Can I prevent a folder of a certain name being created?

You can't, given the user creating the directory has sufficient permission to write on the parent directory.

You can instead leverage the inotify family of system calls provided by the Linux kernel, to watch for the creation (and optionally mv-ing) of directory shop in the given directory, if created (or optionally mv-ed), rm the directory.

The userspace program you need in this case is inotifywait (comes with inotify-tools, install it first if needed).

---

Assuming the directory shop would be residing in /foo/bar directory, let's set a monitoring for /foo/bar/shop creation, and rm instantly if created:

inotifywait -qme create /foo/bar | \
             awk '/,ISDIR shop$/ { system("rm -r -- /foo/bar/shop") }'

• inotifywait -qme create /foo/bar watches /foo/bar directory for any file/directory that might be created i.e. watch for any create event

• If created, awk '/,ISDIR shop$/ { system("rm -r -- /foo/bar/shop") }' checks if the file happens to be a directory and the name is shop (/,ISDIR shop$/), if so rm the directory (system("rm -r -- /foo/bar/shop"))

You need to run the command as a user that has write permission on directory /foo/bar for removal of shop from the directory.

---

If you want to monitor mv-ing operations too, add watch for moved_to event too:

inotifywait -qme create,moved_to /foo/bar | \
             awk '/,ISDIR shop$/ { system("rm -r -- /foo/bar/shop") }'

---

Just to note, if you are looking for a file, not directory, named shop:

inotifywait -qme create /foo/bar | \
                 awk '$NF == "shop" { system("rm -- /foo/bar/shop") }'

inotifywait -qme create,moved_to /foo/bar | \
                 awk '$NF == "shop" { system("rm -- /foo/bar/shop") }'

To answer literally based on the question of preventing a folder of a certain name to be created.

touch shop

You can't create a directory if a file with a identical name existing

mkdir: cannot create directory ‘shop’: File exists

What about hijacking mkdir syscall with LD_PRELOAD...?

$ ls
test.c
$ cat test.c 
#define _GNU_SOURCE

#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <dlfcn.h>

typedef int (*orig_mkdir_func_type)(const char *path, mode_t mode);

int mkdir(const char *path, mode_t mode) {
    if(!strcmp(path, "shop")) return 1;

    orig_mkdir_func_type orig_func;
    orig_func = (orig_mkdir_func_type)dlsym(RTLD_NEXT, "mkdir");
    return orig_func(path, mode);
}
$ gcc -shared -fPIC test.c -o test.so
$ LD_PRELOAD='./test.so' mkdir test
$ LD_PRELOAD='./test.so' mkdir shop
mkdir: cannot create directory ‘shop’: No such file or directory
$ ls
test  test.c  test.so

Note that inside this handler you can log PID of process that want to create this directory instead:

$ cat test.c 
#define _GNU_SOURCE

#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <dlfcn.h>

typedef int (*orig_mkdir_func_type)(const char *path, mode_t mode);

int mkdir(const char *path, mode_t mode) {
    if(!strcmp(path, "shop")) {
        FILE* fp = fopen("/tmp/log.txt", "w");
        fprintf(fp, "PID of evil script: %d\n", (int)getpid());
        fclose(fp);
    }

    orig_mkdir_func_type orig_func;
    orig_func = (orig_mkdir_func_type)dlsym(RTLD_NEXT, "mkdir");
    return orig_func(path, mode);
}
$ gcc -shared -fPIC test.c -o test.so
$ LD_PRELOAD='./test.so' mkdir shop
$ cat /tmp/log.txt 
PID of evil script: 8706

You need to place this in ~/.bashrc of root (or whoever is running your app) to ensure this will be used:

export LD_PRELOAD=/path/to/test.so