Provided by: zsh-common_5.9-6ubuntu3_all 
NAME
zshexpn - zsh expansion and substitution
DESCRIPTION
The following types of expansions are performed in the indicated order in five steps:
History Expansion
This is performed only in interactive shells.
Alias Expansion
Aliases are expanded immediately before the command line is parsed as explained under Aliasing in
zshmisc(1).
Process Substitution
Parameter Expansion
Command Substitution
Arithmetic Expansion
Brace Expansion
These five are performed in left-to-right fashion. On each argument, any of the five steps that
are needed are performed one after the other. Hence, for example, all the parts of parameter
expansion are completed before command substitution is started. After these expansions, all
unquoted occurrences of the characters `\',`'' and `"' are removed.
Filename Expansion
If the SH_FILE_EXPANSION option is set, the order of expansion is modified for compatibility with
sh and ksh. In that case filename expansion is performed immediately after alias expansion,
preceding the set of five expansions mentioned above.
Filename Generation
This expansion, commonly referred to as globbing, is always done last.
The following sections explain the types of expansion in detail.
HISTORY EXPANSION
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.
Immediately before execution, each command is saved in the history list, the size of which is controlled
by the HISTSIZE parameter. The one most recent command is always retained in any case. Each saved
command in the history list is called a history event and is assigned a number, beginning with 1 (one)
when the shell starts up. The history number that you may see in your prompt (see EXPANSION OF PROMPT
SEQUENCES in zshmisc(1)) is the number that is to be assigned to the next command.
Overview
A history expansion begins with the first character of the histchars parameter, which is `!' by default,
and may occur anywhere on the command line, including inside double quotes (but not inside single quotes
'...' or C-style quotes $'...' nor when escaped with a backslash).
The first character is followed by an optional event designator (see the section `Event Designators') and
then an optional word designator (the section `Word Designators'); if neither of these designators is
present, no history expansion occurs.
Input lines containing history expansions are echoed after being expanded, but before any other
expansions take place and before the command is executed. It is this expanded form that is recorded as
the history event for later references.
History expansions do not nest.
By default, a history reference with no event designator refers to the same event as any preceding
history reference on that command line; if it is the only history reference in a command, it refers to
the previous command. However, if the option CSH_JUNKIE_HISTORY is set, then every history reference
with no event specification always refers to the previous command.
For example, `!' is the event designator for the previous command, so `!!:1' always refers to the first
word of the previous command, and `!!$' always refers to the last word of the previous command. With
CSH_JUNKIE_HISTORY set, then `!:1' and `!$' function in the same manner as `!!:1' and `!!$',
respectively. Conversely, if CSH_JUNKIE_HISTORY is unset, then `!:1' and `!$' refer to the first and
last words, respectively, of the same event referenced by the nearest other history reference preceding
them on the current command line, or to the previous command if there is no preceding reference.
The character sequence `^foo^bar' (where `^' is actually the second character of the histchars parameter)
repeats the last command, replacing the string foo with bar. More precisely, the sequence `^foo^bar^' is
synonymous with `!!:s^foo^bar^', hence other modifiers (see the section `Modifiers') may follow the final
`^'. In particular, `^foo^bar^:G' performs a global substitution.
If the shell encounters the character sequence `!"' in the input, the history mechanism is temporarily
disabled until the current list (see zshmisc(1)) is fully parsed. The `!"' is removed from the input,
and any subsequent `!' characters have no special significance.
A less convenient but more comprehensible form of command history support is provided by the fc builtin.
Event Designators
An event designator is a reference to a command-line entry in the history list. In the list below,
remember that the initial `!' in each item may be changed to another character by setting the histchars
parameter.
! Start a history expansion, except when followed by a blank, newline, `=' or `('. If followed
immediately by a word designator (see the section `Word Designators'), this forms a history
reference with no event designator (see the section `Overview').
!! Refer to the previous command. By itself, this expansion repeats the previous command.
!n Refer to command-line n.
!-n Refer to the current command-line minus n.
!str Refer to the most recent command starting with str.
!?str[?]
Refer to the most recent command containing str. The trailing `?' is necessary if this reference
is to be followed by a modifier or followed by any text that is not to be considered part of str.
!# 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 `!#' reference.
!{...} Insulate a history reference from adjacent characters (if necessary).
Word Designators
A word designator indicates which word or words of a given command line are to be included in a history
reference. A `:' usually separates the event specification from the word designator. It may be omitted
only if the word designator begins with a `^', `$', `*', `-' or `%'. Word designators include:
0 The first input word (command).
n The nth argument.
^ The first argument. That is, 1.
$ The last argument.
% The word matched by (the most recent) ?str search.
x-y A range of words; x defaults to 0.
* All the arguments, or a null value if there are none.
x* Abbreviates `x-$'.
x- Like `x*' but omitting word $.
Note that a `%' word designator works only when used in one of `!%', `!:%' or `!?str?:%', and only when
used after a !? expansion (possibly in an earlier command). Anything else results in an error, although
the error may not be the most obvious one.
Modifiers
After the optional word designator, you can add a sequence of one or more of the following modifiers,
each preceded by a `:'. These modifiers also work on the result of filename generation and parameter
expansion, except where noted.
a Turn a file name into an absolute path: prepends the current directory, if necessary; remove `.'
path segments; and remove `..' path segments and the segments that immediately precede them.
This transformation is agnostic about what is in the filesystem, i.e. is on the logical, not the
physical directory. It takes place in the same manner as when changing directories when neither
of the options CHASE_DOTS or CHASE_LINKS is set. For example, `/before/here/../after' is always
transformed to `/before/after', regardless of whether `/before/here' exists or what kind of object
(dir, file, symlink, etc.) it is.
A Turn a file name into an absolute path as the `a' modifier does, and then pass the result through
the realpath(3) library function to resolve symbolic links.
Note: on systems that do not have a realpath(3) library function, symbolic links are not resolved,
so on those systems `a' and `A' are equivalent.
Note: foo:A and realpath(foo) are different on some inputs. For realpath(foo) semantics, see the
`P` modifier.
c Resolve a command name into an absolute path by searching the command path given by the PATH
variable. This does not work for commands containing directory parts. Note also that this does
not usually work as a glob qualifier unless a file of the same name is found in the current
directory.
e Remove all but the part of the filename extension following the `.'; see the definition of the
filename extension in the description of the r modifier below. Note that according to that
definition the result will be empty if the string ends with a `.'.
h [ digits ]
Remove a trailing pathname component, shortening the path by one directory level: this is the
`head' of the pathname. This works like `dirname'. If the h is followed immediately (with no
spaces or other separator) by any number of decimal digits, and the value of the resulting number
is non-zero, that number of leading components is preserved instead of the final component being
removed. In an absolute path the leading `/' is the first component, so, for example, if
var=/my/path/to/something, then ${var:h3} substitutes /my/path. Consecutive `/'s are treated the
same as a single `/'. In parameter substitution, digits may only be used if the expression is in
braces, so for example the short form substitution $var:h2 is treated as ${var:h}2, not as
${var:h2}. No restriction applies to the use of digits in history substitution or globbing
qualifiers. If more components are requested than are present, the entire path is substituted (so
this does not trigger a `failed modifier' error in history expansion).
l Convert the words to all lowercase.
p Print the new command but do not execute it. Only works with history expansion.
P Turn a file name into an absolute path, like realpath(3). The resulting path will be absolute,
will refer to the same directory entry as the input filename, and none of its components will be
symbolic links or equal to `.' or `..'.
Unlike realpath(3), non-existent trailing components are permitted and preserved.
q Quote the substituted words, escaping further substitutions. Works with history expansion and
parameter expansion, though for parameters it is only useful if the resulting text is to be
re-evaluated such as by eval.
Q Remove one level of quotes from the substituted words.
r Remove a filename extension leaving the root name. Strings with no filename extension are not
altered. A filename extension is a `.' followed by any number of characters (including zero) that
are neither `.' nor `/' and that continue to the end of the string. For example, the extension of
`foo.orig.c' is `.c', and `dir.c/foo' has no extension.
s/l/r[/]
Substitute r for l as described below. The substitution is done only for the first string that
matches l. For arrays and for filename generation, this applies to each word of the expanded
text. See below for further notes on substitutions.
The forms `gs/l/r' and `s/l/r/:G' perform global substitution, i.e. substitute every occurrence of
r for l. Note that the g or :G must appear in exactly the position shown.
See further notes on this form of substitution below.
& Repeat the previous s substitution. Like s, may be preceded immediately by a g. In parameter
expansion the & must appear inside braces, and in filename generation it must be quoted with a
backslash.
t [ digits ]
Remove all leading pathname components, leaving the final component (tail). This works like
`basename'. Any trailing slashes are first removed. Decimal digits are handled as described
above for (h), but in this case that number of trailing components is preserved instead of the
default 1; 0 is treated the same as 1.
u Convert the words to all uppercase.
x Like q, but break into words at whitespace. Does not work with parameter expansion.
The s/l/r/ substitution works as follows. By default the left-hand side of substitutions are not
patterns, but character strings. Any character can be used as the delimiter in place of `/'. A
backslash quotes the delimiter character. The character `&', in the right-hand-side r, is replaced by
the text from the left-hand-side l. The `&' can be quoted with a backslash. A null l uses the previous
string either from the previous l or from the contextual scan string s from `!?s'. You can omit the
rightmost delimiter if a newline immediately follows r; the rightmost `?' in a context scan can similarly
be omitted. Note the same record of the last l and r is maintained across all forms of expansion.
Note that if a `&' is used within glob qualifiers an extra backslash is needed as a & is a special
character in this case.
Also note that the order of expansions affects the interpretation of l and r. When used in a history
expansion, which occurs before any other expansions, l and r are treated as literal strings (except as
explained for HIST_SUBST_PATTERN below). When used in parameter expansion, the replacement of r into the
parameter's value is done first, and then any additional process, parameter, command, arithmetic, or
brace references are applied, which may evaluate those substitutions and expansions more than once if l
appears more than once in the starting value. When used in a glob qualifier, any substitutions or
expansions are performed once at the time the qualifier is parsed, even before the `:s' expression itself
is divided into l and r sides.
If the option HIST_SUBST_PATTERN is set, l is treated as a pattern of the usual form described in the
section FILENAME GENERATION below. This can be used in all the places where modifiers are available;
note, however, that in globbing qualifiers parameter substitution has already taken place, so parameters
in the replacement string should be quoted to ensure they are replaced at the correct time. Note also
that complicated patterns used in globbing qualifiers may need the extended glob qualifier notation
(#q:s/.../.../) in order for the shell to recognize the expression as a glob qualifier. Further, note
that bad patterns in the substitution are not subject to the NO_BAD_PATTERN option so will cause an
error.
When HIST_SUBST_PATTERN is set, l may start with a # to indicate that the pattern must match at the start
of the string to be substituted, and a % may appear at the start or after an # to indicate that the
pattern must match at the end of the string to be substituted. The % or # may be quoted with two
backslashes.
For example, the following piece of filename generation code with the EXTENDED_GLOB option:
print -r -- *.c(#q:s/#%(#b)s(*).c/'S${match[1]}.C'/)
takes the expansion of *.c and applies the glob qualifiers in the (#q...) expression, which consists of a
substitution modifier anchored to the start and end of each word (#%). This turns on backreferences
((#b)), so that the parenthesised subexpression is available in the replacement string as ${match[1]}.
