ZSHEXPN(1)ZSHEXPN(1)NAMEzshexpn - zsh command and parameter expansion
DESCRIPTION
The types of expansions performed are history expansion,
alias expansion, process substitution, parameter expan_
sion, command substitution, arithmetic expansion, brace
expansion, filename expansion, and filename generation.
Exansion is done in the above specified order in five
steps. The first is History expansion which is only per
formed in interactive shells. The next step is alias
expansion which is done right before the command line is
parsed. They are followed by process substitution, param_
eter expansion, command substitution, arithmetic expansion
and brace expansion which are preformed in one step in
left-to-right fashion. After these expansions, all
unquoted occurrences of the characters \, ', and " are
removed and the result is subjected to filename expansion
followed by filename generation.
If the SH_FILE_EXPANSION option is set, the order of
expansion is modified for compatibility with sh and ksh.
Filename expansion is performed immediately after alias
substitution, preceding the set of five substitutions men
tioned 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 sub
stituted in one of the ways described here. If so, then
the ~ and the checked portion are replaced with the appro
priate substitute value.
A ~ by itself is replaced by the value of the HOME parame
ter. 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 num
ber 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
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be defined if the text after the ~ is the name of a string
shell parameter whose value begins with a /. It is also
possible to define directory 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 pre
fix 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 /.
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 or alias. If a command exists by that name, the
word is replaced by the full pathname of the command. If
an alias exists by that name, the word is replaced with
the text of the alias.
Filename expansion is performed on the right hand side of
a parameter assignment, including those appearing after
commands of the typeset family. In this case, the right
hand side will be treated as a colon-separated list in the
manner of PATH so that a ~ or an = following a : is eligi
ble for expansion. All such behavior 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 eligi
ble for file expansion as described in the previous para
graph. Quoting the first = also inhibits this.
PROCESS SUBSTITUTION
Each command argument of the form <(list) or >(list) or
=(list) is subject to process substitution. In the case
of the < or > forms, the shell will run process list asyn
chronously connected to a named pipe (FIFO). The name of
this pipe will become the argument to the command. If the
form with > is selected then writing on this file will
provide input for list. If < is used, then the file
passed as an argument will be a named pipe 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 respec
tively, pastes the results together, and sends it to the
processes process1 and process2. Note that the file,
which is passed as an argument to the command, is a system
pipe so programs that expect to lseek(2) on the file will
not work. Also note that the previous example can be more
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compactly and efficiently written as:
paste <(cut -f1 file1) <(cut -f3 file2) > >(pro_
cess1) > >(process2)
The shell uses pipes instead of FIFOs to implement the
latter two process substitutions in the above example.
If = is used, 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(2) on the input file.
PARAMETER EXPANSION
The character $ is used to introduce parameter expansions.
See PARAMETERS below for a description of parameters. In
the expansions discussed below that require a pattern, the
form of the pattern is the same as that used for filename
generation; see Filename Generation.
${name}
The value, if any, of the parameter name is
substituted. The braces are required if
name is followed by a letter, digit, or
underscore that is not to be interpreted as
part of its name. If name is an array
parameter, then the values of each element
of name is substituted, one element per
word. Otherwise, the expansion results in
one word only; no field splitting is done on
the result unless the SH_WORD_SPLIT option
is set.
${+name}
If name is the name of a set parameter `1'
is substituted, otherwise `0' is substi
tuted.
${name:-word}
If name is set and is non-null then substi
tute its value; otherwise substitute word.
If name is missing, substitute word.
${name:=word}
If name is unset or is null then set it to
word; the value of the parameter is then
substituted.
${name::=word}
Set name to word; the value of the parameter
is then substituted.
${name:?word}
If name is set and is non-null, then
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substitute its value; otherwise, print word
and exit from the shell. Interactive shells
do not exit. If word is omitted, then a
standard message is printed.
${name:+word}
If name is set and is non-null then substi
tute word; otherwise substitute nothing.
${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; oth
erwise, 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.
If name is an array and the substitution is
not quoted or the @ flag or the name[@] syn
tax is used, matching is performed on each
array elements separately.
${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. If name is an
array and the substitution is not quoted or
the @ flag or the name[@] syntax is used,
matching is performed on each array elements
separately.
${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 and the substitution is not
quoted or the @ flag or the name[@] syntax
is used, matching is performed on each array
elements separately, and the matched array
elements are removed (use the M flag to
remove the non-matched elements).
${#spec}
If spec is one of the above substitutions,
substitute the length in characters of the
result instead of the result itself. If
spec is an array expression, substitute the
number of elements of the result.
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${^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 sub
stituted with fooabar foobbar foocbar
instead of the default fooa b cbar.
${=spec}
Turn on the SH_WORD_SPLIT option for the
evaluation of spec; if the = is doubled,
turn it off. When this option is set,
parameter values are split into separate
words using IFS as a delimiter before sub
stitution. This is done by default in most
other shells.
${~spec}
Turn on the GLOB_SUBST option for the evalu
ation of spec; if the ~ is doubled, turn it
off. When this option is set, any pattern
characters resulting from the substitution
become eligible for file expansion and file
name generation.
