linux server create symbolic links from filenames - linux

Question

I need to write a shell script to run as a cron task, or preferably on creation of a file in a certain folder.
I have an incoming and an outgoing folder (they will be used to log mail). There will be files created with codes as follows...
bmo-001-012-dfd-11 for outgoing and 012-dfd-003-11 for incoming. I need to filter the project/client code (012-dfd) and then place it in a folder in the specific project folder.
Project folders are located in /projects and follow the format 012-dfd. I need to create symbolic links inside the incoming or outgoing folders of the projects, that leads to the correct file in the general incoming and outgoing folders.
/incoming/012-dfd-003-11.pdf -> /projects/012-dfd/incoming/012-dfd-003-11.pdf
/outgoing/bmo-001-012-dfd-11.pdf -> /projects/012-dfd/outgoing/bmo-001-012-dfd-11.pdf
So my questions
How would I make my script run when a file is added to either incoming or outgoing folder
Additionally, is there any associated disadvantages with running upon file modification compared with running as cron task every 5 mins
How would I get the filename of recent (since script last run) files
How would I extract the code from the filename
How would I use the code to create a symlink in the desired folder
EDIT: What I ended up doing...
while inotifywait outgoing; do find -L . -type l -delete; ls outgoing | php -R '
if(
preg_match("/^\w{3}-\d{3}-(\d{3}-\w{3})-\d{2}(.+)$/", $argn, $m)
&& $m[1] && (file_exists("projects/$m[1]/outgoing/$argn") != TRUE)
){
`ln -s $(pwd)/outgoing/$argn projects/$m[1]/outgoing/$argn;`;
}
'; done;
This works quite well - cleaning up deleted symlinks also (with find -L . -type l -delete) but I would prefer to do it without the overhead of calling php. I just don't know bash well enough yet.

Answer 1

Some near-answers for your task breakdown:
On linux, use inotify, possibly through one of its command-line tools, or script language bindings.
See above
Assuming the project name can be extracted thinking positionally from your examples (meaning not only does the project name follows a strict 7-character format, but what precedes it in the outgoing file also does):
echo `basename /incoming/012-dfd-003-11.pdf` | cut -c 1-7
012-dfd
echo `basename /outgoing/bmo-001-012-dfd-11.pdf`| cut -c 9-15
012-dfd
mkdir -p /projects/$i/incoming/ creates directory /projects/012-dfd/incoming/ if i = 012-dfd,
ln -s /incoming/foo /projects/$i/incoming/foo creates a symbolic link from the latter argument, to the preexisting, former file /incoming/foo.

Answer 2

How would I make my script run when a file is added to either incoming or outgoing folder
Additionally, is there any associated disadvantages with running upon file modification compared with running as cron task
every 5 mins
If a 5 minutes delay isn't an issue, I would go for the cron job (it's easier and -IMHO- more flexible)
How would I get the filename of recent (since script last run) files
If your script runs every 5 minutes, then you can tell that all the files created in between now (and now - 5 minutes) are newso, using the command ls or find you can list those files.
How would I extract the code from the filename
You can use the sed command
How would I use the code to create a symlink in the desired folder
Once you have the desired file names, you can usen ln -s command to create the symbolic link