Tcl 8.7/Tk8.7a5 Documentation > Tcl Commands > concat

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


concat — Join lists together


concat ?arg arg ...?


This command joins each of its arguments together with spaces after trimming leading and trailing white-space from each of them. If all of the arguments are lists, this has the same effect as concatenating them into a single list. Arguments that are empty (after trimming) are ignored entirely. It permits any number of arguments; if no args are supplied, the result is an empty string.


Although concat will concatenate lists, flattening them in the process (so giving the following interactive session):

% concat a b {c d e} {f {g h}}
a b c d e f {g h}

it will also concatenate things that are not lists, as can be seen from this session:

% concat " a b {c   " d "  e} f"
a b {c d e} f

Note also that the concatenation does not remove spaces from the middle of values, as can be seen here:

% concat "a   b   c" { d e f }
a   b   c d e f

(i.e., there are three spaces between each of the a, the b and the c).


append, eval, join


concatenate, join, list
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc.