I have a string "1111222233334444" with numbers, how to make an array out of it,
"1111", "2222", "3333", "4444".
i want a 4 character instance to be instantiated, how is it implemented in powershell?
Simple loop would be enough:
$s = '1111222233334444'
$i = 0; while ($i -lt ($s.Length-3)/4) { $s.Substring($i*4, 4); $i++; }
(Length-3)/4 is for unaligned blocks of 4. Example: If string is 1111222 it gives (7-3)/4=1 full items.
In addition to comment by Olaf, another way is to use Regex. But, instead of using capturing groups and filtering:
$s -split "(....)" -ne ""
I would use:
[Regex]::Matches($s, "\d{4}").Value
Which seems more natural and readable.
Related
It seems so simple. I need a cmdlet to take a two word string, and truncate the first word to just the first character and truncate the second word to 11 characters, and eliminate the space between them. So "Arnold Schwarzenegger" would output to a variable as "ASchwarzeneg"
I literally have no code. My thinking was to
$vars=$var1.split(" ")
$var1=""
foreach $var in $vars{
????
}
I'm totally at a loss as to how to do this, and it seems so simple too. Any help would be appreciated.
Here is one way to do it using the index operator [ ] in combination with the range operator ..:
$vars = 'Arnold Schwarzenegger', 'Short Name'
$names = foreach($var in $vars) {
$i = $var.IndexOf(' ') + 1 # index after the space
$z = $i + 10 # to slice from `$i` until `$i + 10` (11 chars)
$var[0] + [string]::new($var[$i..$z])
}
$names
I have an array and when I try to append a string to it the array converts to a single string.
I have the following data in an array:
$Str
451 CAR,-3 ,7 ,10 ,0 ,3 , 20 ,Over: 41
452 DEN «,40.5,0,7,0,14, 21 , Cover: 4
And I want to append the week of the game in this instance like this:
$Str = "Week"+$Week+$Str
I get a single string:
Week16101,NYG,42.5 ,3 ,10 ,3 ,3 , 19 ,Over 43 102,PHI,- 1,14,7,0,3, 24 , Cover 4 103,
Of course I'd like the append to occur on each row.
Instead of a for loop you could also use the Foreach-Object cmdlet (if you prefer using the pipeline):
$str = "apple","lemon","toast"
$str = $str | ForEach-Object {"Week$_"}
Output:
Weekapple
Weeklemon
Weektoast
Another option for PowerShell v4+
$str = $str.ForEach({ "Week" + $Week + $_ })
Something like this will work for prepending/appending text to each line in an array.
Set array $str:
$str = "apple","lemon","toast"
$str
apple
lemon
toast
Prepend text now:
for ($i=0; $i -lt $Str.Count; $i++) {
$str[$i] = "yogurt" + $str[$i]
}
$str
yogurtapple
yogurtlemon
yogurttoast
This works for prepending/appending static text to each line. If you need to insert a changing variable this may require some modification. I would need to see more code in order to recommend something.
Another solution, which is fast and concise, albeit a bit obscure.
It uses the regex-based -replace operator with regex '^' which matches the position at the start of each input string and therefore effectively prepends the replacement string to each array element (analogously, you could use '$' to append):
# Sample array.
$array = 'one', 'two', 'three'
# Prepend 'Week ' to each element and create a new array.
$newArray = $array -replace '^', 'Week '
$newArray then contains 'Week one', 'Week two', 'Week three'
To show an equivalent foreach solution, which is syntactically simpler than a for solution (but, like the -replace solution above, invariably creates a new array):
[array] $newArray = foreach ($element in $array) { 'Week ' + $element }
Note: The [array] cast is needed to ensure that the result is always an array; without it, if the input array happens to contain just one element, PowerShell would assign the modified copy of that element as-is to $newArray; that is, no array would be created.
As for what you tried:
"Week"+$Week+$Str
Because the LHS of the + operation is a single string, simple string concatenation takes place, which means that the array in $str is stringified, which by default concatenates the (stringified) elements with a space character.
A simplified example:
PS> 'foo: ' + ('bar', 'baz')
foo: bar baz
Solution options:
For per-element operations on an array, you need one of the following:
A loop statement, such as foreach or for.
Michael Timmerman's answer shows a for solution, which - while syntactically more cumbersome than a foreach solution - has the advantage of updating the array in place.
A pipeline that performs per-element processing via the ForEach-Object cmdlet, as shown in Martin Brandl's answer.
An expression that uses the .ForEach() array method, as shown in Patrick Meinecke's answer.
An expression that uses an operator that accepts arrays as its LHS operand and then operates on each element, such as the -replace solution shown above.
Tradeoffs:
Speed:
An operator-based solution is fastest, followed by for / foreach, .ForEach(), and, the slowest option, ForEach-Object.
Memory use:
Only the for option with indexed access to the array elements allows in-place updating of the input array; all other methods create a new array.[1]
[1] Strictly speaking, what .ForEach() returns isn't a .NET array, but a collection of type [System.Collections.ObjectModel.Collection[psobject]], but the difference usually doesn't matter in PowerShell.
I have been reading about arrays in powershell and hash tables, I know the basic workings of an array and how to use foreach loop to get items within the array, my challange here is slightly different. I would like to pay what I call a multi dimension array to a script, and process the items contained within the array.
What is my setup.
$x = (1,"Server1",3,1),(4,"Server2",6,2),(3,"Server3",4,3)
$k = 'serverid','servername','locationid','appid' # key names correspond to data positions in each array in $x
$h = #{}
For($i=0;$i -lt $x[0].length; $i++){
$x |
ForEach-Object{
[array]$h.($k[$i]) += [string]$_[$i]
}
}
What am i trying to achieve ?
I am trying to achieve the structure of a database table within powershell. So literally treating each array item as a row.
So for example
(1,"Server1",3,1),(4,"Server2",6,2),(3,"Server3",4,3)
could be thought of as a table like below
enter image description here
I then want to loop for each item in the array to get the values, similar to the below example
[0].serverid = 1, [0].servername = server1, [0].locationid = 3, [0].applicationID = 1
[1].serverid = 4, [1].servername = server2, [1].locationid = 6, [1].applicationID = 2
what have I done ?
$x = (1,"Server1",3,1),(4,"Server2",6,2),(3,"Server3",4,3)
$k = 'serverid','servername','locationid','appid' # key names correspond to data positions in each array in $x
$h = #{}
For($i=0;$i -lt $x[0].length; $i++){
$x |
ForEach-Object{
[array]$h.($k[$i]) += [string]$_[$i]
}
}
$x
for ($i = 0; $i -lt $x.Count; $i++)
{
$myserverid = $x[$i][0]
$myservername = $x[$i][1]
$mylocationid = $x[$i][2]
$myappid = $x[$i][3]
write-host $myserverid
}
The Issues
If I set the following $x = (1,"Server1",3,1), then the loop is somewhat incorrect which is why I think the approach is wrong (more than one item works i.e $x = (1,"Server1",3,1),(4,"Server2",6,2),(3,"Server3",4,3)). The loop only works if you have more than one item within the array, hence why I want to re-examine the way the loop works.
Thanks in advance
Your approach relies on a nested (jagged) array: That is, you have an array of subarrays, each of which represents the tuple of values you want to assign to properties.
If there's only one subarray, you must create the nested array explicitly, using the unary form of , the array constructor operator:
# Construct a 1-element array that contains the 4-element subarray.
$x = , (1,"Server1",3,1)
With two or more, subarrays, you implicitly get a nested array:
# Construct a 3-element array, each element of which contains a 4-element subarray.
$x = (1,"Server1",3,1), (4,"Server2",6,2), (3,"Server3",4,3)
Note that in PSv5+ you could use a custom class to solve your problem:
class Custom {
[int] $serverid; [string] $servername;[int] $locationid; [int] $appid
Custom($propValueArray) {
$this.serverid = $propValueArray[0]; $this.servername = $propValueArray[1]; $this.locationid = $propValueArray[2]; $this.appid = $propValueArray[3]
}
}
# Use an array cast to construct [Custom] instances.
# Note the need for (...) around the array, because casts have high
# precedence in PowerShell.
[Custom[]] ((1,"Server1",3,1), (4,"Server2",6,2), (3,"Server3",4,3))
This would allow for processing such as:
# Construct all objects
$objects = [Custom[]] ((1,"Server1",3,1), (4,"Server2",6,2), (3,"Server3",4,3))
# Process each object.
foreach ($object in $objects) {
($myserverid = $object.serverid) # assign a property to a var; `()` also outputs
# ...
}
I have a filename and I wish to extract two portions of this and add into variables so I can compare if they are the same.
$name = FILE_20161012_054146_Import_5785_1234.xml
So I want...
$a = 5785
$b = 1234
if ($a = $b) {
# do stuff
}
I have tried to extract the 36th up to the 39th character
Select-Object {$_.Name[35,36,37,38]}
but I get
{5, 7, 8, 5}
Have considered splitting but looks messy.
There are several ways to do this. One of the most straightforward, as PetSerAl suggested is with .Substring():
$_.name.Substring(35,4)
Another way is with square braces, as you tried to do, but it gives you an array of [char] objects, not a string. You can use -join and you can use a range to make that easier:
$_.name[35..38] -join ''
For what you're doing, matching a pattern, you could also use a regular expression with capturing groups:
if ($_.name -match '_(\d{4})_(\d{4})\.xml$') {
if ($Matches[1] -eq $Matches[2]) {
# ...
}
}
This way can be very powerful, but you need to learn more about regex if you're not familiar. In this case it's looking for an underscore _ followed by 4 digits (0-9), followed by an underscore, and four more digits, followed by .xml at the end of the string. The digits are wrapped in parentheses so they are captured separately to be referenced later (in $Matches).
Yet another approach: returns 1234 substring four times.
$FileName = "FILE_20161012_054146_Import_5785_1234.xml"
# $FileName
$FileName.Substring(33,4) # Substring method (zero-based)
-join $FileName[33..36] # indexing from beginning (zero-based)
-join $FileName[-8..-5] # reverse indexing:
# e.g. $FileName[-1] returns the last character
$FileArr = $FileName.Split("_.") # Split (depends only on filename "pattern template")
$FileArr[$FileArr.Count -2] # does not depend on lengths of tokens
Say I have a below existing code.
my $names = &loadNames(); # No duplicate names
my $u1;
my $u2;
for (my $i = 0 ; $i < #$names; $i++) {
if($$names[$i] eq $input_one){
$u1 = loadUserFromOneSource($input_one);
}
if($$names[$i] eq $input_two){
$u2 = loadUserFromSecondSource($input_two);
}
}
Now if I refactored the above code like below
my $names = &loadNames(); #Returns array reference
my $u1 = grep $_ eq $input_one, #$names;
my $u2 = grep $_ eq $input_two, #$names;
$u1 = loadUserFromOneSource($u1) if $u1;
$u2 = loadUserFromSecondSource($u2) if $u2;
Did I really improve anything? Or I made it even worse because I am running two greps on same list.
Clarification:
The sole purpose of asking the question is to understand the performance trade offs between grep and loop. In both cases I'm extracting out two names. But in first example in a single iteration. And second example it's done in two greps. Did I doubled the cost in second approach? Or grep is efficient enough to win over the single iteration? I will try benchmarking when I will back in work.
In general, inbuilts like grep will be faster than manual loops.
However in your particular case there are a couple of gotchas:
The two code examples don't do the same thing. In the first case, the functions may be called multiple times, if the condition is matched more than once. In the second example the functions can be called at most once.
Using an expression like /$foo/ inside a loop or grep, map, etc will result in the regex being compiled each time.
Since you did not a anchor the regex, partial matches may also occur.
I would use grep but change the condition to
my $u1 = grep $_ eq $input_one, #$names;
For one, you're no longer testing for equality in your new code, but for regex inclusion. That could've introduced a bug.
Another solution is just to translate the arrays to a hash so that you can test if a name exists. I.e. perldoc How can I tell whether a certain element is contained in a list or array?
my $names = loadNames(); #Returns array reference
my %hasName = map {$_ => 1} #$names;
my $u1 = $hasName{$input_one} ? loadUserFromOneSource($input_one) : '';
my $u2 = $hasName{$input_two} ? loadUserFromSecondSource($input_two) : '';