The replacement string is quoted so that the parameter is not substituted before the start of filename
generation.
The following f, F, w and W modifiers work only with parameter expansion and filename generation. They
are listed here to provide a single point of reference for all modifiers.
f Repeats the immediately (without a colon) following modifier until the resulting word doesn't
change any more.
F:expr:
Like f, but repeats only n times if the expression expr evaluates to n. Any character can be used
instead of the `:'; if `(', `[', or `{' is used as the opening delimiter, the closing delimiter
should be ')', `]', or `}', respectively.
w Makes the immediately following modifier work on each word in the string.
W:sep: Like w but words are considered to be the parts of the string that are separated by sep. Any
character can be used instead of the `:'; opening parentheses are handled specially, see above.
PROCESS SUBSTITUTION
Each part of a command argument that takes the form `<(list)', `>(list)' or `=(list)' is subject to
process substitution. The expression may be preceded or followed by other strings except that, to
prevent clashes with commonly occurring strings and patterns, the last form must occur at the start of a
command argument, and the forms are only expanded when first parsing command or assignment arguments.
Process substitutions may be used following redirection operators; in this case, the substitution must
appear with no trailing string.
Note that `<<(list)' is not a special syntax; it is equivalent to `< <(list)', redirecting standard input
from the result of process substitution. Hence all the following documentation applies. The second form
(with the space) is recommended for clarity.
In the case of the < or > forms, the shell runs the commands in list as a subprocess of the job executing
the shell command line. If the system supports the /dev/fd mechanism, the command argument is the name
of the device file corresponding to a file descriptor; otherwise, if the system supports named pipes
(FIFOs), the command argument will be a named pipe. If the form with > is selected then writing on this
special file will provide input for list. If < is used, then the file passed as an argument will be
connected to the output of the list process. For example,
paste <(cut -f1 file1) <(cut -f3 file2) |
tee >(process1) >(process2) >/dev/null
cuts fields 1 and 3 from the files file1 and file2 respectively, pastes the results together, and sends
it to the processes process1 and process2.
If =(...) is used instead of <(...), then the file passed as an argument will be the name of a temporary
file containing the output of the list process. This may be used instead of the < form for a program
that expects to lseek (see lseek(2)) on the input file.
There is an optimisation for substitutions of the form =(<<<arg), where arg is a single-word argument to
the here-string redirection <<<. This form produces a file name containing the value of arg after any
substitutions have been performed. This is handled entirely within the current shell. This is
effectively the reverse of the special form $(<arg) which treats arg as a file name and replaces it with
the file's contents.
The = form is useful as both the /dev/fd and the named pipe implementation of <(...) have drawbacks. In
the former case, some programmes may automatically close the file descriptor in question before examining
the file on the command line, particularly if this is necessary for security reasons such as when the
programme is running setuid. In the second case, if the programme does not actually open the file, the
subshell attempting to read from or write to the pipe will (in a typical implementation, different
operating systems may have different behaviour) block for ever and have to be killed explicitly. In both
cases, the shell actually supplies the information using a pipe, so that programmes that expect to lseek
(see lseek(2)) on the file will not work.
Also note that the previous example can be more compactly and efficiently written (provided the MULTIOS
option is set) as:
paste <(cut -f1 file1) <(cut -f3 file2) > >(process1) > >(process2)
The shell uses pipes instead of FIFOs to implement the latter two process substitutions in the above
example.
There is an additional problem with >(process); when this is attached to an external command, the parent
shell does not wait for process to finish and hence an immediately following command cannot rely on the
results being complete. The problem and solution are the same as described in the section MULTIOS in
zshmisc(1). Hence in a simplified version of the example above:
paste <(cut -f1 file1) <(cut -f3 file2) > >(process)
(note that no MULTIOS are involved), process will be run asynchronously as far as the parent shell is
concerned. The workaround is:
{ paste <(cut -f1 file1) <(cut -f3 file2) } > >(process)
The extra processes here are spawned from the parent shell which will wait for their completion.
Another problem arises any time a job with a substitution that requires a temporary file is disowned by
the shell, including the case where `&!' or `&|' appears at the end of a command containing a
substitution. In that case the temporary file will not be cleaned up as the shell no longer has any
memory of the job. A workaround is to use a subshell, for example,
(mycmd =(myoutput)) &!
as the forked subshell will wait for the command to finish then remove the temporary file.
A general workaround to ensure a process substitution endures for an appropriate length of time is to
pass it as a parameter to an anonymous shell function (a piece of shell code that is run immediately with
function scope). For example, this code:
() {
print File $1:
cat $1
} =(print This be the verse)
outputs something resembling the following
File /tmp/zsh6nU0kS:
This be the verse
The temporary file created by the process substitution will be deleted when the function exits.
PARAMETER EXPANSION
The character `$' is used to introduce parameter expansions. See zshparam(1) for a description of
parameters, including arrays, associative arrays, and subscript notation to access individual array
elements.
Note in particular the fact that words of unquoted parameters are not automatically split on whitespace
unless the option SH_WORD_SPLIT is set; see references to this option below for more details. This is an
important difference from other shells. However, as in other shells, null words are elided from unquoted
parameters' expansions.
With default options, after the assignments:
array=("first word" "" "third word")
scalar="only word"
then $array substitutes two words, `first word' and `third word', and $scalar substitutes a single word
`only word'. Note that second element of array was elided. Scalar parameters can be elided too if their
value is null (empty). To avoid elision, use quoting as follows: "$scalar" for scalars and "${array[@]}"
or "${(@)array}" for arrays. (The last two forms are equivalent.)
Parameter expansions can involve flags, as in `${(@kv)aliases}', and other operators, such as
`${PREFIX:-"/usr/local"}'. Parameter expansions can also be nested. These topics will be introduced
below. The full rules are complicated and are noted at the end.
In the expansions discussed below that require a pattern, the form of the pattern is the same as that
used for filename generation; see the section `Filename Generation'. Note that these patterns, along
with the replacement text of any substitutions, are themselves subject to parameter expansion, command
substitution, and arithmetic expansion. In addition to the following operations, the colon modifiers
described in the section `Modifiers' in the section `History Expansion' can be applied: for example,
${i:s/foo/bar/} performs string substitution on the expansion of parameter $i.
In the following descriptions, `word' refers to a single word substituted on the command line, not
necessarily a space delimited word.
${name}
The value, if any, of the parameter name is substituted. The braces are required if the expansion
is to be followed by a letter, digit, or underscore that is not to be interpreted as part of name.
In addition, more complicated forms of substitution usually require the braces to be present;
exceptions, which only apply if the option KSH_ARRAYS is not set, are a single subscript or any
colon modifiers appearing after the name, or any of the characters `^', `=', `~', `#' or `+'
appearing before the name, all of which work with or without braces.
If name is an array parameter, and the KSH_ARRAYS option is not set, then the value of each
element of name is substituted, one element per word. Otherwise, the expansion results in one
word only; with KSH_ARRAYS, this is the first element of an array. No field splitting is done on
the result unless the SH_WORD_SPLIT option is set. See also the flags = and s:string:.
${+name}
If name is the name of a set parameter `1' is substituted, otherwise `0' is substituted.
${name-word}
${name:-word}
If name is set, or in the second form is non-null, then substitute its value; otherwise substitute
word. In the second form name may be omitted, in which case word is always substituted.
${name+word}
${name:+word}
If name is set, or in the second form is non-null, then substitute word; otherwise substitute
nothing.
${name=word}
${name:=word}
${name::=word}
In the first form, if name is unset then set it to word; in the second form, if name is unset or
null then set it to word; and in the third form, unconditionally set name to word. In all forms,
the value of the parameter is then substituted.
${name?word}
${name:?word}
In the first form, if name is set, or in the second form if name is both set and non-null, then
substitute its value; otherwise, print word and exit from the shell. Interactive shells instead
return to the prompt. If word is omitted, then a standard message is printed.
In any of the above expressions that test a variable and substitute an alternate word, note that you can
use standard shell quoting in the word value to selectively override the splitting done by the
SH_WORD_SPLIT option and the = flag, but not splitting by the s:string: flag.
In the following expressions, when name is an array and the substitution is not quoted, or if the `(@)'
flag or the name[@] syntax is used, matching and replacement is performed on each array element
separately.
${name#pattern}
${name##pattern}
If the pattern matches the beginning of the value of name, then substitute the value of name with
the matched portion deleted; otherwise, just substitute the value of name. In the first form, the
smallest matching pattern is preferred; in the second form, the largest matching pattern is
preferred.
${name%pattern}
${name%%pattern}
If the pattern matches the end of the value of name, then substitute the value of name with the
matched portion deleted; otherwise, just substitute the value of name. In the first form, the
smallest matching pattern is preferred; in the second form, the largest matching pattern is
preferred.
${name:#pattern}
If the pattern matches the value of name, then substitute the empty string; otherwise, just
substitute the value of name. If name is an array the matching array elements are removed (use
the `(M)' flag to remove the non-matched elements).
${name:|arrayname}
If arrayname is the name (N.B., not contents) of an array variable, then any elements contained in
arrayname are removed from the substitution of name. If the substitution is scalar, either
because name is a scalar variable or the expression is quoted, the elements of arrayname are
instead tested against the entire expression.
${name:*arrayname}
Similar to the preceding substitution, but in the opposite sense, so that entries present in both
the original substitution and as elements of arrayname are retained and others removed.
${name:^arrayname}
${name:^^arrayname}
Zips two arrays, such that the output array is twice as long as the shortest (longest for `:^^')
of name and arrayname, with the elements alternatingly being picked from them. For `:^', if one of
the input arrays is longer, the output will stop when the end of the shorter array is reached.
Thus,
a=(1 2 3 4); b=(a b); print ${a:^b}
will output `1 a 2 b'. For `:^^', then the input is repeated until all of the longer array has
been used up and the above will output `1 a 2 b 3 a 4 b'.
Either or both inputs may be a scalar, they will be treated as an array of length 1 with the
scalar as the only element. If either array is empty, the other array is output with no extra
elements inserted.
Currently the following code will output `a b' and `1' as two separate elements, which can be
unexpected. The second print provides a workaround which should continue to work if this is
changed.
a=(a b); b=(1 2); print -l "${a:^b}"; print -l "${${a:^b}}"
${name:offset}
${name:offset:length}
This syntax gives effects similar to parameter subscripting in the form $name[start,end], but is
compatible with other shells; note that both offset and length are interpreted differently from
the components of a subscript.
If offset is non-negative, then if the variable name is a scalar substitute the contents starting
offset characters from the first character of the string, and if name is an array substitute
elements starting offset elements from the first element. If length is given, substitute that
many characters or elements, otherwise the entire rest of the scalar or array.
A positive offset is always treated as the offset of a character or element in name from the first
character or element of the array (this is different from native zsh subscript notation). Hence 0
refers to the first character or element regardless of the setting of the option KSH_ARRAYS.
A negative offset counts backwards from the end of the scalar or array, so that -1 corresponds to
the last character or element, and so on.
When positive, length counts from the offset position toward the end of the scalar or array. When
negative, length counts back from the end. If this results in a position smaller than offset, a
diagnostic is printed and nothing is substituted.
