NAME

       foreach - Iterate over all elements in one or more lists

SYNOPSIS

       foreach varname list body
       foreach varlist1 list1 ?varlist2 list2 ...? body
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DESCRIPTION

       The  foreach  command implements a loop where the loop variable(s) take on values from one or more lists.
       In the simplest case there is one loop variable, varname, and one list, list, that is a list of values to
       assign to varname.  The body argument is a Tcl script.  For each element of list (in order from first  to
       last),  foreach  assigns the contents of the element to varname as if the lindex command had been used to
       extract the element, then calls the Tcl interpreter to execute body.

       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.

EXAMPLES

       This loop prints every value in a list together with the square and cube of the value:

              set values {1 3 5 7 2 4 6 8}  ;# Odd numbers first, for fun!
              puts "Value\tSquare\tCube"    ;# Neat-looking header
              foreach x $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 {}
              foreach i {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 {}
              foreach i {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.

SEE ALSO

       for(3tcl), while(3tcl), break(3tcl), continue(3tcl)

KEYWORDS

       foreach, iteration, list, loop

Tcl                                                                                                foreach(3tcl)