array manual page - Tcl Built-In Commands

This command performs one of several operations on the variable given by arrayName. Unless otherwise specified for individual commands below, arrayName must be the name of an existing array variable. The option argument determines what action is carried out by the command. The legal options (which may be abbreviated) are:

array anymore arrayName searchId

Returns 1 if there are any more elements left to be processed in an array search, 0 if all elements have already been returned. SearchId indicates which search on arrayName to check, and must have been the return value from a previous invocation of array startsearch. This option is particularly useful if an array has an element with an empty name, since the return value from array nextelement will not indicate whether the search has been completed.

array default subcommand arrayName args...

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 arrayName if the read would otherwise result in an error. Note that this may cause the append, dict, incr and lappend commands to change their behavior in relation to non-existing array elements.

The subcommand argument controls what exact operation will be performed on the default value of arrayName. Supported subcommands are:

array default exists arrayName: This returns a boolean value indicating whether a default value has been set for the array arrayName. Returns a false value if arrayName does not exist. Raises an error if arrayName is an existing variable that is not an array.
array default get arrayName: This returns the current default value for the array arrayName. Raises an error if arrayName is an existing variable that is not an array, or if arrayName is an array without a default value.
array default set arrayName value: This sets the default value for the array arrayName to value. Returns the empty string. Raises an error if arrayName is an existing variable that is not an array, or if arrayName is an illegal name for an array. If arrayName does not currently exist, it is created as an empty array as well as having its default value set.
array default unset arrayName: This removes the default value for the array arrayName and returns the empty string. Does nothing if arrayName does not have a default value. Raises an error if arrayName is an existing variable that is not an array.

array donesearch arrayName searchId

This command terminates an array search and destroys all the state associated with that search. SearchId indicates which search on arrayName to destroy, and must have been the return value from a previous invocation of array startsearch. Returns an empty string.

array exists arrayName

Returns 1 if arrayName is an array variable, 0 if there is no variable by that name or if it is a scalar variable.

array for {keyVariable valueVariable} arrayName body

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 array for process, the command will terminate with an error.

array get arrayName ?pattern?

Returns a list containing pairs of elements. The first element in each pair is the name of an element in arrayName and the second element of each pair is the value of the array element. The order of the pairs is undefined. If pattern is not specified, then all of the elements of the array are included in the result. If pattern is specified, then only those elements whose names match pattern (using the matching rules of string match) are included. If arrayName 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 array get.

array names arrayName ?mode? ?pattern?

Returns a list containing the names of all of the elements in the array that match pattern. Mode may be one of -exact, -glob, or -regexp. If specified, mode designates which matching rules to use to match pattern against the names of the elements in the array. If not specified, mode defaults to -glob. See the documentation for string match for information on glob style matching, and the documentation for regexp for information on regexp matching. If pattern 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 arrayName is not the name of an array variable, then an empty string is returned.

array nextelement arrayName searchId

Returns the name of the next element in arrayName, or an empty string if all elements of arrayName have already been returned in this search. The searchId argument identifies the search, and must have been the return value of an array startsearch command. Warning: if elements are added to or deleted from the array, then all searches are automatically terminated just as if array donesearch had been invoked; this will cause array nextelement operations to fail for those searches.

array set arrayName list

Sets the values of one or more elements in arrayName. list must have a form like that returned by array get, consisting of an even number of elements. Each odd-numbered element in list is treated as an element name within arrayName, and the following element in list is used as a new value for that array element. If the variable arrayName does not already exist and list is empty, arrayName is created with an empty array value.

array size arrayName

Returns a decimal string giving the number of elements in the array. If arrayName is not the name of an array then 0 is returned.

array startsearch arrayName

This command initializes an element-by-element search through the array given by arrayName, such that invocations of the array nextelement command will return the names of the individual elements in the array. When the search has been completed, the array donesearch command should be invoked. The return value is a search identifier that must be used in array nextelement and array donesearch commands; it allows multiple searches to be underway simultaneously for the same array. It is currently more efficient and easier to use either the array get or array names, together with foreach, to iterate over all but very large arrays. See the examples below for how to do this.

array statistics arrayName

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.

array unset arrayName ?pattern?

Unsets all of the elements in the array that match pattern (using the matching rules of string match). If arrayName is not the name of an array variable or there are no matching elements in the array, no error will be raised. If pattern is omitted and arrayName is an array variable, then the command unsets the entire array. The command always returns an empty string.

EXAMPLES

array set colorcount {
    red   1
    green 5
    blue  4
    white 9
}

foreach {color count} [array get colorcount] {
    puts "Color: $color Count: $count"
}
  → Color: blue Count: 4
    Color: white Count: 9
    Color: green Count: 5
    Color: red Count: 1

foreach color [array names colorcount] {
    puts "Color: $color Count: $colorcount($color)"
}
  → Color: blue Count: 4
    Color: white Count: 9
    Color: green Count: 5
    Color: red Count: 1

foreach color [lsort [array names colorcount]] {
    puts "Color: $color Count: $colorcount($color)"
}
  → Color: blue Count: 4
    Color: green Count: 5
    Color: red Count: 1
    Color: white Count: 9

array statistics colorcount
  → 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

KEYWORDS

array, element names, search

Tcl 9.0 Documentation > Tcl Commands, version 9.0.0 > array

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