The option MULTIBYTE is obeyed, i.e. the offset and length count multibyte characters where
appropriate.
offset and length undergo the same set of shell substitutions as for scalar assignment; in
addition, they are then subject to arithmetic evaluation. Hence, for example
print ${foo:3}
print ${foo: 1 + 2}
print ${foo:$(( 1 + 2))}
print ${foo:$(echo 1 + 2)}
all have the same effect, extracting the string starting at the fourth character of $foo if the
substitution would otherwise return a scalar, or the array starting at the fourth element if $foo
would return an array. Note that with the option KSH_ARRAYS $foo always returns a scalar
(regardless of the use of the offset syntax) and a form such as ${foo[*]:3} is required to extract
elements of an array named foo.
If offset is negative, the - may not appear immediately after the : as this indicates the
${name:-word} form of substitution. Instead, a space may be inserted before the -. Furthermore,
neither offset nor length may begin with an alphabetic character or & as these are used to
indicate history-style modifiers. To substitute a value from a variable, the recommended approach
is to precede it with a $ as this signifies the intention (parameter substitution can easily be
rendered unreadable); however, as arithmetic substitution is performed, the expression ${var:
offs} does work, retrieving the offset from $offs.
For further compatibility with other shells there is a special case for array offset 0. This
usually accesses the first element of the array. However, if the substitution refers to the
positional parameter array, e.g. $@ or $*, then offset 0 instead refers to $0, offset 1 refers to
$1, and so on. In other words, the positional parameter array is effectively extended by
prepending $0. Hence ${*:0:1} substitutes $0 and ${*:1:1} substitutes $1.
${name/pattern/repl}
${name//pattern/repl}
${name:/pattern/repl}
Replace the longest possible match of pattern in the expansion of parameter name by string repl.
The first form replaces just the first occurrence, the second form all occurrences, and the third
form replaces only if pattern matches the entire string. Both pattern and repl are subject to
double-quoted substitution, so that expressions like ${name/$opat/$npat} will work, but obey the
usual rule that pattern characters in $opat are not treated specially unless either the option
GLOB_SUBST is set, or $opat is instead substituted as ${~opat}.
The pattern may begin with a `#', in which case the pattern must match at the start of the string,
or `%', in which case it must match at the end of the string, or `#%' in which case the pattern
must match the entire string. The repl may be an empty string, in which case the final `/' may
also be omitted. To quote the final `/' in other cases it should be preceded by a single
backslash; this is not necessary if the `/' occurs inside a substituted parameter. Note also that
the `#', `%' and `#% are not active if they occur inside a substituted parameter, even at the
start.
If, after quoting rules apply, ${name} expands to an array, the replacements act on each element
individually. Note also the effect of the I and S parameter expansion flags below; however, the
flags M, R, B, E and N are not useful.
For example,
foo="twinkle twinkle little star" sub="t*e" rep="spy"
print ${foo//${~sub}/$rep}
print ${(S)foo//${~sub}/$rep}
Here, the `~' ensures that the text of $sub is treated as a pattern rather than a plain string.
In the first case, the longest match for t*e is substituted and the result is `spy star', while in
the second case, the shortest matches are taken and the result is `spy spy lispy star'.
${#spec}
If spec is one of the above substitutions, substitute the length in characters of the result
instead of the result itself. If spec is an array expression, substitute the number of elements
of the result. This has the side-effect that joining is skipped even in quoted forms, which may
affect other sub-expressions in spec. Note that `^', `=', and `~', below, must appear to the left
of `#' when these forms are combined.
If the option POSIX_IDENTIFIERS is not set, and spec is a simple name, then the braces are
optional; this is true even for special parameters so e.g. $#- and $#* take the length of the
string $- and the array $* respectively. If POSIX_IDENTIFIERS is set, then braces are required
for the # to be treated in this fashion.
${^spec}
${^^spec}
Turn on the RC_EXPAND_PARAM option for the evaluation of spec; if the `^' is doubled, turn it off.
When this option is set, array expansions of the form foo${xx}bar, where the parameter xx is set
to (a b c), are substituted with `fooabar foobbar foocbar' instead of the default `fooa b cbar'.
Note that an empty array will therefore cause all arguments to be removed.
Internally, each such expansion is converted into the equivalent list for brace expansion. E.g.,
${^var} becomes {$var[1],$var[2],...}, and is processed as described in the section `Brace
Expansion' below: note, however, the expansion happens immediately, with any explicit brace
expansion happening later. If word splitting is also in effect the $var[N] may themselves be
split into different list elements.
${=spec}
${==spec}
Perform word splitting using the rules for SH_WORD_SPLIT during the evaluation of spec, but
regardless of whether the parameter appears in double quotes; if the `=' is doubled, turn it off.
This forces parameter expansions to be split into separate words before substitution, using IFS as
a delimiter. This is done by default in most other shells.
Note that splitting is applied to word in the assignment forms of spec before the assignment to
name is performed. This affects the result of array assignments with the A flag.
${~spec}
${~~spec}
Turn on the GLOB_SUBST option for the evaluation of spec; if the `~' is doubled, turn it off.
When this option is set, the string resulting from the expansion will be interpreted as a pattern
anywhere that is possible, such as in filename expansion and filename generation and
pattern-matching contexts like the right hand side of the `=' and `!=' operators in conditions.
In nested substitutions, note that the effect of the ~ applies to the result of the current level
of substitution. A surrounding pattern operation on the result may cancel it. Hence, for
example, if the parameter foo is set to *, ${~foo//\*/*.c} is substituted by the pattern *.c,
which may be expanded by filename generation, but ${${~foo}//\*/*.c} substitutes to the string
*.c, which will not be further expanded.
If a ${...} type parameter expression or a $(...) type command substitution is used in place of name
above, it is expanded first and the result is used as if it were the value of name. Thus it is possible
to perform nested operations: ${${foo#head}%tail} substitutes the value of $foo with both `head' and
`tail' deleted. The form with $(...) is often useful in combination with the flags described next; see
the examples below. Each name or nested ${...} in a parameter expansion may also be followed by a
subscript expression as described in Array Parameters in zshparam(1).
Note that double quotes may appear around nested expressions, in which case only the part inside is
treated as quoted; for example, ${(f)"$(foo)"} quotes the result of $(foo), but the flag `(f)' (see
below) is applied using the rules for unquoted expansions. Note further that quotes are themselves
nested in this context; for example, in "${(@f)"$(foo)"}", there are two sets of quotes, one surrounding
the whole expression, the other (redundant) surrounding the $(foo) as before.
Parameter Expansion Flags
If the opening brace is directly followed by an opening parenthesis, the string up to the matching
closing parenthesis will be taken as a list of flags. In cases where repeating a flag is meaningful, the
repetitions need not be consecutive; for example, `(q%q%q)' means the same thing as the more readable
`(%%qqq)'. The following flags are supported:
# Evaluate the resulting words as numeric expressions and interpret these as character codes.
Output the corresponding characters. Note that this form is entirely distinct from use of the #
without parentheses.
If the MULTIBYTE option is set and the number is greater than 127 (i.e. not an ASCII character) it
is treated as a Unicode character.
% Expand all % escapes in the resulting words in the same way as in prompts (see EXPANSION OF PROMPT
SEQUENCES in zshmisc(1)). If this flag is given twice, full prompt expansion is done on the
resulting words, depending on the setting of the PROMPT_PERCENT, PROMPT_SUBST and PROMPT_BANG
options.
@ In double quotes, array elements are put into separate words. E.g., `"${(@)foo}"' is equivalent
to `"${foo[@]}"' and `"${(@)foo[1,2]}"' is the same as `"$foo[1]" "$foo[2]"'. This is distinct
from field splitting by the f, s or z flags, which still applies within each array element.
A Convert the substitution into an array expression, even if it otherwise would be scalar. This has
lower precedence than subscripting, so one level of nested expansion is required in order that
subscripts apply to array elements. Thus ${${(A)name}[1]} yields the full value of name when name
is scalar.
This assigns an array parameter with `${...=...}', `${...:=...}' or `${...::=...}'. If this flag
is repeated (as in `AA'), assigns an associative array parameter. Assignment is made before
sorting or padding; if field splitting is active, the word part is split before assignment. The
name part may be a subscripted range for ordinary arrays; when assigning an associative array, the
word part must be converted to an array, for example by using `${(AA)=name=...}' to activate field
splitting.
Surrounding context such as additional nesting or use of the value in a scalar assignment may
cause the array to be joined back into a single string again.
a Sort in array index order; when combined with `O' sort in reverse array index order. Note that
`a' is therefore equivalent to the default but `Oa' is useful for obtaining an array's elements in
reverse order.
b Quote with backslashes only characters that are special to pattern matching. This is useful when
the contents of the variable are to be tested using GLOB_SUBST, including the ${~...} switch.
Quoting using one of the q family of flags does not work for this purpose since quotes are not
stripped from non-pattern characters by GLOB_SUBST. In other words,
pattern=${(q)str}
[[ $str = ${~pattern} ]]
works if $str is `a*b' but not if it is `a b', whereas
pattern=${(b)str}
[[ $str = ${~pattern} ]]
is always true for any possible value of $str.
c With ${#name}, count the total number of characters in an array, as if the elements were
concatenated with spaces between them. This is not a true join of the array, so other expressions
used with this flag may have an effect on the elements of the array before it is counted.
C Capitalize the resulting words. `Words' in this case refers to sequences of alphanumeric
characters separated by non-alphanumerics, not to words that result from field splitting.
D Assume the string or array elements contain directories and attempt to substitute the leading part
of these by names. The remainder of the path (the whole of it if the leading part was not
substituted) is then quoted so that the whole string can be used as a shell argument. This is the
reverse of `~' substitution: see the section FILENAME EXPANSION below.
e Perform single word shell expansions, namely parameter expansion, command substitution and
arithmetic expansion, on the result. Such expansions can be nested but too deep recursion may have
unpredictable effects.
f Split the result of the expansion at newlines. This is a shorthand for `ps:\n:'.
F Join the words of arrays together using newline as a separator. This is a shorthand for `pj:\n:'.
g:opts:
Process escape sequences like the echo builtin when no options are given (g::). With the o
option, octal escapes don't take a leading zero. With the c option, sequences like `^X' are also
processed. With the e option, processes `\M-t' and similar sequences like the print builtin.
With both of the o and e options, behaves like the print builtin except that in none of these
modes is `\c' interpreted.
i Sort case-insensitively. May be combined with `n' or `O'.
k If name refers to an associative array, substitute the keys (element names) rather than the values
of the elements. Used with subscripts (including ordinary arrays), force indices or keys to be
substituted even if the subscript form refers to values. However, this flag may not be combined
with subscript ranges. With the KSH_ARRAYS option a subscript `[*]' or `[@]' is needed to operate
on the whole array, as usual.
L Convert all letters in the result to lower case.
n Sort decimal integers numerically; if the first differing characters of two test strings are not
digits, sorting is lexical. `+' and `-' are not treated specially; they are treated as any other
non-digit. Integers with more initial zeroes are sorted before those with fewer or none. Hence
the array `foo+24 foo1 foo02 foo2 foo3 foo20 foo23' is sorted into the order shown. May be
combined with `i' or `O'.
- As n, but a leading minus sign indicates a negative decimal integer. A leading minus sign not
followed by an integer does not trigger numeric sorting. Note that `+' signs are not handled
specially (this may change in the future).
o Sort the resulting words in ascending order; if this appears on its own the sorting is lexical and
case-sensitive (unless the locale renders it case-insensitive). Sorting in ascending order is the
default for other forms of sorting, so this is ignored if combined with `a', `i', `n' or `-'.
