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<head>
<title>rc(1) - Plan 9 from User Space</title>
<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
</head>
<body bgcolor=#ffffff>
<table border=0 cellpadding=0 cellspacing=0 width=100%>
<tr height=10><td>
<tr><td width=20><td>
<tr><td width=20><td><b>RC(1)</b><td align=right><b>RC(1)</b>
<tr><td width=20><td colspan=2>
<br>
<p><font size=+1><b>NAME </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
rc, cd, eval, exec, exit, flag, rfork, shift, wait, whatis, .,
~ – command language<br>
</table>
<p><font size=+1><b>SYNOPSIS </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>rc</font></tt> [ <tt><font size=+1>−srdiIlxepvV</font></tt> ] [ <tt><font size=+1>−c command</font></tt> ] [ <i>file</i> [ <i>arg ...</i> ]]<br>
</table>
<p><font size=+1><b>DESCRIPTION </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>Rc</i> is the Plan 9 shell. It executes command lines read from a
terminal or a file or, with the <tt><font size=+1>−c</font></tt> flag, from <i>rc’s</i> argument list.<br>
<p><font size=+1><b>Command Lines </b></font><br>
A command line is a sequence of commands, separated by ampersands
or semicolons (<tt><font size=+1>&</font></tt> or <tt><font size=+1>;</font></tt>), terminated by a newline. The commands are
executed in sequence from left to right. <i>Rc</i> does not wait for
a command followed by <tt><font size=+1>&</font></tt> to finish executing before starting the
following command. Whenever a command
followed by <tt><font size=+1>&</font></tt> is executed, its process id is assigned to the <i>rc</i>
variable <tt><font size=+1>$apid</font></tt>. Whenever a command <i>not</i> followed by <tt><font size=+1>&</font></tt> exits or is
terminated, the <i>rc</i> variable <tt><font size=+1>$status</font></tt> gets the process’s wait message
(see <a href="../man3/wait.html"><i>wait</i>(3)</a>); it will be the null string if the command was successful.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
A long command line may be continued on subsequent lines by typing
a backslash (<tt><font size=+1>\</font></tt>) followed by a newline. This sequence is treated
as though it were a blank. Backslash is not otherwise a special
character.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
A number-sign (<tt><font size=+1>#</font></tt>) and any following characters up to (but not
including) the next newline are ignored, except in quotation marks.<br>
<p><font size=+1><b>Simple Commands </b></font><br>
A simple command is a sequence of arguments interspersed with
I/O redirections. If the first argument is the name of an <i>rc</i> function
or of one of <i>rc’s</i> built-in commands, it is executed by <i>rc</i>. Otherwise
if the name starts with a slash (<tt><font size=+1>/</font></tt>), it must be the path name
of the program to be executed. Names containing no
initial slash are searched for in a list of directory names stored
in <tt><font size=+1>$path</font></tt>. The first executable file of the given name found in
a directory in <tt><font size=+1>$path</font></tt> is the program to be executed. To be executable,
the user must have execute permission (see <a href="../man3/stat.html"><i>stat</i>(3)</a>) and the file
must be either an executable binary for the current
machine’s CPU type, or a shell script. Shell scripts begin with
a line containing the full path name of a shell (usually <tt><font size=+1>/bin/rc</font></tt>),
prefixed by <tt><font size=+1>#!</font></tt>.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
The first word of a simple command cannot be a keyword unless
it is quoted or otherwise disguised. The keywords are<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>for in while if not switch fn ~ ! @<br>
</font></tt>
</table>
<p><font size=+1><b>Arguments and Variables </b></font><br>
A number of constructions may be used where <i>rc’s</i> syntax requires
an argument to appear. In many cases a construction’s value will
be a list of arguments rather than a single string.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
The simplest kind of argument is the unquoted word: a sequence
of one or more characters none of which is a blank, tab, newline,
or any of the following:<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1># ; & | ^ $ = ` ' { } ( ) < ><br>
</font></tt>
</table>
An unquoted word that contains any of the characters <tt><font size=+1>* ? [</font></tt> is
a pattern for matching against file names. The character <tt><font size=+1>*</font></tt> matches
any sequence of characters, <tt><font size=+1>?</font></tt> matches any single character, and
<tt><font size=+1>[</font></tt><i>class</i><tt><font size=+1>]</font></tt> matches any character in the <i>class</i>. If the first character
of <i>class</i> is <tt><font size=+1>~</font></tt>, the class is complemented. The <i>class</i> may
also contain pairs of characters separated by <tt><font size=+1>−</font></tt>, standing for
all characters lexically between the two. The character <tt><font size=+1>/</font></tt> must
appear explicitly in a pattern, as must the first character of
the path name components <tt><font size=+1>.</font></tt> and <tt><font size=+1>..</font></tt>. A pattern is replaced by a
list of arguments, one for each path name matched, except that
a
pattern matching no names is not replaced by the empty list, but
rather stands for itself. Pattern matching is done after all other
operations. Thus,<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>x=/tmp echo $x^/*.c<br>
</font></tt>
</table>
matches <tt><font size=+1>/tmp/*.c</font></tt>, rather than matching <tt><font size=+1>/*.c</font></tt> and then prefixing
<tt><font size=+1>/tmp</font></tt>.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
A quoted word is a sequence of characters surrounded by single
quotes (<tt><font size=+1>'</font></tt>). A single quote is represented in a quoted word by
a pair of quotes (<tt><font size=+1>''</font></tt>).
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
Each of the following is an argument.<br>
<tt><font size=+1>(</font></tt><i>arguments</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The value of a sequence of arguments enclosed in parentheses is
a list comprising the members of each element of the sequence.
Argument lists have no recursive structure, although their syntax
may suggest it. The following are entirely equivalent:<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>echo hi there everybody<br>
((echo) (hi there) everybody)<br>
</font></tt>
</table>
</table>
<tt><font size=+1>$</font></tt><i>argument<br>
</i><tt><font size=+1>$</font></tt><i>argument</i><tt><font size=+1>(</font></tt><i>subscript</i><tt><font size=+1>)<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The <i>argument</i> after the <tt><font size=+1>$</font></tt> is the name of a variable whose value
is substituted. Multiple levels of indirection are possible, but
of questionable utility. Variable values are lists of strings.
If <i>argument</i> is a number <i>n</i>, the value is the <i>n</i>th element of <tt><font size=+1>$*</font></tt>,
unless <tt><font size=+1>$*</font></tt> doesn’t have <i>n</i> elements, in which case the value is
empty. If <i>argument</i> is followed by a parenthesized list of subscripts,
the value substituted is a list composed of the requested elements
(origin 1). The parenthesis must follow the variable name with
no spaces. Assignments to variables are described below.<br>
</table>
<tt><font size=+1>$#</font></tt><i>argument<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The value is the number of elements in the named variable. A variable
never assigned a value has zero elements.<br>
</table>
$"<i>argument<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The value is a single string containing the components of the
named variable separated by spaces. A variable with zero elements
yields the empty string.<br>
</table>
<tt><font size=+1>`{</font></tt><i>command</i><tt><font size=+1>}<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<i>rc</i> executes the <i>command</i> and reads its standard output, splitting
it into a list of arguments, using characters in <tt><font size=+1>$ifs</font></tt> as separators.
If <tt><font size=+1>$ifs</font></tt> is not otherwise set, its value is <tt><font size=+1>' \t\n'</font></tt>.<br>
</table>
<tt><font size=+1><{</font></tt><i>command</i><tt><font size=+1>}<br>
>{</font></tt><i>command</i><tt><font size=+1>}<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The <i>command</i> is executed asynchronously with its standard output
or standard input connected to a pipe. The value of the argument
is the name of a file referring to the other end of the pipe.
This allows the construction of non-linear pipelines. For example,
the following runs two commands <tt><font size=+1>old</font></tt> and <tt><font size=+1>new
</font></tt>and uses <tt><font size=+1>cmp</font></tt> to compare their outputs<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>cmp <{old} <{new}<br>
</font></tt>
</table>
</table>
<i>argument</i><tt><font size=+1>^</font></tt><i>argument<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The <tt><font size=+1>^</font></tt> operator concatenates its two operands. If the two operands
have the same number of components, they are concatenated pairwise.
