listing conditionally an array of strings - c

Question

I'm trying to list all files and folders in a given directory in C, the following code errors out and i cant figure out whats wrong
#include <sys/types.h>
#include <dirent.h>
#include <regex.h>
#include <stdio.h>
#include <unistd.h>
#include <pwd.h>
enum {
WALK_OK = 0,
WALK_BADPATTERN,
WALK_BADOPEN,
};
int walk_directories(const char *dir, const char *pattern, char* strings[])
{
struct dirent *entry;
regex_t reg;
DIR *d;
int i = 0;
//char array[256][256];
if (regcomp(&reg, pattern, REG_EXTENDED | REG_NOSUB))
return WALK_BADPATTERN;
if (!(d = opendir(dir)))
return WALK_BADOPEN;
while (entry = readdir(d))
if (!regexec(&reg, entry->d_name, 0, NULL, 0) )
//puts(entry->d_name);
strings[i] = (entry->d_name);
i++;
closedir(d);
regfree(&reg);
return WALK_OK;
}
void main()
{
struct passwd *pw = getpwuid(getuid());
char *homedir = pw->pw_dir;
strcat(homedir, "/.themes");
int n = 0;
char *array[256][100];
char *array2[256][100];
walk_directories(homedir, "", array);
for (n = 0; n < 256; n++)
{
//do stuff here later, but just print it for now
printf ("%s\n", array[n]);
}
walk_directories("/usr/share/themes", "", array2);
for (n = 0; n < 256; n++)
{
//do stuff here later, but just print it for now
printf ("%s\n", array2[n]);
}
}
The error at compile time is
test2.c: In function ‘main’:
test2.c:42:2: warning: incompatible implicit declaration of built-in function ‘strcat’ [enabled by default]
test2.c:48:2: warning: passing argument 3 of ‘walk_directories’ from incompatible pointer type [enabled by default]
test2.c:15:5: note: expected ‘char **’ but argument is of type ‘char * (*)[100]’
test2.c:52:6: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘char **’ [-Wformat]
test2.c:55:2: warning: passing argument 3 of ‘walk_directories’ from incompatible pointer type [enabled by default]
test2.c:15:5: note: expected ‘char **’ but argument is of type ‘char * (*)[100]’
test2.c:59:6: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘char **’ [-Wformat]
If it helps, I've implemented what I want already in python, this is the desired result for C
import os
DATA_DIR = "/usr/share"
def walk_directories(dirs, filter_func):
valid = []
try:
for thdir in dirs:
if os.path.isdir(thdir):
for t in os.listdir(thdir):
if filter_func(os.path.join(thdir, t)):
valid.append(t)
except:
logging.critical("Error parsing directories", exc_info=True)
return valid
def _get_valid_themes():
""" Only shows themes that have variations for gtk+-3 and gtk+-2 """
dirs = ( os.path.join(DATA_DIR, "themes"),
os.path.join(os.path.expanduser("~"), ".themes"))
valid = walk_directories(dirs, lambda d:
os.path.exists(os.path.join(d, "gtk-2.0")) and \
os.path.exists(os.path.join(d, "gtk-3.0")))
return valid
print(_get_valid_themes())
thank you
[EDIT]
thanks for the help, only problem im having now is the printf's all spit out rubbish instead of what i expected, ive tried a few things and the while loop looks like this now
while (entry = readdir(d))
if (!regexec(&reg, entry->d_name, 0, NULL, 0) )
//printf("%s\n",entry->d_name);
strcpy(strings[i], (entry->d_name));
//strings[i] = (entry->d_name);
printf("%i\n",i);
i++;
closedir(d);
the i doesnt get printed properly either, this is all i get from the 3 printf statements
0
Adwaita2
\#
0
Radiance
��
\#
�K��
� `���
����
�
��
�
.N=
�O��
�
�
should mention that if i enable
printf("%s\n",entry->d_name);
then it prints the expected output though

Answer 1

You should include string.h to get the declaration of strcat(3).
In your declaration:
int walk_directories(const char *dir, const char *pattern, char* strings[])
The char *strings[] is just syntactic sugar meaning char **strings. Since you're passing a 2D array, that won't work. It looks to me like you're intending to make two arrays of strings, but that's not what these declarations do:
char *array[256][100];
char *array2[256][100];
You probably don't want the *s there. If you take them off, you can change the signature of walk_directories to this:
int walk_directories(const char *dir, const char *pattern, char strings[][100])
And it should work, with the necessary changes inside your function to match. As a bonus, this change will make your printf calls start working, too.
It looks like you're missing some braces around your while loop body.

Answer 2

The first warning indicates that the compiler cannot figure out what arguments the strcat() function is supposed to take. Since this is a standard C function, this warning means that you are missing a #include directive. Specifically, you need to #include <string.h>. When you fix this, you may find that you get different errors and warnings, so work from there.