path: root/Doc/Zsh/compctl.yo

texinode(Programmable Completion)(Zsh Modules)(Zsh Line Editor)(Top)
chapter(Programmable Completion)
cindex(completion, programmable)
cindex(completion, controlling)
findex(compctl)
sect(Description)
startlist()
list(tt(compctl) [ tt(-CDT) ] var(options) [ var(command) ... ])
list(tt(compctl) [ tt(-CDT) ] var(options) \
  [ tt(-x) var(pattern) var(options) tt(-) ... tt(--) ] \
  [ tt(PLUS()) var(options) [ tt(-x) ... tt(--) ] ... [tt(PLUS())] ] \
  [ var(command) ... ])
list(tt(compctl) tt(-M) var(match-specs) ...)
list(tt(compctl) tt(-L) [ tt(-CDT) ] [ var(command) ... ])
list(tt(compctl) tt(PLUS()) var(command) ...)
endlist()

Control the editor's completion behavior according to the supplied set
of var(options).  Various editing commands, notably
tt(expand-or-complete-word), usually bound to tab, will
attempt to complete a word typed by the user, while others, notably
tt(delete-char-or-list), usually bound to ^D in EMACS editing
mode, list the possibilities; tt(compctl) controls what those
possibilities are.  They may for example be filenames (the most common
case, and hence the default), shell variables, or words from a
user-specified list.
startmenu()
menu(Command Flags)
menu(Option Flags)
menu(Alternative Completion)
menu(Extended Completion)
menu(Matching Control)
menu(Example)
endmenu()
texinode(Command Flags)(Option Flags)()(Programmable Completion)
sect(Command Flags)
Completion of the arguments of a command may be different for each
command or may use the default.  The behavior when completing the
command word itself may also be separately specified.  These
correspond to the following flags and arguments, all of which (except
for tt(-L)) may be combined with any combination of the
var(options) described subsequently in noderef(Option Flags):

startitem()
item(var(command) ...)(
controls completion for the named commands, which must be listed last
on the command line.  If completion is attempted for a command with a
pathname containing slashes and no completion definition is found, the
search is retried with the last pathname component. If the command starts
with a tt(=), completion is tried with the pathname of the command.

The strings may also be patterns (i.e. they may contain an unquoted
occurrence of characters used to form patterns in the shell). When 
completion is attempted, the shell first tries all such pattern compctls.
If one matches the command name on the line or if the pathname of the
command on the line matches a pattern, it is used. The patterns are tested
in reverse order, i.e. the pattern compctl defined last overrides all
previously defined pattern compctls. Unless the option list of that compctl
contains an tt(-t) flag with a \tt(c) character, no more compctls are tried.

Note that aliases
are expanded before the command name is determined unless the
tt(COMPLETE_ALIASES) option is set.  Commands should not be combined
with the tt(-C), tt(-D) or tt(-T) flags.
)
item(tt(-C))(
controls completion when the command word itself is being completed.
If no tt(compctl -C) command has been issued,  the names of any
executable command (whether in the path or specific to the shell, such
as aliases or functions) are completed.
)
item(tt(-D))(
controls default completion behavior for the arguments of commands not
assigned any special behavior.  If no tt(compctl -D) command has
been issued, filenames are completed.
)
item(tt(-T))(
supplies completion flags to be used before any other processing is
done, even those given to specific commands with other compctl
definitions.  This is especially useful when combined with extended
completion (the tt(-x) flag, see noderef(Extended Completion) below).
Using this flag you can define default behavior
which will apply to all commands without exception, or you can alter
the standard behavior for all commands.  For example, if your access
to the user database is too slow and/or it contains too many users (so
that completion after `tt(~)' is too slow to be usable), you can use

nofill(tt(compctl -Tx  'C[0,*/*]' -f - 's[~]' -k friends -S/))

to complete the strings in the array tt(friends) after a `tt(~)'.
The first argument is necessary so that this form of ~-completion is
not tried after the directory name is finished.
)
item(tt(-L))(
lists the existing completion behavior in a manner suitable for
putting into a start-up script; the existing behavior is not changed.
Any combination of the above forms may be specified, otherwise all
defined completions are listed.  Any other flags supplied
are ignored.
)
item(em(no argument))(
If no argument is given, tt(compctl) lists all defined completions
in an abbreviated form;  with a list of var(options), all completions
with those flags set (not counting extended completion) are listed.
)
endlist()

If the tt(PLUS()) flag is alone and followed immediately by the var(command)
list, the completion behavior for all the commands in the list is reset to
the default.  In other words, completion will subsequently use the
options specified by the tt(-D) flag.

The form with tt(-M) as the first and only option defines global
matching specifications described below in noderef(Matching Control).
texinode(Option Flags)(Alternative Completion)(Command Flags)(Programmable Completion)
sect(Option Flags)
startlist()
list([ tt(-fcFBdeaRGovNAIOPZEnbjrzu/) ])
list([ tt(-k) var(array) ] [ tt(-g) var(globstring) ] \
  [ tt(-s) var(subststring) ])
list([ tt(-K) var(function) ] [ tt(-H) var(num pattern) ])
list([ tt(-Q) ] [ tt(-P) var(prefix) ] [ tt(-S) var(suffix) ])
list([ tt(-W) var(file-prefix) ])
list([ tt(-q) ] [ tt(-X) var(explanation) ] [ tt(-Y) var(explanation) ])
list([ tt(-y) var(func-or-var) ] [ tt(-l) var(cmd) ] [ tt(-U) ])
list([ tt(-t) var(continue) ] [ tt(-J) var(name) ] [ tt(-V) var(name) ])
list([ tt(-M) var(match-spec) ])
endlist()

The remaining var(options) specify the type of command arguments
to look for during completion.  Any combination of these flags may be
specified; the result is a sorted list of all the possibilities.  The
options are as follows.
startmenu()
menu(Simple Flags)
menu(Flags with Arguments)
menu(Control Flags)
endmenu()
texinode(Simple Flags)(Flags with Arguments)()(Option Flags)
subsect(Simple Flags)
These produce completion lists made up by the shell itself:

startitem()
item(tt(-f))(
Filenames and filesystem paths.
)
item(tt(-/))(
Just filesystem paths.
)
item(tt(-c))(
Command names, including aliases, shell functions, builtins
and reserved words.
)
item(tt(-F))(
Function names.
)
item(tt(-B))(
Names of builtin commands.
)
item(tt(-m))(
Names of external commands.
)
item(tt(-w))(
Reserved words.
)
item(tt(-a))(
Alias names.
)
item(tt(-R))(
Names of regular (non-global) aliases.
)
item(tt(-G))(
Names of global aliases.
)
item(tt(-d))(
This can be combined with tt(-F), tt(-B), tt(-w),
tt(-a), tt(-R) and tt(-G) to get names of disabled
functions, builtins, reserved words or aliases.
)
item(tt(-e))(
This option (to show enabled commands) is in effect by default, but
may be combined with tt(-d); tt(-de) in combination with
tt(-F), tt(-B), tt(-w), tt(-a), tt(-R) and tt(-G)
will complete names of functions, builtins, reserved words or aliases
whether or not they are disabled.
)
item(tt(-o))(
Names of shell options (see
ifzman(zmanref(zshoptions))\
ifnzman(noderef(Options))\
).
)
item(tt(-v))(
Names of any variable defined in the shell.
)
item(tt(-N))(
Names of scalar (non-array) parameters.
)
item(tt(-A))(
Array names.
)
item(tt(-I))(
Names of integer variables.
)
item(tt(-O))(
Names of read-only variables.
)
item(tt(-p))(
Names of parameters used by the shell (including special parameters).
)
item(tt(-Z))(
Names of shell special parameters.
)
item(tt(-E))(
Names of environment variables.
)
item(tt(-n))(
Named directories.
)
item(tt(-b))(
Key binding names.
)
item(tt(-j))(
Job names:  the first word of the job leader's command line.  This is useful
with the tt(kill) builtin.
)
item(tt(-r))(
Names of running jobs.
)
item(tt(-z))(
Names of suspended jobs.
)
item(tt(-u))(
User names.
)
enditem()
texinode(Flags with Arguments)(Control Flags)(Simple Flags)(Option Flags)
subsect(Flags with Arguments)
These have user supplied arguments to determine how the list of
completions is to be made up:

startitem()
item(tt(-k) var(array))(
Names taken from the elements of tt($)var(array) (note that the `tt($)'
does not appear on the command line).
Alternatively, the argument var(array) itself may be a set
of space- or comma-separated values in parentheses, in which any
delimiter may be escaped with a backslash; in this case the argument
should be quoted.  For example,

nofill(tt(compctl -k "(cputime filesize datasize stacksize
    coredumpsize resident descriptors)" limit))
)
item(tt(-g) var(globstring))(
The var(globstring) is expanded using filename globbing; it should be
quoted to protect it from immediate expansion. The resulting
filenames are taken as the possible completions.  Use `tt(*(/))' instead of
`tt(*/)' for directories.  The tt(fignore) special parameter is not
applied to the resulting files.  More than one pattern may be given
separated by blanks. (Note that brace expansion is em(not) part of
globbing.  Use the syntax `tt((either|or))' to match alternatives.)
)
item(tt(-s) var(subststring))(
The var(subststring) is split into words and these words are than
expanded using all shell expansion mechanisms (see
ifzman(zmanref(zshexpn))\
ifnzman(noderef(Expansion))\
).  The resulting words are taken as possible
completions.  The tt(fignore) special parameter is not applied to the
resulting files.  Note that tt(-g) is faster for filenames.
)
item(tt(-K) var(function))(
Call the given function to get the completions.  The function is
passed two arguments: the prefix and the suffix of the word on which
completion is to be attempted, in other words those characters before
the cursor position, and those from the cursor position onwards.  The
whole command line can be accessed with the tt(-c) and tt(-l) flags
of the tt(read) builtin. The
function should set the variable tt(reply) to an array containing
the completions (one completion per element); note that tt(reply)
should not be made local to the function.  From such a function the
command line can be accessed with the tt(-c) and tt(-l) flags to
the tt(read) builtin.  For example,

nofill(tt(function whoson { reply=(`users`); }
compctl -K whoson talk))

completes only logged-on users after `tt(talk)'.  Note that `tt(whoson)' must
return an array, so `tt(reply=`users`)' would be incorrect.
)
item(tt(-H) var(num pattern))(
The possible completions are taken from the last var(num) history
lines.  Only words matching var(pattern) are taken.  If var(num) is
zero or negative the whole history is searched and if var(pattern) is
the empty string all words are taken (as with `tt(*)').  A typical
use is

nofill(tt(compctl -D -f PLUS() -H 0 ''))

which forces completion to look back in the history list for a word if
no filename matches.
)
enditem()
texinode(Control Flags)()(Flags with Arguments)(Option Flags)
subsect(Control Flags)
These do not directly specify types of name to be completed, but
manipulate the options that do:

startitem()
item(tt(-Q))(
This instructs the shell not to quote any metacharacters in the possible
completions.  Normally the results of a completion are inserted into
the command line with any metacharacters quoted so that they are
interpreted as normal characters.  This is appropriate for filenames
and ordinary strings.  However, for special effects, such as inserting
a backquoted expression from a completion array (tt(-k)) so that
the expression will not be evaluated until the complete line is
executed, this option must be used.
)
item(tt(-P) var(prefix))(
The var(prefix) is inserted just before the completed string; any
initial part already typed will be completed and the whole var(prefix)
ignored for completion purposes.  For example,

nofill(tt(compctl -j -P "%" kill))

inserts a `%' after the kill command and then completes job names.
)
item(tt(-S) var(suffix))(
When a completion is found the var(suffix) is inserted after
the completed string.  In the case of menu completion the suffix is
inserted immediately, but it is still possible to cycle through the
list of completions by repeatedly hitting the same key.
)
item(tt(-W) var(file-prefix))(
With directory var(file-prefix):  for command, file, directory and
globbing completion (options tt(-c), tt(-f), tt(-/), tt(-g)), the file
prefix is implicitly added in front of the completion.  For example,

nofill(tt(compctl -/ -W ~/Mail maildirs))

