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。

for commands and \fB.\fP'd files.
An empty string resulting from a leading or trailing colon, or two adjacent
colons is treated as a `.', the current directory.
.\"}}}
.\"{{{  POSIXLY_CORRECT
.IP \fBPOSIXLY_CORRECT\fP
If set, this parameter causes the \fBposix\fP option to be enabled.
See POSIX Mode below.
.\"}}}
.\"{{{  PPID
.IP \fBPPID\fP
The process ID of the shell's parent (readonly).
.\"}}}
.\"{{{  PS1
.IP \fBPS1\fP
\fBPS1\fP is the primary prompt for interactive shells.
.ksh(
Parameter, command and arithmetic substitutions are performed, and
\fB!\fP is replaced with the current command number (see \fBfc\fP
command below).  A literal ! can be put in the prompt by placing !! in PS1.
Note that since the command line editors try to figure out how long the
prompt is (so they know how far it is to edge of the screen),
escape codes in the prompt tend to mess things up.
You can tell the shell not to count certain sequences (such as escape codes)
by prefixing your prompt with a non-printing character (such as control-A)
followed by a carriage return and then delimiting the escape codes with
this non-printing character.
If you don't have any non-printing characters, you're out of luck...
BTW, don't blame me for this hack; it's in the original ksh.
.ksh)
.sh(
The prompt is printed verbatim (\fIi.e.\fP, no substitutions are done).
.sh)
Default is `\fB$\ \fP' for non-root users, `\fB#\ \fP' for root..
.\"}}}
.\"{{{  PS2
.IP \fBPS2\fP
Secondary prompt string, by default `\fB>\fP ', used when more input is
needed to complete a command.
.\"}}}
.\"{{{  PS3
.ksh(
.IP \fBPS3\fP
Prompt used by \fBselect\fP statement when reading a menu selection.
Default is `\fB#?\ \fP'.
.ksh)
.\"}}}
.\"{{{  PS4
.IP \fBPS4\fP
Used to prefix commands that are printed during execution tracing
(see \fBset \-x\fP command below).
.ksh(
Parameter, command and arithmetic substitutions are performed
before it is printed.
.ksh)
.sh(
The prompt is printed verbatim (\fIi.e.\fP, no substitutions are done).
.sh)
Default is `\fB+\ \fP'.
.\"}}}
.\"{{{  PWD
.IP \fBPWD\fP
The current working directory.  Maybe unset or null if shell doesn't
know where it is.
.\"}}}
.\"{{{  RANDOM
.ksh(
.IP \fBRANDOM\fP
A simple random number generator.  Every time \fBRANDOM\fP is
referenced, it is assigned the next number in a random number series.
The point in the series can be set by assigning a number to
\fBRANDOM\fP (see \fIrand\fP(3)).
.ksh)
.\"}}}
.\"{{{  REPLY
.IP \fBREPLY\fP
Default parameter for the \fBread\fP command if no names are given.
Also used in \fBselect\fP loops to store the value that is read from
standard input.
.\"}}}
.\"{{{  SECONDS
.ksh(
.IP \fBSECONDS\fP
The number of seconds since the shell started or, if the parameter has been
assigned an integer value, the number of seconds since the assignment plus
the value that was assigned.
.ksh)
.\"}}}
.\"{{{  TMOUT
.ksh(
.IP \fBTMOUT\fP
If set to a positive integer in an interactive shell, it specifies
the maximum number of seconds the shell will wait for input after
printing the primary prompt (\fBPS1\fP).  If the time is exceeded, the
shell exits.
.ksh)
.\"}}}
.\"{{{  TMPDIR
.IP \fBTMPDIR\fP
The directory shell temporary files are created in.  If this parameter
is not set, or does not contain the absolute path of a writable
directory, temporary files are created in \fB/tmp\fP.
.\"}}}
.\"{{{  VISUAL
.ksh(
.IP \fBVISUAL\fP
If set, this parameter controls the command line editing mode for
interactive shells.  If the last component of the path specified in this
parameter contains the string \fBvi\fP, \fBemacs\fP or \fBgmacs\fP, the
vi, emacs or gmacs (Gosling emacs) editing mode is enabled, respectively.
.ksh)
.\"}}}
.\"}}}
.\"}}}
.\"{{{  Tilde Expansion
.SS "Tilde Expansion"
Tilde expansion, which is done in parallel with parameter substitution,
is done on words starting with an unquoted \fB~\fP.  The characters
following the tilde, up to the first \fB/\fP, if any, are assumed to be
a login name.  If the login name is empty, \fB+\fP or \fB\-\fP, the
value of the \fBHOME\fP, \fBPWD\fP, or \fBOLDPWD\fP parameter is
substituted, respectively.  Otherwise, the password file is searched for
the login name, and the tilde expression is substituted with the
user's home directory.  If the login name is not found in the password
file or if any quoting or parameter substitution occurs in the login name,
no substitution is performed.
