zsh/Doc/Zsh/expn.yo

texinode(Expansion)(Parameters)(Restricted Shell)(Top)
chapter(Expansion)
cindex(expansion)
sect(Description)
The types of expansions performed are

startlist()
list(em(history expansion))
list(em(alias expansion))
list(em(process substitution))
list(em(parameter expansion))
list(em(command substitution))
list(em(arithmetic expansion))
list(em(brace expansion))
list(em(filename expansion))
list(em(filename generation))
endlist()

Expansion is done in the above specified order in five steps.  The
first is em(history expansion), which is only performed in
interactive shells.  The next step is em(alias expansion), which is
done right before the command line is parsed.  They are followed by
em(process substitution), em(parameter expansion), em(command
substitution), em(arithmetic expansion) and em(brace expansion)
which are performed in one step in left-to-right fashion.  After
these expansions, all unquoted occurrences of the characters `tt(\)',
`tt(')' and `tt(")' are removed, and the result is subjected to
em(filename expansion) followed by em(filename generation).

If the tt(SH_FILE_EXPANSION) option is set, the order of expansion is modified
for compatibility with bf(sh) and bf(ksh).  em(Filename expansion)
is performed immediately after em(alias substitution),
preceding the set of five substitutions mentioned above.
startmenu()
menu(History Expansion)
menu(Process Substitution)
menu(Parameter Expansion)
menu(Command Substitution)
menu(Arithmetic Expansion)
menu(Brace Expansion)
menu(Filename Expansion)
menu(Filename Generation)
endmenu()
texinode(History Expansion)(Process Substitution)()(Expansion)
sect(History Expansion)
cindex(history)
cindex(history expansion)
cindex(expansion, history)
History expansion allows you to use words from previous command
lines in the command line you are typing.  This simplifies spelling
corrections and the repetition of complicated commands or arguments.
Command lines are saved in the history list, the size of which
is controlled by the tt(HISTSIZE)
vindex(HISTSIZE, use of)
variable.  The most recent command is retained in any case.
A history expansion begins with the first character of the
tt(histchars) parameter which is `tt(!)'
by default and may occur anywhere on the command line; history
expansions do not nest.  The `tt(!)' can be escaped with `tt(\)'
or can be enclosed between a pair of single quotes (tt('')) to suppress
its special meaning. Double quotes will em(not) work for this.

Input lines containing history expansions are echoed on the
terminal after being expanded, but before any other
expansions take place or the command gets executed.
startmenu()
menu(Event Designators)
menu(Word Designators)
menu(Modifiers)
endmenu()
texinode(Event Designators)(Word Designators)()(History Expansion)
subsect(Event Designators)
cindex(history event designators)
cindex(event designators, history)
An event designator is a reference to a command-line entry in
the history list.

startitem()
item(tt(!))(
Start a history expansion, except when followed by a blank, newline,
`tt(=)' or `tt(LPAR())'.
)
item(tt(!!))(
Refer to the previous command.
By itself, this expansion
repeats the previous command.
)
item(tt(!)var(n))(
Refer to command-line var(n).
)
item(tt(!-)var(n))(
Refer to the current command-line minus var(n).
)
item(tt(!)var(str))(
Refer to the most recent command starting with var(str).
)
item(tt(!?)var(str)[tt(?)])(
Refer to the most recent command containing var(str).
)
item(tt(!#))(
Refer to the current command line typed in so far.  The line is
treated as if it were complete up to and including the word before the
one with the `tt(!#)' reference.
)
item(tt(!{)...tt(}))(
Insulate a history reference from adjacent characters (if necessary).
)
enditem()
texinode(Word Designators)(Modifiers)(Event Designators)(History Expansion)
subsect(Word Designators)
cindex(history word designators)
cindex(word designators, history)
A word designator indicates which word or words of a given command line will
be included in a history reference.  A `tt(:)'
separates the event specification from the word designator.
It can be omitted if the word designator begins with a
`tt(^)', `tt($)', `tt(*)', `tt(-)' or `tt(%)'.
Word designators include:

startsitem()
sitem(tt(0))(The first input word (command).)
sitem(var(n))(The var(n)th argument.)
sitem(tt(^))(The first argument.  That is, tt(1).)
sitem(tt($))(The last argument.)
sitem(tt(%))(The word matched by (the most recent) tt(?)var(str) search.)
sitem(var(x)tt(-)var(y))(A range of words; var(x) defaults to tt(0).)
sitem(tt(*))(All the arguments, or a null value if there are none.)
sitem(var(x)tt(*))(Abbreviates `var(x)tt(-$)'.)
sitem(var(x)tt(-))(Like `var(x)tt(*)' but omitting word tt($).)
endsitem()

Note that a `tt(%)' word designator will only work when used as
`tt(!%)', `tt(!:%)' or `tt(!?)var(str)tt(?:%)',
and only when used after a tt(!?) expansion.  Anything else will result
in an error, although the error may not be the most obvious one.
texinode(Modifiers)()(Word Designators)(History Expansion)
subsect(Modifiers)
cindex(modifiers, history)
cindex(history modifiers)
After the optional word designator, you can add
a sequence of one or more of the following modifiers,
each preceded by a `tt(:)'.  These modifiers also work on the result
of em(filename generation) and em(parameter expansion), except where
noted.

