17

I want to set the following variables to the same value in one single line

Example:  export A=B=C=20

There is a syntax available in 'bash' but how can I accomplish the above in ksh ?

Sathish Kumar
  • 1,180
  • 5
  • 17
  • 32

3 Answers3

30

Ksh93 (or bash) doesn't have such expressions, so it's better to make it explicit. But you can bundle multiple variables (with their initial values) in a single export phrase:

export A=1 B=2 C=3

Testing:

$ (export A=1 B=2 C=3 && ksh -c 'echo A=$A B=$B C=$C D=$D')
A=1 B=2 C=3 D=

Awkward alternatives

There is no C-like shortcut, unless you want this ugly thing:

A=${B:=${C:=1}}; echo $A $B $C
1 1 1

... which does not work with export, nor does it work when B or C are empty or non-existent.

Arithmetic notation

Ksh93 arithmetic notation does actually support C-style chained assignments, but for obvious reasons, this only works with numbers, and you'll then have to do the export separately:

$ ((a=b=c=d=1234))
$ echo $a $b $c $d
1234 1234 1234 1234
$ export a b d
$ ksh -c 'echo a=$a b=$b c=$c d=$d'     # Single quotes prevent immediate substitution
a=1234 b=1234 c= d=d1234                # so new ksh instance has no value for $c

Note how we do not export c, and its value in the child shell is indeed empty.

Henk Langeveld
  • 7,094
  • 38
  • 53
2

Here is my example solution for this:

$> export HTTP_PROXY=http://my.company.proxy:8080 && export http_proxy=$HTTP_PROXY https_proxy=$HTTP_PROXY HTTPS_PROXY=$HTTP_PROXY

$> printenv | grep -i proxy
http_proxy=http://my.company.proxy:8080
HTTPS_PROXY=http://my.company.proxy:8080
https_proxy=http://my.company.proxy:8080
HTTP_PROXY=http://my.company.proxy:8080

Explanation

At first I set the HTTP_PROXY variable with export and execute that command and only after that (&& notes that) set the remaining variables to the same value as of HTTP_PROXY.

papaiatis
  • 4,093
  • 4
  • 22
  • 36
1
export a=60 && export b=60 && export c=60

May not be the best option if you have many variables

Raj
  • 35
  • 1
  • 8
  • Thanks for the answer. But, is there any 'C" equivalent of assignment in shell when exporting multiple variables – Sathish Kumar Oct 09 '15 at 07:04
  • I am not sure what you mean by C equivalent..can you explain. Also if you tell what is the purpose of your question, may be I can answer better – Raj Oct 09 '15 at 07:13
  • In 'C' we can assign multiple variables to the same value eg: int a,b,c; a=b=c=10; I asked that question to group the 'variables' in '.profile' which has the same value – Sathish Kumar Oct 09 '15 at 07:22