foreach - Iterate over all elements in one or more lists
foreach varname list body foreach varlist1 list1 ?varlist2 list2 ...? body
foreach(1t) Tcl Built-In Commands foreach(1t)
______________________________________________________________________________
NAME
foreach - Iterate over all elements in one or more lists
SYNOPSIS
foreach varname list body
foreach varlist1 list1 ?varlist2 list2 ...? body
______________________________________________________________________________
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 ele-
ment of list (in order from first to last), foreach assigns the con-
tents 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.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | runtime/tcl-8 |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
SEE ALSO
for(n), while(n), break(n), continue(n)
KEYWORDS
foreach, iteration, list, loop
NOTES
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from http://prdownloads.sourceforge.net/tcl/tcl-
core8.6.7-src.tar.gz.
Further information about this software can be found on the open source
community website at https://www.tcl.tk/.
Tcl foreach(1t)