checking if a string with asterisk(*) is present within another string - c

Question

I am working on a program to check if a particular string is present in the given string: that is if one string is sub string of another string.
For example:
1)String: YoungPeople --> Substring to be checked: ungPeo
The output should return true.
2)String: Hello How are You? --> Substring to be checked: l*are
The output should return true.
I have used the naive based searching algorithm and it works perfectly fine for the first input.
But I am having trouble in the second kind of input where the asterisk(*) is present which should be treated as a regular expression: i.e. matches zero or more characters.
How should I check for the sub string having an * sign?
Should I try to use the same naive algorithm for searching the character before * and for the string after it? Or is there a better approach to solve this problem?

Answer 1

How should i check for the sub string having an * sign?
Upon reading a *, you need to try 1-2 below.
... use the same naive algorithm for searching ... is there a better approach ...?*
There are better methods. A recursive one follows.
[Edit note: 6/10 found/fixed bug]
As you progress through the string, use recursion to check the rest of the string.
The * simple allows for 2 candidate paths:
1) advance the str
2) advance the substr
Else a matching char allows advancing both.
// StarCompare() helper function
bool StarCmp(const char *str, const char *pat) {
if (*pat == '\0') return 1;
if (*pat == '*') {
if (*str) {
// advance str and use the * again
if (StarCmp(str + 1, pat)) return 1;
}
// let * match nothing and advacne to the next pattern
return StarCmp(str, pat + 1);
}
if (*pat == *str) {
return StarCmp(str + 1, pat + 1);
}
return 0;
}
bool StarCompare(const char *str, const char *pat) {
if (!str || !pat) return 0;
do {
if (StarCmp(str, pat)) return 1;
} while (*str++);
return 0;
}
[Edit Test code in previous version]

Answer 2

The GNU Regex Library seems like what you are looking for. If you are not familiar with regular expression, check this site.

Answer 3

Here is what you have to do:
Split the search string by the * character
Look for each of the parts (in the correct order) in the string you are searching
Alternatively, you can use regexes as other people have suggested.

Answer 4

A good place to look for a well-written implementation of glob matching would be the bash sources. But here's a simple recursive implementation that works:
#include <assert.h>
int
_glob_match(char * pattern, char * str)
{
if (!*pattern) return 1;
if (!*str) return 0;
if (*pattern == '*') return match_any_tail(pattern + 1, str);
if (*pattern != *str) return 0;
else return _glob_match(pattern + 1, str + 1);
}
int
match_any_tail(char * pattern, char * str)
{
for (; *str; str++)
if (_glob_match(pattern, str))
return 1;
return 0;
}
int glob_match(char * pattern, char * str)
{
return match_any_tail (pattern, str);
}
void
main()
{
assert(glob_match("ungPeo", "YoungPeople"));
assert(glob_match("l*are", "Hello How are You?"));
}