Category : C Source Code
Archive   : REGEXP.ZIP
Filename : REGEXP.MAN

 
Output of file : REGEXP.MAN contained in archive : REGEXP.ZIP



RRRREEEEGGGGEEEEXXXXPPPP((((3333)))) UUUUNNNNIIIIXXXX 5555....0000 ((((llllooooccccaaaallll)))) RRRREEEEGGGGEEEEXXXXPPPP((((3333))))



NNNNAAAAMMMMEEEE
regcomp, regexec, regsub, regerror - regular expression
handler

SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
####iiiinnnncccclllluuuuddddeeee <<<>>>

rrrreeeeggggeeeexxxxpppp ****rrrreeeeggggccccoooommmmpppp((((eeeexxxxpppp))))
cccchhhhaaaarrrr ****eeeexxxxpppp;;;;

iiiinnnntttt rrrreeeeggggeeeexxxxeeeecccc((((pppprrrroooogggg,,,, ssssttttrrrriiiinnnngggg))))
rrrreeeeggggeeeexxxxpppp ****pppprrrroooogggg;;;;
cccchhhhaaaarrrr ****ssssttttrrrriiiinnnngggg;;;;

rrrreeeeggggssssuuuubbbb((((pppprrrroooogggg,,,, ssssoooouuuurrrrcccceeee,,,, ddddeeeesssstttt))))
rrrreeeeggggeeeexxxxpppp ****pppprrrroooogggg;;;;
cccchhhhaaaarrrr ****ssssoooouuuurrrrcccceeee;;;;
cccchhhhaaaarrrr ****ddddeeeesssstttt;;;;

rrrreeeeggggeeeerrrrrrrroooorrrr((((mmmmssssgggg))))
cccchhhhaaaarrrr ****mmmmssssgggg;;;;

DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
These functions implement _e_g_r_e_p(1)-style regular expressions
and supporting facilities.

_R_e_g_c_o_m_p compiles a regular expression into a structure of
type _r_e_g_e_x_p, and returns a pointer to it. The space has
been allocated using _m_a_l_l_o_c(3) and may be released by _f_r_e_e.

_R_e_g_e_x_e_c matches a NUL-terminated _s_t_r_i_n_g against the compiled
regular expression in _p_r_o_g. It returns 1 for success and 0
for failure, and adjusts the contents of _p_r_o_g's _s_t_a_r_t_p and
_e_n_d_p (see below) accordingly.

The members of a _r_e_g_e_x_p structure include at least the
following (not necessarily in order):

char *startp[NSUBEXP];
char *endp[NSUBEXP];

where _N_S_U_B_E_X_P is defined (as 10) in the header file. Once a
successful _r_e_g_e_x_e_c has been done using the _r_e_g_e_x_p, each
_s_t_a_r_t_p-_e_n_d_p pair describes one substring within the _s_t_r_i_n_g,
with the _s_t_a_r_t_p pointing to the first character of the
substring and the _e_n_d_p pointing to the first character
following the substring. The 0th substring is the substring
of _s_t_r_i_n_g that matched the whole regular expression. The
others are those substrings that matched parenthesized
expressions within the regular expression, with
parenthesized expressions numbered in left-to-right order of
their opening parentheses.



Page 1 (printed 9/2/87)






RRRREEEEGGGGEEEEXXXXPPPP((((3333)))) UUUUNNNNIIIIXXXX 5555....0000 ((((llllooooccccaaaallll)))) RRRREEEEGGGGEEEEXXXXPPPP((((3333))))



_R_e_g_s_u_b copies _s_o_u_r_c_e to _d_e_s_t, making substitutions according
to the most recent _r_e_g_e_x_e_c performed using _p_r_o_g. Each
instance of `&' in _s_o_u_r_c_e is replaced by the substring
indicated by _s_t_a_r_t_p[_0] and _e_n_d_p[_0]. Each instance of `\_n',
where _n is a digit, is replaced by the substring indicated
by _s_t_a_r_t_p[_n] and _e_n_d_p[_n]. To get a literal `&' or `\_n' into
_d_e_s_t, prefix it with `\'; to get a literal `\' preceding `&'
or `\_n', prefix it with another `\'.

_R_e_g_e_r_r_o_r is called whenever an error is detected in _r_e_g_c_o_m_p,
_r_e_g_e_x_e_c, or _r_e_g_s_u_b. The default _r_e_g_e_r_r_o_r writes the string
_m_s_g, with a suitable indicator of origin, on the standard
error output and invokes _e_x_i_t(2). _R_e_g_e_r_r_o_r can be replaced
by the user if other actions are desirable.