O Sort the resulting words in descending order; `O' without `a', `i', `n' or `-' sorts in reverse
lexical order. May be combined with `a', `i', `n' or `-' to reverse the order of sorting.
P This forces the value of the parameter name to be interpreted as a further parameter name, whose
value will be used where appropriate. Note that flags set with one of the typeset family of
commands (in particular case transformations) are not applied to the value of name used in this
fashion.
If used with a nested parameter or command substitution, the result of that will be taken as a
parameter name in the same way. For example, if you have `foo=bar' and `bar=baz', the strings
${(P)foo}, ${(P)${foo}}, and ${(P)$(echo bar)} will be expanded to `baz'.
Likewise, if the reference is itself nested, the expression with the flag is treated as if it were
directly replaced by the parameter name. It is an error if this nested substitution produces an
array with more than one word. For example, if `name=assoc' where the parameter assoc is an
associative array, then `${${(P)name}[elt]}' refers to the element of the associative subscripted
`elt'.
q Quote characters that are special to the shell in the resulting words with backslashes;
unprintable or invalid characters are quoted using the $'\NNN' form, with separate quotes for each
octet.
If this flag is given twice, the resulting words are quoted in single quotes and if it is given
three times, the words are quoted in double quotes; in these forms no special handling of
unprintable or invalid characters is attempted. If the flag is given four times, the words are
quoted in single quotes preceded by a $. Note that in all three of these forms quoting is done
unconditionally, even if this does not change the way the resulting string would be interpreted by
the shell.
If a q- is given (only a single q may appear), a minimal form of single quoting is used that only
quotes the string if needed to protect special characters. Typically this form gives the most
readable output.
If a q+ is given, an extended form of minimal quoting is used that causes unprintable characters
to be rendered using $'...'. This quoting is similar to that used by the output of values by the
typeset family of commands.
Q Remove one level of quotes from the resulting words.
t Use a string describing the type of the parameter where the value of the parameter would usually
appear. This string consists of keywords separated by hyphens (`-'). The first keyword in the
string describes the main type, it can be one of `scalar', `array', `integer', `float' or
`association'. The other keywords describe the type in more detail:
local for local parameters
left for left justified parameters
right_blanks
for right justified parameters with leading blanks
right_zeros
for right justified parameters with leading zeros
lower for parameters whose value is converted to all lower case when it is expanded
upper for parameters whose value is converted to all upper case when it is expanded
readonly
for readonly parameters
tag for tagged parameters
tied for parameters tied to another parameter in the manner of PATH (colon-separated list) and
path (array), whether these are special parameters or user-defined with `typeset -T'
export for exported parameters
unique for arrays which keep only the first occurrence of duplicated values
hide for parameters with the `hide' flag
hideval
for parameters with the `hideval' flag
special
for special parameters defined by the shell
u Expand only the first occurrence of each unique word.
U Convert all letters in the result to upper case.
v Used with k, substitute (as two consecutive words) both the key and the value of each associative
array element. Used with subscripts, force values to be substituted even if the subscript form
refers to indices or keys.
V Make any special characters in the resulting words visible.
w With ${#name}, count words in arrays or strings; the s flag may be used to set a word delimiter.
W Similar to w with the difference that empty words between repeated delimiters are also counted.
X With this flag, parsing errors occurring with the Q, e and # flags or the pattern matching forms
such as `${name#pattern}' are reported. Without the flag, errors are silently ignored.
z Split the result of the expansion into words using shell parsing to find the words, i.e. taking
into account any quoting in the value. Comments are not treated specially but as ordinary
strings, similar to interactive shells with the INTERACTIVE_COMMENTS option unset (however, see
the Z flag below for related options)
Note that this is done very late, even later than the `(s)' flag. So to access single words in the
result use nested expansions as in `${${(z)foo}[2]}'. Likewise, to remove the quotes in the
resulting words use `${(Q)${(z)foo}}'.
0 Split the result of the expansion on null bytes. This is a shorthand for `ps:\0:'.
The following flags (except p) are followed by one or more arguments as shown. Any character, or the
matching pairs `(...)', `{...}', `[...]', or `<...>', may be used in place of a colon as delimiters, but
note that when a flag takes more than one argument, a matched pair of delimiters must surround each
argument.
p Recognize the same escape sequences as the print builtin in string arguments to any of the flags
described below that follow this argument.
Alternatively, with this option string arguments may be in the form $var in which case the value
of the variable is substituted. Note this form is strict; the string argument does not undergo
general parameter expansion.
For example,
sep=:
val=a:b:c
print ${(ps.$sep.)val}
splits the variable on a :.
~ Strings inserted into the expansion by any of the flags below are to be treated as patterns. This
applies to the string arguments of flags that follow ~ within the same set of parentheses.
Compare with ~ outside parentheses, which forces the entire substituted string to be treated as a
pattern. Hence, for example,
[[ "?" = ${(~j.|.)array} ]]
treats `|' as a pattern and succeeds if and only if $array contains the string `?' as an element.
The ~ may be repeated to toggle the behaviour; its effect only lasts to the end of the
parenthesised group.
j:string:
Join the words of arrays together using string as a separator. Note that this occurs before field
splitting by the s:string: flag or the SH_WORD_SPLIT option.
l:expr::string1::string2:
Pad the resulting words on the left. Each word will be truncated if required and placed in a
field expr characters wide.
The arguments :string1: and :string2: are optional; neither, the first, or both may be given.
Note that the same pairs of delimiters must be used for each of the three arguments. The space to
the left will be filled with string1 (concatenated as often as needed) or spaces if string1 is not
given. If both string1 and string2 are given, string2 is inserted once directly to the left of
each word, truncated if necessary, before string1 is used to produce any remaining padding.
If either of string1 or string2 is present but empty, i.e. there are two delimiters together at
that point, the first character of $IFS is used instead.
If the MULTIBYTE option is in effect, the flag m may also be given, in which case widths will be
used for the calculation of padding; otherwise individual multibyte characters are treated as
occupying one unit of width.
If the MULTIBYTE option is not in effect, each byte in the string is treated as occupying one unit
of width.
Control characters are always assumed to be one unit wide; this allows the mechanism to be used
for generating repetitions of control characters.
m Only useful together with one of the flags l or r or with the # length operator when the MULTIBYTE
option is in effect. Use the character width reported by the system in calculating how much of
the string it occupies or the overall length of the string. Most printable characters have a
width of one unit, however certain Asian character sets and certain special effects use wider
characters; combining characters have zero width. Non-printable characters are arbitrarily
counted as zero width; how they would actually be displayed will vary.
If the m is repeated, the character either counts zero (if it has zero width), else one. For
printable character strings this has the effect of counting the number of glyphs (visibly separate
characters), except for the case where combining characters themselves have non-zero width (true
in certain alphabets).
r:expr::string1::string2:
As l, but pad the words on the right and insert string2 immediately to the right of the string to
be padded.
Left and right padding may be used together. In this case the strategy is to apply left padding
to the first half width of each of the resulting words, and right padding to the second half. If
the string to be padded has odd width the extra padding is applied on the left.
s:string:
Force field splitting at the separator string. Note that a string of two or more characters means
that all of them must match in sequence; this differs from the treatment of two or more characters
in the IFS parameter. See also the = flag and the SH_WORD_SPLIT option. An empty string may also
be given in which case every character will be a separate element.
For historical reasons, the usual behaviour that empty array elements are retained inside double
quotes is disabled for arrays generated by splitting; hence the following:
line="one::three"
print -l "${(s.:.)line}"
produces two lines of output for one and three and elides the empty field. To override this
behaviour, supply the `(@)' flag as well, i.e. "${(@s.:.)line}".
Z:opts:
As z but takes a combination of option letters between a following pair of delimiter characters.
With no options the effect is identical to z. The following options are available:
(Z+c+) causes comments to be parsed as a string and retained; any field in the resulting array
beginning with an unquoted comment character is a comment.
(Z+C+) causes comments to be parsed and removed. The rule for comments is standard: anything
between a word starting with the third character of $HISTCHARS, default #, up to the next
newline is a comment.
(Z+n+) causes unquoted newlines to be treated as ordinary whitespace, else they are treated as if
they are shell code delimiters and converted to semicolons.
Options are combined within the same set of delimiters, e.g. (Z+Cn+).
_:flags:
The underscore (_) flag is reserved for future use. As of this revision of zsh, there are no
valid flags; anything following an underscore, other than an empty pair of delimiters, is treated
as an error, and the flag itself has no effect.
The following flags are meaningful with the ${...#...} or ${...%...} forms. The S, I, and * flags may
also be used with the ${.../...} forms.
S With # or ##, search for the match that starts closest to the start of the string (a `substring
match'). Of all matches at a particular position, # selects the shortest and ## the longest:
% str="aXbXc"
% echo ${(S)str#X*}
abXc
% echo ${(S)str##X*}
a
%
With % or %%, search for the match that starts closest to the end of the string:
% str="aXbXc"
% echo ${(S)str%X*}
aXbc
% echo ${(S)str%%X*}
aXb
%
(Note that % and %% don't search for the match that ends closest to the end of the string, as one
might expect.)
With substitution via ${.../...} or ${...//...}, specifies non-greedy matching, i.e. that the
shortest instead of the longest match should be replaced:
% str="abab"
% echo ${str/*b/_}
_
% echo ${(S)str/*b/_}
_ab
%
I:expr:
Search the exprth match (where expr evaluates to a number). This only applies when searching for
substrings, either with the S flag, or with ${.../...} (only the exprth match is substituted) or
${...//...} (all matches from the exprth on are substituted). The default is to take the first
match.
The exprth match is counted such that there is either one or zero matches from each starting
position in the string, although for global substitution matches overlapping previous replacements
are ignored. With the ${...%...} and ${...%%...} forms, the starting position for the match moves
backwards from the end as the index increases, while with the other forms it moves forward from
the start.
Hence with the string
which switch is the right switch for Ipswich?
substitutions of the form ${(SI:N:)string#w*ch} as N increases from 1 will match and remove
`which', `witch', `witch' and `wich'; the form using `##' will match and remove `which switch is
the right switch for Ipswich', `witch is the right switch for Ipswich', `witch for Ipswich' and
`wich'. The form using `%' will remove the same matches as for `#', but in reverse order, and the
form using `%%' will remove the same matches as for `##' in reverse order.
* Enable EXTENDED_GLOB for substitution via ${.../...} or ${...//...}. Note that `**' does not
disable extendedglob.
B Include the index of the beginning of the match in the result.
E Include the index one character past the end of the match in the result (note this is inconsistent
with other uses of parameter index).
M Include the matched portion in the result.
N Include the length of the match in the result.
R Include the unmatched portion in the result (the Rest).
Rules
Here is a summary of the rules for substitution; this assumes that braces are present around the
substitution, i.e. ${...}. Some particular examples are given below. Note that the Zsh Development
Group accepts no responsibility for any brain damage which may occur during the reading of the following
rules.
1. Nested substitution
If multiple nested ${...} forms are present, substitution is performed from the inside outwards.
