regexp(n) manual page
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regexp - Match a regular expression against a
string
regexp ?switches? exp string ?matchVar? ?subMatchVar subMatchVar
...?
Determines whether the regular expression exp matches part
or all of string and returns 1 if it does, 0 if it doesn’t, unless -inline
is specified (see below). (Regular expression matching is described in the
re_syntax reference page.)
If additional arguments are specified after string
then they are treated as the names of variables in which to return information
about which part(s) of string matched exp. MatchVar will be set to the range
of string that matched all of exp. The first subMatchVar will contain the
characters in string that matched the leftmost parenthesized subexpression
within exp, the next subMatchVar will contain the characters that matched
the next parenthesized subexpression to the right in exp, and so on.
If
the initial arguments to regexp start with - then they are treated as switches.
The following switches are currently supported:
- -about
- Instead of attempting
to match the regular expression, returns a list containing information
about the regular expression. The first element of the list is a subexpression
count. The second element is a list of property names that describe various
attributes of the regular expression. This switch is primarily intended
for debugging purposes.
- -expanded
- Enables use of the expanded regular expression
syntax where whitespace and comments are ignored. This is the same as specifying
the (?x) embedded option (see the re_syntax manual page).
- -indices
- Changes
what is stored in the subMatchVars. Instead of storing the matching characters
from string, each variable will contain a list of two decimal strings giving
the indices in string of the first and last characters in the matching
range of characters.
- -line
- Enables newline-sensitive matching. By default,
newline is a completely ordinary character with no special meaning. With
this flag, ‘[^’ bracket expressions and ‘.’ never match newline, ‘^’ matches an
empty string after any newline in addition to its normal function, and
‘$’ matches an empty string before any newline in addition to its normal
function. This flag is equivalent to specifying both -linestop and -lineanchor,
or the (?n) embedded option (see the re_syntax manual page).
- -linestop
- Changes
the behavior of ‘[^’ bracket expressions and ‘.’ so that they stop at newlines.
This is the same as specifying the (?p) embedded option (see the re_syntax
manual page).
- -lineanchor
- Changes the behavior of ‘^’ and ‘$’ (the ‘‘anchors’’) so
they match the beginning and end of a line respectively. This is the same
as specifying the (?w) embedded option (see the re_syntax manual page).
- -nocase
- Causes upper-case characters in string to be treated as lower case
during the matching process.
- -all
- Causes the regular expression to be matched
as many times as possible in the string, returning the total number of
matches found. If this is specified with match variables, they will contain
information for the last match only.
- -inline
- Causes the command to return,
as a list, the data that would otherwise be placed in match variables.
When using -inline, match variables may not be specified. If used with -all,
the list will be concatenated at each iteration, such that a flat list
is always returned. For each match iteration, the command will append the
overall match data, plus one element for each subexpression in the regular
expression. Examples are:
regexp -inline -- {\w(\w)} " inlined "
=> {in n}
regexp -all -inline -- {\w(\w)} " inlined "
=> {in n li i ne e}
- -start index
- Specifies a character index offset into the string to start
matching the regular expression at. When using this switch, ‘^’ will not match
the beginning of the line, and \A will still match the start of the string
at index. If -indices is specified, the indices will be indexed starting
from the absolute beginning of the input string. index will be constrained
to the bounds of the input string.
- --
- Marks the end of switches. The argument
following this one will be treated as exp even if it starts with a -.
If
there are more subMatchVar’s than parenthesized subexpressions within exp,
or if a particular subexpression in exp doesn’t match the string (e.g. because
it was in a portion of the expression that wasn’t matched), then the corresponding
subMatchVar will be set to ‘‘-1 -1’’ if -indices has been specified or to an empty
string otherwise.
Find the first occurrence of a word starting with
foo in a string that is not actually an instance of foobar, and get the
letters following it up to the end of the word into a variable:
regexp {\<foo(?!bar\>)(\w*)} $string -> restOfWord
Note that the whole matched substring has been placed in the variable ->
which is a name chosen to look nice given that we are not actually interested
in its contents.
Find the index of the word badger (in any case) within
a string and store that in the variable location:
regexp -indices {(?i)\<badger\>} $string location
Count the number of octal digits in a string:
regexp -all {[0-7]} $string
List all words (consisting of all sequences of non-whitespace characters)
in a string:
regexp -all -inline {\S+} $string
re_syntax(n)
, regsub(n)
match, regular expression, string
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