| ActiveTcl User Guide |

## Tcl/Tk Documentation > TclCmd > concat

### Tcl/Tk Applications | Tcl Commands | Tk Commands | Tcl Library | Tk Library

### NAME

concat - Join lists together

### SYNOPSIS

concat ?arg arg ...?

### DESCRIPTION

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

### EXAMPLES

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).

### SEE ALSO

append, eval, join

### KEYWORDS

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