If not, then one operand must have one component, and the other
must be non-empty, and concatenation is distributive.<br>
</table>
<p><font size=+1><b>Free Carets </b></font><br>
In most circumstances, <i>rc</i> will insert the <tt><font size=+1>^</font></tt> operator automatically
between words that are not separated by white space. Whenever
one of <tt><font size=+1>$ ' `</font></tt> follows a quoted or unquoted word or an unquoted
word follows a quoted word with no intervening blanks or tabs,
a <tt><font size=+1>^</font></tt> is inserted between the two. If an unquoted word
immediately follows a <tt><font size=+1>$</font></tt> and contains a character other than an
alphanumeric, underscore, or <tt><font size=+1>*</font></tt>, a <tt><font size=+1>^</font></tt> is inserted before the first
such character. Thus<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>cc −$flags $stem.c
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
</font></tt>
</table>
is equivalent to<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>cc −^$flags $stem^.c<br>
</font></tt>
</table>
<p><font size=+1><b>I/O Redirections </b></font><br>
The sequence <tt><font size=+1>></font></tt><i>file</i> redirects the standard output file (file descriptor
1, normally the terminal) to the named <i>file</i>; <tt><font size=+1>>></font></tt><i>file</i> appends standard
output to the file. The standard input file (file descriptor 0,
also normally the terminal) may be redirected from a file by the
sequence <tt><font size=+1><</font></tt><i>file</i>, or from an inline ‘here document’ by the
sequence <tt><font size=+1><<</font></tt><i>eof-marker</i>. The contents of a here document are lines
of text taken from the command input stream up to a line containing
nothing but the <i>eof-marker</i>, which may be either a quoted or unquoted
word. If <i>eof-marker</i> is unquoted, variable names of the form <tt><font size=+1>$</font></tt><i>word</i>
have their values substituted from <i>rc’s
</i>environment. If <tt><font size=+1>$</font></tt><i>word</i> is followed by a caret (<tt><font size=+1>^</font></tt>), the caret is
deleted. If <i>eof-marker</i> is quoted, no substitution occurs.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
Redirections may be applied to a file-descriptor other than standard
input or output by qualifying the redirection operator with a
number in square brackets. For example, the diagnostic output
(file descriptor 2) may be redirected by writing <tt><font size=+1>cc junk.c >[2]junk</font></tt>.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
A file descriptor may be redirected to an already open descriptor
by writing <tt><font size=+1>>[</font></tt><i>fd0</i><tt><font size=+1>=</font></tt><i>fd1</i><tt><font size=+1>]</font></tt> or <tt><font size=+1><[</font></tt><i>fd0</i><tt><font size=+1>=</font></tt><i>fd1</i><tt><font size=+1>]</font></tt>. <i>Fd1</i> is a previously opened
file descriptor and <i>fd0</i> becomes a new copy (in the sense of <a href="../man3/dup.html"><i>dup</i>(3)</a>)
of it. A file descriptor may be closed by writing <tt><font size=+1>>[</font></tt><i>fd0</i><tt><font size=+1>=]</font></tt> or <tt><font size=+1><[</font></tt><i>fd0</i><tt><font size=+1>=]</font></tt>.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
Redirections are executed from left to right. Therefore, <tt><font size=+1>cc junk.c
>/dev/null >[2=1]</font></tt> and <tt><font size=+1>cc junk.c >[2=1] >/dev/null</font></tt> have different effects:
the first puts standard output in <tt><font size=+1>/dev/null</font></tt> and then puts diagnostic
output in the same place, where the second directs diagnostic
output to the
terminal and sends standard output to <tt><font size=+1>/dev/null</font></tt>.<br>
<p><font size=+1><b>Compound Commands </b></font><br>
A pair of commands separated by a pipe operator (<tt><font size=+1>|</font></tt>) is a command.
The standard output of the left command is sent through a pipe
to the standard input of the right command. The pipe operator
may be decorated to use different file descriptors. <tt><font size=+1>|[</font></tt><i>fd</i><tt><font size=+1>]</font></tt> connects
the output end of the pipe to file descriptor <i>fd</i> rather
than 1. <tt><font size=+1>|[</font></tt><i>fd0</i><tt><font size=+1>=</font></tt><i>fd1</i><tt><font size=+1>]</font></tt> connects output to <i>fd1</i> of the left command
and input to <i>fd0</i> of the right command.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
A pair of commands separated by <tt><font size=+1>&&</font></tt> or <tt><font size=+1>||</font></tt> is a command. In either
case, the left command is executed and its exit status examined.
