path: root/doc/array.n

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.TH array n 8.7 Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
array \- Manipulate array variables
.SH SYNOPSIS
\fBarray \fIoption arrayName\fR ?\fIarg arg ...\fR?
.BE
.SH DESCRIPTION
.PP
This command performs one of several operations on the
variable given by \fIarrayName\fR.
Unless otherwise specified for individual commands below,
\fIarrayName\fR must be the name of an existing array variable.
The \fIoption\fR argument determines what action is carried
out by the command.
The legal \fIoptions\fR (which may be abbreviated) are:
.TP
\fBarray anymore \fIarrayName searchId\fR
Returns 1 if there are any more elements left to be processed
in an array search, 0 if all elements have already been
returned.
\fISearchId\fR indicates which search on \fIarrayName\fR to
check, and must have been the return value from a previous
invocation of \fBarray startsearch\fR.
This option is particularly useful if an array has an element
with an empty name, since the return value from
\fBarray nextelement\fR will not indicate whether the search
has been completed.
.TP
\fBarray default \fIsubcommand arrayName args...\fR
.VS TIP508
Manages the default value of the array. Arrays initially have no default
value, but this command allows you to set one; the default value will be
returned when reading from an element of the array \farrayName\fR if the read
would otherwise result in an error. Note that this may cause the \fBappend\fR,
\fBdict\fR, \fBincr\fR and \fBlappend\fR commands to change their behavior in
relation to non-existing array elements.
.RS
.PP
The \fIsubcommand\fR argument controls what exact operation will be performed
on the default value of \fIarrayName\fR. Supported \fIsubcommand\fRs are:
.VE TIP508
.TP
\fBarray default exists \fIarrayName\fR
.VS TIP508
This returns a boolean value indicating whether a default value has been set
for the array \fIarrayName\fR. Returns a false value if \fIarrayName\fR does
not exist. Raises an error if \fIarrayName\fR is an existing variable that is
not an array.
.VE TIP508
.TP
\fBarray default get \fIarrayName\fR
.VS TIP508
This returns the current default value for the array \fIarrayName\fR.  Raises
an error if \fIarrayName\fR is an existing variable that is not an array, or
if \fIarrayName\fR is an array without a default value.
.VE TIP508
.TP
\fBarray default set \fIarrayName value\fR
.VS TIP508
This sets the default value for the array \fIarrayName\fR to \fIvalue\fR.
Returns the empty string. Raises an error if \fIarrayName\fR is an existing
variable that is not an array, or if \fIarrayName\fR is an illegal name for an
array. If \fIarrayName\fR does not currently exist, it is created as an empty
array as well as having its default value set.
.VE TIP508
.TP
\fBarray default unset \fIarrayName\fR
.VS TIP508
This removes the default value for the array \fIarrayName\fR and returns the
empty string. Does nothing if \fIarrayName\fR does not have a default
value. Raises an error if \fIarrayName\fR is an existing variable that is not
an array.
.VE TIP508
.RE
.TP
\fBarray donesearch \fIarrayName searchId\fR
This command terminates an array search and destroys all the
state associated with that search.  \fISearchId\fR indicates
which search on \fIarrayName\fR to destroy, and must have
been the return value from a previous invocation of
\fBarray startsearch\fR.  Returns an empty string.
.TP
\fBarray exists \fIarrayName\fR
Returns 1 if \fIarrayName\fR is an array variable, 0 if there
is no variable by that name or if it is a scalar variable.
.TP
\fBarray for {\fIkeyVariable valueVariable\fB} \fIarrayName body\fP
The first argument is a two element list of variable names for the
key and value of each entry in the array.  The second argument is the
array name to iterate over.  The third argument is the body to execute
for each key and value returned.
The ordering of the returned keys is undefined.
If an array element is deleted or a new array element is inserted during
the \fIarray for\fP process, the command will terminate with an error.
.TP
\fBarray get \fIarrayName\fR ?\fIpattern\fR?
Returns a list containing pairs of elements.  The first
element in each pair is the name of an element in \fIarrayName\fR
and the second element of each pair is the value of the
array element.  The order of the pairs is undefined.
If \fIpattern\fR is not specified, then all of the elements of the
array are included in the result.
If \fIpattern\fR is specified, then only those elements whose names
match \fIpattern\fR (using the matching rules of
\fBstring match\fR) are included.
If \fIarrayName\fR is not the name of an array variable, or if
the array contains no elements, then an empty list is returned.
If traces on the array modify the list of elements, the elements
returned are those that exist both before and after the call to
\fBarray get\fR.
.TP
\fBarray names \fIarrayName\fR ?\fImode\fR? ?\fIpattern\fR?
Returns a list containing the names of all of the elements in
the array that match \fIpattern\fR.  \fIMode\fR may be one of
\fB\-exact\fR, \fB\-glob\fR, or \fB\-regexp\fR.  If specified, \fImode\fR
designates which matching rules to use to match \fIpattern\fR against
the names of the elements in the array.  If not specified, \fImode\fR
defaults to \fB\-glob\fR.  See the documentation for \fBstring match\fR
for information on glob style matching, and the documentation for
\fBregexp\fR for information on regexp matching.
If \fIpattern\fR is omitted then the command returns all of
the element names in the array.  If there are no (matching) elements
in the array, or if \fIarrayName\fR is not the name of an array
variable, then an empty string is returned.
.TP
\fBarray nextelement \fIarrayName searchId\fR
Returns the name of the next element in \fIarrayName\fR, or
an empty string if all elements of \fIarrayName\fR have
already been returned in this search.  The \fIsearchId\fR
argument identifies the search, and must have
been the return value of an \fBarray startsearch\fR command.
Warning:  if elements are added to or deleted from the array,
then all searches are automatically terminated just as if
\fBarray donesearch\fR had been invoked; this will cause
\fBarray nextelement\fR operations to fail for those searches.
.TP
\fBarray set \fIarrayName list\fR
Sets the values of one or more elements in \fIarrayName\fR.
\fIlist\fR must have a form like that returned by \fBarray get\fR,
consisting of an even number of elements.
Each odd-numbered element in \fIlist\fR is treated as an element
name within \fIarrayName\fR, and the following element in \fIlist\fR
is used as a new value for that array element.
If the variable \fIarrayName\fR does not already exist
and \fIlist\fR is empty,
\fIarrayName\fR is created with an empty array value.
.TP
\fBarray size \fIarrayName\fR
Returns a decimal string giving the number of elements in the
array.
If \fIarrayName\fR is not the name of an array then 0 is returned.
.TP
\fBarray startsearch \fIarrayName\fR
This command initializes an element-by-element search through the
array given by \fIarrayName\fR, such that invocations of the
\fBarray nextelement\fR command will return the names of the
individual elements in the array.
When the search has been completed, the \fBarray donesearch\fR
command should be invoked.
The return value is a
search identifier that must be used in \fBarray nextelement\fR
and \fBarray donesearch\fR commands; it allows multiple
searches to be underway simultaneously for the same array.
It is currently more efficient and easier to use either the \fBarray
get\fR or \fBarray names\fR, together with \fBforeach\fR, to iterate
over all but very large arrays.  See the examples below for how to do
this.
.TP
\fBarray statistics \fIarrayName\fR
Returns statistics about the distribution of data within the hashtable
that represents the array.  This information includes the number of
entries in the table, the number of buckets, and the utilization of
the buckets.
.TP
\fBarray unset \fIarrayName\fR ?\fIpattern\fR?
Unsets all of the elements in the array that match \fIpattern\fR (using the
matching rules of \fBstring match\fR).  If \fIarrayName\fR is not the name
of an array variable or there are no matching elements in the array, no
error will be raised.  If \fIpattern\fR is omitted and \fIarrayName\fR is
an array variable, then the command unsets the entire array.
The command always returns an empty string.
.SH EXAMPLES
.CS
\fBarray set\fR colorcount {
    red   1
    green 5
    blue  4
    white 9
}

