Hi,

I'm wanting to Reverse find and replace a particular character in a
Powershell string. e.g. reverse find "b" in "abcabc" and replace with
"d" to give "abcadc". Could someone please advise how this could be
achieved ?



Thanks,

Patrick

Sorry - also should have stated that just the first instance of a
particular character should be replaced.

On Jan 8, 11:23*am, Patrick <prynh...@newsgroup> wrote:

> Hi,
>
> I'm wanting to Reverse find and replace a particular character in a
> Powershell string. *e.g. reverse find "b" in "abcabc" and replace with
> "d" to give "abcadc". *Could someone please advise how this could be
> achieved ?
>
> Thanks,
>
> Patrick

Try these:

$s = 'abcabcabcabc'
$find = 'b'
$replace = '_'

# last instance
$s -replace "^(.*)($find)(.*)$", "`$1$replace`$3"

# first instance
$s -replace "^([^$find]*)($find)(.*)$", "`$1$replace`$3"

--
Robert

Hello Patrick,

> Sorry - also should have stated that just the first instance of a
> particular character should be replaced.
>
> On Jan 8, 11:23 am, Patrick <prynh...@newsgroup> wrote:
>

>> Hi,
>>
>> I'm wanting to Reverse find and replace a particular character in a
>> Powershell string. e.g. reverse find "b" in "abcabc" and replace
>> with "d" to give "abcadc". Could someone please advise how this
>> could be achieved ?
>>
>> Thanks,
>>
>> Patrick
>>

In your example it's the last instance of the character that is being replaced.

Is that what you want?

You can do this like this:
$test = "abcabc"
$newstring = $test.Substring(0,$test.lastindexof("b")) + "d" + $test.substring($test.lastindexof("b")+1
,$test.length - $test.lastindexof("b")-1)

Or like this one-liner
("abcabc").Substring(0,("abcabc").lastindexof("b")) + "d" + ("abcabc").substring(("abcabc").lastindexof("b")+1
,("abcabc").length - ("abcabc").lastindexof("b")-1)

Someone smarter than me will show up with a regex method, which I won't understand


Karl
http://unlockpowershell.wordpress.com/

Thanks Robert. I see that $1 and $3 are the regexp matches either side
of $find. I was able to get correct output for the values provided
below. However, the following example does not appear to work with
this code:

$s = '123123123123'
$find = '2'
$replace = '9'

$s -replace "^(.*)($find)(.*)$", "`$1$replace`$3"
$s -replace "^([^$find]*)($find)(.*)$", "`$1$replace`$3"

I incorrectly get "$193, and $193123123123" respectively. I presume
that "2" is a special case (i.e. $2)

Regards,

Patrick


On Jan 8, 11:58*am, "Robert Robelo" <Ki...@newsgroup>
wrote:

> Try these:
>
> $s = 'abcabcabcabc'
> $find = 'b'
> $replace = '_'
>
> # last instance
> $s -replace "^(.*)($find)(.*)$", "`$1$replace`$3"
>
> # first instance
> $s -replace "^([^$find]*)($find)(.*)$", "`$1$replace`$3"
>
> --
> Robert

Ah yes - I was meaning the first character in the reverse find, i.e.
the last character :-)

Actually, any combination of a string involving digits seems to break:

$s = '789789789a9'
$find = 'a'
$replace = '9'

etc

On Jan 8, 12:09*pm, Patrick <prynh...@newsgroup> wrote:

> Thanks Robert. I see that $1 and $3 are the regexp matches either side
> of $find. *I was able to get correct output for the values provided
> below. *However, the following example does not appear to work with
> this code:
>
> $s = '123123123123'
> $find = '2'
> $replace = '9'
>
> $s -replace "^(.*)($find)(.*)$", "`$1$replace`$3"
> $s -replace "^([^$find]*)($find)(.*)$", "`$1$replace`$3"
>
> I incorrectly get "$193, and $193123123123" respectively. *I presume
> that "2" is a special case (i.e. $2)
>
> Regards,
>
> Patrick
>
> On Jan 8, 11:58*am, "Robert Robelo" <Ki...@newsgroup>
> wrote:
>

> > Try these:

>

> > $s = 'abcabcabcabc'
> > $find = 'b'
> > $replace = '_'

>

> > # last instance
> > $s -replace "^(.*)($find)(.*)$", "`$1$replace`$3"

>

> > # first instance
> > $s -replace "^([^$find]*)($find)(.*)$", "`$1$replace`$3"

>

> > --
> > Robert

I think you'll need to use a real regex for this:
$string = "abcabc"
$r = new-object System.Text.RegularExpressions.Regex
("b",[System.Text.RegularExpressions.RegexOptions]::RightToLeft)
$r.replace($string,"d",1)


"Patrick" wrote:

> Hi,
>
> I'm wanting to Reverse find and replace a particular character in a
> Powershell string. e.g. reverse find "b" in "abcabc" and replace with
> "d" to give "abcadc". Could someone please advise how this could be
> achieved ?
>
> Thanks,
>
> Patrick
> .
>

Right, to fix this Just isolate the variable names with braces:

$s1 = 'abcabcabcabc'
$find = 'b'; $replace = 'd'
$s1 -replace "^([^$find]*)($find)(.*)$", "`${1}${replace}`${3}"
$s1 -replace "^(.*)($find)(.*)$", "`${1}${replace}`${3}"

$s2 = '123123123123'
$find = '2'; $replace = '9'
$s2 -replace "^([^$find]*)($find)(.*)$", "`${1}${replace}`${3}"
$s2 -replace "^(.*)($find)(.*)$", "`${1}${replace}`${3}"

$s3 = '789a789a789a9'
$find = 'a'; $replace = '9'
$s3 -replace "^([^$find]*)($find)(.*)$", "`${1}${replace}`${3}"
$s3 -replace "^(.*)($find)(.*)$", "`${1}${replace}`${3}"

--
Robert