startitem()
item(tt(h))(
Remove a trailing pathname component, leaving the head.
)
item(tt(r))(
Remove a trailing suffix of the form `tt(.)var(xxx)', leaving the basename.
)
item(tt(e))(
Remove all but the suffix.
)
item(tt(t))(
Remove all leading pathname components, leaving the tail.
)
item(tt(p))(
Print the new command but do not execute it.  Only works with history
expansion.
)
item(tt(q))(
Quote the substituted words, escaping further substitutions.  Only
works with history expansion.
)
item(tt(x))(
Like tt(q), but break into words at each blank.
)
item(tt(l))(
Convert the words to all lowercase.
)
item(tt(u))(
Convert the words to all uppercase.
)
item(tt(f))(
(This and the following
tt(F), tt(w) and tt(W) modifier only work with parameter and
filename expansion.)
Repeats the immediately (without a colon) following modifier until the
resulting word doesn't change any more.
)
item(tt(F:)var(expr)tt(:))(
Like tt(f), but repeats only var(n) times if the expression
var(expr) evaluates to var(n).  Any character can be used instead of
the `tt(:)', if any of `tt(LPAR())', `tt([)', or `tt({)'
is used as the opening delimiter
the second one has to be 'tt(RPAR())', `tt(])', or `tt(})' respectively.
)
item(tt(w))(
Makes the immediately following modifier work on each word in the
string.
)
item(tt(W:)var(sep)tt(:))(
Like tt(w) but words are considered to be the parts of the string
that are separated by var(sep). Any character can be used instead of
the `tt(:)'; opening parentheses are handled specially, see above.
)
item(tt(s/)var(l)tt(/)var(r)[tt(/)])(
Substitute var(r) for var(l) as described below.
Unless preceded immediately by a tt(g), with no colon between,
the substitution is done only for the
first string that matches var(l).  For arrays and filename
expansion, this applies to each word of the expanded text.
)
item(tt(&))(
Repeat the previous tt(s) substitution.  Like tt(s), may be preceded
immediately by a tt(g).  In variable expansion the tt(&) must appear
inside braces, and in filename expansion it must be quoted with a
backslash.
)
enditem()

The tt(s/l/r/) substitution works as follows.  The left-hand side of
substitutions are not regular expressions, but character strings.  Any
character can be used as the delimiter in place of `tt(/)'.  A
backslash quotes the delimiter character.  The character `tt(&)', in
the right-hand-side var(r), is replaced by the text from the
left-hand-side var(l).  The `tt(&)' can be quoted with a backslash.  A
null var(l) uses the previous string either from the previous var(l)
or from the contextual scan string var(s) from `tt(!?)var(s)'.  You can
omit the rightmost delimiter if a newline immediately follows var(r);
the rightmost `tt(?)' in a context scan can similarly be omitted.
Note the same record of the last var(l) and var(r) is maintained
across all forms of expansion.

By default, a history reference with no event specification refers to the same
line as the last history reference on that command line, unless it is the
first history reference in a command.  In that case, a history reference
with no event specification always refers to the previous command.  However,
if the option tt(CSH_JUNKIE_HISTORY) is set,
pindex(CSH_JUNKIE_HISTORY, use of)
then history reference with no
event specification will em(always) refer to the previous command.

For example, `tt(!!:1)'
will always refer to the first word of the previous command, and `tt(!!$)'
will always refer to the last word of the previous command.  And with
tt(CSH_JUNKIE_HISTORY) set, then `tt(!:1)' and `tt(!$)'
will function in the same manner as `tt(!!:1)' and `tt(!!$)',
respectively.  However, if tt(CSH_JUNKIE_HISTORY) is unset, then
`tt(!:1)' and `tt(!$)'
will refer to the first and last words respectively, of the last command
referenced on the current command line.  However, if they are the first history
reference on the command line, then they refer to the previous command.

The character sequence `tt(^)var(foo)tt(^)var(bar)'
repeats the last command, replacing the string var(foo) with var(bar).

If the shell encounters the character sequence `tt(!")'
in the input, the history mechanism is temporarily disabled until
the current list is fully parsed.  The `tt(!")'
is removed from the input, and any subsequent `tt(!)'
characters have no special significance.

A less convenient but more comprehensible
form of command history support
is provided by the tt(fc) builtin.
findex(fc, use of)
texinode(Process Substitution)(Parameter Expansion)(History Expansion)(Expansion)
sect(Process Substitution)
cindex(process substitution)
cindex(substitution, process)
Each command argument of the form
`tt(<LPAR())var(list)tt(RPAR())',
`tt(>LPAR())var(list)tt(RPAR())' or
`tt(=LPAR())var(list)tt(RPAR())'
is subject to process substitution.
In the case of the tt(<) or tt(>) forms, the shell will run process
var(list) asynchronously, connected to a named pipe (FIFO).
The name of this pipe will become the argument to the command.
If the form with tt(>)
is selected then writing on this file will provide input for var(list).
If tt(<) is used, then the file passed as an argument will
be a named pipe connected to the output of the var(list) process.
For example,

