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regexp(5)             Standards, Environments, and Macros            regexp(5)

NAME
       regexp, compile, step, advance - simple regular expression compile and
       match routines

SYNOPSIS
       #define INIT declarations
       #define GETC(void) getc code
       #define PEEKC(void) peekc code
       #define UNGETC(void) ungetc code
       #define RETURN(ptr) return code
       #define ERROR(val) error code

       extern char *loc1, *loc2, *locs;

       #include <regexp.h>

       char *compile(char *instring, char *expbuf, const char *endfug, int
       eof);

       int step(const char *string, const char *expbuf);

       int advance(const char *string, const char *expbuf);

DESCRIPTION
       Regular Expressions (REs) provide a mechanism to select specific
       strings from a set of character strings. The Simple Regular Expressions
       described below differ from the  Internationalized Regular Expressions
       described on the  regex(5) manual page in the following ways:

          o  only Basic Regular Expressions are supported

          o  the Internationalization features--character class, equivalence
             class, and multi-character collation--are not supported.

       The functions step(), advance(), and compile() are general purpose
       regular expression matching routines to be used in programs that
       perform regular expression matching. These functions are defined by the
       <regexp.h> header.

       The functions step() and advance() do pattern matching given a
       character string and a compiled regular expression as input.

       The function compile() takes as input a regular expression as defined
       below and produces a compiled expression that can be used with step()
       or advance().

   Basic Regular Expressions
       A regular expression specifies a set of character strings. A member of
       this set of strings is said to be matched by the regular expression.
       Some characters have special meaning when used in a regular expression;
       other characters stand for themselves.

       The following one-character REs match a single character:

       1.1   An ordinary character ( not one of those discussed in 1.2 below)
             is a one-character RE that matches itself.

       1.2   A backslash (\) followed by any special character is a one-
             character RE that matches the special character itself. The
             special characters are:

             a.    ., *, [, and \ (period, asterisk, left square bracket, and
                   backslash, respectively), which are always special, except
                   when they appear within square brackets ([]; see 1.4
                   below).

             b.    ^ (caret or circumflex), which is special at the beginning
                   of an entire RE (see 4.1 and 4.3 below), or when it
                   immediately follows the left of a pair of square brackets
                   ([]) (see 1.4 below).

             c.    $ (dollar sign), which is special at the end of an entire
                   RE (see 4.2 below).

             d.    The character used to bound (that is, delimit) an entire
                   RE, which is special for that RE (for example, see how
                   slash (/) is used in the g command, below.)

       1.3   A period (.) is a one-character RE that matches any character
             except new-line.

       1.4   A non-empty string of characters enclosed in square brackets ([])
             is a one-character RE that matches any one character in that
             string. If, however, the first character of the string is a
             circumflex (^), the one-character RE matches any character except
             new-line and the remaining characters in the string. The ^ has
             this special meaning only if it occurs first in the string. The
             minus (-) may be used to indicate a range of consecutive
             characters; for example, [0-9] is equivalent to [0123456789]. The
             - loses this special meaning if it occurs first (after an initial
             ^, if any) or last in the string. The right square bracket (])
             does not terminate such a string when it is the first character
             within it (after an initial ^, if any); for example, []a-f]
             matches either a right square bracket (]) or one of the ASCII
             letters a through f inclusive. The four characters listed in
             1.2.a above stand for themselves within such a string of
             characters.

       The following rules may be used to construct REs from one-character
       REs:

       2.1   A one-character RE is a RE that matches whatever the one-
             character RE matches.

       2.2   A one-character RE followed by an asterisk (*) is a RE that
             matches 0 or more occurrences of the one-character RE. If there
             is any choice, the longest leftmost string that permits a match
             is chosen.

       2.3   A one-character RE followed by \{m\}, \{m,\}, or \{m,n\} is a RE
             that matches a range of occurrences of the one-character RE. The
             values of m and n must be non-negative integers less than 256;
             \{m\} matches exactly m occurrences; \{m,\} matches at least m
             occurrences; \{m,n\} matches any number of occurrences between m
             and n inclusive. Whenever a choice exists, the RE matches as many
             occurrences as possible.

       2.4   The concatenation of REs is a RE that matches the concatenation
             of the strings matched by each component of the RE.

       2.5   A RE enclosed between the character sequences \( and \) is a RE
             that matches whatever the unadorned RE matches.