If the operator is <tt><font size=+1>&&</font></tt> the right command is executed if the left
command’s status is null. <tt><font size=+1>||</font></tt> causes the right command to be executed
if the left command’s status is non-null.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
The exit status of a command may be inverted (non-null is changed
to null, null is changed to non-null) by preceding it with a <tt><font size=+1>!</font></tt>.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
The <tt><font size=+1>|</font></tt> operator has highest precedence, and is left-associative
(i.e. binds tighter to the left than the right). <tt><font size=+1>!</font></tt> has intermediate
precedence, and <tt><font size=+1>&&</font></tt> and <tt><font size=+1>||</font></tt> have the lowest precedence.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
The unary <tt><font size=+1>@</font></tt> operator, with precedence equal to <tt><font size=+1>!</font></tt>, causes its operand
to be executed in a subshell.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
Each of the following is a command.<br>
<tt><font size=+1>if (</font></tt> <i>list</i> <tt><font size=+1>)</font></tt> <i>command<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
A <i>list</i> is a sequence of commands, separated by <tt><font size=+1>&</font></tt>, <tt><font size=+1>;</font></tt>, or newline.
It is executed and if its exit status is null, the <i>command</i> is
executed.<br>
</table>
<tt><font size=+1>if not</font></tt> <i>command<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The immediately preceding command must have been <tt><font size=+1>if(</font></tt><i>list</i><tt><font size=+1>)</font></tt> <i>command</i>.
If its condition was non-zero, the <i>command</i> is executed.<br>
</table>
<tt><font size=+1>for(</font></tt><i>name</i> <tt><font size=+1>in</font></tt> <i>arguments</i><tt><font size=+1>)</font></tt> <i>command<br>
</i><tt><font size=+1>for(</font></tt><i>name</i><tt><font size=+1>)</font></tt> <i>command<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The <i>command</i> is executed once for each <i>argument</i> with that argument
assigned to <i>name</i>. If the argument list is omitted, <tt><font size=+1>$*</font></tt> is used.<br>
</table>
<tt><font size=+1>while(</font></tt><i>list</i><tt><font size=+1>)</font></tt> <i>command<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The <i>list</i> is executed repeatedly until its exit status is non-null.
Each time it returns null status, the <i>command</i> is executed. An
empty <i>list</i> is taken to give null status.<br>
</table>
<tt><font size=+1>switch(</font></tt><i>argument</i><tt><font size=+1>){</font></tt><i>list</i><tt><font size=+1>}<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The <i>list</i> is searched for simple commands beginning with the word
<tt><font size=+1>case</font></tt>. (The search is only at the ‘top level’ of the <i>list</i>. That
is, <tt><font size=+1>cases</font></tt> in nested constructs are not found.) <i>Argument</i> is matched
against each word following <tt><font size=+1>case</font></tt> using the pattern-matching algorithm
described above, except that <tt><font size=+1>/</font></tt> and the
first characters of <tt><font size=+1>.</font></tt> and <tt><font size=+1>..</font></tt> need not be matched explicitly. When
a match is found, commands in the list are executed up to the
next following <tt><font size=+1>case</font></tt> command (at the top level) or the closing
brace.<br>
</table>
<tt><font size=+1>{</font></tt><i>list</i><tt><font size=+1>}<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Braces serve to alter the grouping of commands implied by operator
priorities. The <i>body</i> is a sequence of commands separated by <tt><font size=+1>&</font></tt>,
<tt><font size=+1>;</font></tt>, or newline.<br>
</table>
<tt><font size=+1>fn</font></tt> <i>name</i><tt><font size=+1>{</font></tt><i>list</i><tt><font size=+1>}<br>
fn</font></tt> <i>name<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The first form defines a function with the given <i>name</i>. Subsequently,
whenever a command whose first argument is <i>name</i> is encountered,
the current value of the remainder of the command’s argument list
will be assigned to <tt><font size=+1>$*</font></tt>, after saving its current value, and <i>rc</i>
will execute the <i>list</i>. The second form removes
<i>name</i>’s function definition.<br>
</table>
<tt><font size=+1>fn</font></tt> <i>note</i><tt><font size=+1>{</font></tt><i>list</i><tt><font size=+1>}<br>
fn</font></tt> <i>note<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
A function with a special name will be called when <i>rc</i> receives
a corresponding note; see <a href="../man3/notify.html"><i>notify</i>(3)</a>. The valid note names (and
corresponding notes) are <tt><font size=+1>sighup</font></tt> (<tt><font size=+1>hangup</font></tt>), <tt><font size=+1>sigint</font></tt> (<tt><font size=+1>interrupt</font></tt>),
<tt><font size=+1>sigalrm</font></tt> (<tt><font size=+1>alarm</font></tt>), and <tt><font size=+1>sigfpe</font></tt> (floating point trap). By default
<i>rc</i> exits on receiving any signal, except when
run interactively, in which case interrupts and quits normally
cause <i>rc</i> to stop whatever it’s doing and start reading a new command.