At each level, the substitution takes account of whether the current value is a scalar or an
array, whether the whole substitution is in double quotes, and what flags are supplied to the
current level of substitution, just as if the nested substitution were the outermost. The flags
are not propagated up to enclosing substitutions; the nested substitution will return either a
scalar or an array as determined by the flags, possibly adjusted for quoting. All the following
steps take place where applicable at all levels of substitution.
Note that, unless the `(P)' flag is present, the flags and any subscripts apply directly to the
value of the nested substitution; for example, the expansion ${${foo}} behaves exactly the same as
${foo}. When the `(P)' flag is present in a nested substitution, the other substitution rules are
applied to the value before it is interpreted as a name, so ${${(P)foo}} may differ from
${(P)foo}.
At each nested level of substitution, the substituted words undergo all forms of single-word
substitution (i.e. not filename generation), including command substitution, arithmetic expansion
and filename expansion (i.e. leading ~ and =). Thus, for example, ${${:-=cat}:h} expands to the
directory where the cat program resides. (Explanation: the internal substitution has no parameter
but a default value =cat, which is expanded by filename expansion to a full path; the outer
substitution then applies the modifier :h and takes the directory part of the path.)
2. Internal parameter flags
Any parameter flags set by one of the typeset family of commands, in particular the -L, -R, -Z, -u
and -l options for padding and capitalization, are applied directly to the parameter value. Note
these flags are options to the command, e.g. `typeset -Z'; they are not the same as the flags used
within parameter substitutions.
At the outermost level of substitution, the `(P)' flag (rule 4.) ignores these transformations
and uses the unmodified value of the parameter as the name to be replaced. This is usually the
desired behavior because padding may make the value syntactically illegal as a parameter name, but
if capitalization changes are desired, use the ${${(P)foo}} form (rule 25.).
3. Parameter subscripting
If the value is a raw parameter reference with a subscript, such as ${var[3]}, the effect of
subscripting is applied directly to the parameter. Subscripts are evaluated left to right;
subsequent subscripts apply to the scalar or array value yielded by the previous subscript. Thus
if var is an array, ${var[1][2]} is the second character of the first word, but ${var[2,4][2]} is
the entire third word (the second word of the range of words two through four of the original
array). Any number of subscripts may appear. Flags such as `(k)' and `(v)' which alter the
result of subscripting are applied.
4. Parameter name replacement
At the outermost level of nesting only, the `(P)' flag is applied. This treats the value so far
as a parameter name (which may include a subscript expression) and replaces that with the
corresponding value. This replacement occurs later if the `(P)' flag appears in a nested
substitution.
If the value so far names a parameter that has internal flags (rule 2.), those internal flags are
applied to the new value after replacement.
5. Double-quoted joining
If the value after this process is an array, and the substitution appears in double quotes, and
neither an `(@)' flag nor a `#' length operator is present at the current level, then words of the
value are joined with the first character of the parameter $IFS, by default a space, between each
word (single word arrays are not modified). If the `(j)' flag is present, that is used for
joining instead of $IFS.
6. Nested subscripting
Any remaining subscripts (i.e. of a nested substitution) are evaluated at this point, based on
whether the value is an array or a scalar. As with 3., multiple subscripts can appear. Note that
${foo[2,4][2]} is thus equivalent to ${${foo[2,4]}[2]} and also to "${${(@)foo[2,4]}[2]}" (the
nested substitution returns an array in both cases), but not to "${${foo[2,4]}[2]}" (the nested
substitution returns a scalar because of the quotes).
7. Modifiers
Any modifiers, as specified by a trailing `#', `%', `/' (possibly doubled) or by a set of
modifiers of the form `:...' (see the section `Modifiers' in the section `History Expansion'), are
applied to the words of the value at this level.
8. Character evaluation
Any `(#)' flag is applied, evaluating the result so far numerically as a character.
9. Length
Any initial `#' modifier, i.e. in the form ${#var}, is used to evaluate the length of the
expression so far.
10. Forced joining
If the `(j)' flag is present, or no `(j)' flag is present but the string is to be split as given
by rule 11., and joining did not take place at rule 5., any words in the value are joined together
using the given string or the first character of $IFS if none. Note that the `(F)' flag
implicitly supplies a string for joining in this manner.
11. Simple word splitting
If one of the `(s)' or `(f)' flags are present, or the `=' specifier was present (e.g. ${=var}),
the word is split on occurrences of the specified string, or (for = with neither of the two flags
present) any of the characters in $IFS.
If no `(s)', `(f)' or `=' was given, but the word is not quoted and the option SH_WORD_SPLIT is
set, the word is split on occurrences of any of the characters in $IFS. Note this step, too,
takes place at all levels of a nested substitution.
12. Case modification
Any case modification from one of the flags `(L)', `(U)' or `(C)' is applied.
13. Escape sequence replacement
First any replacements from the `(g)' flag are performed, then any prompt-style formatting from
the `(%)' family of flags is applied.
14. Quote application
Any quoting or unquoting using `(q)' and `(Q)' and related flags is applied.
15. Directory naming
Any directory name substitution using `(D)' flag is applied.
16. Visibility enhancement
Any modifications to make characters visible using the `(V)' flag are applied.
17. Lexical word splitting
If the '(z)' flag or one of the forms of the '(Z)' flag is present, the word is split as if it
were a shell command line, so that quotation marks and other metacharacters are used to decide
what constitutes a word. Note this form of splitting is entirely distinct from that described by
rule 11.: it does not use $IFS, and does not cause forced joining.
18. Uniqueness
If the result is an array and the `(u)' flag was present, duplicate elements are removed from the
array.
19. Ordering
If the result is still an array and one of the `(o)' or `(O)' flags was present, the array is
reordered.
20. RC_EXPAND_PARAM
At this point the decision is made whether any resulting array elements are to be combined element
by element with surrounding text, as given by either the RC_EXPAND_PARAM option or the `^' flag.
21. Re-evaluation
Any `(e)' flag is applied to the value, forcing it to be re-examined for new parameter
substitutions, but also for command and arithmetic substitutions.
22. Padding
Any padding of the value by the `(l.fill.)' or `(r.fill.)' flags is applied.
23. Semantic joining
In contexts where expansion semantics requires a single word to result, all words are rejoined
with the first character of IFS between. So in `${(P)${(f)lines}}' the value of ${lines} is split
at newlines, but then must be joined again before the `(P)' flag can be applied.
If a single word is not required, this rule is skipped.
24. Empty argument removal
If the substitution does not appear in double quotes, any resulting zero-length argument, whether
from a scalar or an element of an array, is elided from the list of arguments inserted into the
command line.
Strictly speaking, the removal happens later as the same happens with other forms of substitution;
the point to note here is simply that it occurs after any of the above parameter operations.
25. Nested parameter name replacement
If the `(P)' flag is present and rule 4. has not applied, the value so far is treated as a
parameter name (which may include a subscript expression) and replaced with the corresponding
value, with internal flags (rule 2.) applied to the new value.
Examples
The flag f is useful to split a double-quoted substitution line by line. For example, ${(f)"$(<file)"}
substitutes the contents of file divided so that each line is an element of the resulting array. Compare
this with the effect of $(<file) alone, which divides the file up by words, or the same inside double
quotes, which makes the entire content of the file a single string.
The following illustrates the rules for nested parameter expansions. Suppose that $foo contains the
array (bar baz):
"${(@)${foo}[1]}"
This produces the result b. First, the inner substitution "${foo}", which has no array (@) flag,
produces a single word result "bar baz". The outer substitution "${(@)...[1]}" detects that this
is a scalar, so that (despite the `(@)' flag) the subscript picks the first character.
"${${(@)foo}[1]}"
This produces the result `bar'. In this case, the inner substitution "${(@)foo}" produces the
array `(bar baz)'. The outer substitution "${...[1]}" detects that this is an array and picks the
first word. This is similar to the simple case "${foo[1]}".
As an example of the rules for word splitting and joining, suppose $foo contains the array `(ax1 bx1)'.
Then
${(s/x/)foo}
produces the words `a', `1 b' and `1'.
${(j/x/s/x/)foo}
produces `a', `1', `b' and `1'.
${(s/x/)foo%%1*}
produces `a' and ` b' (note the extra space). As substitution occurs before either joining or
splitting, the operation first generates the modified array (ax bx), which is joined to give "ax
bx", and then split to give `a', ` b' and `'. The final empty string will then be elided, as it
is not in double quotes.
COMMAND SUBSTITUTION
A command enclosed in parentheses preceded by a dollar sign, like `$(...)', or quoted with grave accents,
like ``...`', 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 IFS parameter.
The substitution `$(cat foo)' may be replaced by the faster `$(<foo)'. In this case foo undergoes single
word shell expansions (parameter expansion, command substitution and arithmetic expansion), but not
filename generation.
If the option GLOB_SUBST is set, the result of any unquoted command substitution, including the special
form just mentioned, is eligible for filename generation.
ARITHMETIC EXPANSION
A string of the form `$[exp]' or `$((exp))' is substituted with the value of the arithmetic expression
exp. exp is subjected to parameter expansion, command substitution and arithmetic expansion before it is
evaluated. See the section `Arithmetic Evaluation'.
BRACE EXPANSION
A string of the form `foo{xx,yy,zz}bar' is expanded to the individual words `fooxxbar', `fooyybar' and
`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 `{n1..n2}', where n1 and n2 are integers, is expanded to every number between
n1 and n2 inclusive. If either number begins with a zero, all the resulting numbers will be padded with
leading zeroes to that minimum width, but for negative numbers the - character is also included in the
width. If the numbers are in decreasing order the resulting sequence will also be in decreasing order.
An expression of the form `{n1..n2..n3}', where n1, n2, and n3 are integers, is expanded as above, but
only every n3th number starting from n1 is output. If n3 is negative the numbers are output in reverse
order, this is slightly different from simply swapping n1 and n2 in the case that the step n3 doesn't
evenly divide the range. Zero padding can be specified in any of the three numbers, specifying it in the
third can be useful to pad for example `{-99..100..01}' which is not possible to specify by putting a 0
on either of the first two numbers (i.e. pad to two characters).
An expression of the form `{c1..c2}', where c1 and c2 are single characters (which may be multibyte
characters), is expanded to every character in the range from c1 to c2 in whatever character sequence is
used internally. For characters with code points below 128 this is US ASCII (this is the only case most
users will need). If any intervening character is not printable, appropriate quotation is used to render
it printable. If the character sequence is reversed, the output is in reverse order, e.g. `{d..a}' is
substituted as `d c b a'.
If a brace expression matches none of the above forms, it is left unchanged, unless the option BRACE_CCL
(an abbreviation for `brace character class') is set. In that case, it is expanded to a list of the
individual characters between the braces sorted into the order of the characters in the ASCII character
set (multibyte characters are not currently handled). The syntax is similar to a [...] expression in
filename generation: `-' is treated specially to denote a range of characters, but `^' or `!' as the
first character is treated normally. For example, `{abcdef0-9}' expands to 16 words 0 1 2 3 4 5 6 7 8 9
a b c d e f.
Note that brace expansion is not part of filename generation (globbing); an expression such as
*/{foo,bar} is split into two separate words */foo and */bar before filename generation takes place. In
particular, note that this is liable to produce a `no match' error if either of the two expressions does
not match; this is to be contrasted with */(foo|bar), which is treated as a single pattern but otherwise
has similar effects.
To combine brace expansion with array expansion, see the ${^spec} form described in the section
`Parameter Expansion' above.
