In the general case there can be more than one value list
(e.g., *list1* and *list2*),
and each value list can be associated with a list of loop variables
(e.g., *varlist1* and *varlist2*).
During each iteration of the loop
the variables of each *varlist* are assigned
consecutive values from the corresponding *list*.
Values in each *list* are used in order from first to last,
and each value is used exactly once.
The total number of loop iterations is large enough to use
up all the values from all the value lists.
If a value list does not contain enough
elements for each of its loop variables in each iteration,
empty values are used for the missing elements.

The **break** and **continue** statements may be
invoked inside *body*, with the same effect as in the **for**
command. **Foreach** returns an empty string.

set values {1 3 5 7 2 4 6 8} ;# Odd numbers first, for fun! puts "Value\tSquare\tCube" ;# Neat-looking headerforeachx $values { ;# Now loop and print... puts " $x\t [expr {$x**2}]\t [expr {$x**3}]" }

The following loop uses i and j as loop variables to iterate over pairs of elements of a single list.

set x {}foreach{i j} {a b c d e f} { lappend x $j $i } # The value of x is "b a d c f e" # There are 3 iterations of the loop.

The next loop uses i and j to iterate over two lists in parallel.

set x {}foreachi {a b c} j {d e f g} { lappend x $i $j } # The value of x is "a d b e c f {} g" # There are 4 iterations of the loop.

The two forms are combined in the following example.

set x {}foreachi {a b c} {j k} {d e f g} { lappend x $i $j $k } # The value of x is "a d e b f g c {} {}" # There are 3 iterations of the loop.

Copyright © 1995-1997 Roger E. Critchlow Jr.
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc.