Powershell String Comparison and List Filtering

Home , Glob (programming)

PowerShell String Comparison and List Filtering This reference brings together relevant operators plus key language constructs to compare strings in either scalar or array context. (Available online at Simple-Talk.com at http://bit.ly/l7g6Fj.)

Operator 1 String Array LEGEND Equality Boolean Sub–list –eq "abc" –eq "def" False "dog","dogwood","cat","Dog" –eq "dog" ("dog","Dog") Equality –ceq "abc" –eq "Abc" True "dog","dogwood","cat","Dog" –ceq "Cat" ( ) Wilcard "abc" –ceq "Abc" False @() –eq "dog" ( ) –ieq "Abc" –ceq "Abc" True Regex

Equality/negated Boolean Sub–list ne – "abc" –ne "def" True "dog","cat","Dog" –ne "dog" ("cat") –cne "abc" –ne "Abc" False "dog","cat","Dog" –cne "dog" ("cat","Dog") 1 Each operator has three variations: "abc" –cne "Abc" True @() –ne "dog" ( ) > default (e.g. –eq), –ine "Abc" –cne "Abc" False > case-sensitive (e.g. –ceq), and > case-insensitive e.g. –ieq). Wildcard (glob) 2 Boolean Sub–list Note that the default in each case is like – "dog" –like "dog*" True "f42e","12a8","a000","948f" –like "[a-f]*" ("f42e","a000") case–insensitive so –eq is exactly –clike "kookaburra" –like "k??k*burra" True "f42e","12a8","a000","948f" – like "[a-f]" ( ) equivalent to –ieq; the latter is –ilike "kookaburra" –like "k?k*burra" False "dove","wren","Warbler" –like "w*" ("wren","Warbler") provided if you have a preference for "kookaburra" –clike "K*" False "dove","wren","Warbler" –clike "w*" ("wren") being explicit. See about_Comparison_Operators. "kookaburra" –clike "[kK]*" True

2 Wildcards include: Wildcard/negated 2 Boolean Sub–list –notlike > asterisk (*) for any number of "coelacanth" –notlike "cat" True "dove","wren","Warbler" –notlike "w*" ("dove") chars; cnotlike – "dog" –notlike "D?g" False "dove","wren","Warbler" –cnotlike "w*" ("dove","Warbler") > question mark (?) for any single –inotlike "dog" –cnotlike "D?g" True "dove","wren","Warbler" –notlike "*" ( ) char;

> brackets ([ ]) for single, enumerated Regular expression 3 Boolean 4 Sub–list –match char or char range. "archaeopteryx" –match "arch.*" True "nutria","beaver","muskrat" –match "[mn]u.*" ("nutria","muskrat") Must match input in its entirety. –cmatch "archaeopteryx" –match ".*(ae|ea).*" True "a4.001","b3.902","c3.4he" –match "\.[0-9]{2,}" ("a4.001","b3.902") See about_Wildcards. "archaeopteryx" –match "ae|ea" True "notebook","book","bookend" –match "book$" ("notebook","book") –imatch 3 Regular expressions provide a "notebook","book","bookend" –match "^book$" ("book") powerful but complex matching Regex/negated 3 Boolean 4 Sub–list construct; the PowerShell reference notmatch (about_Regular_Expressions) – "bird" -notmatch "Bird.*" False "dove","wren","Warbler" -notmatch "w.*" ("dove") –cnotmatch documents only a portion of it; "bird" -cnotmatch "Bird.*" True "dove","wren","Warbler" -cnotmatch "w.*" ("dove","Warbler") –inotmatch PowerShell actually supports the full Membership .contains() Boolean Not Available .NET implementation—see Regular Expression Language Elements . contains() "archaeopteryx".contains("aeo") True "archaeopteryx".contains("aeiou") False 4 Populates $Matches where: > $Matches[0] contains entire match Membership Boolean 5 Boolean > $Matches [n] contains nth match –contains "dog" –contains "Dog" True "dog","dogwood" –contains "Dog" True 5 –contains technically only operates –ccontains "dog" –ccontains "Dog" False "dog","dogwood" –ccontains "Dog" False on a list; with a scalar it is equivalent –icontains "dog" –contains "d" False "dog","dogwood","catfish" –ccontains "cat" False to –eq.

Membership/negated Boolean 5 Boolean 6 The switch statement implicitly uses notcontains –eq in selecting a match; specifying – "dog" notcontains "Dog" False "dog","dogwood" notcontains "Dog" False –cnotcontains – – –CaseSensitive modifies this to –ceq. "dog" –cnotcontains "Dog" True "dog","dogwood" –cnotcontains "Dog" True The –Wildcard and –Regex –inotcontains parameters may be used to effect Switch command 6 switch ( ) Arbitrary switch ( ) Arbitrary (or { { # iterates through the list –like or –match, respectively. This syntax applies {} (or no {} no return {} return {} value) Similarly adding –CaseSensitive to all variants below. . . . value) . . . modifies these to –clike or –cmatch. } }

Switch syntax even allows specifying Branch/equality Switch ("maybe") { Null Switch ("dog","bird","lizard") { dog : housepet your own arbitrary operator or more Switch [ –Exact ] "yes" {10} { "dog","cat" –contains $_ } { "$_ : housepet" } bird : not sure complex Boolean expression: instead [ –CaseSensitive ] "no" {20} Default { "$_ : not sure" } of specifying a choice as a simple } } lizard : not sure value (string, number, or variable) Branch/wildcard 2 Switch –wildcard ("a13") { 10 Switch –wildcard –case ("dog","bird","Dog") { dog : not sure use a code block to specify an Switch –Wildcard "a??" {10} "D*" { "$_ : housepet" } bird : housepet expression, where the standard $_ "b??" {20} "b??d" { "$_ : housepet" } automatic variable references the [ –CaseSensitive ] default {$null} Default { "$_ : not sure" } Dog : housepet } } input value. See about_Switch. Branch/regex 3 Switch –regex ("sR9X2T") { 4 20 switch –regex ("dog", "cat", "catfish", "catbird") { dog : Null Switch Regex "^[a-l]" {10} "cat(?!fish)" { "$_ : land" } cat : land 7 This deliberate error shows that – "^[m-y]" {20} "seal|whale|dolphin|catfish" { "$_ : sea" } catfish : sea switch evaluates every expression [ –CaseSensitive ] "^[z]" {99} "owl|eagle|osprey|catbird" { "$_ : air" } unless you use break statements! default {$null} default { ("$_ : " + $null) } catbird : land } } catbird : air 7 8 Select–String examples use a custom

ss alias for brevity. Select–String string Sub list – This syntax applies 9 This might look like a wildcard, but it to all variants below. is a regex! As a wildcard, it would Select–String/equality "dog" | ss –simple "dog" "dog" "dog","Dog" | ss –simple "dog" ("dog","Dog") have returned ("ab3","abcd") only. ss 8 –SimpleMatch "dog" | ss –simple "do" "dog" "dog","Dog","dogbone" | ss –case –simple "dog" ("dog","dogbone") Other References: [ –CaseSensitive ] about_Operators Not Available Not Available Conditional Operators Select–String/wildcard Operator enumeration Select–String/regex "coelacanth" | ss "c..l.*th" "coelacanth" "a1","a2","ab3","AB3" | ss "ab.*" ("ab3","AB3") Mastering PowerShell, chapter 7 ss 8 [ –CaseSensitive ] "coelacanth" | ss "c.*" "coelacanth" "a1","a2","ab3","AB3" | ss –case "ab.*" ("ab3")

"dog" | ss simple -NotMatch "dog" "dog","Cat","catfish" | ss not "Cat.*h" 2011.06.08 ● Version 1.0.1 Select–String/negated – Null – ("dog","Cat") ss 8 –NotMatch "dog" | ss –simple -NotMatch "cat" "dog" "dog","Cat","catfish" | ss –simple -not -case "Cat" ("dog","catfish") Download the latest version from [–SimpleMatch ] "dog" | ss –not "" "dog","dogbone" | ss –not "dog" Null Simple-Talk http://bit.ly/l7g6Fj

[ –CaseSensitive ]