re-assign value to shell variable

[kobewins]

I am looking for the better coding to re-assign value to a shell variable, but not simply overwirte.

For example:

var=2
{code block}
var=3 ### I don't want to simply overwirte var
### Instead
: ${var:=3}
{other code}

Is that the out-of-date style? Are there better ways to do it?

Many thanks.

 

[PHV]

Is that the out-of-date style
No, this is something different:
[!]: ${var:=3}[/!]
if var is not set or is null then it is set to 3; the value of var is then substituted.

In your shell's man page pay attention to Parameter substitution

Hope This Helps, PH.
Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884 or FAQ181-2886

 

[kobewins]

Thanks, PHV.

 

[kobewins]

I should use "Expansion Operator": $(var:+3} instead.

 

[kobewins]

var=${var:+3}
is what I exactly wanted.

In this case, I know that var exists and isn't NULL. Then the value of var is reset to 3.