nofill(tt(paste <LPAR()cut -f1) var(file1)tt(RPAR() <LPAR()cut -f3) var(file2)tt(RPAR() | tee >LPAR())var(process1)tt(RPAR() >LPAR())var(process2)tt(RPAR() >/dev/null))

cuts fields 1 and 3 from the files var(file1) and var(file2) respectively,
pastes the results together, and sends it to the processes
var(process1) and var(process2).
Note that the file, which is passed as an argument to the command,
is a system pipe, so programs that expect to lseek (see manref(lseek)(2))
on the file will not work.
Also note that the previous example can be more compactly and
efficiently written as:

nofill(tt(paste <LPAR()cut -f1) var(file1)tt(RPAR() <LPAR()cut -f3) var(file2)tt(RPAR() > >LPAR())var(process1)tt(RPAR() > >LPAR())var(process2)tt(RPAR()))

The shell uses pipes instead of FIFOs to implement the latter
two process substitutions in the above example.

If tt(=) is used,
then the file passed as an argument will be the name
of a temporary file containing the output of the var(list)
process.  This may be used instead of the tt(<)
form for a program that expects to lseek (see manref(lseek)(2))
on the input file.
texinode(Parameter Expansion)(Command Substitution)(Process Substitution)(Expansion)
sect(Parameter Expansion)
cindex(parameter expansion)
cindex(expansion, parameter)
The character `tt($)' is used to introduce parameter expansions.
See
ifzman(\
zmanref(zshparam)
)\
ifnzman(\
noderef(Parameters)
)\
for a description of parameters.
In the expansions discussed below that require a pattern, the form of
the pattern is the same as that used for filename generation;
see noderef(Filename Generation).  In addition to the following
operations, the file modifiers described in
noderef(Modifiers) in noderef(History Expansion) can be
applied:  for example, tt(${i:s/foo/bar/}) performs string
substitution on the value of parameter tt($i).

startitem()
item(tt(${)var(name)tt(}))(
The value, if any, of the parameter var(name) is substituted.
The braces are required if var(name) is followed by
a letter, digit, or underscore that is not to be interpreted
as part of its name.

If var(name) is an array parameter, then the values of each
element of var(name) is substituted, one element per word.
Otherwise, the expansion results in one word only; no field
splitting is done on the result unless the tt(SH_WORD_SPLIT)
option is set.
)
item(tt(${PLUS())var(name)tt(}))(
If var(name) is the name of a set parameter `tt(1)' is substituted,
otherwise `tt(0)' is substituted.
)
item(tt(${)var(name)tt(:-)var(word)tt(}))(
If var(name) is set and is non-null then substitute its
value; otherwise substitute var(word). If var(name) is
missing, substitute var(word).
)
item(tt(${)var(name)tt(:=)var(word)tt(}))(
If var(name) is unset or is null then
set it to var(word); the value of the parameter is then
substituted.
)
item(tt(${)var(name)tt(:?)var(word)tt(}))(
If var(name) is set and is non-null, then substitute
its value; otherwise, print var(word) and exit from the shell.
If var(word) is omitted, then a standard message is printed.
)
item(tt(${)var(name)tt(:PLUS())var(word)tt(}))(
If var(name) is set and is non-null then substitute
var(word); otherwise substitute nothing.
)
enditem()

If the colon is omitted from one of the above expressions
containing a colon, then the shell only checks whether
var(name) is set or not, not whether it is null.

startitem()
item(tt(${)var(name)tt(::=)var(word)tt(}))(
Set var(name) to var(word); the value of the parameter is then
substituted.
)
xitem(tt(${)var(name)tt(#)var(pattern)tt(}))
item(tt(${)var(name)tt(##)var(pattern)tt(}))(
If the var(pattern) matches the beginning of the value of
var(name), then substitute the value of var(name) with
the matched portion deleted; otherwise, just
substitute the value of var(name).  In the first
form, the smallest matching pattern is preferred;
in the second form, the largest matching pattern is
preferred. If var(name) is an array and the substitution
is not quoted or the tt((@)) flag or the `var(name)tt([@])' syntax
is used, matching is performed on each array elements separately.
)
xitem(tt(${)var(name)tt(%)var(pattern)tt(}))
item(tt(${)var(name)tt(%%)var(pattern)tt(}))(
If the var(pattern) matches the end of the value of
var(name), then substitute the value of var(name) with
the matched portion deleted; otherwise, just
substitute the value of var(name).  In the first
form, the smallest matching pattern is preferred;
in the second form, the largest matching pattern is
preferred. If var(name) is an array and the substitution
is not quoted or the tt((@)) flag or the `var(name)tt([@])' syntax
is used, matching is performed on each array elements separately.
)
item(tt(${)var(name)tt(:#)var(pattern)tt(}))(
If the var(pattern) matches the value of var(name), then substitute
the empty string; otherwise, just substitute the value of var(name).
If var(name) is an array and the substitution
is not quoted or the tt((@)) flag or the `var(name)tt([@])' syntax
is used, matching is performed on each array elements separately, and
the matched array elements are removed (use the tt((M)) flag to
remove the non-matched elements).
)
item(tt(${#)var(spec)tt(}))(
If var(spec) is one of the above substitutions, substitute
the length in characters of the result instead of
the result itself.  If var(spec) is an array expression,
substitute the number of elements of the result.
)
item(tt(${^)var(spec)tt(}))(
pindex(RC_EXPAND_PARAM, use of)
cindex(array expansion style, rc)
cindex(rc, array expansion style)
Turn on the tt(RC_EXPAND_PARAM) option for the
evaluation of var(spec); if the `tt(^)' is doubled, turn it off.
When this option is set, array expansions of the form
`var(foo)tt(${)var(xx)tt(})var(bar)',
where the parameter var(xx)
is set to tt(LPAR())var(a b c)tt(RPAR()), are substituted with
`var(fooabar foobbar foocbar)' instead of the default
`var(fooa b cbar)'.