The second form causes <i>rc</i> to handle a signal in the default manner.
<i>Rc</i> recognizes an artificial note, <tt><font size=+1>sigexit</font></tt>, which occurs when <i>rc</i>
is about to finish executing.
</table>
<i>name</i><tt><font size=+1>=</font></tt><i>argument command<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Any command may be preceded by a sequence of assignments interspersed
with redirections. The assignments remain in effect until the
end of the command, unless the command is empty (i.e. the assignments
stand alone), in which case they are effective until rescinded
by later assignments.
</table>
<p><font size=+1><b>Built-in Commands </b></font><br>
These commands are executed internally by <i>rc</i>, usually because
their execution changes or depends on <i>rc</i>’s internal state.<br>
<tt><font size=+1>.</font></tt> <i>file ...<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Execute commands from <i>file</i>. <tt><font size=+1>$*</font></tt> is set for the duration to the
remainder of the argument list following <i>file</i>. <i>File</i> is searched
for using <tt><font size=+1>$path</font></tt>.<br>
</table>
<tt><font size=+1>builtin</font></tt> <i>command ...<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Execute <i>command</i> as usual except that any function named <i>command</i>
is ignored in favor of the built-in meaning.<br>
</table>
<tt><font size=+1>cd [</font></tt><i>dir</i><tt><font size=+1>]<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Change the current directory to <i>dir</i>. The default argument is <tt><font size=+1>$home</font></tt>.
<i>dir</i> is searched for in each of the directories mentioned in <tt><font size=+1>$cdpath</font></tt>.<br>
</table>
<tt><font size=+1>eval [</font></tt><i>arg ...</i><tt><font size=+1>]<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The arguments are concatenated separated by spaces into a single
string, read as input to <i>rc</i>, and executed.<br>
</table>
<tt><font size=+1>exec [</font></tt><i>command ...</i><tt><font size=+1>]<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
This instance of <i>rc</i> replaces itself with the given (non-built-in)
<i>command</i>.<br>
</table>
<tt><font size=+1>flag</font></tt> <i>f</i> <tt><font size=+1>[+−]<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Either set (<tt><font size=+1>+</font></tt>), clear (<tt><font size=+1>−</font></tt>), or test (neither <tt><font size=+1>+</font></tt> nor <tt><font size=+1>−</font></tt>) the flag
<i>f</i>, where <i>f</i> is a single character, one of the command line flags
(see Invocation, below).<br>
</table>
<tt><font size=+1>exit [</font></tt><i>status</i><tt><font size=+1>]<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Exit with the given exit status. If none is given, the current
value of <tt><font size=+1>$status</font></tt> is used.<br>
</table>
<tt><font size=+1>rfork</font></tt> [<tt><font size=+1>nNeEsfFm</font></tt>]<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Become a new process group using <tt><font size=+1>rfork(</font></tt><i>flags</i><tt><font size=+1>)</font></tt> where <i>flags</i> is composed
of the bitwise OR of the <tt><font size=+1>rfork</font></tt> flags specified by the option letters
(see <a href="../man2/fork.html"><i>fork</i>(2)</a>). If no <i>flags</i> are given, they default to <tt><font size=+1>ens</font></tt>. The
<i>flags</i> and their meanings are: <tt><font size=+1>n</font></tt> is <tt><font size=+1>RFNAMEG</font></tt>; <tt><font size=+1>N</font></tt> is <tt><font size=+1>RFCNAMEG</font></tt>; <tt><font size=+1>e</font></tt> is
<tt><font size=+1>RFENVG</font></tt>; <tt><font size=+1>E</font></tt> is <tt><font size=+1>RFCENVG</font></tt>; <tt><font size=+1>s</font></tt> is
<tt><font size=+1>RFNOTEG</font></tt>; <tt><font size=+1>f</font></tt> is <tt><font size=+1>RFFDG</font></tt>; <tt><font size=+1>F</font></tt> is <tt><font size=+1>RFCFDG</font></tt>; and <tt><font size=+1>m</font></tt> is <tt><font size=+1>RFNOMNT</font></tt>.<br>
</table>
<tt><font size=+1>shift [</font></tt><i>n</i><tt><font size=+1>]<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Delete the first <i>n</i> (default 1) elements of <tt><font size=+1>$*</font></tt>.<br>
</table>
<tt><font size=+1>wait [</font></tt><i>pid</i><tt><font size=+1>]<br>
</font></tt>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Wait for the process with the given <i>pid</i> to exit. If no <i>pid</i> is
given, all outstanding processes are waited for.<br>
</table>
<tt><font size=+1>whatis</font></tt> <i>name ...<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Print the value of each <i>name</i> in a form suitable for input to <i>rc</i>.
