing for or	while loop, if any.
			 If n is specified break n levels.

     continue [	n ]	 Resume	the next iteration of the enclosing for	or
			 while loop.  If n is specified	resume at the n-th
			 enclosing loop.

     cd	[ arg ]		 Change	the current directory to arg.  The shell
			 parameter HOME	is the default arg.  The shell
			 parameter CDPATH defines the search path for the
			 directory containing arg.  Alternative	directory
			 names are separated by	a colon	(:).  The default path
			 is <null> (specifying the current directory).	Note
			 that the current directory is specified by a null
			 pathname.  It can appear immediately after the	equal
			 sign or between the colon delimiters anywhere else in
			 the path list.	 If arg	begins with a /	the search
			 path is not used.  Otherwise, each directory in the
			 path is searched for arg.  The	cd command cannot be
			 executed by rsh.

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bsh(1)									bsh(1)

     echo [ arg	... ]	 Echo arguments.  See echo(1) for usage	and

     eval [ arg	... ]	 The arguments are read	as input to the	shell and the
			 resulting command(s) executed.

     exec [ arg	... ]	 The command specified by the arguments	is executed in
			 place of this shell without creating a	new process.
			 Input/output arguments	can appear and,	if no other
			 arguments are given, cause the	shell input/output to
			 be modified.

     exit [ n ]		 Causes	a shell	to exit	with the exit status specified
			 by n.	If n is	omitted, the exit status is that of
			 the last command executed (an end-of-file also	causes
			 the shell to exit.)

     export [ name ... ] The given names are marked for	automatic export to
			 the environment of subsequently-executed commands.
			 If no arguments are given, variable names that	have
			 been marked for export	during the current shell's
			 execution are listed.	(Variable names	exported from
			 a parent shell	are listed only	if they	have been
			 exported again	during the current shell's execution.)
			 Function names	are not	exported.

     getopts		 Use in	shell scripts to support command syntax
			 standards (see	intro(1)); it parses positional
			 parameters and	checks for legal options.  See
			 getopts(1) for	usage and description.

     hash [ -r ] [ name	... ]
			 For each name,	the location in	the search path	of the
			 command specified by name is determined and
			 remembered by the shell.  The -r option causes	the
			 shell to forget all remembered	locations.  If no
			 arguments are given, information about	remembered
			 commands is presented.	 hits is the number of times a
			 command has been invoked by the shell process.	 cost
			 is a measure of the work required to locate a command
			 in the	search path.  If a command is found in a
			 "relative" directory in the search path, after
			 changing to that directory, the stored	location of
			 that command is recalculated.	Commands for which
			 this is done are indicated by an asterisk (*)
			 adjacent to the hits information.  cost is
			 incremented when the recalculation is done.

     limit [ -h	] [ resource [maximum-use ] ]
			 Limits	the consumption	by the current process and
			 each process it creates to not	individually exceed
			 maximum-use on	the specified resource.	 If no

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			 maximum-use is	given, then the	current	limit is
			 printed; if no	resource is given, then	all
			 limitations are given.	 If the	-h flag	is given, the
			 hard limits are used instead of the current limits.
			 The hard limits impose	a ceiling on the values	of the
			 current limits.  Only the superuser can raise the
			 hard limits, but a user can lower or raise the
			 current limits	within the legal range.

			 Resources controllable	currently include cputime, the
			 maximum number	of cpu-seconds to be used by each
			 process, filesize, the	largest	single file that can
			 be created, datasize, the maximum growth of the data
			 region	via sbrk(2) beyond the end of the program
			 text, stacksize, the maximum size of the
			 automatically-extended	stack region, coredumpsize,
			 the size of the largest core dump created, memoryuse,
			 the maximum amount of physical	memory a process can
			 have allocated	to it at a given time, descriptors,
			 the maximum number of open files, and vmemory,	the
			 maximum total virtual size of the process, including
			 text, data, heap, shared memory, mapped files,	stack,
			 and so	on.

			 The maximum-use can be	given as a (floating point or
			 integer) number followed by a scale factor.  For all
			 limits	other than cputime the default scale is	k or
			 kilobytes (1024 bytes); a scale factor	of m or
			 megabytes can also be used.  For cputime the default
			 scaling is seconds, while m for minutes or h for
			 hours,	or a time of the form mm:ss giving minutes and
			 seconds can be	used.

