regular expression doesnt work while execute in c

i am trying to build regular expression with the regex.h lib.

i checked my expression in https://regex101.com/ with the the input
"00001206 ffffff00 00200800 00001044" and i checked it in python as well, both gave me the expected result.
when i ran the code below in c (over unix) i got "no match" print.
any one have any suggest?

regex_t regex;
int reti;
reti = regcomp(&regex, "([0-9a-fA-F]8( |$))+$", 0);
if (reti)

fprintf(stderr, "Could not compile regexn");
exit(1);


reti = regexec(&regex, "00001206 ffffff00 00200800 00001044", 0, NULL, 0);
if (!reti)

printf("Match");

else if (reti == REG_NOMATCH)
printf("No match bla blan");



1 Answer
1

Your pattern contains a $ anchor, capturing groups with (...) and the interval quantifier m,n, so you need to pass REG_EXTENDED to the regex compile method:

$

(...)

m,n

REG_EXTENDED

regex_t regex;
int reti;
reti = regcomp(&regex, "([0-9a-fA-F]8( |$))+$", REG_EXTENDED); // <-- See here
if (reti)

fprintf(stderr, "Could not compile regexn");
exit(1);


reti = regexec(&regex, "00001206 ffffff00 00200800 00001044", 0, NULL, 0);
if (!reti)

printf("Match");

else if (reti == REG_NOMATCH)
printf("No match bla blan");



See the online C demo printing Match.

Match

However, I believe you need to match the entire string, and disallow whitespace at the end, so probably

reti = regcomp(&regex, "^[0-9a-fA-F]8( [0-9a-fA-F]8)*$", REG_EXTENDED);


will be more precise as it will not allow any arbitrary text in front and won't allow a trailing space.

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