searching for a file name using only an extension - c

Question

prev problem was not described well.
I need to retrieve a file name and assign that name to a variable. The only thing is that the file can have any name.
The thing that I know is the file extension and there can only be one file of this extension.
Is there any way to implement this in C?
Update #1
File extension is *.knb and target is Linux system.
#include <stdio.h>
#include <dirent.h>
#define LOG_() do{fprintf(stdout, " UNIT TESTING...\n");}while(0)
char* knbname;
void fName(void);
int main()
{
LOG_();
fName(void);
//do some more code
return 0;
}
void fName(void){
DIR *d;
struct dirent *dir;
d = opendir(".");
if (d)
{
//find file with *.knb extension and place name into knbname
}
closedir(d);
}
I don't know how to find for a *.knb file in the fName() function and how to assign name to knbname. Any help will be appreciated

Answer 1

You are reinventing POSIX's glob() function. Here is an example of how to use it (see the flags in manpage for more options):
#include <glob.h>
int main(void)
{
glob_t glob_res = { 0 };
glob("*.knb", 0, NULL, &glob_res);
if (glob_res.gl_pathc == 0) puts("No match.");
else printf("First match is %s\n", glob_res.gl_pathv[0]);
globfree(&glob_res);
return 0;
}

Answer 2

After Andrew pointed out some major flaw in the previous design, i will make another attempt for a solution...
int hasExtension(char *filename, char *extension);
int main(void)
{
DIR *directory;
struct dirent *entry;
if(NULL == (directory = opendir(".")))
{
perror("Failed to open directory\n");
exit(1);
}
while( NULL != (entry = readdir(directory)) )
{
if(DT_REG == entry->d_type) { // Regualar files only
if(hasExtension(entry->d_name, ".knb"))
{
printf("Match - %s\n", entry->d_name);
} else {
printf("No match - %s\n", entry->d_name);
}
}
}
closedir(directory);
return 0;
}
int hasExtension(char *filename, char *extension)
{
size_t filename_len, extension_len;
if((NULL == filename) || (NULL ==extension))
return 0;
filename_len = strlen(filename);
extension_len = strlen(extension);
if(filename_len < extension_len)
return 0;
return !strcmp(filename + filename_len - extension_len, extension);
}