RRRREEEEGGGGUUUULLLLAAAARRRR EEEEXXXXPPPPRRRREEEESSSSSSSSIIIIOOOONNNN SSSSYYYYNNNNTTTTAAAAXXXX
A regular expression is zero or more _b_r_a_n_c_h_e_s, separated by
`|'. It matches anything that matches one of the branches.

A branch is zero or more _p_i_e_c_e_s, concatenated. It matches a
match for the first, followed by a match for the second,
etc.

A piece is an _a_t_o_m possibly followed by `*', `+', or `?'.
An atom followed by `*' matches a sequence of 0 or more
matches of the atom. An atom followed by `+' matches a
sequence of 1 or more matches of the atom. An atom followed
by `?' matches a match of the atom, or the null string.

An atom is a regular expression in parentheses (matching a
match for the regular expression), a _r_a_n_g_e (see below), `.'
(matching any single character), `^' (matching the null
string at the beginning of the input string), `$' (matching
the null string at the end of the input string), a `\'
followed by a single character (matching that character), or
a single character with no other significance (matching that
character).

A _r_a_n_g_e is a sequence of characters enclosed in `[]'. It
normally matches any single character from the sequence. If
the sequence begins with `^', it matches any single
character _n_o_t from the rest of the sequence. If two
characters in the sequence are separated by `-', this is
shorthand for the full list of ASCII characters between them
(e.g. `[0-9]' matches any decimal digit). To include a
literal `]' in the sequence, make it the first character
(following a possible `^'). To include a literal `-', make
it the first or last character.


AAAAMMMMBBBBIIIIGGGGUUUUIIIITTTTYYYY
If a regular expression could match two different parts of
the input string, it will match the one which begins



Page 2 (printed 9/2/87)






RRRREEEEGGGGEEEEXXXXPPPP((((3333)))) UUUUNNNNIIIIXXXX 5555....0000 ((((llllooooccccaaaallll)))) RRRREEEEGGGGEEEEXXXXPPPP((((3333))))



earliest. If both begin in the same place but match
different lengths, or match the same length in different
ways, life gets messier, as follows.

In general, the possibilities in a list of branches are
considered in left-to-right order, the possibilities for
`*', `+', and `?' are considered longest-first, nested
constructs are considered from the outermost in, and
concatenated constructs are considered leftmost-first. The
match that will be chosen is the one that uses the earliest
possibility in the first choice that has to be made. If
there is more than one choice, the next will be made in the
same manner (earliest possibility) subject to the decision
on the first choice. And so forth.

For example, `(ab|a)b*c' could match `abc' in one of two
ways. The first choice is between `ab' and `a'; since `ab'
is earlier, and does lead to a successful overall match, it
is chosen. Since the `b' is already spoken for, the `b*'
must match its last possibility-the empty string-since it
must respect the earlier choice.

In the particular case where no `|'s are present and there
is only one `*', `+', or `?', the net effect is that the
longest possible match will be chosen. So `ab*', presented
with `xabbbby', will match `abbbb'. Note that if `ab*' is
tried against `xabyabbbz', it will match `ab' just after
`x', due to the begins-earliest rule. (In effect, the
decision on where to start the match is the first choice to
be made, hence subsequent choices must respect it even if
this leads them to less-preferred alternatives.)

SSSSEEEEEEEE AAAALLLLSSSSOOOO
egrep(1), expr(1)

DDDDIIIIAAAAGGGGNNNNOOOOSSSSTTTTIIIICCCCSSSS
_R_e_g_c_o_m_p returns NULL for a failure (_r_e_g_e_r_r_o_r permitting),
where failures are syntax errors, exceeding implementation
limits, or applying `+' or `*' to a possibly-null operand.

HHHHIIIISSSSTTTTOOOORRRRYYYY
Both code and manual page were written at U of T. They are
intended to be compatible with the Bell V8 _r_e_g_e_x_p(3), but
are not derived from Bell code.

BBBBUUUUGGGGSSSS
Empty branches and empty regular expressions are not
portable to V8.

The restriction against applying `*' or `+' to a possibly-
null operand is an artifact of the simplistic
implementation.



Page 3 (printed 9/2/87)






RRRREEEEGGGGEEEEXXXXPPPP((((3333)))) UUUUNNNNIIIIXXXX 5555....0000 ((((llllooooccccaaaallll)))) RRRREEEEGGGGEEEEXXXXPPPP((((3333))))



Does not support _e_g_r_e_p's newline-separated branches; neither
does the V8 _r_e_g_e_x_p(3), though.

Due to emphasis on compactness and simplicity, it's not
strikingly fast. It does give special attention to handling
simple cases quickly.

















































Page 4 (printed 9/2/87)





  3 Responses to “Category : C Source Code
Archive   : REGEXP.ZIP
Filename : REGEXP.MAN

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

  2. This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.

  3. But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: http://www.os2museum.com/wp/mtswslnk/