ksh.man

一个开放源代码的 AT&T 的 Korn Shell 的复制品, 支持大多数 ksh89 的特性。

of \fBin\fP and \fBesac\fP (\fIe.g.\fP, \fBcase $foo { *) echo bar; }\fP).
The exit status of a \fBcase\fP statement is that of the executed \fIlist\fP;
if no \fIlist\fP is executed, the exit status is zero.
.\"}}}
.\"{{{  for name [ in word ... term ] do list done
.IP "\fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP ... \fIterm\fP ] \fBdo\fP \fIlist\fP \fBdone\fP"
where \fIterm\fP is either a newline or a \fB;\fP.
For each \fIword\fP in the specified word list, the parameter \fIname\fP is
set to the word and \fIlist\fP is executed.  If \fBin\fP is not used to
specify a word list, the positional parameters (\fB"$1"\fP, \fB"$2"\fP,
\fIetc.\fP) are used instead.
For historical reasons, open and close braces may be used instead
of \fBdo\fP and \fBdone\fP (\fIe.g.\fP, \fBfor i; { echo $i; }\fP).
The exit status of a \fBfor\fP statement is the last exit status
of \fIlist\fP; if \fIlist\fP is never executed, the exit status is zero.
.\"}}}
.\"{{{  if list then list [ elif list then list ] ... [ else list ] fi
.IP "\fBif\fP \fIlist\fP \fBthen\fP \fIlist\fP [\fBelif\fP \fIlist\fP \fBthen\fP \fIlist\fP] ... [\fBelse\fP \fIlist\fP] \fBfi\fP"
If the exit status of the first \fIlist\fP is zero, the second \fIlist\fP
is executed; otherwise the \fIlist\fP following the \fBelif\fP, if any, is
executed with similar consequences.  If all the lists following the \fBif\fP
and \fBelif\fPs fail (\fIi.e.\fP, exit with non-zero status), the \fIlist\fP
following the \fBelse\fP is executed.
The exit status of an \fBif\fP statement is that
of non-conditional \fIlist\fP that is executed; if no non-conditional
\fIlist\fP is executed, the exit status is zero.
.\"}}}
.\"{{{  select name [ in word ... ] do list done
.ksh(
.IP "\fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ... \fIterm\fP ] \fBdo\fP \fIlist\fP \fBdone\fP"
where \fIterm\fP is either a newline or a \fB;\fP.
The \fBselect\fP statement provides an automatic method of presenting
the user with a menu and selecting from it.
An enumerated list of the specified \fIwords\fP is printed on standard
error, followed by a prompt (\fBPS3\fP, normally `\fB#? \fP').
A number corresponding to one of the enumerated words is then read
from standard input, \fIname\fP is set to the selected word (or is
unset if the selection is not valid), \fBREPLY\fP
is set to what was read (leading/trailing space is stripped),
and \fIlist\fP is executed.
If a blank line (\fIi.e.\fP, zero or more \fBIFS\fP characters) is entered,
the menu is re-printed without executing \fIlist\fP.
When \fIlist\fP completes, the enumerated list is printed if \fBREPLY\fP
is null, the prompt is printed and so on.
This process is continues until an end-of-file is read, an interrupt is
received or a break statement is executed inside the loop.
If \fBin\fP \fIword\fP \fB\&...\fP is omitted, the positional parameters
are used (\fIi.e.\fP, \fB"$1"\fP, \fB"$2"\fP, \fIetc.\fP).
For historical reasons, open and close braces may be used instead
of \fBdo\fP and \fBdone\fP (\fIe.g.\fP, \fBselect i; { echo $i; }\fP).
The exit status of a \fBselect\fP statement is zero if a break statement
is used to exit the loop, non-zero otherwise.
.ksh)
.\"}}}
.\"{{{  until list do list done
.IP "\fBuntil\fP \fIlist\fP \fBdo\fP \fIlist\fP \fBdone\fP"
This works like \fBwhile\fP, except that the body is executed only while the
exit status of the first \fIlist\fP is non-zero.