Internally, each such expansion is converted into the
equivalent list for brace expansion.  E.g., tt(${^var}) becomes
tt({$var[1],$var[2],)...tt(}), and is processed as described in
noderef(Brace Expansion) above.
If word splitting is also in effect the
tt($var[)var(N)tt(]) may themselves be split into different list
elements.
)
item(tt(${=)var(spec)tt(}))(
pindex(SH_WORD_SPLIT, use of)
cindex(field splitting, sh style)
cindex(sh, field splitting style)
Turn on the tt(SH_WORD_SPLIT) option for the
evaluation of var(spec); if the `tt(=)' is doubled, turn it off.
vindex(IFS, use of)
When this option is set, parameter values are split into
separate words using tt(IFS) as a delimiter
before substitution.
This is done by default in most other shells.
)
item(tt(${~)var(spec)tt(}))(
pindex(GLOB_SUBST)
Turn on the tt(GLOB_SUBST) option for the evaluation of
var(spec); if the `tt(~)' is doubled, turn it off.  When this option is
set, any pattern characters resulting
from the substitution become eligible for file expansion and filename
generation.
)
enditem()

If a tt(${)...tt(}) type parameter expression or a
tt($LPAR())...tt(RPAR()) type command substitution is used in place of
var(name) above, it is substituted first and the result is used as if
it were the value of var(name).  Thus it is
possible to perform nested operations:  tt(${${foo#head}%tail})
substitues the value of tt($foo) with both tt(head) and tt(tail)
deleted.  The form with tt($LPAR())...tt(RPAR()) is often useful in
combination with the flags described next; see the example below.
subsect(Parameter Expansion Flags)
cindex(parameter expansion flags)
cindex(flags, parameter expansion)
cindex(expansion, parameter, flags)
If the opening brace is directly followed by an opening parenthesis,
the string up to the matching closing parenthesis will be taken as a
list of flags.  Where arguments are valid, any character, or the
matching pairs `tt(LPAR())...tt(RPAR())', `tt({)...tt(})',
`tt([)...tt(])', or `tt(<)...tt(>)',  may be used
in place of the colon as delimiters.  The following flags are supported:

startitem()
item(tt(A))(
Create an array parameter with
tt(${)...tt(:=)...tt(}) or tt(${)...tt(::=)...tt(}).
Assignment is made before sorting or padding.
)
item(tt(@))(
In double quotes, array elements are put into separate words.
E.g., `tt("${(@)foo}")' is equivalent to `tt("${foo[@]}")' and
`tt("${(@)foo[1,2]}")' is the same as `tt("$foo[1]" "$foo[2]")'.
)
item(tt(e))(
Perform em(parameter expansion), em(command substitution) and
em(arithmetic expansion) on the result. Such expansions can be
nested but too deep recursion may have unpredictable effects.
)
item(tt(o))(
Sort the resulting words in ascending order.
)
item(tt(O))(
Sort the resulting words in descending order.
)
item(tt(i))(
With tt(o) or tt(O), sort case-independently.
)
item(tt(L))(
Convert all letters in the result to lower case.
)
item(tt(U))(
Convert all letters in the result to upper case.
)
item(tt(C))(
Capitalize the resulting words.
)
item(tt(c))(
With tt(${#)var(name)tt(}), count the total number of characters in an array,
as if the elements were concatenated with spaces between them.
)
item(tt(w))(
With tt(${#)var(name)tt(}), count words in arrays or strings; the tt(s)
flag may be used to set a word delimiter.
)
item(tt(W))(
Similar to tt(w) with the difference that empty words between
repeated delimiters are also counted.
)
item(tt(p))(
Recognize the same escape sequences as the tt(print) builtin
in string arguments to subsequent flags.
)
item(tt(l:)var(expr)tt(::)var(string1)tt(::)var(string2)tt(:))(
Pad the resulting words on the left.  Each word will be truncated if
required and placed in a field var(expr) characters wide.  The space
to the left will be filled with var(string1) (concatenated as often
as needed) or spaces if var(string1) is not given.  If both
var(string1) and var(string2) are given, this string will be placed
exactly once directly to the left of the resulting word.
)
item(tt(r:)var(expr)tt(::)var(string1)tt(::)var(string2)tt(:))(
As tt(l), but pad the words on the right.
)
item(tt(j:)var(string)tt(:))(
Join the words of arrays together using var(string) as a separator.
pindex(SH_WORD_SPLIT, use of)
Note that this occurs before field splitting by the tt(SH_WORD_SPLIT)
option.
)
item(tt(F))(
Join the words of arrays together using newline as a separator.
This is a shorthand for `tt(pj:\n:)'.
)
item(tt(s:)var(string)tt(:))(
Force field splitting (see the option tt(SH_WORD_SPLIT)) at the
separator var(string).  Splitting only occurs in places where an
array value is valid.
)
item(tt(f))(
Split the result of the expansion to lines. This is a shorthand
for `tt(ps:\n:)'.
)
item(tt(S))(
(This and all remaining flags are used with the tt(${)...tt(#)...tt(}) or
tt(${)...tt(%)...tt(}) forms.)
Search substrings as well as beginnings or ends.
)
item(tt(I:)var(expr)tt(:))(
Search the var(expr)th match (where var(expr) evaluates to a number).
)
item(tt(M))(
Include the matched portion in the result.
)
item(tt(R))(
Include the unmatched portion in the result (the em(R)est).
)
item(tt(B))(
Include the index of the beginning of the match in the result.
)
item(tt(E))(
Include the index of the end of the match in the result.
)
item(tt(N))(
Include the length of the match in the result.
)
enditem()
subsect(Example)
The flag tt(f) is useful to split a double-quoted substitution line by
line.  For example, `tt("${(f)$LPAR()<)var(file)tt(RPAR()}")'
will substitue the contents of var(file) divided so that one line is
supplied per argument to var(cmd).  Compare this with the effect of
`tt($)tt(LPAR()<)var(file)tt(RPAR())' alone, which divides the file
up by words, or the same inside double quotes, where the entire
contents of the file are passed as a single argument.
texinode(Command Substitution)(Arithmetic Expansion)(Parameter Expansion)(Expansion)
sect(Command Substitution)
cindex(command substitution)
cindex(substitution, command)
A command enclosed in parentheses
preceded by a dollar sign, like `tt($LPAR())...tt(RPAR())', or quoted with grave
accents, like `tt(`)...tt(`)', is replaced with its standard output, with any
trailing newlines deleted.
If the substitution is not enclosed in double quotes, the
output is broken into words using the tt(IFS) parameter.
vindex(IFS, use of)
The substitution `tt($LPAR()cat) var(foo)tt(RPAR())' may be replaced
by the equivalent but faster `tt($LPAR()<)var(foo)tt(RPAR())'.
In either case, if the option tt(GLOB_SUBST) is set,
the output is eligible for filename generation.
texinode(Arithmetic Expansion)(Brace Expansion)(Command Substitution)(Expansion)
sect(Arithmetic Expansion)
cindex(arithmetic expansion)
cindex(expansion, arithmetic)
A string of the form `tt($[)var(exp)tt(])' or
`tt($LPAR()LPAR())var(exp)tt(RPAR()RPAR())' is substituted
with the value of the arithmetic expression var(exp).  var(exp) is
subjected to em(parameter expansion), em(command substitution)
and em(arithmetic expansion) before it is evaluated.
See noderef(Arithmetic Evaluation).
texinode(Brace Expansion)(Filename Expansion)(Arithmetic Expansion)(Expansion)
sect(Brace Expansion)
cindex(brace expansion)
cindex(expansion, brace)
A string of the form
`var(foo)tt({)var(xx)tt(,)var(yy)tt(,)var(zz)tt(})var(bar)'
is expanded to the individual words
`var(fooxxbar)', `var(fooyybar)' and `var(foozzbar)'.
Left-to-right order is preserved.  This construct
may be nested.  Commas may be quoted in order to
include them literally in a word.

An expression of the form `tt({)var(n1)tt(..)var(n2)tt(})',
where var(n1) and var(n2) are integers,
is expanded to every number between
var(n1) and var(n2) inclusive.  If either number begins with a
zero, all the resulting numbers will be padded with leading zeroes to
that minimum width.  If the numbers are in decreasing order the
resulting sequence will also be in decreasing order.

If a brace expression matches none of the above forms, it is left
unchanged, unless the tt(BRACE_CCL) option is set.
pindex(BRACE_CCL, use of)
In that case, it is expanded to a sorted list of the individual
characters between the braces, in the manner of a search set.
`tt(-)' is treated specially as in a search set, but `tt(^)' or `tt(!)' as
the first character is treated normally.
texinode(Filename Expansion)(Filename Generation)(Brace Expansion)(Expansion)
sect(Filename Expansion)
cindex(filename expansion)
cindex(expansion, filename)
Each word is checked to see if it begins with an unquoted `tt(~)'.
If it does, then the word up to a `tt(/)',
or the end of the word if there is no `tt(/)',
is checked to see if it can be substituted in one of the ways
described here.  If so, then the `tt(~)' and the checked portion are
replaced with the appropriate substitute value.

A `tt(~)' by itself is replaced by the value of tt($HOME).
A `tt(~)' followed by a `tt(PLUS())' or a `tt(-)' is replaced by the value of
tt($PWD) or tt($OLDPWD), respectively.