If the colon is omitted from one of the above expressions
containing a colon, then the shell only checks whether
name is set or not, not whether it is null.
If a ${...} type parameter expression or a $(...) type
command substitution is used in place of name above, it is
substituted first and the result is used as it were the
value of name.
If the opening brace is directly followed by an opening
parentheses the string up to the matching closing paren
theses will be taken as a list of flags. Where arguments
are valid, any character, or the matching pairs `(...)',
`{...}', `[...]', or `<...>', may be used in place of the
colon as delimiters. The following flags are supported:
A Create an array parameter with ${...:=...}
or ${...::=...}. Assignment is made before
sorting or padding.
@ In double quotes, array elements are put
into separate words. Eg. "${(@)foo}" is
equivalent to "${foo[@]}" and
"${(@)foo[1,2]}" is the same as "$foo[1]"
"$foo[2]".
e Perform parameter expansion, command substi_
tution and arithmetic expansion on the
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result. Such expansions can be nested but
too deep recursion may have unpredictable
effects.
o Sort the resulting words in ascending order.
O Sort the resulting words in descending
order.
i With o or O, sort case-independently.
L Convert all letters in the result to lower
case.
U Convert all letters in the result to upper
case.
C Capitalize the resulting words.
c With ${#name}, count the total number of
characters in an array, as if the elements
were concatenated with spaces between them.
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.
p Recognize the same escape sequences as the
print builtin in string arguments to subse
quent flags.
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
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, this string
is inserted once directly to the left of
each word, before padding.
r:expr::string1::string2:
As l..., but pad the words on the right and
insert string2 on the right.
j:string:
Join the words of arrays together using
string as a separator. Note that this
occurs before word splitting by the
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SH_WORD_SPLIT option.
F Join the words of arrays together using new
line as a separator. This is a shorthand
for pj:\n:.
s:string:
Force word splitting (see the option
SH_WORD_SPLIT) at the separator string.
Splitting only occurs in places where an
array value is valid, and joining always
occurs before splitting.
f Split the result of the expansion to lines.
This is a shorthand for ps:\n:.
(All remaining flags are useful only with the
${...#...} or ${...%...} forms.)
S Search substrings as well as beginnings or
ends.
I:expr:
Search the expr'th match (where expr evalu
ates to a number).
M Include the matched portion in the result.
R Include the unmatched portion in the result
(the Rest).
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.
N Include the length of the match in the
result.
COMMAND SUBSTITUTION
A command enclosed in parentheses preceded by a dollar
sign, like so: $(...) or quoted with grave accents: `...`
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 eligi
ble for filename generation.
ARITHMETIC EXPANSION
A string of the form $[exp] or $((exp)) is substituted
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with the value of the arithmetic expression exp. exp is
subjected to parameter expansion, command substitution and
arithmetic expansion before it is evaluated. See ARITH
METIC EVALUATION in zshmisc(1).
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 resulting 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 individ
ual 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.
FILENAME GENERATION (GLOBBING)
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 # char
acters also denote a pattern; otherwise (except for an
initial ~, see Filename Expansion above) 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 mes
sage, 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 file
name generation, the character / must be matched explic
itly; also, a . must be matched explicitly at the begin
ning 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 match
ing, the / and . are not treated specially.
* 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
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character in the list.
[^...]
[!...] like [...], except that it matches any char
acter which is not in the given set.
<x-y> matches any number in the range x to y,
inclusive. If x is omitted, the number must
be less than or equal to y. If y is omit
ted, the number must be greater than or
equal to x. A pattern of the form <->
matches any number.
^x matches anything except the pattern x.
x|y matches either x or y.
x# matches zero or more occurrences of the pat
tern x.
x## matches one or more occurrences of the pat
tern x.
Parentheses may be used for grouping. Note that the |
character must be within parentheses, so that the lexical
analyzer does not think it is a pipe character. Also note
that "/" has a higher precedence than "^"; that is:
ls ^foo/bar
will search directories in "." except "./foo" for a file
named bar.
A pathname component of the form (foo/)# matches a path
consisting of zero or more directories matching the pat
tern foo. As a shorthand, **/ is equivalent to (*/)#.
Thus:
ls (*/)#bar
or
ls **/bar
does a recursive directory search for files named bar, not
following symbolic links. To follow symbolic links, use
the form ***/.
If used for filename generation, a pattern may contain an
exclusion specifier. Such patterns are of the form
pat1~pat2. This pattern will generate all files matching
pat1, but which do not match pat2. For example, *.c~lex.c
will match all files ending in .c, except the file lex.c.
This may appear inside parentheses. Note that "~" has a
higher precedence than "|", so that pat1|pat2~pat3 matches
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any time that pat1 matches, or if pat2 matches while pat3
does not. Note also that "/" characters are not treated
specially in the exclusion specifier so that a "*" will
match multiple path segments if they appear in the pattern
to the left of the "~".