.\"}}}
.\"{{{  while list do list done
.IP "\fBwhile\fP \fIlist\fP \fBdo\fP \fIlist\fP \fBdone\fP"
A \fBwhile\fP is a prechecked loop.  Its body is executed as often
as the exit status of the first \fIlist\fP is zero.
The exit status of a \fBwhile\fP statement is the last exit status
of the \fIlist\fP in the body of the loop; if the body is not executed,
the exit status is zero.
.\"}}}
.\"{{{  function name { list }
.IP "\fBfunction\fP \fIname\fP \fB{\fP \fIlist\fP \fB}\fP"
Defines the function \fIname\fP.
See Functions below.
Note that redirections specified after a function definition are
performed whenever the function is executed, not when the function
definition is executed.
.\"}}}
.\"{{{  name () command
.IP "\fIname\fP \fB()\fP \fIcommand\fP"
Mostly the same as \fBfunction\fP.
See Functions below.
.\"}}}
.\"{{{  time [-p] [ pipeline ]
.IP "\fBtime\fP [ \fB-p\fP ] [ \fIpipeline\fP ]"
The \fBtime\fP reserved word is described in the Command Execution section.
.\"}}}
.\"{{{  (( expression ))
.ksh(
.IP "\fB((\fP \fIexpression\fP \fB))\fP"
The arithmetic expression \fIexpression\fP is evaluated;
equivalent to \fBlet "\fP\fIexpression\fP\fB"\fP.
See Arithmetic Expressions and the \fBlet\fP command below.
.ksh)
.\"}}}
.\"{{{  [[ expression ]]
.ksh(
.IP "\fB[[\fP \fIexpression\fP \fB]]\fP"
Similar to the \fBtest\fP and \fB[\fP \&... \fB]\fP commands (described later),
with the following exceptions:
.RS
.nr P2 \n(PD
.nr PD 0
.IP \ \ \(bu
Field splitting and file name generation are not performed on
arguments.
.IP \ \ \(bu
The \fB\-a\fP (and) and \fB\-o\fP (or) operators are replaced with
\fB&&\fP and \fB||\fP, respectively.
.IP \ \ \(bu
Operators (\fIe.g.\fP, \fB\-f\fP, \fB=\fP, \fB!\fP, \fIetc.\fP) must be unquoted.
.IP \ \ \(bu
The second operand of \fB!=\fP and \fB=\fP
expressions are patterns (\fIe.g.\fP, the comparison in
.ce
\fB[[ foobar = f*r ]]\fP
succeeds).
.IP \ \ \(bu
There are two additional binary operators: \fB<\fP and \fB>\fP
which return true if their first string operand is less than,
or greater than, their second string operand, respectively.
.IP \ \ \(bu
The single argument form
of \fBtest\fP, which tests if the argument has non-zero length, is not valid
- explicit operators must be always be used, \fIe.g.\fP, instead of
.ce
\fB[\fP \fIstr\fP \fB]\fP
use
.ce
\fB[[ \-n \fP\fIstr\fP\fB ]]\fP
.IP \ \ \(bu
Parameter, command and arithmetic substitutions are performed as
expressions are evaluated and lazy expression evaluation is used for
the \fB&&\fP and \fB||\fP operators.
This means that in the statement
.ce
\fB[[ -r foo && $(< foo) = b*r ]]\fP
the \fB$(< foo)\fP is evaluated if and only if the file \fBfoo\fP exists
and is readable.
.nr PD \n(P2
.RE
.ksh)
.\"}}}
.\"}}}
.\"}}}
.\"{{{  Quoting
.SS Quoting
Quoting is used to prevent the shell from treating characters or words
specially.
There are three methods of quoting: First, \fB\e\fP quotes
the following character, unless it is at the end of a line, in which
case both the \fB\e\fP and the newline are stripped.