			 For both resource names and scale factors,
			 unambiguous prefixes of the names suffice.

     newgrp [ arg ... ]	 Equivalent to exec newgrp arg ....  See newgrp(1) for
			 usage and description.

     pwd		 Print the current working directory.  See pwd(1) for
			 usage and description.

     read [ name ... ]	 One line is read from the standard input and, using
			 the internal field separator, IFS (normally space or
			 tab), to delimit word boundaries, the first word is
			 assigned to the first name, the second	word to	the
			 second	name, and so on, with leftover words assigned
			 to the	last name.  Lines can be continued using
			 \newline.  Characters other than newline can be
			 quoted	by preceding them with a backslash.  These
			 backslashes are removed before	words are assigned to
			 names,	and no interpretation is done on the character

								       Page 12

bsh(1)									bsh(1)

			 that follows the backslash.  The return code is 0
			 unless	an end-of-file is encountered.

     readonly [	name ... ]
			 The given names are marked readonly and the values of
			 the these names cannot	be changed by subsequent
			 assignment.  If no arguments are given, a list	of all
			 readonly names	is printed.

     return [ n	]	 Causes	a function to exit with	the return value
			 specified by n.  If n is omitted, the return status
			 is that of the	last command executed.

     set [ --aefhkntuvx	[ arg ... ] ]

			 -a   Mark variables that are modified or created for

			 -e   Exit immediately if a command exits with a
			      nonzero exit status.

			 -f   Disable filename generation.

			 -h   Locate and remember function commands as
			      functions	are defined (function commands are
			      normally located when the	function is executed).

			 -k   All keyword arguments are	placed in the
			      environment for a	command, not just those	that
			      precede the command name.

			 -n   Read commands but	do not execute them.

			 -t   Exit after reading and executing one command.

			 -u   Treat unset variables as an error	when

			 -v   Print shell input	lines as they are read.

			 -x   Print commands and their arguments as they are

			 --   Do not change any	of the flags; useful in
			      setting $1 to -.

			 Using + rather	than - causes these flags to be	turned
			 off.  These flags can also be used upon invocation of
			 the shell.  The current set of	flags can be found in
			 $-.  The remaining arguments are positional
			 parameters and	are assigned, in order,	to $1, $2,
			 ....  If no arguments are given the values of all

								       Page 13

bsh(1)									bsh(1)

			 names are printed.

     shift [ n ]	 The positional	parameters from	$n+1 ...  are renamed
			 $1 ....  If n is not given, it	is assumed to be 1.

     test		 Evaluate conditional expressions.  See	test(1)	for
			 usage and description.

     times		 Print the accumulated user and	system times for
			 processes run from the	shell.

     trap [ arg	] [ n ]	...
			 The command arg is to be read and executed when the
			 shell receives	signal(s) n.  (Note that arg is
			 scanned once when the trap is set and once when the
			 trap is taken.)  Trap commands	are executed in	order
			 of signal number.  Any	attempt	to set a trap on a
			 signal	that was ignored on entry to the current shell
			 is ineffective.  An error results when	an attempt is
			 made to trap signal 11	(SIGSEGV--segmentation fault).
			 If arg	is absent all trap(s) n	are reset to their
			 original values.  If arg is the null string this
			 signal	is ignored by the shell	and by the commands it
			 invokes.  If n	is 0 the command arg is	executed on
			 exit from the shell.  The trap	command	with no
			 arguments prints a list of commands associated	with
			 each signal number.

     type [ name ... ]	 For each name,	indicate how it	would be interpreted
			 if used as a command name.

     ulimit [ n	]	 Impose	a size limit of	n blocks on files written by
			 the shell and its child processes (files of any size
			 can be	read).	If n is	omitted, the current limit is
			 printed.  You can lower your own ulimit, but only a
			 superuser (see	su(1M))	can raise a ulimit.

     umask [ nnn ]	 The user file creation	mask is	set to nnn (see
			 umask(1)).  If	nnn is omitted,	the current value of
			 the mask is printed.

     unlimit [ -h ] [ resource ]
			 Removes the limitation	on resource.  If no resource
			 is specified, then all	resource limitations are
			 removed.  If -h is given, the corresponding hard
			 limits	are removed.  Only the superuser can do	this.

     unset [ name ... ]	 For each name,	remove the corresponding variable or
			 function.  The	variables PATH,	PS1, PS2, MAILCHECK
			 and IFS cannot	be unset.

								       Page 14

bsh(1)									bsh(1)

     wait [ n ]		 Wait for your background process whose	process	id is
			 n and report its termination status.  If n is
			 omitted, all your shell's currently active background
			 processes are waited for and the return code is zero.