The output is an assignment to any variable, the definition of
any function, a call to <tt><font size=+1>builtin</font></tt> for any built-in command, or the
completed pathname of any executable file.<br>
</table>
<tt><font size=+1>~</font></tt> <i>subject pattern ...<br>
</i>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
The <i>subject</i> is matched against each <i>pattern</i> in sequence. If it
matches any pattern, <tt><font size=+1>$status</font></tt> is set to zero. Otherwise, <tt><font size=+1>$status</font></tt>
is set to one. Patterns are the same as for file name matching,
except that <tt><font size=+1>/</font></tt> and the first character of <tt><font size=+1>.</font></tt> and <tt><font size=+1>..</font></tt> need not be
matched explicitly. The <i>patterns</i> are not subjected to
file name matching before the <tt><font size=+1>~</font></tt> command is executed, so they need
not be enclosed in quotation marks.<br>
</table>
<p><font size=+1><b>Environment </b></font><br>
The <i>environment</i> is a list of strings made available to executing
binaries by the kernel. <i>Rc</i> creates an environment entry for each
variable whose value is non-empty, and for each function. The
string for a variable entry has the variable’s name followed by
<tt><font size=+1>=</font></tt> and its value. If the value has more than one component,
these are separated by SOH (001) characters. The string for a
function is just the <i>rc</i> input that defines the function. The name
of a function in the environment is the function name preceded
by <tt><font size=+1>fn#</font></tt>.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
When <i>rc</i> starts executing it reads variable and function definitions
from its environment.<br>
<p><font size=+1><b>Special Variables </b></font><br>
The following variables are set or used by <i>rc</i>.<br>
<tt><font size=+1>$*</font></tt> Set to <i>rc</i>’s argument list during initialization. Whenever a
<tt><font size=+1>.</font></tt> command or a function is executed, the current value is saved
and <tt><font size=+1>$*</font></tt> receives the new argument list. The saved value is restored
on completion of the <tt><font size=+1>.</font></tt> or function.<br>
<tt><font size=+1>$apid</font></tt> Whenever a process is started asynchronously with <tt><font size=+1>&</font></tt>, <tt><font size=+1>$apid</font></tt>
is set to its process id.<br>
<tt><font size=+1>$home</font></tt> The default directory for <tt><font size=+1>cd</font></tt>.<br>
<tt><font size=+1>$ifs</font></tt> The input field separators used in backquote substitutions.
If <tt><font size=+1>$ifs</font></tt> is not set in <i>rc</i>’s environment, it is initialized to blank,
tab and newline.<br>
<tt><font size=+1>$path</font></tt> The search path used to find commands and input files for
the <tt><font size=+1>.</font></tt> command. If not set in the environment, it is initialized
by parsing the <tt><font size=+1>$PATH</font></tt> variable (as in <a href="../man1/sh.html"><i>sh</i>(1)</a>) or by <tt><font size=+1>path=(. /bin)</font></tt>.
The variables <tt><font size=+1>$path</font></tt> and <tt><font size=+1>$PATH</font></tt> are maintained together: changes
to one will be reflected in the other.
<tt><font size=+1>$pid</font></tt> Set during initialization to <i>rc</i>’s process id.<br>
<tt><font size=+1>$prompt</font></tt> When <i>rc</i> is run interactively, the first component of <tt><font size=+1>$prompt</font></tt>
is printed before reading each command. The second component is
printed whenever a newline is typed and more lines are required
to complete the command. If not set in the environment, it is
initialized by <tt><font size=+1>prompt=('% ' ' ')</font></tt>.
