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Heisenberg_1452's avatar
Heisenberg_1452
Historic F5 Account
Feb 28, 2014

string equal/compare/match vs. switch

All,

Very new to iRules. Wondering if anyone knows what is more efficient:

switch $foo {
        "bar" {...}
        "bar1" {...}
        "bar2" {...}
        default {...}
}

vs.

if {string equal $foo "bar"} {...}
elseif {string equal $foo "bar1" {...}
elseif {string equal $foo "bar2" {...}
else {...}

vs.

if {string compare $foo "bar"} {...}
elseif {string compare $foo "bar1" {...}
elseif {string compare $foo "bar2" {...}
else {...}

vs.

if {string match $foo "bar"} {...}  Seems like this would not be the most optimal
elseif {string match $foo "bar1" {...}
elseif {string match $foo "bar2" {...}
else {...}

or simply,

if {$foo equals "bar"} {...}
elseif {$foo equals "bar1" {...}
elseif {$foo equals "bar2" {...}
else {...}

Cheers!

application delivery
devops
iRules

3 Replies

  • Kevin_Stewart's avatar
    Kevin_Stewart
    Icon for Employee rankEmployee
    Feb 28, 2014

    Here's a fun way to test the efficiency of each command. Create a text file in the shell:

    !/usr/bin/tclsh

proc random { } {
    set mylist [list "bar" "bar1" "bar2" "blah"]
    set index [expr int(rand() * 4)]
    return [lindex $mylist $index]
}

set foo [random]

set timer [time {
    switch $foo {
        "bar" { set test "bar" }
        "bar1" { set test "bar1" }
        "bar2" { set test "bar2" }
        default {set test "def" }
    }
} 1000000]

puts "switch: $timer"


set timer [time {
    if { [string equal $foo "bar"] } {
        set test "bar"
    } elseif { [string equal $foo "bar1"] } {
        set test "bar1"
    } elseif { [string equal $foo "bar2"] } {
        set test "bar2"
    } else {
        set test "def"
    }
} 1000000]

puts "str equal: $timer"


set timer [time {
    if { [string compare $foo "bar"] } {
        set test "bar"
    } elseif { [string compare $foo "bar1"] } {
        set test "bar1"
    } elseif { [string compare $foo "bar2"] } {
        set test "bar2"
    } else {
        set test "def"
    }
} 1000000]

puts "compare: $timer"


set time [time {
    if { [string match $foo "bar"] } {
        set test "bar"
    } elseif { [string match $foo "bar1"] } {
        set test "bar1"
    } elseif { [string match $foo "bar2"] } {
        set test "bar2"
    } else {
        set test "def"
    }
} 1000000]

puts "match: $timer"


set timer [time {
    if { $foo == "bar" } {
        set test "bar"
    } elseif { $foo == "bar1" } {
        set test "bar1"
    } elseif { $foo == "bar2" } {
        set test "bar2"
    } else {
        set test "def"
    }
} 1000000]

puts "equals: $timer"

    Then chmod the file and run in it. It may be an anomaly, but I almost consistently get lower times for match and compare, followed closely by switch.