completes any subdirectories to any depth beneath the directory
tt(~/Mail), although that prefix does not appear on the command line.
The var(suffix) may also be of the form accepted by the tt(-k) flag, i.e.
the name of an array or a literal list in parenthesis. In this cases all
words are used as prefixes.
)
item(tt(-q))(
If used with a suffix as specified by the tt(-S) option, this
causes the suffix to be removed if the next character typed is a blank
or does not insert anything (the same rule as used for the
tt(AUTO_REMOVE_SLASH) option).  The option is most useful for list
separators (comma, colon, etc.).
)
item(tt(-l) var(cmd))(
This option restricts the range
of command line words that are considered to be arguments.  If
combined with one of the extended completion patterns `tt(p[)...tt(])',
`tt(r[)...tt(])', or `tt(R[)...tt(])'  (see noderef(Extended Completion)
below) the range is restricted to the range of arguments
specified in the brackets.  Completion is then performed as if these
had been given as arguments to the var(cmd) supplied with the
option. If the var(cmd) string is empty the first word in the range
is instead taken as the command name, and command name completion
performed on the first word in the range.  For example,

nofill(tt(compctl -x 'r[-exec,;]' -l '' -- find))

completes arguments between `tt(-exec)' and the following `tt(;)' (or the end
of the command line if there is no such string) as if they were
a separate command line.
)
item(tt(-U))(
Use the whole list of possible completions, whether or not they
actually match the word on the command line.  The word typed so far
will be deleted.  This is most useful with a function (given by the
tt(-K) option) which can examine the word components passed to it
(or via the tt(read) builtin's tt(-c) and tt(-l) flags) and
use its own criteria to decide what matches.  If there is no
completion, the original word is retained.  Since the produced 
possible completions seldom seldom have interesting common prefixes
and suffixes, menucompletion is started immediatly if tt(AUTO_MENU) is
set and this flag is used.
)
item(tt(-y) var(func-or-var))(
The list provided by var(func-or-var) is displayed instead of the list
of completions whenever a listing is required; the actual completions
to be inserted are not affected.  It can be provided in two
ways. Firstly, if var(func-or-var) begins with a tt($) it defines a
variable, or if it begins with a left parenthesis a literal
array, which contains the list.  A variable may have been set by a
call to a function using the tt(-K) option.  Otherwise it contains the
name of a function which will be executed to create the list.  The
function will be passed as an argument list all matching completions,
including prefixes and suffixes expanded in full, and should set the
array var(reply) to the result.  In both cases, the display list will
only be retrieved after a complete list of matches has been created.

Note that the returned list does not have to correspond, even in
length, to the original set of matches, and may be passed as a scalar
instead of an array.  No special formatting of characters is
performed on the output in this case; in particular, newlines are
printed literally and if they appear output in columns is suppressed.
)
item(tt(-X) var(explanation))(
Print var(explanation) when trying completion on the current set of
options. A `tt(%n)' in this string is replaced by the number of matches.
The explanation only appears if completion was tried and there was
no unique match, or when listing completions.
The sequences tt(%B), tt(%b), tt(%S), tt(%s), tt(%U), and tt(%u) specify
output attributes (bold, standout, and underline) as in prompts.
)
item(tt(-Y) var(explanation))(
Identical to tt(-X), except that the var(explanation) first undergoes
expansion following the usual rules for strings in double quotes.
The expansion will be carried out after any functions are called for
the tt(-K) or tt(-y) options, allowing them to set variables.
)
item(tt(-J))(
This gives the name of the group the matches should be placed in. Groups
are listed and sorted separately. Also, menucompletion will offer the matches
in the groups in the order, in which the groups were defined. If no group
name is explicitly given, the matches are stored in a group named var(default).
The first time a group name is encountered, a group with that name is created.
After that all matches with the same group name are stored in that group.
)
item(tt(-V))(
Like tt(-J), but the matches in the group will not be sorted in the listing and
with menucompletion. These unsorted groups are in a different name space than
the sorted ones. I.e. it is possible to have a sorted and a unsorted group
with the same name and the matches in those groups will not be mixed.
)
item(tt(-t) var(continue))(
The var(continue)-string contains a set of characters that specify if 
and when completion should continue to produce matches where it normally
would not do that. The character tt(c) means that completion continues
with the next suitable compctl (i.e. if you don't specify this in a
tt(compctl -T), compctls for commands are never used). The character
tt(PLUS()) is used to continue with the matches for the next alternative
completion (see below). The characters tt(-) and tt(x) may be used in
sub-lists for extended completion (see below). They will make the completion
code use the flag list after the next tt(-) (if the corresponding pattern
matches) and the default flag list (those before the tt(-x)), respectively.
)
item(tt(-M) var(match-spec))(
This defines additional matching control specifications that should be used
only when testing words for the list of flags this flag appears in. The format
of the var(match-spec) string is described below in noderef(Matching Control).
)
enditem()
texinode(Alternative Completion)(Extended Completion)(Option Flags)(Programmable Completion)
sect(Alternative Completion)
startlist()
list(tt(compctl) [ tt(-CDT) ] var(options) tt(PLUS()) var(options) [ tt(PLUS()) ... ] \
[ tt(PLUS()) ] var(command) ...)
endlist()