       2.6   The expression \n matches the same string of characters as was
             matched by an expression enclosed between \( and \) earlier in
             the same RE. Here n is a digit; the sub-expression specified is
             that beginning with the n-th occurrence of \( counting from the
             left. For example, the expression ^\(.*\)\1$ matches a line
             consisting of two repeated appearances of the same string.

       An RE may be constrained to match words.

       3.1   \< constrains a RE to match the beginning of a string or to
             follow a character that is not a digit, underscore, or letter.
             The first character matching the RE must be a digit, underscore,
             or letter.

       3.2   \> constrains a RE to match the end of a string or to precede a
             character that is not a digit, underscore, or letter.

       An entire RE may be constrained to match only an initial segment or
       final segment of a line (or both).

       4.1   A circumflex (^) at the beginning of an entire RE constrains that
             RE to match an initial segment of a line.

       4.2   A dollar sign ($) at the end of an entire RE constrains that RE
             to match a final segment of a line.

       4.3   The construction ^entire RE$ constrains the entire RE to match
             the entire line.

       The null RE (for example, //) is equivalent to the last RE encountered.

   Addressing with REs
       Addresses are constructed as follows:

       1. The character "." addresses the current line.

       2. The character "$" addresses the last line of the buffer.

       3. A decimal number n addresses the n-th line of the buffer.

       4. 'x addresses the line marked with the mark name character x, which
          must be an ASCII lower-case letter (a-z). Lines are marked with the
          k command described below.

       5. A RE enclosed by slashes (/) addresses the first line found by
          searching forward from the line following the current line toward
          the end of the buffer and stopping at the first line containing a
          string matching the RE. If necessary, the search wraps around to the
          beginning of the buffer and continues up to and including the
          current line, so that the entire buffer is searched.

       6. A RE enclosed in question marks (?) addresses the first line found
          by searching backward from the line preceding the current line
          toward the beginning of the buffer and stopping at the first line
          containing a string matching the RE. If necessary, the search wraps
          around to the end of the buffer and continues up to and including
          the current line.

       7. An address followed by a plus sign (+) or a minus sign (-) followed
          by a decimal number specifies that address plus (respectively minus)
          the indicated number of lines. A shorthand for .+5 is .5.

       8. If an address begins with + or -, the addition or subtraction is
          taken with respect to the current line; for example, -5 is
          understood to mean .-5.

       9. If an address ends with + or -, then 1 is added to or subtracted
          from the address, respectively. As a consequence of this rule and of
          Rule 8, immediately above, the address - refers to the line
          preceding the current line. (To maintain compatibility with earlier
          versions of the editor, the character ^ in addresses is entirely
          equivalent to -.) Moreover, trailing + and - characters have a
          cumulative effect, so -- refers to the current line less 2.

       10.
          For convenience, a comma (,) stands for the address pair 1,$, while
          a semicolon (;) stands for the pair .,$.

   Characters With Special Meaning
       Characters that have special meaning except when they appear within
       square brackets ([]) or are preceded by \ are:  ., *, [, \. Other
       special characters, such as $ have special meaning in more restricted
       contexts.

       The character ^ at the beginning of an expression permits a successful
       match only immediately after a newline, and the character $ at the end
       of an expression requires a trailing newline.

       Two characters have special meaning only when used within square
       brackets. The character - denotes a range, [c-c], unless it is just
       after the open bracket or before the closing bracket, [-c] or [c-] in
       which case it has no special meaning. When used within brackets, the
       character ^ has the meaning complement of if it immediately follows the
       open bracket (example: [^c]); elsewhere between brackets (example:
       [c^]) it stands for the ordinary character ^.

       The special meaning of the \ operator can be escaped only by preceding
       it with another \, for example \\.

   Macros
       Programs must have the following five macros declared before the
       #include <regexp.h> statement. These macros are used by the compile()
       routine. The macros GETC, PEEKC, and UNGETC operate on the regular
       expression given as input to compile().

       GETC  This macro returns the value of the next character (byte) in the
             regular expression pattern. Successive calls to  GETC should
             return successive characters of the regular expression.

       PEEKC This macro returns the next character (byte) in the regular
             expression. Immediately successive calls to  PEEKC should return
             the same character, which should also be the next character
             returned by GETC.

       UNGETC
             This macro causes the argument c to be returned by the next call
             to GETC and PEEKC. No more than one character of pushback is ever
             needed and this character is guaranteed to be the last character
             read by GETC. The return value of the macro UNGETC(c) is always
             ignored.

