ZSHEXPN(1) ZSHEXPN(1)
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 one step in left-to-right fashion. 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 expan-sion, expansion,
sion, 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 argu-ments. arguments.
ments. 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
Prompt Expansion 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; history expansions do not nest. The `!' can be
escaped with `\' or can be enclosed between a pair of single quotes ('') to suppress its special
meaning. Double quotes will not work for this. Following this history character is an optional
event designator (see the section `Event Designators') and then an optional word designator (the sec-tion section
tion `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.
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 refer-ence reference
ence 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 preced-ing preceding
ing 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 param-eter) parameter)
eter) 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 temporar-ily temporarily
ily 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 refer-ence reference
ence 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 his-tory history
tory 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.
h Remove a trailing pathname component, leaving the head. This works like `dirname'.
r Remove a filename extension of the form `.xxx', leaving the root name.
e Remove all but the extension.
t Remove all leading pathname components, leaving the tail. This works like `basename'.
p Print the new command but do not execute it. Only works with history expansion.
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.
x Like q, but break into words at whitespace. Does not work with parameter expansion.
l Convert the words to all lowercase.
u Convert the words to all uppercase.
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 occur-rence occurrence
rence of r for l. Note that the g or :G must appear in exactly the position shown.
& 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.
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.
If the option HIST_SUBST_PATTERN is set, l is treated as a pattern of the usual form desribed 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 parame-ters parameters
ters 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 qualifer. Fur-ther, Further,
ther, 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 *.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 backrefer-ences backreferences
ences ((#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 command argument of the form `<(list)', `>(list)' or `=(list)' is subject to process substitu-tion. substitution.
tion. In the case of the < or > forms, the shell runs process list asynchronously. 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 tempo-
rary 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 $(<arg) which treats arg as a file name and replaces it
with the file's contents.
The = form is useful as both the /dev/fd and the named pipe implementation of <(...) have drawbacks.
In the former case, some programmes may automatically close the file descriptor in question before
examining the file on the command line, particularly if this is necessary for security reasons such
as when the programme is running setuid. In the second case, if the programme does not actually open
the file, the subshell attempting to read from or write to the pipe will (in a typical implementa-
tion, different operating systems may have different behaviour) block for ever and have to be killed
explicitly. In both cases, the shell actually supplies the information using a pipe, so that pro-grammes programmes
grammes that expect to lseek (see lseek(2)) on the file will not work.
Also note that the previous example can be more compactly and efficiently written (provided the MUL-TIOS MULTIOS
TIOS option is set) as:
paste <(cut -f1 file1) <(cut -f3 file2) \
> >(process1) > >(process2)
The shell uses pipes instead of FIFOs to implement the latter two process substitutions in the above
example.
There is an additional problem with >(process); when this is attached to an external command, the
parent shell does not wait for process to finish and hence an immediately following command cannot
rely on the results being complete. The problem and solution are the same as described in the sec-tion section
tion MULTIOS in zshmisc(1). Hence in a simplified version of the example above:
paste <(cut -f1 file1) <(cut -f3 file2) > >(process)
(note that no MULTIOS are involved), process will be run asynchronously. The workaround is:
{ paste <(cut -f1 file1) <(cut -f3 file2) } > >(process)
The extra processes here are spawned from the parent shell which will wait for their completion.
PARAMETER EXPANSION
The character `$' 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 white-space whitespace
space 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.
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, com-mand command
mand substitution, and arithmetic expansion. In addition to the following operations, the colon mod-ifiers modifiers
ifiers 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.
${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}
If name is set and is non-null then substitute its value; otherwise substitute word. If name
is missing, substitute 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
the s:string: flag.
${name:=word}
${name::=word}
In the first form, if name is unset or is null then set it to word; in the second form, uncon-ditionally unconditionally
ditionally set name to word. In both forms, the value of the parameter is then substituted.
${name:?word}
If name is set and is 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 stan-dard standard
dard message is printed.
${name:+word}
If name is set and is non-null then substitute word; otherwise substitute nothing. 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 the s:string: flag.
If the colon is omitted from one of the above expressions containing a colon, then the shell only
checks whether name is set, not whether its value is null.
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/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.
