concat(n) Tcl Built-In Commands concat(n)

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# [NAME](#NAME)

concat - Join lists together

# [SYNOPSIS](#SYNOPSIS)

**concat** ?*arg arg ...*?

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# [DESCRIPTION](#DESCRIPTION)

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 *arg*s are supplied, the result is an empty string.

# [EXAMPLES](#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**).

For *true* list concatenation, the **list** command should be used with expansion of each input list:

```
% list {*}"a   b   c" {*}{ d e f }
a b c d e f
```

# [SEE ALSO](#SEE_ALSO)

[append(n)](/man/os/tcl/append.n), [eval(n)](/man/os/tcl/eval.n), [join(n)](/man/os/tcl/join.n), [list(n)](/man/os/tcl/list.n)

# [KEYWORDS](#KEYWORDS)

concatenate, join, list

8.3 Tcl

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Document: concat(n) from tcl 9.1.0-r2 (Chainguard OS)
Source: https://downloads.sourceforge.net/project/tcl/Tcl/9.1.0/tcl9.1.0-src.tar.gz