The form with `tt(PLUS())' specifies alternative options. Completion is
tried with the options before the first `tt(PLUS())'. If this produces no
matches completion is tried with the flags after the `tt(PLUS())' and so on. If
there are no flags after the last `tt(PLUS())' and a match has not been found
up to that point, default completion is tried.
If the list of flags contains a tt(-t) with a tt(PLUS()) character, the next
list of flags is used even if the current list produced matches.
texinode(Extended Completion)(Matching Control)(Alternative Completion)(Programmable Completion)
sect(Extended Completion)
startlist()
list(tt(compctl) [ tt(-CDT) ] var(options) \
tt(-x) var(pattern) var(options) tt(-) ... tt(--) \
[ var(command) ... ])
list(tt(compctl) [ tt(-CDT) ] var(options) \
[ tt(-x) var(pattern) var(options) tt(-) ... tt(--) ] \
[ tt(PLUS()) var(options) [ tt(-x) ... tt(--) ] ... [tt(PLUS())] ] \
[ var(command) ... ])
endlist()

The form with `tt(-x)' specifies extended completion for the
commands given; as shown, it may be combined with alternative
completion using `tt(PLUS())'.  Each var(pattern) is examined in turn; when a
match is found, the corresponding var(options), as described in
noderef(Option Flags) above, are used to generate possible
completions.  If no var(pattern) matches, the var(options) given
before the tt(-x) are used.

Note that each pattern should be supplied as a single argument and
should be quoted to prevent expansion of metacharacters by the
shell.

A var(pattern) is built of sub-patterns separated by commas; it
matches if at least one of these sub-patterns matches (they are
`or'ed). These sub-patterns are in turn composed of other
sub-patterns separated by white spaces which match if all of the
sub-patterns match (they are `and'ed).  An element of the
sub-patterns is of the form `var(c)tt([)...tt(][)...tt(])', where the pairs of
brackets may be repeated as often as necessary, and matches if any of
the sets of brackets match (an `or').  The example below makes this
clearer.

The elements may be any of the following:

startitem()
item(tt(s[)var(string)tt(])...)(
Matches if the current word on the command line starts with
one of the strings given in brackets.  The var(string) is not removed
and is not part of the completion.
)
item(tt(S[)var(string)tt(])...)(
Like tt(s[)var(string)tt(]) except that the var(string) is part of the
completion.
)
item(tt(p[)var(from)tt(,)var(to)tt(])...)(
Matches if the number of the current word is between one of
the var(from) and var(to) pairs inclusive. The comma and var(to)
are optional; var(to) defaults to the same value as var(from).  The
numbers may be negative: tt(-)var(n) refers to the var(n)'th last word
on the line.
)
item(tt(c[)var(offset)tt(,)var(string)tt(])...)(
Matches if the var(string) matches the word offset by
var(offset) from the current word position.  Usually var(offset)
will be negative.
)
item(tt(C[)var(offset)tt(,)var(pattern)tt(])...)(
Like tt(c) but using pattern matching instead.
)
item(tt(w[)var(index)tt(,)var(string)tt(])...)(
Matches if the word in position var(index) is equal
to the corresponding var(string).  Note that the word count is made
after any alias expansion.
)
item(tt(W[)var(index)tt(,)var(pattern)tt(])...)(
Like tt(w) but using pattern matching instead.
)
item(tt(n[)var(index)tt(,)var(string)tt(])...)(
Matches if the current word contains var(string).  Anything up to and
including the var(index)th occurrence of this string will not be
considered part of the completion, but the rest will.  var(index) may
be negative to count from the end: in most cases, var(index) will be
1 or -1.  For example,