Both pattern and repl are subject to double-quoted substitution, so that expressions like
${name/$opat/$npat} will work, but note the usual rule that pattern characters in $opat are
not treated specially unless either the option GLOB_SUBST is set, or $opat is instead substi-tuted substituted
tuted 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 parame-ter, parameter,
ter, even at the start.
The first `/' may be preceded by a `:', in which case the match will only succeed if it
matches the entire word. 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 ele-ments elements
ments of the result. Note that `^', `=', and `~', below, must appear to the left of `#' when
these forms are combined.
${^spec}
Turn on the RC_EXPAND_PARAM option for the evaluation of spec; if the `^' is doubled, turn it
off. When this option is set, array expansions of the form foo${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'.
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. If word splitting is also in effect the $var[N] may themselves be
split into different list elements.
${=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}
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 pat-tern pattern
tern anywhere that is possible, such as in filename expansion and filename generation and pat-tern-matching pattern-matching
tern-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 pos-sible possible
sible 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 sur-rounding surrounding
rounding the whole expression, the other (redundant) surrounding the $(foo) as before.
Parameter Expansion Flags
If the opening brace is directly followed by an opening parenthesis, the string up to the matching
closing parenthesis will be taken as a list of flags. In cases where repeating a flag is meaningful,
the repetitions need not be consecutive; for example, `(q%q%q)' means the same thing as the more
readable `(%%qqq)'. The following flags are supported:
# Evaluate the resulting words as numeric expressions and output the characters corresponding to
the resulting integer. Note that this form is entirely distinct from use of the # without
parentheses.
If the MULTIBYTE option is set and the number is greater than 127 (i.e. not an ASCII charac-ter) character)
ter) it is treated as a Unicode character.
% Expand all % escapes in the resulting words in the same way as in prompts (see the section
`Prompt Expansion'). If this flag is given twice, full prompt expansion is done on the result-ing resulting
ing words, depending on the setting of the PROMPT_PERCENT, PROMPT_SUBST and PROMPT_BANG
options.
@ In double quotes, array elements are put into separate words. E.g., `"${(@)foo}"' is equiva-lent equivalent
lent to `"${foo[@]}"' and `"${(@)foo[1,2]}"' is the same as `"$foo[1]" "$foo[2]"'. This is
distinct from field splitting by the the f, s or z flags, which still applies within each
array element.
A Create an array parameter with `${...=...}', `${...:=...}' or `${...::=...}'. If this flag is
repeated (as in `AA'), create an associative array parameter. Assignment is made before sort-ing sorting
ing or padding. The name part may be a subscripted range for ordinary arrays; the word part
must be converted to an array, for example by using `${(AA)=name=...}' to activate field
splitting, when creating an associative array.
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.
c With ${#name}, count the total number of characters in an array, as if the elements were con-catenated concatenated
catenated with spaces between them.
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.
e Perform 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 to lines. 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:'.
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.
L Convert all letters in the result to lower case.
n Sort decimal numbers numerically; if the first differing characters of two test strings are
not digits, sorting is lexical. Numbers with initial zeroes are sorted before those without.
Hence the array `foo1 foo02 foo2 foo3 foo20 foo23' is sorted into the order shown. Trailing
non-digits are not sorted; the order of `2foo' and `2bar' is not defined. May be combined
with `i' or `O'.
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'
or `n'.
O Sort the resulting words in descending order; `O' without `a', `i' or `n' sorts in reverse
lexical order. May be combined with `a', `i' or `n' 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. If used with a nested parameter or command substi-tution, substitution,
tution, 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'.
q Quote the resulting words with backslashes. 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. If it is given four times, the words are quoted in single quotes preceded by a $.
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 usu-ally usually
ally 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
export for exported parameters
unique for arrays which keep only the first occurrence of duplicated values
hide for parameters with the `hide' 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 associa-tive associative
tive array element. Used with subscripts, force values to be substituted even if the sub-script subscript
script form refers to indices or keys.
V Make any special characters in the resulting words visible.
w With ${#name}, count words in arrays or strings; the s flag may be used to set a word delim-iter. delimiter.
iter.
W Similar to w with the difference that empty words between repeated delimiters are also
counted.
X With this flag, parsing errors occurring with the Q, e and # flags or the pattern matching
forms such as `${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. tak-ing taking
ing into account any quoting in the value.