FILENAME EXPANSION
Each word is checked to see if it begins with an unquoted `~'. If it does, then the word up to a `/', or
the end of the word if there is no `/', is checked to see if it can be substituted in one of the ways
described here. If so, then the `~' and the checked portion are replaced with the appropriate substitute
value.
A `~' by itself is replaced by the value of $HOME. A `~' followed by a `+' or a `-' is replaced by
current or previous working directory, respectively.
A `~' followed by a number is replaced by the directory at that position in the directory stack. `~0' is
equivalent to `~+', and `~1' is the top of the stack. `~+' followed by a number is replaced by the
directory at that position in the directory stack. `~+0' is equivalent to `~+', and `~+1' is the top of
the stack. `~-' followed by a number is replaced by the directory that many positions from the bottom of
the stack. `~-0' is the bottom of the stack. The PUSHD_MINUS option exchanges the effects of `~+' and
`~-' where they are followed by a number.
Dynamic named directories
If the function zsh_directory_name exists, or the shell variable zsh_directory_name_functions exists and
contains an array of function names, then the functions are used to implement dynamic directory naming.
The functions are tried in order until one returns status zero, so it is important that functions test
whether they can handle the case in question and return an appropriate status.
A `~' followed by a string namstr in unquoted square brackets is treated specially as a dynamic directory
name. Note that the first unquoted closing square bracket always terminates namstr. The shell function
is passed two arguments: the string n (for name) and namstr. It should either set the array reply to a
single element which is the directory corresponding to the name and return status zero (executing an
assignment as the last statement is usually sufficient), or it should return status non-zero. In the
former case the element of reply is used as the directory; in the latter case the substitution is deemed
to have failed. If all functions fail and the option NOMATCH is set, an error results.
The functions defined as above are also used to see if a directory can be turned into a name, for example
when printing the directory stack or when expanding %~ in prompts. In this case each function is passed
two arguments: the string d (for directory) and the candidate for dynamic naming. The function should
either return non-zero status, if the directory cannot be named by the function, or it should set the
array reply to consist of two elements: the first is the dynamic name for the directory (as would appear
within `~[...]'), and the second is the prefix length of the directory to be replaced. For example, if
the trial directory is /home/myname/src/zsh and the dynamic name for /home/myname/src (which has 16
characters) is s, then the function sets
reply=(s 16)
The directory name so returned is compared with possible static names for parts of the directory path, as
described below; it is used if the prefix length matched (16 in the example) is longer than that matched
by any static name.
It is not a requirement that a function implements both n and d calls; for example, it might be
appropriate for certain dynamic forms of expansion not to be contracted to names. In that case any call
with the first argument d should cause a non-zero status to be returned.
The completion system calls `zsh_directory_name c' followed by equivalent calls to elements of the array
zsh_directory_name_functions, if it exists, in order to complete dynamic names for directories. The code
for this should be as for any other completion function as described in zshcompsys(1).
As a working example, here is a function that expands any dynamic names beginning with the string p: to
directories below /home/pws/perforce. In this simple case a static name for the directory would be just
as effective.
zsh_directory_name() {
emulate -L zsh
setopt extendedglob
local -a match mbegin mend
if [[ $1 = d ]]; then
# turn the directory into a name
if [[ $2 = (#b)(/home/pws/perforce/)([^/]##)* ]]; then
typeset -ga reply
reply=(p:$match[2] $(( ${#match[1]} + ${#match[2]} )) )
else
return 1
fi
elif [[ $1 = n ]]; then
# turn the name into a directory
[[ $2 != (#b)p:(?*) ]] && return 1
typeset -ga reply
reply=(/home/pws/perforce/$match[1])
elif [[ $1 = c ]]; then
# complete names
local expl
local -a dirs
dirs=(/home/pws/perforce/*(/:t))
dirs=(p:${^dirs})
_wanted dynamic-dirs expl 'dynamic directory' compadd -S\] -a dirs
return
else
return 1
fi
return 0
}
Static named directories
A `~' followed by anything not already covered consisting of any number of alphanumeric characters or
underscore (`_'), hyphen (`-'), or dot (`.') 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 `~' is the name of a string shell parameter whose
value begins with a `/'. Note that trailing slashes will be removed from the path to the directory
(though the original parameter is not modified).
It is also possible to define directory names using the -d option to the hash builtin.
When the shell prints a path (e.g. when expanding %~ in prompts or when printing the directory stack),
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 `~' followed by the name of the directory. The shorter of the two ways of referring to
the directory is used, i.e. either the directory name or the full path; the name is used if they are the
same length. The parameters $PWD and $OLDPWD are never abbreviated in this fashion.
`=' expansion
If a word begins with an unquoted `=' and the EQUALS option is set, the remainder of the word is taken as
the name of a command. If a command exists by that name, the word is replaced by the full pathname of
the command.
Notes
Filename expansion is performed on the right hand side of a parameter assignment, including those
appearing after commands of the typeset family. In this case, the right hand side will be treated as a
colon-separated list in the manner of the PATH parameter, so that a `~' or an `=' following a `:' is
eligible for expansion. All such behaviour can be disabled by quoting the `~', the `=', or the whole
expression (but not simply the colon); the EQUALS option is also respected.
If the option MAGIC_EQUAL_SUBST is set, any unquoted shell argument in the form `identifier=expression'
becomes eligible for file expansion as described in the previous paragraph. Quoting the first `=' also
inhibits this.
FILENAME GENERATION
If a word contains an unquoted instance of one of the characters `*', `(', `|', `<', `[', or `?', it is
regarded as a pattern for filename generation, unless the GLOB option is unset. If the EXTENDED_GLOB
option is set, the `^' and `#' 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 NULL_GLOB option is set, in which case the word is
deleted; or unless the NOMATCH option is unset, in which case the word is left unchanged.
In filename generation, the character `/' must be matched explicitly; also, a `.' must be matched
explicitly at the beginning of a pattern or after a `/', unless the GLOB_DOTS option is set. No filename
generation pattern matches the files `.' or `..'. In other instances of pattern matching, the `/' and
`.' are not treated specially.
Glob Operators
* Matches any string, including the null string.
? Matches any character.
[...] Matches any of the enclosed characters. Ranges of characters can be specified by separating two
characters by a `-'. A `-' or `]' may be matched by including it as the first character in the
list. There are also several named classes of characters, in the form `[:name:]' with the
following meanings. The first set use the macros provided by the operating system to test for the
given character combinations, including any modifications due to local language settings, see
ctype(3):
[:alnum:]
The character is alphanumeric
[:alpha:]
The character is alphabetic
[:ascii:]
The character is 7-bit, i.e. is a single-byte character without the top bit set.
[:blank:]
The character is a blank character
[:cntrl:]
The character is a control character
[:digit:]
The character is a decimal digit
[:graph:]
The character is a printable character other than whitespace
[:lower:]
The character is a lowercase letter
[:print:]
The character is printable
[:punct:]
The character is printable but neither alphanumeric nor whitespace
[:space:]
The character is whitespace
[:upper:]
The character is an uppercase letter
[:xdigit:]
The character is a hexadecimal digit
Another set of named classes is handled internally by the shell and is not sensitive to the
locale:
[:IDENT:]
The character is allowed to form part of a shell identifier, such as a parameter name; this
test respects the POSIX_IDENTIFIERS option
[:IFS:]
The character is used as an input field separator, i.e. is contained in the IFS parameter
[:IFSSPACE:]
The character is an IFS white space character; see the documentation for IFS in the
zshparam(1) manual page.
[:INCOMPLETE:]
Matches a byte that starts an incomplete multibyte character. Note that there may be a
sequence of more than one bytes that taken together form the prefix of a multibyte
character. To test for a potentially incomplete byte sequence, use the pattern
`[[:INCOMPLETE:]]*'. This will never match a sequence starting with a valid multibyte
character.
[:INVALID:]
Matches a byte that does not start a valid multibyte character. Note this may be a
continuation byte of an incomplete multibyte character as any part of a multibyte string
consisting of invalid and incomplete multibyte characters is treated as single bytes.
[:WORD:]
The character is treated as part of a word; this test is sensitive to the value of the
WORDCHARS parameter
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 `[[:alnum:]]'. Named character sets can be used
alongside other types, e.g. `[[:alpha:]0-9]'.
[^...]
[!...] Like [...], except that it matches any character which is not in the given set.
<[x]-[y]>
Matches any number in the range x to y, inclusive. Either of the numbers may be omitted to make
the range open-ended; hence `<->' matches any number. To match individual digits, the [...] form
is more efficient.
Be careful when using other wildcards adjacent to patterns of this form; for example, <0-9>* will
actually match any number whatsoever at the start of the string, since the `<0-9>' will match the
first digit, and the `*' will match any others. This is a trap for the unwary, but is in fact an
inevitable consequence of the rule that the longest possible match always succeeds. Expressions
such as `<0-9>[^[:digit:]]*' can be used instead.
(...) Matches the enclosed pattern. This is used for grouping. If the KSH_GLOB option is set, then a
`@', `*', `+', `?' or `!' immediately preceding the `(' is treated specially, as detailed below.
The option SH_GLOB prevents bare parentheses from being used in this way, though the KSH_GLOB
option is still available.
Note that grouping cannot extend over multiple directories: it is an error to have a `/' within a
group (this only applies for patterns used in filename generation). There is one exception: a
group of the form (pat/)# appearing as a complete path segment can match a sequence of
directories. For example, foo/(a*/)#bar matches foo/bar, foo/any/bar, foo/any/anyother/bar, and
so on.
x|y Matches either x or y. This operator has lower precedence than any other. The `|' character must
be within parentheses, to avoid interpretation as a pipeline. The alternatives are tried in order
from left to right.
^x (Requires EXTENDED_GLOB to be set.) Matches anything except the pattern x. This has a higher
precedence than `/', so `^foo/bar' will search directories in `.' except `./foo' for a file named
`bar'.
x~y (Requires EXTENDED_GLOB to be set.) Match anything that matches the pattern x but does not match
y. This has lower precedence than any operator except `|', so `*/*~foo/bar' will search for all
files in all directories in `.' and then exclude `foo/bar' if there was such a match. Multiple
patterns can be excluded by `foo~bar~baz'. In the exclusion pattern (y), `/' and `.' are not
treated specially the way they usually are in globbing.
x# (Requires EXTENDED_GLOB to be set.) Matches zero or more occurrences of the pattern x. This
operator has high precedence; `12#' is equivalent to `1(2#)', rather than `(12)#'. It is an error
for an unquoted `#' to follow something which cannot be repeated; this includes an empty string, a
pattern already followed by `##', or parentheses when part of a KSH_GLOB pattern (for example,
`!(foo)#' is invalid and must be replaced by `*(!(foo))').
x## (Requires EXTENDED_GLOB to be set.) Matches one or more occurrences of the pattern x. This
operator has high precedence; `12##' is equivalent to `1(2##)', rather than `(12)##'. No more
than two active `#' characters may appear together. (Note the potential clash with glob
qualifiers in the form `1(2##)' which should therefore be avoided.)
ksh-like Glob Operators
If the KSH_GLOB option is set, the effects of parentheses can be modified by a preceding `@', `*', `+',
`?' or `!'. This character need not be unquoted to have special effects, but the `(' must be.
@(...) Match the pattern in the parentheses. (Like `(...)'.)