nofill(tt(compctl -s '`users`' -x 'n[1,@]' -k hosts -- talk))

will usually complete usernames, but if you insert an tt(@) after the
name, names from the array var(hosts) (assumed to contain hostnames,
though you must make the array yourself) will be completed.  Other
commands such as tt(rcp) can be handled similarly.
)
item(tt(N[)var(index)tt(,)var(string)tt(])...)(
Like tt(n) except that the string will be
taken as a character class.  Anything up to and including the
var(index)th occurrence of any of the characters in var(string)
will not be considered part of the completion.
)
item(tt(m[)var(min)tt(,)var(max)tt(])...)(
Matches if the total number of words lies between var(min) and
var(max) inclusive.
)
item(tt(r[)var(str1)tt(,)var(str2)tt(])...)(
Matches if the cursor is after a word with prefix var(str1).  If there
is also a word with prefix var(str2) on the command line it matches
only if the cursor is before this word. If the comma and var(str2) are
omitted, it matches if the cursor is after a word with prefix var(str1).
)
item(tt(R[)var(str1)tt(,)var(str2)tt(])...)(
Like tt(r) but using pattern matching instead.
)
enditem()
texinode(Matching Control)(Example)(Extended Completion)(Programmable Completion)
sect(Matching Control)

Matching specifications are used to describe that certain strings
on the command line match possibly different strings in the words produced
by the completion code.

Matching specification strings consist of one or more matching
descriptions separated by whitespace. Each description consists of
a letter followed by a colon and the patterns describing which character
sequences on the line match which character sequences in the words.

The letters understood are: tt(l), tt(r), tt(m), tt(L), tt(R), and tt(M).
startitem()
item(tt(m) and tt(M))(
These describe patterns that match anywhere in the words. The colon should
be followed by two patterns separated by an equal sign. The pattern on the
left side describes the substrings that are to be matched on the command line,
the pattern on the right side describes the substrings matched in the word.
)
item(tt(l) and tt(L))(
These letters are for patterns that are anchored by another pattern on
the left side. In this case the colon has to be followed by the pattern
for the anchor, a pipe symbol, the pattern for the command line, an equal
sign, and the pattern for the word. Patterns anchored on the left side match
only if the anchor-pattern matches directly before the line pattern and if
the string in the word before the word pattern matches the string before
the line pattern in the line string.
)
item(tt(r) and tt(R))(
Like tt(l) and tt(L) with the difference that the line and word patterns
are anchored on the right side. Also, here the pattern for the anchor has
to come after the pattern for the line, again separated by a pipe symbol.
)
enditem()

Each pattern is either an empty string or consists of a sequence of
character (possibly quoted), question marks, character classes, and
correspondence classes. Normal characters match only themselves, question
marks match any character, and character classes are formed as for
globbing and match the same characters as there.
Correspondence classes are formed like character classes with two
differences: they are delimited by a pair of braces and negated
classes are not allowed (i.e. the characters tt(!) and tt(^) have no
special meaning directly after the opening brace).

Correspondence classes are used to conveniently describe that several
characters on the line match several other characters in the word. For 
example, if you want to define the any lowercase letter on the line
matches the corresponding uppercase letter in the word all you need to 
write down is: `tt(m:{a-z}={A-Z})'. More than one correspondence class
may be given on either side of the equal sign, in this case the first
class on the left says which character matches for the first class on
the right, the second class on either side work together, and so on.
If one side has more such classes than the other side, the superfluous
classes behave like normal character classes. In anchor patterns
correspondence classes always behave like normal character classes.

The word pattern may also be a single star (tt(*)). This means that
the line pattern matches any number of characters in the word. In this 
case the pattern has to be anchored (on any side) and the line pattern 
matches all characters in the word up to a character sequence that
matches the anchor.

For anchors the empty string as a pattern has a special meaning. Such
empty anchors match only the beginning (in the case of an left side
anchor) or end (for right side anchors) of the command line string or
word.

The distinction between the lowercase and the uppercase forms of the
specification characters is used to define which matched substring
should be put in the match and the generated command line. The
lowercase forms use the substring from the word, so this should be
used if the exact words produced by the completion code need to be
used. The uppercase forms use the substring from the command line and
should be used if the typed string need to be retained.

