Use powershell ForEach-Object to match and replace string with regex

Question

I use the below pipeline to read a file and replace a line in it and save it to another file, but found that the string in target file is not replaced, it's still the old one.

original line is : name-1a2b3c4d

new line should be: name-6a5e4r3h

(Get-Content "test1.xml") | ForEach-Object {$_ -replace '^name-.*$', "name-6a5e4r3h"} | Set-Content "test2.xml"

Anything missing there?

Have you tried using XML parsing? Don't know if that's applicable, but if you know in what element of the XML you need to replace your string, that may be "cleaner" — Poorkenny
– Poorkenny, Commented Mar 8, 2013 at 10:15

mjolinor · Accepted Answer · 2013-03-08 11:32:06Z

15

One thing you're missing is that the -replace operator works just fine on an array, which means you don't need that foreach-object loop at all:

(Get-Content "test1.xml") -replace '^name-.*$', 'name-6a5e4r3h' | Set-Content test2.xml

answered Mar 8, 2013 at 11:32

mjolinor

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E.V.I.L. · Accepted Answer · 2013-03-08 09:19:27Z

2

You're not changing the $_ variable.

You might try:

$lines = Get-Content $file
$len = $lines.count
for($i=0;$i-lt$len;$i++){
    $lines[$i] = $lines[$i] -replace $bad, $good
}
$lines > $outfile

answered Mar 8, 2013 at 9:19

E.V.I.L.

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3 Comments

user1201530 Over a year ago

Thanks. But doesn't -replace and pipeline results in string replacement? If I want to use original way how to change $_?

user1201530 Over a year ago

I also tried not using regex but fixed string and it works. Such as below (Get-Content "test1.xml") | ForEach-Object {$_ -replace 'name-1a2b3c4d', "name-6a5e4r3h"} | Set-Content "test2.xml"

CB. Over a year ago

@user1201530 The first parameter for -replace is always a regex. When you use 'name-1a2b3c4d' you are omiting the ^ (at the start of the line) and the $ (at the end of the line). Maybe in your original file name-1a2b3c4d doesn't match ^.

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