Re: bash append

[Edwin Mons <e@xxxxx>]

Op 14 jan 2013, om 18:12 heeft casper-enosig@xxxxxxxxxxx het volgende geschreven:

> Op 14-01-13 17:59, H schreef:
>> Hi enosiggers,
>> 
>> I'm stuck with this simple bash script :
>> 
>> cat append.sh
>> #!/bin/bash
>> set -x
>> declare -gx TODO="Todo:"
>> TODO+=' aap.'
>> [ -f /isernie ] || (
>>    TODO+=' noot.'
>> )
>> TODO+=' mies.'
>> echo "[$TODO]"
>> 
>> Output is :
>> 
>> ./append.sh
>> + set -x
>> + declare -gx TODO=Todo:
>> + TODO+=' aap.'
>> + '[' -f /isernie ']'
>> + TODO+=' noot.'
>> + TODO+=' mies.'
>> + echo '[Todo: aap. mies.]'
>> [Todo: aap. mies.]
>> 
>> Afaik bash does not have name scoping.
>> 
>> What must I do to have 'noot' appended here ?
>> 
>> ps. this is on GNU bash, version 4.2.37(1)-release
> 
> Your problem is that TODO+=' noot.' is executed inside a subshell, as
> denoted by the parenthesis ( and ) .
> 
> My solution:
> 
> #!/bin/bash
> set -x
> declare -gx TODO="Todo:"
> TODO+=' aap.'
> TODO+=$( [ -f /isernie ] || echo " noot." )
> TODO+=' mies.'
> echo "[$TODO]"

What's wrong with

if [ ! -f /isernie ]; then
	TODO+=' noot'
fi

and avoid the sub-shell problem altogether (test/[ is internal in bash)?

Groetjes,
Edwin