A `tt(~)' followed by a number is replaced by the directory at that
position in the directory stack.
`tt(~0)' is equivalent to `tt(~PLUS())',
and `tt(~1)' is the top of the stack.
`tt(~PLUS())' followed by a number is replaced by the directory at that
position in the directory stack.
`tt(~PLUS()0)' is equivalent to `tt(~PLUS())',
and `tt(~PLUS()1)' is the top of the stack.
`tt(~-)' followed by a number is replaced by the directory that
many positions from the bottom of the stack.
`tt(~-0)' is the bottom of the stack.
pindex(PUSHD_MINUS, use of)
The tt(PUSHD_MINUS)
option exchanges the effects of `tt(~PLUS())' and `tt(~-)' where they are
followed by a number.

cindex(directories, named)
cindex(named directories)
A `tt(~)' followed by anything not already covered is looked up as a
named directory, and replaced by the value of that named directory if found.
Named directories are typically home directories for users on the system.
They may also be defined if the text after the `tt(~)' is the name
of a string shell parameter whose value begins with a `tt(/)'.
It is also possible to define directory names using the tt(-d) option to the
tt(hash) builtin.

In certain circumstances (in prompts, for instance), when the shell
prints a path, the path is checked to see if it has a named
directory as its prefix.  If so, then the prefix portion
is replaced with a `tt(~)' followed by the name of the directory.
The shortest way of referring to the directory is used,
with ties broken in favour of using a named directory,
except when the directory is tt(/) itself.

If a word begins with an unquoted `tt(=)'
and the tt(EQUALS) option is set,
the remainder of the word is taken as the
name of a command or alias.  If a command
exists by that name, the word is replaced
by the full pathname of the command.
If an alias exists by that name, the word
is replaced with the text of the alias.

Filename expansion is performed on the right hand side of a parameter
assignment, including those appearing after commands of the
tt(typeset) family.  In this case, the right hand side will be treated
as a colon-separated list in the manner of the tt(PATH) parameter,
so that a `tt(~)' or an `tt(=)' following a `tt(:)' is eligible for expansion.
All such behaviour can be
disabled by quoting the `tt(~)', the `tt(=)', or the whole expression (but not
simply the colon); the tt(EQUALS) option is also respected.

If the option tt(MAGIC_EQUAL_SUBST) is set, any unquoted shell
argument in the form `var(identifier)tt(=)var(expression)' becomes eligible
for file expansion as described in the previous paragraph.  Quoting the
first `tt(=)' also inhibits this.
texinode(Filename Generation)()(Filename Expansion)(Expansion)
sect(Filename Generation)
cindex(filename generation)
cindex(globbing)
If a word contains an unquoted instance of one of the characters
`tt(*)', `tt(LPAR())', `tt(|)', `tt(<)', `tt([)', or `tt(?)', it is regarded
as a pattern for filename generation, unless the tt(GLOB) option is unset.
pindex(GLOB, use of)
If the tt(EXTENDED_GLOB) option is set,
pindex(EXTENDED_GLOB, use of)
the `tt(^)' and `tt(#)' characters also denote a pattern; otherwise
they are not treated specially by the shell.

The word is replaced with a list of sorted filenames that match
the pattern.  If no matching pattern is found, the shell gives
an error message, unless the tt(NULL_GLOB) option is set,
pindex(NULL_GLOB, use of)
in which case the word is deleted; or unless the tt(NOMATCH)
option is unset, in which case the word is left unchanged.
pindex(NOMATCH, use of)