Note that this is done very late, as for the `(s)' flag. So to access single words in the
result, one has to use nested expansions as in `${${(z)foo}[2]}'. Likewise, to remove the
quotes in the resulting words one would do: `${(Q)${(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.
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 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 l and r when the MULTIBYTE option is in effect. Use the character
width reported by the system in calculating the how much of the string it occupies. Most
printable characters have a width of one unit, however certain Asian character sets and cer-tain certain
tain special effects use wider characters.
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 pad-ding padding
ding 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.
The following flags are meaningful with the ${...#...} or ${...%...} forms. The S and I flags may
also be used with the ${.../...} forms.
S Search substrings as well as beginnings or ends; with # start from the beginning and with %
start from the end of the string. With substitution via ${.../...} or ${...//...}, specifies
non-greedy matching, i.e. that the shortest instead of the longest match should be replaced.
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 substi-tuted) substituted)
tuted) 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 replace-ments replacements
ments 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.
B Include the index of the beginning of the match in the result.
E Include the index of the end of the match in the result.
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 sub-stitution, substitution,
stitution, 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 fol-lowing following
lowing rules.
1. Nested Substitution
If multiple nested ${...} forms are present, substitution is performed from the inside out-wards. outwards.
wards. 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}.
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 expan-sion expansion
sion 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. 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.
3. Parameter Name Replacement
The effect of any (P) flag, which treats the value so far as a parameter name and replaces it
with the corresponding value, is applied.
4. Double-Quoted Joining
If the value after this process is an array, and the substitution appears in double quotes,
and no (@) flag is present at the current level, the 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.
5. 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 2., 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).
6. Modifiers
Any modifiers, as specified by a trailing `#', `%', `/' (possibly doubled) or by a set of mod-ifiers modifiers
ifiers of the form :... (see the section `Modifiers' in the section `History Expansion'), are
applied to the words of the value at this level.
7. Forced Joining
If the `(j)' flag is present, or no `(j)' flag is present but the string is to be split as
given by rules 8. or 9., and joining did not take place at step 4., 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.
8. Forced Splitting
If one of the `(s)', `(f)' or `(z)' 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.
9. Shell Word Splitting
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 $IFS. Note this step,
too, takes place at all levels of a nested substitution.
10. Uniqueness
If the result is an array and the `(u)' flag was present, duplicate elements are removed from
the array.
11. Ordering
If the result is still an array and one of the `(o)' or `(O)' flags was present, the array is
reordered.
12. Re-Evaluation
Any `(e)' flag is applied to the value, forcing it to be re-examined for new parameter substi-tutions, substitutions,
tutions, but also for command and arithmetic substitutions.
13. Padding
Any padding of the value by the `(l.fill.)' or `(r.fill.)' flags is applied.
14. Semantic Joining
In contexts where expansion semantics requires a single word to result, all words are rejoined
with the first character of IFS between. So in `${(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.
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 "${(@)...[1]}" detects
that this is a scalar, so that (despite the `(@)' flag) the subscript picks the first charac-
ter.
"${${(@)foo}[1]}"
This produces the result `bar'. In this case, the inner substitution "${(@)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 `$(cat foo)' may be replaced by the equivalent but faster `$(<foo)'. In
either case, if the option GLOB_SUBST is set, the output is eligible for filename generation.
ARITHMETIC EXPANSION
A string of the form `$[exp]' or `$((exp))' is substituted with the value of the arithmetic expres-
sion 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. If the numbers are in decreasing order the result-ing resulting
ing sequence will also be in decreasing order.
If a brace expression matches none of the above forms, it is left unchanged, unless the BRACE_CCL
option is set. In that case, it is expanded to a sorted list of the individual characters between
the braces, in the manner of a search set. `-' is treated specially as in a search set, but `^' or
`!' as the first character is treated normally.
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 expres-sions expressions
sions 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 appropri-ate appropriate
ate substitute value.
A `~' by itself is replaced by the value of $HOME. A `~' followed by a `+' or a `-' is replaced by
the value of $PWD or $OLDPWD, 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.
