BIG-IP zero-or-one finder

string index counts characters from 0: index 0 is the first character, end the last, and end-1 the one before it. An index below 0, or at the length or beyond, returns an empty string, not an error.

Counts

characters

First

0

Last

end

Nothing there

""

Example string index abcd end-1 returns c

string range takes a first and a last index, both counted from 0 and both included: string range $s 0 2 returns three characters. A first index below 0 is read as 0, and a last index past the end is read as end.

Counts

characters, both ends included

First

0

Last

end

Nothing there

""

Example string range abcdef 2 3 returns cd

Watch out Because the last index is included, the result has last minus first plus one characters. The first N characters are string range $s 0 N-1, not N.

string first and string last return the index where the text starts, counted from 0, or -1 when it is not there. The optional start index of string first (and last index of string last) uses the same numbering.

Counts

characters

First

0

Nothing there

-1

Example string first q xyz returns -1

Watch out In an if, 0 is false and every other number is true. So if [string first ...] skips the body when the text is at the very start (index 0) and runs it when the text is missing (-1). Test [string first ...] >= 0 instead.

string replace takes first and last indexes like string range; string wordstart and string wordend take an index and return one; string is with -failindex stores the index of the first character that failed. All count from 0, and the index arguments accept end.

Counts

characters

First

0

Last

end

Example string replace abcdef 1 2 XY returns aXYdef

lindex counts elements from 0: index 0 is the first element and end the last. A negative index, or one at the number of elements or beyond, returns an empty string.

Counts

list elements

First

0

Last

end

Nothing there

""

Example lindex {a b c} 0 returns a

lrange returns the elements from first to last, counted from 0 and both included: lrange $l 0 1 is the first two. A first index below 0 is read as 0, and a last index past the end as end.

Counts

list elements, both ends included

First

0

Last

end

Nothing there

""

Example lrange {a b c d e} 0 1 returns a b

lsearch returns the index of the first matching element, counted from 0, or -1 when nothing matches. -start takes an index in the same numbering.

Counts

list elements

First

0

Nothing there

-1

Example lsearch {a b c} z returns -1

Watch out The same trap as string first: a match at index 0 is false in an if, and no match (-1) is true. Compare the result with -1.

linsert, lreplace and lset take indexes counted from 0. linsert at 0 (or below) puts the new elements first, and at end (or past the end) appends them.

Counts

list elements

First

0

Last

end

Example linsert {a b c} 0 X returns X a b c

lsort -index sorts a list of lists by one element of each sublist, counted from 0: -index 1 sorts by the second element. end and end-N are allowed.

Counts

elements inside each sublist

First

0

Last

end

Example lsort -index 1 {{a 2} {b 1}} returns {b 1} {a 2}

split makes a list, and lindex counts it from 0. When the string starts with the separator, the first element is the empty text before it.

Counts

list elements after the split

First

0

Nothing there

""

Example lindex [split /api/v2/users /] 1 returns api

Watch out A path starts with a slash, so split /api/v2/users / gives four elements, the first one empty: the first segment, api, is element 1, not 0.

With -indices, regexp stores each match as a pair of indexes, the first and the last character, counted from 0 and both included. A group that took no part in the match gets -1 -1. -start takes an index in the same numbering.

Counts

characters

First

0

Nothing there

-1 -1

Example regexp -indices {(b+)} abbbc m; set m returns 1 3

These clock format fields start at 0: %w is the weekday with Sunday 0, %H the hour from 00 to 23, %M and %S from 00 to 59, and %U and %W the week of the year from 00 (in tclsh 8.4.6, 1 January 1970, a Thursday, is week 00 for both).

Counts

weekdays, hours, minutes, seconds, weeks

First

0 / 00

Example clock format 0 -format {%w %H %U %W} -gmt 1 returns 4 00 00 00

In binary scan, @ moves the cursor to an absolute byte position, and position 0 is the first byte. A position past the end leaves the cursor after the last byte.

Counts

bytes

First

@0

Example binary scan ABC @1a1 x; set x returns B

info level is 0 at the top (the global level) and 1 inside a proc called from there. uplevel and upvar take a relative level, where 1 (the caller) is the default, or an absolute one written with #: #0 is the global level.

Counts

levels of the call stack

First

#0

Example proc lv {} { info level }; lv returns 1

rand() returns a value between 0 and 1, never 1 itself, so int(rand()*N) is a whole number from 0 to N-1: exactly the lindex positions of a list with N elements.

Counts

list positions

First

0

Last

N-1

Example expr {int(rand()*3)} returns 0, 1, 2

substr starts at an index counted from 0: F5's page says the skip count is the index of the first character returned, where 0 is the first character. The terminator is either a length or a text to stop before.

Counts

characters

First

0

Example substr "abcdefghijklm" 2 4 returns cdef

F5's pages disagree F5's rule says a numeric terminator returns that many characters, so 0 would return nothing, yet the published example with 0 returns the rest of the string, and the API page marks that line as not working on 11.5.4 and 11.6.0.

findstr finds the search text, then skips a number of characters counted from the first character of the match: 0, the default, returns the match itself. To start right after the search text, skip its length.

Counts

characters from the match

First

0

Example findstr "aaa123456xxyz" "aaa" 3 "xyz" returns 123456x

Watch out substr counts its skip from the start of the string and findstr from the start of the match, although F5's substr page says the two use these arguments in the same way.

HTTP::header at returns the name of the header at a zero-based index, so 0 is the first header line. Asking for the value of a header that is not there returns an empty string.

Counts

header lines

First

0

Nothing there

""

Example HTTP::header value header_1 returns value_3

Watch out When a header appears more than once, HTTP::header value works on the last one, while SIP::header without an index returns the first. HTTP::header values returns them all.

The payload commands take a byte offset counted from 0: F5's HTTP::payload page says that to replace the whole payload the offset should be 0, and the TCP, UDP and SSL payload pages show the same base in their examples.

Counts

bytes

First

0

Example TCP::payload replace 0 [TCP::payload length] "" returns the collected TCP payload is now empty (F5's example)

SSL::cert and SSL::cert issuer take an index from 0: F5's page says zero denotes the first certificate in the chain the peer sent and one the next. SSL::cert count is the total, so the last index is the count minus 1.

Counts

certificates in the peer's chain

First

0

Last

[SSL::cert count] - 1

Example SSL::cert 0 returns the first certificate the peer sent (F5's examples use it as the client's own certificate)

F5's pages disagree One of F5's examples has the comment "Check if there is more than one client cert" above a test for a count greater than 0, which means at least one.

SSL::extensions -index returns the N-th extension, zero-indexed in F5's words, and SSL::extensions count is how many arrived.

Counts

TLS extensions

First

0

Last

[SSL::extensions count] - 1

Example SSL::extensions -index 0 returns the first extension received, as bytes

Watch out F5's own example loops from 0 and prints the number plus one for people: count from 0 in code and from 1 in messages.

With -index, class match and class search return entry indexes, and class element takes one; F5's example lists the first three matches as 0 1 2. Without an option, class match returns 1 for a match and 0 for none.

Counts

data group entries

First

0

Example class search -all -index string_dg starts_with "abc" returns 0 1 2

Watch out F5 warns that these indexes are not guaranteed to stay the same when the data group changes, even between events.

F5's pages disagree An example comment on F5's page calls lindex $element 1 the key, but in the name and value pair that index is the value.

TMM::cmp_unit returns the number (0-x) of the CPU, the TMM instance, running the rule, and F5's example calls 0 the first TMM instance. TMM::cmp_group returns the group (0-x), which is always 0 on platforms other than a chassis. TMM::cmp_count is how many TMMs run.

Counts

TMM instances and groups

First

0

Last

[TMM::cmp_count] - 1

Example TMM::cmp_unit returns 0 on the first TMM instance

SIP::route and SIP::record-route take a numeric zero-based index (or the word top), and SIP::via takes a zero-based index too, according to the tmsh copy of its page. Without an index, SIP::via returns the first Via.

Counts

SIP header entries

First

0

Example SIP::via 0 returns the protocol part of the first Via header

DIAMETER::avp picks the Nth AVP with a given code by a zero-based index, and leaving the index out works exactly like index 0, the first one.

Counts

AVPs with the same code

First

0

Example DIAMETER::avp data get 8 octetstring index 1 vendor-id 3375 returns mno

F5's RADIUS::avp examples read repeated attributes with index 0, 1, 2 and so on, and stop at the first empty result. The page never states the base in words.

Counts

attribute instances

First

0

Nothing there

""

Example RADIUS::avp 26 "string" index 0 vendor-id 10415 vendor-type 13 returns the first matching vendor-specific attribute, as a string

MESSAGE::field value takes an optional index that F5's page calls 0-based. A field that is not there returns an empty string, and the order of repeated fields depends on the protocol.

Counts

field instances

First

0

Nothing there

""

Example MESSAGE::field value Via 0 returns the first Via field of the message

NAME::response address takes an index from 0 to 15 inclusive; without one it returns the list of up to 16 records, and null when none came back. F5 deprecated it in version 15.1 in favour of the RESOLVER and DNSMSG commands.

Counts

address records

First

0

Last

15

Nothing there

null

Example NAME::response address 0 returns the first address returned by NAME::lookup

The JSON::array commands, which F5 lists as introduced in BIG-IP 21.0.0, count positions from 0: inserting at an index equal to the size appends, and removing slides the later values down by one. The page never writes the base in words.

Counts

array values

First

0

Last

[JSON::array size $ary] - 1

Example JSON::array get $ary 0 returns the first value of the array

RESOLV::lookup and DNSMSG::section return Tcl lists, so lindex 0 is the first item; F5's RESOLV::lookup page uses exactly that to get a single address.