*(...) Match any number of occurrences. (Like `(...)#', except that recursive directory searching is not
supported.)
+(...) Match at least one occurrence. (Like `(...)##', except that recursive directory searching is not
supported.)
?(...) Match zero or one occurrence. (Like `(|...)'.)
!(...) Match anything but the expression in parentheses. (Like `(^(...))'.)
Precedence
The precedence of the operators given above is (highest) `^', `/', `~', `|' (lowest); the remaining
operators are simply treated from left to right as part of a string, with `#' and `##' applying to the
shortest possible preceding unit (i.e. a character, `?', `[...]', `<...>', or a parenthesised
expression). As mentioned above, a `/' used as a directory separator may not appear inside parentheses,
while a `|' must do so; in patterns used in other contexts than filename generation (for example, in case
statements and tests within `[[...]]'), a `/' is not special; and `/' is also not special after a `~'
appearing outside parentheses in a filename pattern.
Globbing Flags
There are various flags which affect any text to their right up to the end of the enclosing group or to
the end of the pattern; they require the EXTENDED_GLOB option. All take the form (#X) where X may have
one of the following forms:
i Case insensitive: upper or lower case characters in the pattern match upper or lower case
characters.
l Lower case characters in the pattern match upper or lower case characters; upper case characters
in the pattern still only match upper case characters.
I Case sensitive: locally negates the effect of i or l from that point on.
b Activate backreferences for parenthesised groups in the pattern; this does not work in filename
generation. When a pattern with a set of active parentheses is matched, the strings matched by
the groups are stored in the array $match, the indices of the beginning of the matched parentheses
in the array $mbegin, and the indices of the end in the array $mend, with the first element of
each array corresponding to the first parenthesised group, and so on. These arrays are not
otherwise special to the shell. The indices use the same convention as does parameter
substitution, so that elements of $mend and $mbegin may be used in subscripts; the KSH_ARRAYS
option is respected. Sets of globbing flags are not considered parenthesised groups; only the
first nine active parentheses can be referenced.
For example,
foo="a_string_with_a_message"
if [[ $foo = (a|an)_(#b)(*) ]]; then
print ${foo[$mbegin[1],$mend[1]]}
fi
prints `string_with_a_message'. Note that the first set of parentheses is before the (#b) and
does not create a backreference.
Backreferences work with all forms of pattern matching other than filename generation, but note
that when performing matches on an entire array, such as ${array#pattern}, or a global
substitution, such as ${param//pat/repl}, only the data for the last match remains available. In
the case of global replacements this may still be useful. See the example for the m flag below.
The numbering of backreferences strictly follows the order of the opening parentheses from left to
right in the pattern string, although sets of parentheses may be nested. There are special rules
for parentheses followed by `#' or `##'. Only the last match of the parenthesis is remembered:
for example, in `[[ abab = (#b)([ab])# ]]', only the final `b' is stored in match[1]. Thus extra
parentheses may be necessary to match the complete segment: for example, use `X((ab|cd)#)Y' to
match a whole string of either `ab' or `cd' between `X' and `Y', using the value of $match[1]
rather than $match[2].
If the match fails none of the parameters is altered, so in some cases it may be necessary to
initialise them beforehand. If some of the backreferences fail to match -- which happens if they
are in an alternate branch which fails to match, or if they are followed by # and matched zero
times -- then the matched string is set to the empty string, and the start and end indices are set
to -1.
Pattern matching with backreferences is slightly slower than without.
B Deactivate backreferences, negating the effect of the b flag from that point on.
cN,M The flag (#cN,M) can be used anywhere that the # or ## operators can be used except in the
expressions `(*/)#' and `(*/)##' in filename generation, where `/' has special meaning; it cannot
be combined with other globbing flags and a bad pattern error occurs if it is misplaced. It is
equivalent to the form {N,M} in regular expressions. The previous character or group is required
to match between N and M times, inclusive. The form (#cN) requires exactly N matches; (#c,M) is
equivalent to specifying N as 0; (#cN,) specifies that there is no maximum limit on the number of
matches.
m Set references to the match data for the entire string matched; this is similar to backreferencing
and does not work in filename generation. The flag must be in effect at the end of the pattern,
i.e. not local to a group. The parameters $MATCH, $MBEGIN and $MEND will be set to the string
matched and to the indices of the beginning and end of the string, respectively. This is most
useful in parameter substitutions, as otherwise the string matched is obvious.
For example,
arr=(veldt jynx grimps waqf zho buck)
print ${arr//(#m)[aeiou]/${(U)MATCH}}
forces all the matches (i.e. all vowels) into uppercase, printing `vEldt jynx grImps wAqf zhO
bUck'.
Unlike backreferences, there is no speed penalty for using match references, other than the extra
substitutions required for the replacement strings in cases such as the example shown.
M Deactivate the m flag, hence no references to match data will be created.
anum Approximate matching: num errors are allowed in the string matched by the pattern. The rules for
this are described in the next subsection.
s, e Unlike the other flags, these have only a local effect, and each must appear on its own: `(#s)'
and `(#e)' are the only valid forms. The `(#s)' flag succeeds only at the start of the test
string, and the `(#e)' flag succeeds only at the end of the test string; they correspond to `^'
and `$' in standard regular expressions. They are useful for matching path segments in patterns
other than those in filename generation (where path segments are in any case treated separately).
For example, `*((#s)|/)test((#e)|/)*' matches a path segment `test' in any of the following
strings: test, test/at/start, at/end/test, in/test/middle.
Another use is in parameter substitution; for example `${array/(#s)A*Z(#e)}' will remove only
elements of an array which match the complete pattern `A*Z'. There are other ways of performing
many operations of this type, however the combination of the substitution operations `/' and `//'
with the `(#s)' and `(#e)' flags provides a single simple and memorable method.
Note that assertions of the form `(^(#s))' also work, i.e. match anywhere except at the start of
the string, although this actually means `anything except a zero-length portion at the start of
the string'; you need to use `(""~(#s))' to match a zero-length portion of the string not at the
start.
q A `q' and everything up to the closing parenthesis of the globbing flags are ignored by the
pattern matching code. This is intended to support the use of glob qualifiers, see below. The
result is that the pattern `(#b)(*).c(#q.)' can be used both for globbing and for matching against
a string. In the former case, the `(#q.)' will be treated as a glob qualifier and the `(#b)' will
not be useful, while in the latter case the `(#b)' is useful for backreferences and the `(#q.)'
will be ignored. Note that colon modifiers in the glob qualifiers are also not applied in
ordinary pattern matching.
u Respect the current locale in determining the presence of multibyte characters in a pattern,
provided the shell was compiled with MULTIBYTE_SUPPORT. This overrides the MULTIBYTE option; the
default behaviour is taken from the option. Compare U. (Mnemonic: typically multibyte characters
are from Unicode in the UTF-8 encoding, although any extension of ASCII supported by the system
library may be used.)
U All characters are considered to be a single byte long. The opposite of u. This overrides the
MULTIBYTE option.
For example, the test string fooxx can be matched by the pattern (#i)FOOXX, but not by (#l)FOOXX,
(#i)FOO(#I)XX or ((#i)FOOX)X. The string (#ia2)readme specifies case-insensitive matching of readme with
up to two errors.
When using the ksh syntax for grouping both KSH_GLOB and EXTENDED_GLOB must be set and the left
parenthesis should be preceded by @. Note also that the flags do not affect letters inside [...] groups,
in other words (#i)[a-z] still matches only lowercase letters. Finally, note that when examining whole
paths case-insensitively every directory must be searched for all files which match, so that a pattern of
the form (#i)/foo/bar/... is potentially slow.
Approximate Matching
When matching approximately, the shell keeps a count of the errors found, which cannot exceed the number
specified in the (#anum) flags. Four types of error are recognised:
1. Different characters, as in fooxbar and fooybar.
2. Transposition of characters, as in banana and abnana.
3. A character missing in the target string, as with the pattern road and target string rod.
4. An extra character appearing in the target string, as with stove and strove.
Thus, the pattern (#a3)abcd matches dcba, with the errors occurring by using the first rule twice and the
second once, grouping the string as [d][cb][a] and [a][bc][d].
Non-literal parts of the pattern must match exactly, including characters in character ranges: hence
(#a1)??? matches strings of length four, by applying rule 4 to an empty part of the pattern, but not
strings of length two, since all the ? must match. Other characters which must match exactly are initial
dots in filenames (unless the GLOB_DOTS option is set), and all slashes in filenames, so that a/bc is two
errors from ab/c (the slash cannot be transposed with another character). Similarly, errors are counted
separately for non-contiguous strings in the pattern, so that (ab|cd)ef is two errors from aebf.
When using exclusion via the ~ operator, approximate matching is treated entirely separately for the
excluded part and must be activated separately. Thus, (#a1)README~READ_ME matches READ.ME but not
READ_ME, as the trailing READ_ME is matched without approximation. However, (#a1)README~(#a1)READ_ME
does not match any pattern of the form READ?ME as all such forms are now excluded.
Apart from exclusions, there is only one overall error count; however, the maximum errors allowed may be
altered locally, and this can be delimited by grouping. For example, (#a1)cat((#a0)dog)fox allows one
error in total, which may not occur in the dog section, and the pattern (#a1)cat(#a0)dog(#a1)fox is
equivalent. Note that the point at which an error is first found is the crucial one for establishing
whether to use approximation; for example, (#a1)abc(#a0)xyz will not match abcdxyz, because the error
occurs at the `x', where approximation is turned off.
Entire path segments may be matched approximately, so that `(#a1)/foo/d/is/available/at/the/bar' allows
one error in any path segment. This is much less efficient than without the (#a1), however, since every
directory in the path must be scanned for a possible approximate match. It is best to place the (#a1)
after any path segments which are known to be correct.
Recursive Globbing
A pathname component of the form `(foo/)#' matches a path consisting of zero or more directories matching
the pattern foo.
As a shorthand, `**/' is equivalent to `(*/)#'; note that this therefore matches files in the current
directory as well as subdirectories. Thus:
ls -ld -- (*/)#bar
or
ls -ld -- **/bar
does a recursive directory search for files named `bar' (potentially including the file `bar' in the
current directory). This form does not follow symbolic links; the alternative form `***/' does, but is
otherwise identical. Neither of these can be combined with other forms of globbing within the same path
segment; in that case, the `*' operators revert to their usual effect.
Even shorter forms are available when the option GLOB_STAR_SHORT is set. In that case if no /
immediately follows a ** or *** they are treated as if both a / plus a further * are present. Hence:
setopt GLOBSTARSHORT
ls -ld -- **.c
is equivalent to
ls -ld -- **/*.c
Glob Qualifiers
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.
If the option BARE_GLOB_QUAL is set, then a trailing set of parentheses containing no `|' or `('
characters (or `~' 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 `(^x)', can be forced to be treated as part of
the glob pattern by doubling the parentheses, in this case producing `((^x))'.
If the option EXTENDED_GLOB is set, a different syntax for glob qualifiers is available, namely `(#qx)'
where x is any of the same glob qualifiers used in the other format. The qualifiers must still appear at
the end of the pattern. However, with this syntax multiple glob qualifiers may be chained together.