Patterns used for filename generation may also end in a
list of qualifiers enclosed in parentheses. The quali
fiers specify which filenames that otherwise match the
given pattern will be inserted in the argument list. A
qualifier may be any one of the following:
/ 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)
ddev files on the device dev
l[-|+]ct
files having a link count less than ct (-),
greater than ct (+), or is 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 it is a number,
if not, than the character after the u will
be used as a separator and the string
between it and the next matching separator
(`(', `[', `{', and `<' match `)', `]', `}',
and `>' respectively, any other character
matches itself) will be taken as a user name
and the user id of this user will be taken
(e.g. u:foo: or u[foo] for 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
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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 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 traling qualifier mark to the file
names, 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
More than one of these lists can be combined, separated by
commas. The whole list matches if at least one of the sub
lists matches (they are `or'ed', the qualifiers in the
sublists are `and'ed').
If a : appears in a qualifier list, the remainder of the
expression in parenthesis is interpreted as a modifier
(see the subsection Modifiers of the section HISTORY
EXPANSION). Note that each modifier must be introduced by
a separate :. Note also that the result after modifica
tion 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 filename generation is performed.
Thus:
ls *(-/)
lists all directories and symbolic links that point to
directories, and
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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 symlinks, 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.
HISTORY EXPANSION
History substitution allows you to use words from previous
command lines in the command line you are typing. This
simplifies spelling corrections and the repetition of com
plicated commands or arguments. Command lines are saved
in the history list, the size of which is controlled by
the HISTSIZE variable. The most recent command is
retained in any case. A history substitution begins with
the fist character of the histchars parameter which is !
by default and may occur anywhere on the command line;
history substitutions 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.
Input lines containing history substitutions are echoed on
the terminal after being expanded, but before any other
substitutions take place or the command gets executed.
Event Designators
An event designator is a reference to a command-line entry
in the history list.
! Start a history substitution, except when
followed by a blank, newline, =, or (.
!! Refer to the previous command. By itself,
this substitution repeats the previous com
mand.
!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.
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!?str[?]
Refer to the most recent command containing
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 will be included in a history reference. A
`:' separates the event specification from the word desig
nator. It can be omitted if the word designator begins
with a ^, $, *, - or %. Word designators include:
0 The first input word (command).
n The n'th 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; -y abbreviates 0-y.
* All the arguments, or a null value if there
is just one word in the event.
x* Abbreviates x-$.
x- Like x* but omitting word $.
Note that a `%' word designator will only work when used
as !%, !:%, !?str?:% and only when used after a !? substi
tution. Anything else will result 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 file_
name and parameter expansion.
h Remove a trailing pathname component, leav
ing the head.
r Remove a trailing suffix of the form `.xxx',
leaving the basename.
e Remove all but the suffix.
t Remove all leading pathname components,
leaving the tail.
& Repeat the previous substitution.
g Apply the change to the first occurrence of
a match in each word, by prefixing the above
(for example, g&).
p Print the new command but do not execute it.
q Quote the substituted words, escaping fur
ther substitutions.
x Like q, but break into words at each blank.
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l Convert the words to all lowercase.
u Convert the words to all uppercase.
f Repeats the immediately (without a colon)
following modifier until the resulting word
doesn't change any more. This and the fol
lowing F, w and W modifier only work with
parameter and filename expansion.
F:expr:
Like f, but repeats only n times if the
expression expr evaluates to n. Any charac
ter can be used instead of the `:', if any
of `(', `[', or `{' is used as the opening
delimiter the second one has to 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.
s/l/r[/]
Substitute r for l.
Unless preceded by a g, the substitution is done only for
the first string that matches l.
The left-hand side of substitutions are not regular
expressions, 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, is replaced by the text from the left-hand-
side. The & can be quoted with a backslash. A null l
uses the previous string either from a l or from a contex
tual scan string s from !?s. You can omit the rightmost
delimiter if a newline immediately follows r; the right
most ? in a context scan can similarly be omitted.
By default, a history reference with no event specifica
tion refers to the same line as the last history reference
on that command line, unless it is the first history ref
erence in a command. In that case, a history reference
with no event specification always refers to the previous
command. However, if the option CSH_JUNKIE_HISTORY is
set, then history reference with no event specification
will always refer to the previous command. For example,
!!:1 will always refer to the first word of the previous
command and !!$ will always refer to the last word of the
previous command. And with CSH_JUNKIE_HISTORY set, then
!:1 and !$ will function in the same manner as !!:1 and
!!$, respectively. However, if CSH_JUNKIE_HISTORY is
unset, then !:1 and !$ will refer to the first and last
words respectively, of the last command referenced on the
current command line. However, if they are the first
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history reference on the command line, then they refer to
the previous command.
The character sequence ^foo^bar repeats the last command,
replacing the string "foo" with the string "bar".
If the shell encounters the character sequence !" in the
input, the history mechanism is temporarily disabled until
the current list is fully parsed. The !" is removed from
the input, and any subsequent ! characters have no spe
cial significance.
A less convenient but more comprehensible form of command
history support is provided by the fc builtin (see the
entry in zshbuiltins(1)).
zsh version 3.0 June 26, 1996 15