Counts

addresses and records

First

0

Last

end

Nothing there

""

Example lindex [RESOLV::lookup $hostname] 0 returns the first address the lookup returned

F5's pages disagree F5's DNSMSG::record example stores lindex $answer 1 in a variable named first_rr, but index 1 is the second record.

whereis returns a Tcl list with the continent, the country and the state, in that order, so F5's example reads the continent with lindex 0 and the country with lindex 1.

Counts

list positions

First

0

Example lindex [whereis [IP::client_addr]] 1 returns the client's country code

active_members -list returns a Tcl list of address and port pairs for the active members, and members -list covers every member, so lindex 0 is the first pair in the list.

Counts

pool members

First

0

Example lindex [active_members -list my_pool] 0 returns 192.168.1.1 80

Watch out F5's pages do not say in what order the members come, so the first pair is not a particular member: do not build logic on a position.

An event's priority runs from 0 to 1000 inclusive and defaults to 500, and lower numbers run first, so priority 0 runs before the higher numbers on that event. The DevCentral iRules Style Guide asks for a priority on every event, with 500 when you have no other starting point.

Counts

event priority values

First

0

Last

1000

Example when HTTP_REQUEST priority 0 { ... } returns this HTTP_REQUEST body runs before the ones at the default 500

F5's pages disagree The same F5 page also says a priority can be assigned between 1 and 1000.

MR::connection_instance returns text in the form instance of total, and F5's page says incoming connections return 0 of 1: the instance counts from 0.

Counts

connection instances

First

0

Example MR::connection_instance returns 0 of 1

Route domain 0 is the default: F5's routing guide says that with no route domains created every route belongs to route domain 0, and that an address without a %ID uses the partition's default route domain, or route domain 0 in Common. The tmsh reference adds that when no route is found, the system searches route domain 0.

Counts

route domains

First

0

Example 10.10.10.30%2:80 returns a pool member on 10.10.10.30, port 80, in route domain 2

A pool member's priority-group runs from 0 to 65535 and defaults to 0, and higher numbers get traffic first, so 0 is the lowest group: its members receive traffic only when every member in the higher groups is unavailable. A min-active-members of 0 turns priority group activation off.

Counts

priority groups

First

0

Last

65535

Example priority-group 0 returns the lowest priority group (the default)

Watch out Here the bigger number wins, the opposite of event priority, LTM policy ordinals and GTM order, where the lower number goes first.

Inside an LTM policy rule, conditions and actions are numbered 0, 1 and so on, as F5's tmsh example shows. Rules carry an ordinal: the lower value comes first, and DevCentral's article on matching strategies says 0 is the default and is not shown.

Counts

rules, conditions and actions

First

0

Example conditions add { 0 { http-host host not values { askf5.com } request } } returns the first condition of the rule

F5's pages disagree The iControl REST reference describes the ordinal as a positive integer, while the default is 0.

In BIG-IP DNS, a wide IP's pools and a pool's members carry an order that starts at 0: F5's lab creates the first pool with order 0, and the AS3 schema defaults memberOrder to 0. Global Availability takes the first pool in the list for as long as it is available.

Counts

pools and members, in order

First

0

Example pools add { www.example.com_pool { order 0 } } returns the wide IP's first pool

acl-order places an APM ACL in the list of ACLs, and a lower number sits higher in the list.

Counts

ACL positions

First

0

Example create acl MyACL { acl-order 3 ... } returns MyACL's place in the list of ACLs

F5's pages disagree The tmsh reference describes acl-order 3 as the third ACL in the list, which counts from 1, while F5's Ansible module documentation says the lowest number, 0, is the topmost, which makes 3 the fourth.

TMM instances are numbered from 0: tmsh shows Sys::TMM: 0.0 to 0.7 on an eight-TMM platform, and the processes start at tmm.0. With HTSplit only even IDs are used: the 10th TMM has the ID 18.

Counts

TMM instances

First

0

Example tmsh show sys tmm-info | grep Sys::TMM returns Sys::TMM: 0.0 ... Sys::TMM: 0.7

In iControl REST paging, $skip is how many objects to skip, so the first page is $skip=0 (F5's bug note fetches the first 100 pools that way), and $top is how many to return.

Counts

objects to skip

First

$skip=0

Example GET /mgmt/tm/ltm/pool?$skip=0&$top=100 returns the first 100 pools

Syslog severities run from 0, the most severe (emerg), to 7 (debug). In a BIG-IP log line, the digit between the colons after the message code is the severity, with 0 being the highest.

Counts

severity levels

First

0 = emerg

Last

7 = debug

Example 01220001:3: returns severity 3, err

Watch out A bigger number is less severe: 3 (err) is worse than 6 (info).

BIG-IP uses the syslog facilities local0 to local7, and local0 is BIG-IP's own: F5 maps it to /var/log/ltm, where iRule messages logged with local0 land. The local-syslog default facility is local0.

Counts

syslog facilities

First

local0

Last

local7

Example log local0. "hello" returns a line in /var/log/ltm