They are treated as a logical AND of the individual sets of flags. Also, as the syntax is unambiguous,
the expression will be treated as glob qualifiers just as long any parentheses contained within it are
balanced; appearance of `|', `(' or `~' does not negate the effect. Note that qualifiers will be
recognised in this form even if a bare glob qualifier exists at the end of the pattern, for example
`*(#q*)(.)' will recognise executable regular files if both options are set; however, mixed syntax should
probably be avoided for the sake of clarity. Note that within conditions using the `[[' form the
presence of a parenthesised expression (#q...) at the end of a string indicates that globbing should be
performed; the expression may include glob qualifiers, but it is also valid if it is simply (#q). This
does not apply to the right hand side of pattern match operators as the syntax already has special
significance.
A qualifier may be any one of the following:
/ directories
F `full' (i.e. non-empty) directories. Note that the opposite sense (^F) expands to empty
directories and all non-directories. Use (/^F) for empty directories.
. plain files
@ symbolic links
= sockets
p named pipes (FIFOs)
* executable plain files (0100 or 0010 or 0001)
% device files (character or block special)
%b block special files
%c character special files
r owner-readable files (0400)
w owner-writable files (0200)
x owner-executable files (0100)
A group-readable files (0040)
I group-writable files (0020)
E group-executable files (0010)
R world-readable files (0004)
W world-writable files (0002)
X world-executable files (0001)
s setuid files (04000)
S setgid files (02000)
t files with the sticky bit (01000)
fspec files with access rights matching spec. This spec may be a octal number optionally preceded by a
`=', a `+', or a `-'. If none of these characters is given, the behavior is the same as for `='.
The octal number describes the mode bits to be expected, if combined with a `=', the value given
must match the file-modes exactly, with a `+', at least the bits in the given number must be set
in the file-modes, and with a `-', the bits in the number must not be set. Giving a `?' instead of
a octal digit anywhere in the number ensures that the corresponding bits in the file-modes are not
checked, this is only useful in combination with `='.
If the qualifier `f' is followed by any other character anything up to the next matching character
(`[', `{', and `<' match `]', `}', and `>' respectively, any other character matches itself) is
taken as a list of comma-separated sub-specs. Each sub-spec may be either an octal number as
described above or a list of any of the characters `u', `g', `o', and `a', followed by a `=', a
`+', or a `-', followed by a list of any of the characters `r', `w', `x', `s', and `t', or an
octal digit. The first list of characters specify which access rights are to be checked. If a `u'
is given, those for the owner of the file are used, if a `g' is given, those of the group are
checked, a `o' means to test those of other users, and the `a' says to test all three groups. The
`=', `+', and `-' again says how the modes are to be checked and have the same meaning as
described for the first form above. The second list of characters finally says which access rights
are to be expected: `r' for read access, `w' for write access, `x' for the right to execute the
file (or to search a directory), `s' for the setuid and setgid bits, and `t' for the sticky bit.
Thus, `*(f70?)' gives the files for which the owner has read, write, and execute permission, and
for which other group members have no rights, independent of the permissions for other users. The
pattern `*(f-100)' gives all files for which the owner does not have execute permission, and
`*(f:gu+w,o-rx:)' gives the files for which the owner and the other members of the group have at
least write permission, and for which other users don't have read or execute permission.
estring
+cmd The string will be executed as shell code. The filename will be included in the list if and only
if the code returns a zero status (usually the status of the last command).
In the first form, the first character after the `e' will be used as a separator and anything up
to the next matching separator will be taken as the string; `[', `{', and `<' match `]', `}', and
`>', respectively, while any other character matches itself. Note that expansions must be quoted
in the string to prevent them from being expanded before globbing is done. string is then
executed as shell code. The string globqual is appended to the array zsh_eval_context the
duration of execution.
During the execution of string the filename currently being tested is available in the parameter
REPLY; the parameter may be altered to a string to be inserted into the list instead of the
original filename. In addition, the parameter reply may be set to an array or a string, which
overrides the value of REPLY. If set to an array, the latter is inserted into the command line
word by word.
For example, suppose a directory contains a single file `lonely'. Then the expression
`*(e:'reply=(${REPLY}{1,2})':)' will cause the words `lonely1' and `lonely2' to be inserted into
the command line. Note the quoting of string.
The form +cmd has the same effect, but no delimiters appear around cmd. Instead, cmd is taken as
the longest sequence of characters following the + that are alphanumeric or underscore. Typically
cmd will be the name of a shell function that contains the appropriate test. For example,
nt() { [[ $REPLY -nt $NTREF ]] }
NTREF=reffile
ls -ld -- *(+nt)
lists all files in the directory that have been modified more recently than reffile.
ddev files on the device dev
l[-|+]ct
files having a link count less than ct (-), greater than ct (+), or equal to ct
U files owned by the effective user ID
G files owned by the effective group ID
uid files owned by user ID id if that is a number. Otherwise, id specifies a user name: the character
after the `u' will be taken as a separator and the string between it and the next matching
separator will be taken as a user name. The starting separators `[', `{', and `<' match the final
separators `]', `}', and `>', respectively; any other character matches itself. The selected
files are those owned by this user. For example, `u:foo:' or `u[foo]' selects files owned by user
`foo'.
gid like uid but with group IDs or names
a[Mwhms][-|+]n
files accessed exactly n days ago. Files accessed within the last n days are selected using a
negative value for n (-n). Files accessed more than n days ago are selected by a positive n value
(+n). Optional unit specifiers `M', `w', `h', `m' or `s' (e.g. `ah5') cause the check to be
performed with months (of 30 days), weeks, hours, minutes or seconds instead of days,
respectively. An explicit `d' for days is also allowed.
Any fractional part of the difference between the access time and the current part in the
appropriate units is ignored in the comparison. For instance, `echo *(ah-5)' would echo files
accessed within the last five hours, while `echo *(ah+5)' would echo files accessed at least six
hours ago, as times strictly between five and six hours are treated as five hours.
m[Mwhms][-|+]n
like the file access qualifier, except that it uses the file modification time.
c[Mwhms][-|+]n
like the file access qualifier, except that it uses the file inode change time.
L[+|-]n
files less than n bytes (-), more than n bytes (+), or exactly n bytes in length.
If this flag is directly followed by a size specifier `k' (`K'), `m' (`M'), or `p' (`P') (e.g.
`Lk-50') the check is performed with kilobytes, megabytes, or blocks (of 512 bytes) instead. (On
some systems additional specifiers are available for gigabytes, `g' or `G', and terabytes, `t' or
`T'.) If a size specifier is used a file is regarded as "exactly" the size if the file size
rounded up to the next unit is equal to the test size. Hence `*(Lm1)' matches files from 1 byte
up to 1 Megabyte inclusive. Note also that the set of files "less than" the test size only
includes files that would not match the equality test; hence `*(Lm-1)' only matches files of zero
size.
^ negates all qualifiers following it
- toggles between making the qualifiers work on symbolic links (the default) and the files they
point to, if any; any symbolic link for whose target the `stat' system call fails (whatever the
cause of the failure) is treated as a file in its own right
M sets the MARK_DIRS option for the current pattern
T appends a trailing qualifier mark to the filenames, analogous to the LIST_TYPES option, for the
current pattern (overrides M)
N sets the NULL_GLOB option for the current pattern
D sets the GLOB_DOTS option for the current pattern
n sets the NUMERIC_GLOB_SORT option for the current pattern
Yn enables short-circuit mode: the pattern will expand to at most n filenames. If more than n
matches exist, only the first n matches in directory traversal order will be considered.
Implies oN when no oc qualifier is used.
oc specifies how the names of the files should be sorted. The following values of c sort in the
following ways:
n By name.
L By the size (length) of the files.
l By number of links.
a By time of last access, youngest first.
m By time of last modification, youngest first.
c By time of last inode change, youngest first.
d By directories: files in subdirectories appear before those in the current directory at
each level of the search -- this is best combined with other criteria, for example `odon'
to sort on names for files within the same directory.
N No sorting is performed.
estring
+cmd Sort by shell code (see below).
Note that the modifiers ^ and - are used, so `*(^-oL)' gives a list of all files sorted by file
size in descending order, following any symbolic links. Unless oN is used, multiple order
specifiers may occur to resolve ties.
The default sorting is n (by name) unless the Y glob qualifier is used, in which case it is N
(unsorted).
oe and o+ are special cases; they are each followed by shell code, delimited as for the e glob
qualifier and the + glob qualifier respectively (see above). The code is executed for each
matched file with the parameter REPLY set to the name of the file on entry and globsort appended
to zsh_eval_context. The code should modify the parameter REPLY in some fashion. On return, the
value of the parameter is used instead of the file name as the string on which to sort. Unlike
other sort operators, oe and o+ may be repeated, but note that the maximum number of sort
operators of any kind that may appear in any glob expression is 12.
Oc like `o', but sorts in descending order; i.e. `*(^oc)' is the same as `*(Oc)' and `*(^Oc)' is the
same as `*(oc)'; `Od' puts files in the current directory before those in subdirectories at each
level of the search.
[beg[,end]]
specifies which of the matched filenames should be included in the returned list. The syntax is
the same as for array subscripts. beg and the optional end may be mathematical expressions. As in
parameter subscripting they may be negative to make them count from the last match backward. E.g.:
`*(-OL[1,3])' gives a list of the names of the three largest files.
Pstring
The string will be prepended to each glob match as a separate word. string is delimited in the
same way as arguments to the e glob qualifier described above. The qualifier can be repeated; the
words are prepended separately so that the resulting command line contains the words in the same
order they were given in the list of glob qualifiers.
A typical use for this is to prepend an option before all occurrences of a file name; for example,
the pattern `*(P:-f:)' produces the command line arguments `-f file1 -f file2 ...'
If the modifier ^ is active, then string will be appended instead of prepended. Prepending and
appending is done independently so both can be used on the same glob expression; for example by
writing `*(P:foo:^P:bar:^P:baz:)' which produces the command line arguments `foo baz file1 bar
...'
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). Some qualifiers,
however, affect all matches generated, independent of the sublist in which they are given. These are the
qualifiers `M', `T', `N', `D', `n', `o', `O' and the subscripts given in brackets (`[...]').
If a `:' appears in a qualifier list, the remainder of the expression in parenthesis is interpreted as a
modifier (see the section `Modifiers' in the section `History Expansion'). Each modifier must be
introduced by a separate `:'. 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 `(:...)' even if
no actual filename generation is performed, although note that the presence of the parentheses causes the
entire expression to be subjected to any global pattern matching options such as NULL_GLOB. Thus:
ls -ld -- *(-/)
lists all directories and symbolic links that point to directories, and
ls -ld -- *(-@)
lists all broken symbolic links, and
ls -ld -- *(%W)
lists all world-writable device files in the current directory, and
ls -ld -- *(W,X)
lists all files in the current directory that are world-writable or world-executable, and
print -rC1 /tmp/foo*(u0^@:t)
outputs the basename of all root-owned files beginning with the string `foo' in /tmp, ignoring symlinks,
and
ls -ld -- *.*~(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 GLOB_DOTS is explicitly switched off) except for lex.c, lex.h, parse.c and parse.h.
print -rC1 b*.pro(#q:s/pro/shmo/)(#q.:s/builtin/shmiltin/)
demonstrates how colon modifiers and other qualifiers may be chained together. The ordinary qualifier
`.' is applied first, then the colon modifiers in order from left to right. So if EXTENDED_GLOB is set
and the base pattern matches the regular file builtin.pro, the shell will print `shmiltin.shmo'.