In filename generation,
the character `tt(/)' must be matched explicitly;
also, a `tt(.)' must be matched
explicitly at the beginning of a pattern or after a `tt(/)', unless the
tt(GLOB_DOTS) option is set.
pindex(GLOB_DOTS, use of)
No filename generation pattern
matches the files `tt(.)' or `tt(..)'.  In other instances of pattern
matching, the `tt(/)' and `tt(.)' are not treated specially.
subsect(Glob Operators)
startitem()
item(tt(*))(
Matches any string, including the null string.
)
item(tt(?))(
Matches any character.
)
item(tt([)...tt(]))(
Matches any of the enclosed characters.  Ranges of characters
can be specified by separating two characters by a `tt(-)'.
A `tt(-)' or `tt(])' may be matched by including it as the
first character in the list.
There are also several named classes of characters, in the form
`tt([:)var(name)(tt:])' with the following meanings:  `tt([:alnum:])'
alphanumeric, `tt([:alpha:])' alphabetic,
`tt([:blank:])' space or tab,
`tt([:cntrl:])' control character, `tt([:digit:])' decimal
digit, `tt([:graph:])' printable character except whitespace,
`tt([:lower:])' lowercase letter, `tt([:print:])' printable character,
`tt([:punct:])' printable character neither alphanumeric nor whitespace,
`tt([:space:])' whitespace character, `tt([:upper:])' uppercase letter, 
`tt([:xdigit:])' hexadecimal digit.  These use the macros provided by
the operating system to test for the given character combinations,
including any modifications due to local language settings:  see
manref(ctype)(3).  Note that the square brackets are additional
to those enclosing the whole set of characters, so to test for a
single alphanumeric character you need `tt([[:alnum:]])'.  Named
character sets can be used alongside other types,
e.g. `tt([[:alpha:]0-9])'.
)
xitem(tt([^)...tt(]))
item(tt([!)...tt(]))(
Like tt([)...tt(]), except that it matches any character which is
not in the given set.
)
item(tt(<)[var(x)]tt(-)[var(y)]tt(>))(
Matches any number in the range var(x) to var(y), inclusive.
Either of the numbers may be omitted to make the range open-ended;
hence `tt(<->)' matches any number.
)
item(tt(LPAR())...tt(RPAR()))(
Matches the enclosed pattern.  This is used for grouping.
If the tt(KSH_GLOB) option is set, then a
`tt(@)', `tt(*)', `tt(+)', `tt(?)' or `tt(!)' immediately preceding
the `tt(LPAR())' is treated specially, as detailed below.
)
item(var(x)tt(|)var(y))(
Matches either var(x) or var(y).
This operator has lower precedence than any other.
The `tt(|)' character
must be within parentheses, to avoid interpretation as a pipeline.
)
item(tt(^)var(x))(
(Requires tt(EXTENDED_GLOB) to be set.)
Matches anything except the pattern var(x).
This has a higher precedence than `tt(/)', so `tt(^foo/bar)'
will search directories in `tt(.)' except `tt(./foo)'
for a file named `tt(bar)'.
)
item(var(x)tt(~)var(y))(
(Requires tt(EXTENDED_GLOB) to be set.)
Match anything that matches the pattern var(x) but does not match var(y).
This has lower precedence than any operator except `tt(|)', so
`tt(*/*~foo/bar)' will search for all files in all directories in `tt(.)'
and then exclude `tt(foo/bar)' if there was such a match.
It groups left-to-right, so multiple patterns can be excluded by
`var(foo)tt(~)var(bar)tt(~)var(baz)'.
In the exclusion pattern (var(y)), `tt(/)' and `tt(.)' are not treated
specially the way they usually are in globbing.
)
item(var(x)tt(#))(
(Requires tt(EXTENDED_GLOB) to be set.)
Matches zero or more occurrences of the pattern var(x).
This operator has high precedence; `tt(12#)' is equivalent to `tt(1(2#))',
rather than `tt((12)#)'.
)
item(var(x)tt(##))(
(Requires tt(EXTENDED_GLOB) to be set.)
Matches one or more occurrences of the pattern var(x).
This operator has high precedence; `tt(12##)' is equivalent to `tt(1(2##))',
rather than `tt((12)##)'.
)
enditem()
subsect(ksh-like Glob Operators)
pindex(KSH_GLOB, use of)
If the tt(KSH_GLOB) option is set, the effects of parentheses can be
modified by a preceding `tt(@)', `tt(*)', `tt(+)', `tt(?)' or `tt(!)'.
This character need not be unquoted to have special effects,
but the `tt(LPAR())' must be.

startitem()
item(tt(@LPAR())...tt(RPAR()))(
Match the pattern in the parentheses.  (Like `tt(LPAR())...tt(RPAR())'.)
)
item(tt(*LPAR())...tt(RPAR()))(
Match any number of occurrences.  (Like `tt(LPAR())...tt(RPAR()#)'.)
)
item(tt(PLUS()LPAR())...tt(RPAR()))(
Match at least one occurrence.  (Like `tt(LPAR())...tt(RPAR()##)'.)
)
item(tt(?LPAR())...tt(RPAR()))(
Match zero or one occurrence.  (Like `tt(LPAR()|)...tt(RPAR())'.)
)
item(tt(!LPAR())...tt(RPAR()))(
Match anything but the expression in parentheses.
(Like `tt(LPAR()^LPAR())...tt(RPAR()RPAR())'.)
)
enditem()
subsect(Recursive Globbing)
A pathname component of the form `tt(LPAR())var(foo)tt(/RPAR()#)'
matches a path consisting of zero or more directories
matching the pattern var(foo).
As a shorthand, `tt(**/)' is equivalent to `tt((*/)#)'.
Thus:

nofill(tt(ls (*/)#bar))

or

nofill(tt(ls **/bar))

does a recursive directory search for files named `tt(bar)', not following
symbolic links.  To follow links, use `tt(***/)'.
subsect(Glob Qualifiers)
cindex(globbing, qualifiers)
cindex(qualifiers, globbing)
Patterns used for filename generation may end in a
list of qualifiers enclosed in parentheses.
The qualifiers specify which filenames that otherwise match the given pattern
will be inserted in the argument list.

pindex(BARE_GLOB_QUAL, use of)
If the option tt(BARE_GLOB_QUAL) is set, then a trailing set of parentheses
containing no `tt(|)' or `tt(LPAR())' characters (or `tt(~)' if it is special)
is taken as a set of
glob qualifiers.  A glob subexpression that would normally be taken as glob
qualifiers, for example `tt((^x))', can be forced to be treated as part of
the glob pattern by doubling the parentheses, for example `tt(((^x)))'.