       RETURN(ptr)
             This macro is used on normal exit of the compile() routine. The
             value of the argument ptr is a pointer to the character after the
             last character of the compiled regular expression. This is useful
             to programs which have memory allocation to manage.

       ERROR(val)
             This macro is the abnormal return from the compile() routine. The
             argument val is an error number (see ERRORS below for meanings).
             This call should never return.

   compile()
       The syntax of the compile() routine is as follows:

              compile(instring, expbuf, endbuf, eof)

       The first parameter, instring, is never used explicitly by the
       compile() routine but is useful for programs that pass down different
       pointers to input characters. It is sometimes used in the INIT
       declaration (see below). Programs which call functions to input
       characters or have characters in an external array can pass down a
       value of (char *)0 for this parameter.

       The next parameter, expbuf, is a character pointer. It points to the
       place where the compiled regular expression will be placed.

       The parameter endbuf is one more than the highest address where the
       compiled regular expression may be placed. If the compiled expression
       cannot fit in (endbuf-expbuf) bytes, a call to ERROR(50) is made.

       The parameter eof is the character which marks the end of the regular
       expression. This character is usually a /.

       Each program that includes the <regexp.h> header file must have a
       #define statement for INIT. It is used for dependent declarations and
       initializations. Most often it is used to set a register variable to
       point to the beginning of the regular expression so that this register
       variable can be used in the declarations for GETC, PEEKC, and UNGETC.
       Otherwise it can be used to declare external variables that might be
       used by GETC, PEEKC and UNGETC.  (See EXAMPLES below.)

   step(), advance()
       The first parameter to the step() and advance() functions is a pointer
       to a string of characters to be checked for a match. This string should
       be null terminated.

       The second parameter, expbuf, is the compiled regular expression which
       was obtained by a call to the function compile().

       The function step() returns non-zero if some substring of string
       matches the regular expression in expbuf and  0 if there is no match.
       If there is a match, two external character pointers are set as a side
       effect to the call to step(). The variable loc1 points to the first
       character that matched the regular expression; the variable loc2 points
       to the character after the last character that matches the regular
       expression. Thus if the regular expression matches the entire input
       string, loc1 will point to the first character of string and loc2 will
       point to the null at the end of string.

       The function advance() returns non-zero if the initial substring of
       string matches the regular expression in expbuf. If there is a match,
       an external character pointer, loc2, is set as a side effect. The
       variable loc2 points to the next character in string after the last
       character that matched.

       When advance() encounters a * or \{ \} sequence in the regular
       expression, it will advance its pointer to the string to be matched as
       far as possible and will recursively call itself trying to match the
       rest of the string to the rest of the regular expression. As long as
       there is no match, advance() will back up along the string until it
       finds a match or reaches the point in the string that initially matched
       the  * or \{ \}. It is sometimes desirable to stop this backing up
       before the initial point in the string is reached. If the external
       character pointer locs is equal to the point in the string at sometime
       during the backing up process, advance() will break out of the loop
       that backs up and will return zero.

       The external variables circf, sed, and nbra are reserved.

EXAMPLES
       Example 1: The following is an example of how the regular expression
       macros and calls might be defined by an application program:

       #define INIT         register char *sp = instring;
       #define GETC       (*sp++)
       #define PEEKC      (*sp)
       #define UNGETC(c)    (--sp)
       #define RETURN(*c)    return;
       #define ERROR(c)     regerr
       #include <regexp.h>
        . . .
             (void) compile(*argv, expbuf, &expbuf[ESIZE],'\0');
        . . .
             if (step(linebuf, expbuf))
                               succeed;

DIAGNOSTICS
       The function compile() uses the macro RETURN on success and the macro
       ERROR on failure (see above). The functions step() and advance() return
       non-zero on a successful match and zero if there is no match. Errors
       are:

       11    range endpoint too large.

       16    bad number.

       25    \ digit out of range.

       36    illegal or missing delimiter.

       41    no remembered search string.

       42    \( \) imbalance.

       43    too many \(.

       44    more than 2 numbers given in \{ \}.

       45    } expected after \.

       46    first number exceeds second in \{ \}.

       49    [ ] imbalance.

       50    regular expression overflow.

SEE ALSO
       regex(5)

SunOS 5.9                         2 Apr 1996                         regexp(5)

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | DIAGNOSTICS | SEE ALSO

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