A `~' followed by anything not already covered is looked up as a named directory, and replaced by the
value of that named directory if found. Named directories are typically home directories for users
on the system. They may also be defined if the text after the `~' 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 direc-tory directory
tory names using the -d option to the hash builtin.
In certain circumstances (in prompts, for instance), when the shell prints a path, the path is
checked to see if it has a named directory as its prefix. If so, then the prefix portion is replaced
with a `~' followed by the name of the directory. The shortest way of referring to the directory is
used, with ties broken in favour of using a named directory, except when the directory is / itself.
The parameters $PWD and $OLDPWD are never abbreviated in this fashion.
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.
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=expres-sion' `identifier=expression'
sion' 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 set-
tings, 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 either space or tab
[: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:]l
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
[:IFS:]
The character is used as an input field separator, i.e. is contained in the IFS parame-ter parameter
ter
[:IFSSPACE:]
The character is an IFS white space character; see the documentation for IFS in the
zshparam(1) manual page.
[: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 suc-ceeds. succeeds.
ceeds. 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.
^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 qual-ifiers qualifiers
ifiers 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 `(...)#'.)
+(...) Match at least one occurrence. (Like `(...)##'.)
?(...) 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 parenthe-ses, parentheses,
ses, while a `|' must do so; in patterns used in other contexts than filename generation (for exam-ple, example,
ple, in case statements and tests within `[[...]]'), a `/' is not special; and `/' is also not spe-cial special
cial 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 charac-ters characters
ters 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 file-name filename
name 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'. Note that the first parenthesis is before the (#b) and does not cre-ate create
ate 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.
m Set references to the match data for the entire string matched; this is similar to backrefer-encing backreferencing
encing 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 perform-ing performing
ing 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 exam-ining examining
ining 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 estab-lishing establishing
lishing 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 (*/)#bar
or
ls **/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.
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.
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)
% 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 num-ber number
ber 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 char-acter character
acter (`[', `{', 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 per-mission, permission,
mission, 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). The first
character after the `e' will be used as a separator and anything up to the next matching sepa-rator separator
rator 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.
During the execution of string the filename currently being tested is available in the parame-ter parameter
ter 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 com-mand command
mand 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 lonely2' to be inserted into the
command line. Note the quotation marks.
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 -l *(+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 char-acter character
acter after the `u' will be taken as a separator and the string between it and the next match-ing matching
ing 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. For instance, `echo *(ah-5)' would echo files accessed within the last 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 `k' (`K'), `m' (`M'), or `p' (`P') (e.g. `Lk-50') the check is per-formed performed
formed with kilobytes, megabytes, or blocks (of 512 bytes) instead.
^ negates all qualifiers following it
- toggles between making the qualifiers work on symbolic links (the default) and the files they
point to
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
oc specifies how the names of the files should be sorted. If c is n they are sorted by name (the
default); if it is L they are sorted depending on the size (length) of the files; if l they
are sorted by the number of links; if a, m, or c they are sorted by the time of the last
access, modification, or inode change respectively; if d, 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;
if N, no sorting is performed. Note that a, m, and c compare the age against the current
time, hence the first name in the list is the youngest file. Also 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.
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 back-ward. backward.
ward. E.g.: `*(-OL[1,3])' gives a list of the names of the three largest files.
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 brack-ets brackets
ets (`[...]').
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'). Note that each modi-fier modifier
fier 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. Thus:
ls *(-/)
lists all directories and symbolic links that point to directories, and
ls *(%W)
lists all world-writable device files in the current directory, and
ls *(W,X)
lists all files in the current directory that are world-writable or world-executable, and
echo /tmp/foo*(u0^@:t)
outputs the basename of all root-owned files beginning with the string `foo' in /tmp, ignoring sym-links, symlinks,
links, and
ls *.*~(lex|parse).[ch](^D^l1)
lists all files having a link count of one whose names contain a dot (but not those starting with a
dot, since GLOB_DOTS is explicitly switched off) except for lex.c, lex.h, parse.c and parse.h.
print b*.pro(#q:s/pro/shmo/)(#q.:s/builtin/shmiltin/)
demonstrates how colon modifiers and other qualifiers may be chained together. The ordinary quali-fier qualifier
fier `.' 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'.
zsh 4.3.4 April 19, 2006 ZSHEXPN(1)
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