Second, a single quote (\fB'\fP) quotes everything up to the next single
quote (this may span lines).
Third, a double quote (\fB"\fP) quotes all characters,
except \fB$\fP, \fB`\fP and \fB\e\fP, up to the next unquoted double quote.
\fB$\fP and \fB`\fP inside double quotes have their usual meaning (\fIi.e.\fP,
parameter, command or arithmetic substitution) except no field splitting
is carried out on the results of double-quoted substitutions.
If a \fB\e\fP inside a double-quoted string is followed by \fB\e\fP, \fB$\fP,
\fB`\fP or \fB"\fP, it is replaced by the second character; if it is
followed by a newline, both the \fB\e\fP and the newline are stripped;
otherwise, both the \fB\e\fP and the character following are unchanged.
.PP
Note: see POSIX Mode below for a special rule regarding sequences
of the form \fB"\fP...\fB`\fP...\fB\e"\fP...\fB`\fP..\fB"\fP.
.\"}}}
.\"{{{  Aliases
.SS "Aliases"
There are two types of aliases: normal command aliases and tracked
aliases.  Command aliases are normally used as a short hand for a long
or often used command.  The shell expands command aliases (\fIi.e.\fP,
substitutes the alias name for its value) when it reads the first word
of a command.  An expanded alias is re-processed to check for more
aliases.  If a command alias ends in a space or tab, the following word
is also checked for alias expansion.  The alias expansion process stops
when a word that is not an alias is found, when a quoted word is found
or when an alias word that is currently being expanded is found.
.PP
The following command aliases are defined automatically by the shell:
.ft B
.RS
.ksh(
autoload='typeset \-fu'
.br
functions='typeset \-f'
.br
.ksh)
hash='alias \-t'
.ksh(
.br
history='fc \-l'
.br
integer='typeset \-i'
.br
local='typeset'
.br
login='exec login'
.br
newgrp='exec newgrp'
.br
nohup='nohup '
.br
r='fc \-e \-'
.br
stop='kill \-STOP'
.br
suspend='kill \-STOP $$'
.ksh)
.br
type='whence \-v'
.RE
.ft P
.PP
Tracked aliases allow the shell to remember where it found a particular
command.  The first time the shell does a path search for a command that
is marked as a tracked alias, it saves the full path of the command.
The next time the command is executed, the shell checks the saved path
to see that it is still valid, and if so, avoids repeating the path
search.  Tracked aliases can be listed and created using \fBalias
\-t\fP.  Note that changing the \fBPATH\fP parameter clears the saved
paths for all tracked aliases.  If the \fBtrackall\fP option is set (\fIi.e.\fP,
\fBset \-o trackall\fP or \fBset \-h\fP), the shell tracks all
commands.  This option is set automatically for non-interactive shells.
For interactive shells, only the following commands are automatically
tracked: \fBcat\fP, \fBcc\fP, \fBchmod\fP, \fBcp\fP, \fBdate\fP, \fBed\fP,
\fBemacs\fP, \fBgrep\fP, \fBls\fP, \fBmail\fP, \fBmake\fP, \fBmv\fP,
\fBpr\fP, \fBrm\fP, \fBsed\fP, \fBsh\fP, \fBvi\fP and \fBwho\fP.
.\"}}}
.\"{{{  Substitution
.SS "Substitution"
The first step the shell takes in executing a simple-command is to
perform substitutions on the words of the command.
There are three kinds of substitution: parameter, command and arithmetic.
Parameter substitutions, which are described in detail in the next section,
take the form \fB$name\fP or \fB${\fP...\fB}\fP; command substitutions take
the form \fB$(\fP\fIcommand\fP\fB)\fP or \fB`\fP\fIcommand\fP\fB`\fP;
and arithmetic substitutions take the form \fB$((\fP\fIexpression\fP\fB))\fP.