   Invocation    [Toc]    [Back]
     If	the shell is invoked through exec(2) and the first character of
     argument zero is -, commands are initially	read from /etc/profile and
     from $HOME/.profile, if such files	exist.	Thereafter, commands are read
     as	described below, which is also the case	when the shell is invoked as
     /bin/sh.  The flags below are interpreted by the shell on invocation
     only; Note	that unless the	-c or -s flag is specified, the	first argument
     is	assumed	to be the name of a file containing commands, and the
     remaining arguments are passed as positional parameters to	that command

     -c	string
	  If the -c flag is present, commands are read from string.

     -s	  If the -s flag is present or if no arguments remain, commands	are
	  read from the	standard input.	 Any remaining arguments specify the
	  positional parameters.  Shell	output (except for Special Commands)
	  is written to	file descriptor	2.

     -i	  If the -i flag is present or if the shell input and output are
	  attached to a	terminal, this shell is	interactive.  In this case
	  TERMINATE is ignored (so that	kill 0 does not	kill an	interactive
	  shell) and INTERRUPT is caught and ignored (so that wait is
	  interruptible).  In all cases, QUIT is ignored by the	shell.

     -p	  If the -p flag is present, the shell skips the processing of the
	  system profile (/etc/profile)	and the	user profile (.profile)	when
	  it starts.

     -r	  If the -r flag is present the	shell is a restricted shell.

     The remaining flags and arguments are described under the set command

   Job Control (jsh)    [Toc]    [Back]
     When the shell is invoked as jsh, Job Control is enabled in addition to
     all of the	functionality described	previously for sh.  Typically Job
     Control is	enabled	for the	interactive shell only.	 Noninteractive	shells
     typically do not benefit from the added functionality of Job Control.

     With Job Control enabled every command or pipeline	the user enters	at the
     terminal is called	a job.	All jobs exist in one of the following states:
     foreground, background, or	stopped.  These	terms are defined as follows:
     1)	a job in the foreground	has read and write access to the controlling
     terminal; 2) a job	in the background is denied read access	and has
     conditional write access to the controlling terminal (see stty(1)); 3) a
     stopped job is a job that has been	placed in a suspended state, usually

								       Page 15

bsh(1)									bsh(1)

     as	a result of a SIGTSTP signal (see signal(2)).  Jobs in the foreground
     can be stopped by INTERRUPT or QUIT signals from the keyboard; background
     jobs cannot be stopped by these signals.

     Every job the shell starts	is assigned a positive integer,	called a job
     number, which is tracked by the shell and is used,	later, as an
     identifier	to indicate a specific job.  Additionally the shell keeps
     track of the current and previous jobs.  The current job is the most
     recent job	to be started or restarted.  The previous job is the first
     noncurrent	job.

     The acceptable syntax for a Job Identifier	is of the form:


     where jobid can be	specified in any of the	following formats:

     % or +    For the current job.

     -	       For the previous	job.

     ?string   Specify the job for which the command line uniquely contains

     n	       For job number n, where n is a job number.

     pref      Where pref is a unique prefix of	the command name (for example,
	       if the command ls -l foo	were running in	the background,	it
	       could be	referred to as %ls); pref cannot contain blanks	unless
	       it is quoted.

     When Job Control is enabled, the following	commands are added to the
     user's environment	to manipulate jobs:

     bg	[%jobid	...]	 Resumes the execution of a stopped job	in the
			 background.  If %jobid	is omitted the current job is

     fg	[%jobid	...]	 Resumes the execution of a stopped job	in the
			 foreground, also moves	an executing background	job
			 into the foreground.  If %jobid is omitted the
			 current job is	assumed.

     jobs [-p|-l] [%jobid ...]

     jobs -x command [arguments]
			 Reports all jobs that are stopped or executing	in the
			 background.  If %jobid	is omitted, all	jobs that are
			 stopped or running in the background are reported.
			 The following options modify/enhance the output of

								       Page 16

bsh(1)									bsh(1)

			 -l   Report the process group ID and working
			      directory	of the jobs.

			 -p   Report only the process group ID of the jobs.

			 -x   Replace any jobid	found in command or arguments
			      with the corresponding process group ID, and
			      then execute command passing it arguments.

     kill [-signal] %jobid
			 Builtin version of kill to provide the	functionality
			 of the	kill command for processes identified with a

     stop %jobid . . .	 Stops the execution of	a background job(s).

     suspend		 Stops the execution of	the current shell (but not if
			 it is the login shell).

     wait [%jobid ...]	 wait builtin accepts a	job identifier.	 If %jobid is
			 omitted, wait behaves as described above under
			 Special Commands.

