How to change directory structure in Linux/Unix from Command Line? - linux

Question

Here is what I want to do: Given Directory "XYZ", I want to be able to setup XYZ in way that once there is new sub-directory ("ABC") created in it, by default that subdirectory contains 3 sub-directories as well ("1","2","3"). Eg: ls -la /ABC/XYZ/ would display 3 folders without me creating those 3 folders manually

Answer 1

use inotify to monitor filesystem events and execute relative operations when capture 'create driectory ABC in XYZ' event. this is a sample from http://onestraw.net/essay/inotify/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/inotify.h>
#define MONITOR_PATH "/var/onestraw/"
#define MONITOR_MASK IN_CREATE | IN_DELETE | IN_ACCESS | IN_MODIFY
inline void _err(const char *str)
{
perror(str);
exit(1);
}
inline void inotify_loop(int fd)
{
char buf[4096];
size_t len;
struct inotify_event *event;
while (1) {
len = read(fd, buf, sizeof(buf));
if (len < 0) {
_err("read() failed");
}
for (event = (struct inotify_event *)buf;
(char *)event < &buf[len];
event =
(struct inotify_event *)((char *)event + sizeof(*event) +
event->len)) {
if (event->mask & IN_CREATE)
printf("add %s\n", event->name);
if (event->mask & IN_DELETE)
printf("delete %s\n", event->name);
if (event->mask & IN_ACCESS)
printf("access %s\n", event->name);
if (event->mask & IN_MODIFY)
printf("modify %s\n", event->name);
}
}
}
int main(int argc, char *argv[])
{
int fd;
if ((fd = inotify_init()) < 0) {
_err("inotify_init() failed");
}
//if (inotify_add_watch(fd, argv[1], MONITOR_MASK) < 0) {
if (inotify_add_watch(fd, MONITOR_PATH, MONITOR_MASK) < 0) {
_err("inotify_add_watch() failed");
}
inotify_loop(fd);
return 0;
}

Answer 2

In order to do that from the command line, install the inotify-tools.
sudo apt-get install inotify-tools
and then you can use the following command to monitor the XYZ directory for create events.
while ret=$(inotifywait -e create /tmp/XYZ); do mkdir /tmp/XYZ/{1,2,3}; done
As soon as any directory or file is created in XYZ, the commands in the while block will execute. mkdir in this case, creating further directories. you can add further checks as per your requirement in the block.