1. Computing
Linux / Unix Command: regexp
Command Library

NAME

regexp - Match a regular expression against a string

 

SYNOPSIS

regexp ?switches? exp string ?matchVar? ?subMatchVar subMatchVar ...?



 

DESCRIPTION

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 METASYNTAX, below).
-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 `$' matches an empty string before any newline in addition to its normal function. This flag is equivalent to specifying both -linestop and -lineanchor, or the (?n) embedded option (see METASYNTAX, below).
-linestop
Changes the behavior of `[^' bracket expressions and `.' so that they stop at newlines. This is the same as specifying the (?p) embedded option (see METASYNTAX, below).
-lineanchor
Changes the behavior of `^' and `$' (the ``anchors'') so they match the beginning and end of a line respectively. This is the same as specifying the (?w) embedded option (see METASYNTAX, below).
-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 continue 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.

 

SEE ALSO

re_syntax(n), regsub(n)

 

KEYWORDS

match, regular expression, string


Important: Use the man command (% man) to see how a command is used on your particular computer.

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