   Restricted Shell (/usr/lib/rsh) Only
     /usr/lib/rsh is used to set up login names	and execution environments
     whose capabilities	are more controlled than those of the standard shell.
     The actions of /usr/lib/rsh are identical to those	of sh, except that the
     following are disallowed:

     o	changing directory (see	cd(1))
     o	setting	the value of $PATH
     o	specifying path	or command names containing /
     o	redirecting output (> and >>)

     The restrictions above are	enforced after .profile	is interpreted.

     A restricted shell	can be invoked in one of the following ways:  (1) rsh
     is	the filename part of the last entry in the /etc/passwd file (see
     passwd(4)); (2) the environment variable SHELL exists and rsh is the
     filename part of its value; (3) the shell is invoked and rsh is the
     filename part of argument 0; (4) the shell	is invoke with the -r option.

     When a command to be executed is found to be a shell procedure,
     /usr/lib/rsh invokes sh to	execute	it.  Thus, it is possible to provide
     to	the end-user shell procedures that have	access to the full power of
     the standard shell, while imposing	a limited menu of commands; this
     scheme assumes that the end-user does not have write and execute
     permissions in the	same directory.

     The net effect of these rules is that the writer of the .profile (see
     profile(4)) has complete control over user	actions	by performing
     guaranteed	setup actions and leaving the user in an appropriate directory

								       Page 17

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     (probably not the login directory).

     The system	administrator often sets up a directory	of commands (that is,
     /usr/rbin)	that can be safely invoked by a	restricted shell.  IRIX
     provides a	restricted editor, red(1).

EXIT STATUS    [Toc]    [Back]

     Errors detected by	the shell, such	as syntax errors, cause	the shell to
     return a nonzero exit status.  If the shell is being used
     noninteractively execution	of the shell file is abandoned.	 Otherwise,
     the shell returns the exit	status of the last command executed (see also
     the exit command above).

   jsh Only
     If	the shell is invoked as	jsh and	an attempt is made to exit the shell
     while there are stopped jobs, the shell issues one	warning:

	  UX:jsh:WARNING:there are stopped jobs

     This is the only message.	If another exit	attempt	is made	and there are
     still stopped jobs, they are sent a SIGHUP	signal from the	kernel and the
     shell is exited.

FILES    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

     cd(1), echo(1), env(1), getopts(1), intro(1), login(1), newgrp(1),
     pwd(1), systune(1m), test(1), umask(1), wait(1), xargs(1),	dup(2),
     exec(2), fork(2), getrlimit(2), pipe(2), signal(2), ulimit(2),

CAVEATS    [Toc]    [Back]

     Positional	parameters have	a range	of 0 to	9.  Attempting to use the
     positional	parameter $10 gives the	contents of $1 followed	by a 0,	which
     is	probably not the desired result.

     Words used	for filenames in input/output redirection are not interpreted
     for filename generation (see Filename Generation, above).	For example,
     cat file1 >a* creates a file with the name	a*.

     Because commands in pipelines are run as separate processes, variables
     set in a pipeline have no effect on the parent shell.

     If	you get	the error message "cannot fork,	too many processes", try using
     the wait(1) command to clean up your background processes.	 If this
     doesn't help, the system process table is probably	full or	you have too
     many active foreground processes.	(There is a limit to the number	of
     process ids associated with your login, and to the	number the system can

								       Page 18

bsh(1)									bsh(1)

     keep track	of.)

     For compatibility with the	POSIX builtin executables linked to
     /sbin/builtin_exec, the Korn shell	parameter expansion
     ${parameter##pattern} has been implemented	only for the specific pattern
     '*/' to emulate basename. This allows the Bourne shell builtins to	work
     correctly when called with	fullpaths e.g. /sbin/jobs.

NOTES    [Toc]    [Back]

     Sometimes,	particularly when using	wildcards, the shell will fail to
     execute a command,	and complain with the message
	Arg list or environment	too large
     This can often be avoided by using	multiple commands, the xargs(1)
     command, or by increasing the ncargs kernel parameter with	the
     systune(1m) command.

BUGS    [Toc]    [Back]

     Only the last process in a	pipeline can be	waited for.

     If	a command is executed, and a command with the same name	is installed
     in	a directory in the search path before the directory where the original
     command was found,	the shell continues to exec the	original command.  Use
     the hash command to correct this situation.

     Prior to IRIX Release 5.0,	the rsh	command	invoked	the restricted shell.
     This restricted shell command is /usr/lib/rsh and it can be executed by
     using the full pathname.  Beginning with IRIX Release 5.0,	the rsh
     command is	the remote shell.  See rsh_bsd(1C).

								       PPPPaaaaggggeeee 11119999
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