I have a string
$string = "Active Directory"
and I want to make another string
Active_Directory_Results.txt
I would like to just do
$otherstring = "$string.Replace(" ","_")_Results.txt"
but that doesn't work out. What would be the correct way to pull this off?
You should not use invoke-expression for that. The original answer is good:
$otherstring = $string.Replace(" ","_") + "_Results.txt"
But really, you can just use a $(subexpression):
$otherstring = "$($string.Replace(" ","_"))_Results.txt"
The $() tells PowerShell to evaluate that BEFORE defining the string.
As an alternative, you can also use string formatting:
$otherstring = "{0}_Results.txt" -f $string.Replace(" ","_")
Proving once again that with scripting languages, there's always more than one right way ...
I'm not on my windows machine right now, but how does $otherstring = $string.Replace(" ","_") + "_Results.txt" work?
Check the invoke-expression command. It allows you to execute code in a string.
Like:
PS> $command = '$otherstring = $string.Replace(" ","_") + "_Results.txt"'
PS> Invoke-Expression $command
Related
My string is:
$dst = "Folder_1\SubFolder_2\3\4\5"
My goal is to have:
$dst_OK = "SubFolder_2\3\4\5"
I tried use split function like this:
$dst_OK = $dst.split("\")[0]
but the result is Folder_1 only.
You could use the following regex to remove the left side of the string:
$dst_OK = $dst -replace '^.*?\\'
However, since it looks like you are dealing with a path, you may consider to using builtin function within the System.IO.Path namespace.
You can do it with this snippet:
$first, $rest = "Folder_1\SubFolder_2\3\4\5" -split '\\'
$rest = $rest -join '\'
Other solution :
($dst -split "\\", 2)[1]
Solution 2
$dst.Substring($dst.IndexOf('\')+1)
I want to get "localhost" (or whatever text) inside this string:
XML-Execute-Result: <host>localhost</host>
I want a general method, like a way to reuse an expression value
(like with sed in linux)
sed 's/*[0-9]$/\$&/'
Thank you very much for any reply
$text = "XML-Execute-Result: <host>localhost</host>"
if ($text -match "\<host\>(?<host>.*?)\</host\>")
{
$myhost = $matches.host
}
PS> if ($text -match "<host>(.*?)</host>") {$matches[1]}
localhost
My code:
RETVAL1=-1
if [ $RETVAL1 -le 0 ] ; then
RETVAL1=$RETVAL1+1
print "RETVAL1: $RETVAL1"
fi
And it prints RETVAL1: -1+1
Any idea how to repair it please?
To perform arithmetic operation, use the let command: let RETVAL1=RETVAL1+1
Moreover, enclosing the expression between $(( and )) would also interpret it as an arithmetic operation. echo $((RETVAL+1))
Use the let command. This command performs arithmic operations. The + operator performs string addition.
Use it like this:
let RETVAL1=RETVAL1+1
You can also use the expr command for more general expressions.
One way:
((RETVAL1=RETVAL1+1))
Shell variables don't work like variables in most programming languages. If you want to add 1 to an integer stored in a variable, you'll need an arithmetic expression. I'm no ksh wizard, but the usual Bourne-derived-shell arithmetic expression syntax is:
RETVAL1=$((RETVAL1 + 1))
or
((RETVAL1 = RETVAL1 + 1))
Whatever you want to call it, I'm trying to figure out a way to take the contents of an existing string and evaluate them as a double-quoted string. For example, if I create the following strings:
$string = 'The $animal says "meow"'
$animal = 'cat'
Then, Write-Host $string would produce The $animal says "meow". How can I have $string re-evaluated, to output (or assign to a new variable) The cat says "meow"?
How annoying...the limitations on comments makes it very difficult (if it's even possible) to include code with backticks. Here's an unmangled version of the last two comments I made in response to zdan below:
----------
Actually, after thinking about it, I realized that it's not reasonable to expect The $animal says "meow" to be interpolated without escaping the double quotes, because if it were a double-quoted string to begin with, the evaluation would break if the double quotes weren't escaped. So I suppose the answer would be that it's a two step process:
$newstring = $string -replace '"', '`"'
iex "`"$string`""
One final comment for posterity: I experimented with ways of getting that all on one line, and almost anything that you'd think works breaks once you feed it to iex, but this one works:
iex ('"' + ($string -replace '"', '`"') + '"')
Probably the simplest way is
$ExecutionContext.InvokeCommand.ExpandString($var)
You could use Invoke-Expression to have your string reparsed - something like this:
$string = 'The $animal says `"meow`"'
$animal = 'cat'
Invoke-Expression "Write-Host `"$string`""
Note how you have to escape the double quotes (using a backtick) inside your string to avoid confusing the parser. This includes any double quotes in the original string.
