TCL : Concatenate a variable and a string

Question

Assume we have a variable 'a' set to 12345 :

set a 12345

Now how do i set a new variable 'b' which contains the value of 'a' and another string say 9876

workaround is something like

set a "12345"
set u "9876"

set b $a$u

but i dont want to specify $u instead i want the direct string to used..

score 39 · Accepted Answer · answered Mar 09 '11 at 06:46

39

You can do:

set b ${a}9876

or, assuming b is either set to the empty string or not defined:

append b $a 9876

The call to append is more efficient when $a is long (see append doc).

answered Mar 09 '11 at 06:46

Trey Jackson

Hey Trey, good answer. Is it better to use double quotes in these cases, or does it make no odds? E.g. `set b "${a}9876"` – TrojanName Mar 09 '11 at 10:14
3

@Brian: Tcl doesn't care, but you might want to do that if it makes for prettier formatting. – Donal Fellows Mar 09 '11 at 10:19
2

you would only require grouping of some sort if you were trying to concat something with a space in it, depending on whether you also need variable substitution {} or "" would be needed – jk. Mar 09 '11 at 10:35
1

There is also the `join` command, but this is intended mainly for strings with strings--as far as I understand it. – Raj Oct 18 '16 at 02:55
1

@Raj To use the `join` command you'd need to make a list, something like `set b [join [list $a "9876"] ""]` – Trey Jackson Oct 19 '16 at 15:34
Thanks for the clarification, @TreyJackson. I was missing that information. – Raj Oct 19 '16 at 23:18

score 7 · Answer 2 · answered Mar 09 '11 at 18:09

7

other option is to use set command. since set a gives value of a we can use it to set value of b like below

set b [set a]9876

answered Mar 09 '11 at 18:09

vaichidrewar

score 4 · Answer 3 · answered Dec 17 '14 at 08:12

4

Or，you can use format

set b [format %s%s $a $u]

answered Dec 17 '14 at 08:12

Harry Lee

score 3 · Answer 4 · answered Dec 13 '14 at 08:25

3

From Tcl 8.6.2 onwards, there is string cat which can be used to solve this problem.

set b [string cat $a 9876]

answered Dec 13 '14 at 08:25

Donal Fellows

score 1 · Answer 5 · answered Sep 20 '13 at 06:57

1

Other option is to use concat command like below.

set b [concat $a\9876]

answered Sep 20 '13 at 06:57

MANJUNATH MULAGE

score 0 · Answer 6 · answered Nov 18 '14 at 18:06

I don't get what you mean the direct string... I'm not sure if you want... However, if you want the value of 12349876 you can do:

% set b [concat $a$u]
12349876

If you want $a or $u to be part of the string, just add a backslash '\' before the desired variable.

6 Answers6