Sort the elements of a list 

Tclsh Built-In Commands


lsort ?options? list


This command sorts the elements of list, returning a new list in sorted order. The implementation of the lsort command uses the merge-sort algorithm which is a stable sort that has O(n log n) performance characteristics.

By default ASCII sorting is used with the result returned in increasing order. However, any of the following options may be specified before list to control the sorting process (unique abbreviations are accepted):


Use string comparison with ASCII collation order. This is the default.


Use dictionary-style comparison. This is the same as -ascii except (a) case is ignored except as a tie-breaker and (b) if two strings contain embedded numbers, the numbers compare as integers, not characters. For example, in -dictionary mode, bigBoy sorts between bigbang and bigboy, and x10y sorts between x9y and x11y.


Convert list elements to integers and use integer comparison.


Convert list elements to floating-point values and use floating comparison.

-command command 

Use command as a comparison command. To compare two elements, evaluate a Tcl script consisting of command with the two elements appended as additional arguments. The script should return an integer less than, equal to, or greater than zero if the first element is to be considered less than, equal to, or greater than the second, respectively.


Sort the list in increasing order (smallest items first). This is the default.


Sort the list in decreasing order (largest items first).

-index index 

If this option is specified, each of the elements of list must itself be a proper Tcl sublist. Instead of sorting based on whole sublists, lsort will extract the index'th element from each sublist and sort based on the given element. The keyword end is allowed for the index to sort on the last sublist element. For example,

lsort -integer -index 1 {{First 24} {Second 18} {Third 30}}

returns {Second 18} {First 24} {Third 30}. This option is much more efficient than using -command to achieve the same effect.


If this option is specified, then only the last set of duplicate elements found in the list will be retained. Note that duplicates are determined relative to the comparison used in the sort. Thus if -index 0 is used, {1 a} and {1 b} would be considered duplicates and only the second element, {1 b}, would be retained.


Windows 8.1. Windows Server 2012 R2. Windows 10. Windows Server 2016. Windows Server 2019. Windows 11. Windows Server 2022.


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