Also note that the first command should be a command, if you need to use the resulting string, just pipe the output using write-output and assign that to a variable you can use later:
$result = Invoke-Expression "write-output `"$string`""
As noted in your comments, if you can't modify the creation of the string to escape the double quotes, you will have to do this yourself. You can also wrap this in a function to make it look a little clearer:
function Invoke-String($str) {
$escapedString = $str -replace '"', '`"'
Invoke-Expression "Write-Output `"$escapedString`""
}
So now it would look like this:
# ~> $string = 'The $animal says "meow"'
# ~> $animal = 'cat'
# ~> Invoke-String $string
The cat says "meow"
You can use the -f operator. This is the same as calling [String]::Format as far as I can determine.
PS C:\> $string = 'The {0} says "meow"'
PS C:\> $animal = 'cat'
PS C:\> Write-Host ($string -f $animal)
The cat says "meow"
This avoids the pitfalls associated with quote stripping (faced by ExpandString and Invoke-Expression) and arbitrary code execution (faced by Invoke-Expression).
I've tested that it is supported in version 2 and up; I am not completely certain it's present in PowerShell 1.
Edit: It turns out that string interpolation behavior is different depending on the version of PowerShell. I wrote a better version of the xs (Expand-String) cmdlet with unit tests to deal with that behavior over here on GitHub.
This solution is inspired by this answer about shortening calls to object methods while retaining context. You can put the following function in a utility module somewhere, and it still works when you call it from another module:
function xs
{
[CmdletBinding()]
param
(
# The string containing variables that will be expanded.
[parameter(ValueFromPipeline=$true,
Position=0,
Mandatory=$true)]
[string]
$String
)
process
{
$escapedString = $String -replace '"','`"'
$code = "`$ExecutionContext.InvokeCommand.ExpandString(`"$escapedString`")"
[scriptblock]::create($code)
}
}
Then when you need to do delayed variable expansion, you use it like this:
$MyString = 'The $animal says $sound.'
...
$animal = 'fox'
...
$sound = 'simper'
&($MyString | xs)
&(xs $MyString)
PS> The fox says simper.
PS> The fox says simper.
$animal and $sound aren't expanded until the last two lines. This allows you to set up a $MyString up front and delay expansion until the variables have the values you want.
Invoke-Expression "`"$string`""
In my perl script I want to have both versions of $config directory:
my $config='$home/client/config';
and
my $config_resolved="$home/client/config";
But I want to get $config_resolved from $config, i.e. something like this:
my $config_resolved=resolve_vars($config);
How can I do such thing in perl?
From the Perl FAQ (which every Perl programmer should read at least once):
How can I expand variables in text strings?
(contributed by brian d foy)
If you can avoid it, don't, or if you can
use a templating system, such as Text::Template or Template Toolkit,
do that instead. You might even be able to get the job done with
sprintf or printf:
my $string = sprintf 'Say hello to %s and %s', $foo, $bar;
However, for the one-off simple case where I don't want to pull out a
full templating system, I'll use a string that has two Perl scalar
variables in it. In this example, I want to expand $foo and $bar to
their variable's values:
my $foo = 'Fred';
my $bar = 'Barney';
$string = 'Say hello to $foo and $bar';
One way I can do this involves the substitution operator and a double /e flag. The
first /e evaluates $1 on the replacement side and turns it into $foo. The
second /e starts with $foo and replaces it with its value. $foo,
then, turns into 'Fred', and that's finally what's left in the string:
$string =~ s/(\$\w+)/$1/eeg; # 'Say hello to Fred and Barney'
The /e will also silently ignore violations of strict, replacing undefined
variable names with the empty string. Since I'm using the /e flag
(twice even!), I have all of the same security problems I have with
eval in its string form. If there's something odd in $foo, perhaps
something like #{[ system "rm -rf /" ]}, then I could get myself in
trouble.
To get around the security problem, I could also pull the
values from a hash instead of evaluating variable names. Using a
single /e, I can check the hash to ensure the value exists, and if it
doesn't, I can replace the missing value with a marker, in this case
??? to signal that I missed something:
my $string = 'This has $foo and $bar';
my %Replacements = (
foo => 'Fred',
);
# $string =~ s/\$(\w+)/$Replacements{$1}/g;
$string =~ s/\$(\w+)/
exists $Replacements{$1} ? $Replacements{$1} : '???'
/eg;
print $string;
I use eval for this.
So, you must replace all scalars (their names) with their values.
$config = 'stringone';
$boo = '$config/any/string';
$boo =~ s/(\$\w+)/eval($1)/eg;
print $boo;
Because you are using my to declare it as private variable, you might as well use a /ee modifier. This can find variables declared to be in local scope:
$boo =~ s/(\$\w+)/$1/eeg;
This is most tidily and safely done by the double-eval modifier on s///.
In the program below, the first /e evaluates the string $1 to get $home, while the second evaluates $home to get the variable's value HOME.
use strict;
my $home = 'HOME';
my $config = '$home/client/config';
my $config_resolved = resolve_vars($config);
print $config_resolved, "\n";
sub resolve_vars {
(my $str = shift) =~ s/(\$\w+)/$1/eeg;
return $str;
}
output
HOME/client/config