Tcl 8.7/Tk8.7 Documentation > Tcl Commands > lappend

Tcl/Tk Applications | Tcl Commands | Tk Commands | Tcl C API | Tk C API

NAME

lappend — Append list elements onto a variable

SYNOPSIS

lappend varName ?value value value ...?

DESCRIPTION

This command treats the variable given by varName as a list and appends each of the value arguments to that list as a separate element, with spaces between elements. If varName does not exist, it is created as a list with elements given by the value arguments. If varName indicate an element that does not exist of an array that has a default value set, list that is comprised of the default value with all the value arguments appended as elements will be stored in the array element. Lappend is similar to append except that the values are appended as list elements rather than raw text. This command provides a relatively efficient way to build up large lists. For example, “lappend a $b” is much more efficient than “set a [concat $a [list $b]]” when $a is long.

EXAMPLE

Using lappend to build up a list of numbers.

% set var 1
1
% lappend var 2
1 2
% lappend var 3 4 5
1 2 3 4 5

SEE ALSO

list, lindex, linsert, llength, lset, lsort, lrange

KEYWORDS

append, element, list, variable
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc.
Copyright © 2001 Kevin B. Kenny <kennykb(at)acm.org>. All rights reserved.