concat命令

concat ---- 将列表连接起来

语法:
concat ?arg arg ...?

该命令将在截除参数起始的空格和结尾的空格，并以空格来隔离并连接各参数。如果所有的参数都是列表，则将被合并为一个列表

Although concat will concatenate lists (so the command:

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

will return "a b c d e f {g h}" as its result), it will also concatenate things that are not lists, and hence the command:

concat " a b {c   " d "  e} f"

will return "a b {c d e} f" as its result.

Note that the concatenation does not remove spaces from the middle of its arguments, so the command:

concat "a   b   c" { d e f }

will return "a b c d e f" (i.e. with three spaces between the a, the b and the c).