Examples:

startitem()
The option tt(-o) produces option names in all-lowercase form, without 
underscores, and without the optional tt(no) at the beginning even
though the buitlins tt(setopt) and tt(unsetopt) understand opotion
names with uppercase letters, underscores, and the optional tt(no).
So we want to be able to say, that in this case an prefix tt(no) and
any underscore may be ignored when trying to match the produced words, 
and that uppercase letters on the line match the corresponding
lowercase letters in the words. This can be done with:

indent(
tt(compctl -M 'L:|[nN][oO]= M:_= M:{A-Z}={a-z}' -o setopt unsetopt)
)

The first part says that the pattern `tt([nN][oO])' at the beginning
(note the empty anchor before the pipe symbol) of the string on the
line matches the the empty string in the produced words, i.e. it need
not be there. The second part says that an underscore anywhere on the
line need not be present in the word, and the third part uses
correspondence classes as in the example above to say that any
uppercase letter on the line matches the corresponding lowercase
letter in the word. The use of the uppercase forms of the
specification characters (tt(L) and tt(M)) guarantees that the special 
wrinting on the command line (and especially the option tt(no)) will
not be erased.

As a second example we will make completion case insensitive. For this 
we use the form of tt(compctl) that defines matching specification that
are to be used everywhere, i.e. a tt(compctl) with tt(-M) as the only
option given.

The pattern needed was already explained above, this gives us:

indent(
tt(compctl -M 'm:{a-z}={A-Z}')
)

This makes lowercase letters match their uppercase counterparts. If we 
want to make uppercase letters match the lowercase forms, we would
have to use:

indent(
tt(compctl -M 'm:{a-z}={A-Z} m:{A-Z}={a-z}')
)

A nice example for the use of tt(*) patterns is partial word
completion. Sometimes you would like to make strings like tt(c.s.u)
complete to strings like tt(comp.source.unix), i.e. you consider the
word to consist of multiple parts (separated by the dot in the
example) and each part should be completed separately. Defining such
forms of matching is simple, for example if we want to separately
complete word parts separated by dots, commas, underscores, and
hyphens, we can do this by saying:

indent(
tt(compctl -M 'r:|[.,_-]=* r:|=*')
)

The first specification says that an empty string on the line before
one of our special characters matches any number of characters in the
word which has the effect we wanted. The second specification is
needed to make this work when the cursor is in the middle of the word
and the option tt(COMPLETE_IN_WORD) is set. In this case the
completion code would normally try to match word that end with the
string that is already on the command line, but in our example we
would like the code to match words even if they contain extra
characters after the string on the line. Hence we say that the empty
string at the end of the string on the line matches any characters at
the end of the word.

The form of tt(compctl) that defines the global matching
specifications is a bit more powerful than described until now. It
accepts not only one specification strin, but any number of them. When 
completion is attempted, the code first uses the definitions from the
first string. If no words could be matched with these specifications,
it tries the whole thing again with the specifications from the second 
string, and so on. This allows one to define simple and fast matches
to be used first, more powerful matchers as a second choice, and so on.

As an example we would like to make the code match words that contain
the string on the line as a substring (anywhere, not just at the
beginning). But since this could produce more matches than we want,
this should be tried only if the matchers described above don't
produce any matches. E.g.:

indent(
tt(compctl -M 'r:|[.,_-]=* r:|=*' 'l:|=* r:|=*')
)

If using the first specification string does not produce matches, the
second one is tried. The two descriptions it this string say that the
empty string at the beginning and end of the string on the line
matches any characters at the beginning or end of the word.
enditem()
texinode(Example)()(Matching Control)(Programmable Completion)
sect(Example)
nofill(tt(compctl -u -x 's[tt(PLUS())] c[-1,-f],s[-f+PLUS()]' -g '~/Mail/*(:t)' \ 
    - 's[-f],c[-1,-f]' -f -- mail))

This is to be interpreted as follows:

If the current command is tt(mail), then

indent(
if ((the current word begins with tt(PLUS()) and the previous word is tt(-f))
or (the current word begins with tt(-f+PLUS()))), then complete the
non-directory part (the `tt(:t)' glob modifier) of files in the directory
tt(~/Mail); else

if the current word begins with tt(-f) or the previous word was tt(-f), then
complete any file; else

complete user names.
)