.PP
If a substitution appears outside of double quotes, the results of the
substitution are generally subject to word or field splitting according to
the current value of the \fBIFS\fP parameter.
The \fBIFS\fP parameter specifies a list of characters which 
are used to break a string up into several words;
any characters from the set space, tab and newline that appear in the
IFS characters are called \fIIFS white space\fP.
Sequences of one or more IFS white space characters, in combination with
zero or one non-IFS white space characters delimit a field.
As a special case, leading and trailing IFS white space is stripped (\fIi.e.\fP,
no leading or trailing empty field is created by it); leading or trailing
non-IFS white space does create an empty field.
Example: if \fBIFS\fP is set to `<space>:', the sequence of characters
`<space>A<space>:<space><space>B::D' contains four fields: `A', `B', `' and `D'.
Note that if the \fBIFS\fP parameter is set to the null string, no
field splitting is done; if the parameter is unset, the default value
of space, tab and newline is used.
.PP
The results of substitution are, unless otherwise specified, also subject
to brace expansion and file name expansion (see the relevant sections
below).
.PP
A command substitution is replaced by the output generated by the specified
command, which is run in a subshell.
For \fB$(\fP\fIcommand\fP\fB)\fP substitutions, normal quoting rules
are used when \fIcommand\fP is parsed, however, for the
\fB`\fP\fIcommand\fP\fB`\fP form, a \fB\e\fP followed by any of
\fB$\fP, \fB`\fP or \fB\e\fP is stripped (a \fB\e\fP followed by any other
character is unchanged).
As a special case in command substitutions, a command of the form
\fB<\fP \fIfile\fP is interpreted to mean substitute the contents
of \fIfile\fP ($(< foo) has the same effect as $(cat foo), but it
is carried out more efficiently because no process is started).
.br
.\"todo: fix this( $(..) parenthesis counting).
NOTE: \fB$(\fP\fIcommand\fP\fB)\fP expressions are currently parsed by
finding the matching parenthesis, regardless of quoting.  This will hopefully
be fixed soon.
.PP
Arithmetic substitutions are replaced by the value of the specified
expression.
For example, the command \fBecho $((2+3*4))\fP prints 14.
See Arithmetic Expressions for a description of an \fIexpression\fP.
.\"}}}
.\"{{{  Parameters
.SS "Parameters"
Parameters are shell variables; they can be assigned values and
their values can be accessed using a parameter substitution.
A parameter name is either one of the special single punctuation or digit
character parameters described below, or a letter followed by zero or more
letters or digits (`_' counts as a letter).
The later form can be treated as arrays by appending an array
index of the form: \fB[\fP\fIexpr\fP\fB]\fP where \fIexpr\fP is
an arithmetic expression.
Array indicies are currently limited to the range 0 through 1023, inclusive.
Parameter substitutions take the form \fB$\fP\fIname\fP,
\fB${\fP\fIname\fP\fB}\fP or
\fB${\fP\fIname\fP\fB[\fP\fIexpr\fP\fB]}\fP, where \fIname\fP is a
parameter name.
If substitution is performed on a parameter (or an array parameter element)
that is not set, a null
string is substituted unless the \fBnounset\fP option (\fBset \-o nounset\fP
or \fBset \-u\fP) is set, in which case an error occurs.
.PP
.\"{{{  parameter assignment
Parameters can be assigned values in a number of ways.
First, the shell implicitly sets some parameters like \fB#\fP, \fBPWD\fP,
etc.; this is the only way the special single character parameters are
set.
Second, parameters are imported from the shell's environment at startup.
Third, parameters can be assigned values on the command line, for example,
`\fBFOO=bar\fP' sets the parameter FOO to bar; multiple parameter
assignments can be given on a single command line and they can
be followed by a simple-command, in which case the assignments are
in effect only for the duration of the command (such assignments are
also exported, see below for implications of this).
Note that both the parameter name and the \fB=\fP must be unquoted for