A qualifier may be any one of the following:

startitem()
item(tt(/))(
directories
)
item(tt(.))(
plain files
)
item(tt(@))(
symbolic links
)
item(tt(=))(
sockets
)
item(tt(p))(
named pipes (FIFOs)
)
item(tt(*))(
executable plain files (0100)
)
item(tt(%))(
device files (character or block special)
)
item(tt(%b))(
block special files
)
item(tt(%c))(
character special files
)
item(tt(r))(
owner-readable files (0400)
)
item(tt(w))(
owner-writable files (0200)
)
item(tt(x))(
owner-executable files (0100)
)
item(tt(A))(
group-readable files (0040)
)
item(tt(I))(
group-writable files (0020)
)
item(tt(E))(
group-executable files (0010)
)
item(tt(R))(
world-readable files (0004)
)
item(tt(W))(
world-writable files (0002)
)
item(tt(X))(
world-executable files (0001)
)
item(tt(s))(
setuid files (04000)
)
item(tt(S))(
setgid files (02000)
)
item(tt(t))(
files with the sticky bit (01000)
)
item(tt(d)var(dev))(
files on the device var(dev)
)
item(tt(l)[tt(-)|tt(PLUS())]var(ct))(
files having a link count less than var(ct) (tt(-)), greater than
var(ct) (tt(PLUS())), or is equal to var(ct)
)
item(tt(U))(
files owned by the effective user ID
)
item(tt(G))(
files owned by the effective group ID
)
item(tt(u)var(id))(
files owned by user ID var(id) if it is a number, if not, than the
character after the `tt(u)' will be used as a separator and the string
between it and the next matching separator
(`tt(LPAR())', `tt([)', `tt({)', and `tt(<)'
match `tt(RPAR())', `tt(])', `tt(})', and `tt(>)' respectively,
any other character matches
itself) will be taken as a user name, and the user ID of this user will
be taken (e.g. `tt(u:foo:)' or `tt(u[foo])' for user `tt(foo)')
)
item(tt(g)var(id))(
like tt(u)var(id) but with group IDs or names
)
item(tt(a)[tt(Mwhm)][tt(-)|tt(PLUS())]var(n))(
files accessed exactly var(n) days ago.  Files accessed within the
last var(n) days are selected using a negative value for var(n)
(tt(-)var(n)).  Files accessed more than var(n) days ago are selected by a
positive var(n) value (tt(PLUS())var(n)).  Optional unit specifiers `tt(M)',
`tt(w)', `tt(h)' or `tt(m)' (e.g. `tt(ah5)') cause the check to be
performed with months (of 30 days), weeks, hours, or minutes instead of
days, respectively.  For instance, `tt(echo *(ah-5))' would echo files
accessed within the last five hours.
)
item(tt(m)[tt(Mwhm)][tt(-)|tt(PLUS())]var(n))(
like the file access qualifier, except that it uses the file modification
time.
)
item(tt(c)[tt(Mwhm)][tt(-)|tt(PLUS())]var(n))(
like the file access qualifier, except that it uses the file inode change
time.
)
item(tt(L)[tt(PLUS())|tt(-)]var(n))(
files less than var(n) bytes (tt(-)), more than var(n) bytes (tt(PLUS())), or
exactly var(n) bytes in length. If this flag is directly followed by a `tt(k)'
(`tt(K)'), `tt(m)' (`tt(M)'), or `tt(p)' (`tt(P)') (e.g. `tt(Lk-50)')
the check is performed with kilobytes, megabytes, or blocks (of 512 bytes)
instead.
)
item(tt(^))(
negates all qualifiers following it
)
item(tt(-))(
toggles between making the qualifiers work on symbolic links (the
default) and the files they point to
)
item(tt(M))(
sets the tt(MARK_DIRS) option for the current pattern
pindex(MARK_DIRS, setting in pattern)
)
item(tt(T))(
appends a trailing qualifier mark to the file names, analogous to the
tt(LIST_TYPES) option, for the current pattern (overrides tt(M))
)
item(tt(N))(
sets the tt(NULL_GLOB) option for the current pattern
pindex(NULL_GLOB, setting in pattern)
)
item(tt(D))(
sets the tt(GLOB_DOTS) option for the current pattern
pindex(GLOB_DOTS, setting in pattern)
)
enditem()

More than one of these lists can be combined, separated by commas. The
whole list matches if at least one of the sublists matches (they are
`or'ed, the qualifiers in the sublists are `and'ed).

If a `tt(:)' appears in a qualifier list, the remainder of the expression in
parenthesis is interpreted as a modifier (see noderef(Modifiers)
in noderef(History Expansion)).  Note that
each modifier must be introduced by a separate `tt(:)'.  Note also that the
result after modification does not have to be an existing file.  The
name of any existing file can be followed by a modifier of the form
`tt((:..))' even if no actual filename generation is performed.
Thus:

nofill(tt(ls *(-/)))

lists all directories and symbolic links that point to directories,
and

nofill(tt(ls *(%W)))

lists all world-writable device files in the current directory, and

nofill(tt(ls *(W,X)))

lists all files in the current directory that are
world-writable or world-executable, and

nofill(tt(echo /tmp/foo*(u0^@:t)))

outputs the basename of all root-owned files beginning with the string
`tt(foo)' in tt(/tmp), ignoring symlinks, and

nofill(tt(ls *.*~(lex|parse).[ch](^D^l1)))

lists all files having a link count of one whose names contain a dot
(but not those starting with a dot, since tt(GLOB_DOTS) is explicitly
switched off) except for tt(lex.c), tt(lex.h), tt(parse.c) and tt(parse.h).