foreach {color count} [\fBarray get\fR colorcount] {
    puts "Color: $color Count: $count"
}
  \fB\(->\fR Color: blue Count: 4
    Color: white Count: 9
    Color: green Count: 5
    Color: red Count: 1

foreach color [\fBarray names\fR colorcount] {
    puts "Color: $color Count: $colorcount($color)"
}
  \fB\(->\fR Color: blue Count: 4
    Color: white Count: 9
    Color: green Count: 5
    Color: red Count: 1

foreach color [lsort [\fBarray names\fR colorcount]] {
    puts "Color: $color Count: $colorcount($color)"
}
  \fB\(->\fR Color: blue Count: 4
    Color: green Count: 5
    Color: red Count: 1
    Color: white Count: 9

\fBarray statistics\fR colorcount
  \fB\(->\fR 4 entries in table, 4 buckets
    number of buckets with 0 entries: 1
    number of buckets with 1 entries: 2
    number of buckets with 2 entries: 1
    number of buckets with 3 entries: 0
    number of buckets with 4 entries: 0
    number of buckets with 5 entries: 0
    number of buckets with 6 entries: 0
    number of buckets with 7 entries: 0
    number of buckets with 8 entries: 0
    number of buckets with 9 entries: 0
    number of buckets with 10 or more entries: 0
    average search distance for entry: 1.2
.CE
.SH "SEE ALSO"
list(n), string(n), variable(n), trace(n), foreach(n)
.SH KEYWORDS
array, element names, search
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