<tt><font size=+1>$status</font></tt> Set to the wait message of the last-executed program. (unless
started with <tt><font size=+1>&). !</font></tt> and <tt><font size=+1>~</font></tt> also change <tt><font size=+1>$status</font></tt>. Its value is used
to control execution in <tt><font size=+1>&&</font></tt>, <tt><font size=+1>||</font></tt>, <tt><font size=+1>if</font></tt> and <tt><font size=+1>while</font></tt> commands. When <i>rc</i> exits
at end-of-file of its input or on executing an <tt><font size=+1>exit</font></tt> command with
no argument, <tt><font size=+1>$status</font></tt> is its
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
exit status.<br>
</table>
</table>
<p><font size=+1><b>Invocation </b></font><br>
If <i>rc</i> is started with no arguments it reads commands from standard
input. Otherwise its first non-flag argument is the name of a
file from which to read commands (but see <tt><font size=+1>−c</font></tt> below). Subsequent
arguments become the initial value of <tt><font size=+1>$*</font></tt>. <i>Rc</i> accepts the following
command-line flags.<br>
<tt><font size=+1>−c</font></tt> <i>string</i> Commands are read from <i>string</i>.<br>
<tt><font size=+1>−s</font></tt> Print out exit status after any command where the status is
non-null.<br>
<tt><font size=+1>−e</font></tt> Exit if <tt><font size=+1>$status</font></tt> is non-null after executing a simple command.<br>
<tt><font size=+1>−i</font></tt> If <tt><font size=+1>−i</font></tt> is present, or <i>rc</i> is given no arguments and its standard
input is a terminal, it runs interactively. Commands are prompted
for using <tt><font size=+1>$prompt</font></tt>.<br>
<tt><font size=+1>−I</font></tt> Makes sure <i>rc</i> is not run interactively.<br>
<tt><font size=+1>−l</font></tt> If <tt><font size=+1>−l</font></tt> is given or the first character of argument zero is <tt><font size=+1>−</font></tt>,
<i>rc</i> reads commands from <tt><font size=+1>$home/lib/profile</font></tt>, if it exists, before
reading its normal input.<br>
<tt><font size=+1>−p</font></tt> A no-op.<br>
<tt><font size=+1>−d</font></tt> A no-op.<br>
<tt><font size=+1>−v</font></tt> Echo input on file descriptor 2 as it is read.<br>
<tt><font size=+1>−x</font></tt> Print each simple command before executing it.<br>
<tt><font size=+1>−r</font></tt> Print debugging information (internal form of commands as they
are executed).<br>
</table>
<p><font size=+1><b>SOURCE </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>/usr/local/plan9/src/cmd/rc<br>
</font></tt>
</table>
<p><font size=+1><b>SEE ALSO </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
Tom Duff, “Rc – The Plan 9 Shell”.<br>
</table>
<p><font size=+1><b>BUGS </b></font><br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
There should be a way to match patterns against whole lists rather
than just single strings.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
Using <tt><font size=+1>~</font></tt> to check the value of <tt><font size=+1>$status</font></tt> changes <tt><font size=+1>$status</font></tt>.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
Functions that use here documents don’t work.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
Free carets don’t get inserted next to keywords.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
The <tt><font size=+1><{</font></tt><i>command</i><tt><font size=+1>}</font></tt> syntax depends on the underlying operating system
providing a file descriptor device tree at <tt><font size=+1>/dev/fd</font></tt>.
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
By default, FreeBSD 5 does not provide file descriptors greater
than 2 in <tt><font size=+1>/dev/fd</font></tt>. To fix this, add<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
<tt><font size=+1>/fdescfs /dev/fd fdescfs rw 0 0<br>
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
</font></tt>
</table>
to <tt><font size=+1>/etc/fstab</font></tt>, and then <tt><font size=+1>mount /dev/fd</font></tt>. (Adding the line to <tt><font size=+1>fstab</font></tt>
ensures causes FreeBSD to mount the file system automatically
at boot time.)<br>
</table>
<td width=20>
<tr height=20><td>
</table>
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<tr><td><td>
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</center>
</table>
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