.PP
In parameter assignments (those preceding a simple-command or those
occurring in the arguments of \fBalias\fP, \fBexport\fP, \fBreadonly\fP,
and \fBtypeset\fP), tilde expansion is done after any unquoted colon
(\fB:\fP), and login names are also delimited by colons.
.PP
The home directory of previously expanded login names are cached and
re-used.  The \fBalias \-d\fP command may be used to list, change and
add to this cache (\fIe.g.\fP, `alias \-d fac=/usr/local/facilities; cd
~fac/bin').
.\"}}}
.\"{{{  Brace Expansion
.ksh(
.SS "Brace Expansion (alternation)"
Brace expressions, which take the form
.RS
\fIprefix\fP\fB{\fP\fIstr\fP1\fB,\fP...\fB,\fP\fIstr\fPN\fB}\fP\fIsuffix\fP
.RE
are expanded to N words, each of which is the concatenation of
\fIprefix\fP, \fIstr\fPi and \fIsuffix\fP
(\fIe.g.\fP, `a{c,b{X,Y},d}e' expands to four word: ace, abXe, abYe, and ade).
As noted in the example, brace expressions can be nested and the resulting
words are not sorted.
Brace expressions must contain an unquoted comma (\fB,\fP) for expansion
to occur (\fIi.e.\fP, \fB{}\fP and \fB{foo}\fP are not expanded).
Brace expansion is carried out after parameter substitution and before
file name generation.
.ksh)
.\"}}}
.\"{{{  File Name Patterns
.SS "File Name Patterns"
.PP
A file name pattern is a word containing one or more unquoted \fB?\fP or
\fB*\fP characters or \fB[\fP..\fB]\fP sequences.  Once brace expansion has
been performed, the shell replaces file name patterns with the sorted names
of all the files that match the pattern (if no files match, the word is
left unchanged).  The pattern elements have the following meaning:
.IP \fB?\fP
matches any single character.
.IP \fB*\fP
matches any sequence of characters.
.IP \fB[\fP..\fB]\fP
matches any of the characters inside the brackets.  Ranges of characters
can be specified by separating two characters by a \fB\-\fP, \fIe.g.\fP,
\fB[a0\-9]\fP matches the letter \fBa\fP or any digit.
In order to represent itself, a
\fB\-\fP must either be quoted or the first or last character in the character
list.  Similarly, a \fB]\fP must be quoted or the first character in the list
if it is represent itself instead of the end of the list.  Also, a \fB!\fP
appearing at the start of the list has special meaning (see below), so to
represent itself it must be quoted or appear later in the list.
.IP \fB[!\fP..\fB]\fP
like \fB[\fP..\fB]\fP, except it matches any character not inside the brackets.
.ksh(
.IP "\fB*(\fP\fIpattern\fP\fB|\fP ... \fP|\fP\fIpattern\fP\fB)\fP"
matches any string of characters that matches zero or more occurances
of the specified patterns.
Example: the pattern \fB*(foo|bar)\fP matches the strings
`', `foo', `bar', `foobarfoo', \fIetc.\fP.
.IP "\fB+(\fP\fIpattern\fP\fB|\fP ... \fP|\fP\fIpattern\fP\fB)\fP"
matches any string of characters that matches one or more occurances
of the specified patterns.
Example: the pattern \fB+(foo|bar)\fP matches the strings
`foo', `bar', `foobarfoo', \fIetc.\fP.
.IP "\fB?(\fP\fIpattern\fP\fB|\fP ... \fP|\fP\fIpattern\fP\fB)\fP"
matches the empty string or a string that matches one of the
specified patterns.
Example: the pattern \fB?(foo|bar)\fP only matches the strings
`', `foo' and `bar'.
.IP "\fB@(\fP\fIpattern\fP\fB|\fP ... \fP|\fP\fIpattern\fP\fB)\fP"
matches a string that matches one of the
specified patterns.
Example: the pattern \fB@(foo|bar)\fP only matches the strings
`foo' and `bar'.
.IP "\fB!(\fP\fIpattern\fP\fB|\fP ... \fP|\fP\fIpattern\fP\fB)\fP"
matches any string that does not match one of the specified
patterns.
Examples: the pattern \fB!(foo|bar)\fP matches all strings except
`foo' and `bar'; the pattern \fB!(*)\fP matches no strings;
the pattern \fB!(?)*\fP matches all strings (think about it).
.ksh)
.PP
Note that pdksh currently never matches \fB.\fP and \fB..\fP, but the original
ksh, Bourne sh and bash do, so this may have to change (too bad).
.PP
Note that none of the above pattern elements match either a period (\fB.\fP)
at the start of a file name or a slash (\fB/\fP), even if they are explicitly
used in a \fB[\fP..\fB]\fP sequence; also, the names \fB.\fP and \fB..\fP
are never matched, even by the pattern \fB.*\fP.
.PP
If the \fBmarkdirs\fP option is set, any directories that result from
file name generation are marked with a trailing \fB/\fP.
.PP
.\" todo: implement this ([[:alpha:]], \fIetc.\fP)
The POSIX character classes (\fIi.e.\fP,
\fB[:\fP\fIclass-name\fP\fB:]\fP inside a \fB[\fP..\fB]\fP expression)
are not yet implemented.
.\"}}}
.\"{{{  Input/Output Redirection
.SS "Input/Output Redirection"
When a command is executed, its standard input, standard output and
standard error (file descriptors 0, 1 and 2, respectively) are normally
inherited from the shell.
Three exceptions to this are commands in pipelines, for which standard input
and/or standard output are those set up by the pipeline, asynchronous commands
created when job control is disabled, for which standard input is initially
set to be from \fB/dev/null\fP, and commands for which any of the following
redirections have been specified:
.IP "\fB>\fP \fIfile\fP"
standard output is redirected to \fIfile\fP.  If \fIfile\fP does not exist,
it is created; if it does exist, is a regular file and the \fBnoclobber\fP
option is set, an error occurs, otherwise the file is truncated.
Note that this means the command \fIcmd < foo > foo\fP will open
\fIfoo\fP for reading and then truncate it when it opens it for writing,
before \fIcmd\fP gets a chance to actually read \fIfoo\fP.
.IP "\fB>|\fP \fIfile\fP"
same as \fB>\fP, except the file is truncated, even if the \fBnoclobber\fP
option is set.
.IP "\fB>>\fP \fIfile\fP"
same as \fB>\fP, except the file an existing file is appended to instead
of being truncated.  Also, the file is opened in append mode, so writes
always go to the end of the file (see \fIopen\fP(2)).
.IP "\fB<\fP \fIfile\fP"
standard input is redirected from \fIfile\fP, which is opened for reading.
.IP "\fB<>\fP \fIfile\fP"
same as \fB<\fP, except the file is opened for reading and writing.
.IP "\fB<<\fP \fImarker\fP"
after reading the command line containing this kind of redirection (called a
here document), the shell copies lines from the command source into a temporary
file until a line matching \fImarker\fP is read.
When the command is executed, standard input is redirected from the temporary
file.
If \fImarker\fP contains no quoted characters, the contents of the
temporary file are processed as if enclosed in double quotes each time
the command is executed, so parameter, command and arithmetic substitutions
are performed, along with backslash (\fB\e\fP) escapes for
\fB$\fP, \fB`\fP, \fB\e\fP and \fB\enewline\fP.
If multiple here documents are used on the same command line, they are
saved in order.
.IP "\fB<<-\fP \fImarker\fP"
same as \fB<<\fP, except leading tabs are stripped from lines in the
here document.
.IP "\fB<&\fP \fIfd\fP"
standard input is duplicated from file descriptor \fIfd\fP.
\fIfd\fP can be a single digit, indicating the number of an existing
file descriptor, the letter \fBp\fP, indicating the file descriptor
associated with the output of the current co-process, or
the character \fB\-\fP, indicating standard input is to be closed.
.IP "\fB>&\fP \fIfd\fP"
same as \fB<&\fP, except the operation is done on standard output.
.PP
In any of the above redirections, the file descriptor that is redirected
(\fIi.e.\fP, standard input or standard output) can be explicitly given by
preceding the redirection with a single digit.
Parameter, command and arithmetic substitutions, tilde substitutions and
(if the shell is interactive) file name generation are all performed
on the \fIfile\fP, \fImarker\fP and \fIfd\fP arguments of redirections.
Note however, that the results of any file name generation are only used
if a single file is matched; if multiple files match, the word with the
unexpanded file name generation characters is used.
Note that in restricted shells, redirections which can create files cannot
be used.
.PP
For simple-commands, redirections may appear anywhere in the command, for
compound-commands (\fBif\fP statements, \fIetc.\fP), any redirections must
appear at the end.
Redirections are processed after pipelines are created and in the order they
are given, so
.RS
\fBcat /foo/bar 2>&1 > /dev/null | cat \-n\fP
.RE
will print an error with a line number prepended to it.
.\"}}}
.\"{{{  Arithmetic Expressions
.SS "Arithmetic Expressions"
Integer arithmetic expressions can be used
.ksh(
with the \fBlet\fP command,
.ksh)
inside \fB$((\fP..\fB))\fP expressions,
inside array references (\fIe.g.\fP, \fIname\fP\fB[\fP\fIexpr\fP\fB]\fP),
as numeric arguments to the \fBtest\fP command,
and as the value of an assignment to an integer parameter.
.PP
Expression may contain alpha-numeric parameter identifiers, array
references, and integer constants and may be combined with the
following C operators (listed and grouped in increasing order of precedence).