UNIX for Dummies Questions & Answers

Folks;
Could some one tell me what these 2 regular expressions mean:

[^\n\r]*/([^/\n\r]*)/[^/\n\r]*

(\d\d\d\d/\d\d/\d\d/[-_\.\w\d]*?)

Is this homework?

No, It's a task to extract fields out of directory tree

[^\n\r]*/([^/\n\r]*)/[^/\n\r]*

Match 0 or more characters except carriage returns or line feeds,
Followed by a single / character,
Next match 0 or more characters except / characters, carriage returns or line feeds again, group this for later retrieval,
Match another single /
Finally, another match of 0 or more chars except / returns and feeds as before.

In english: extract the second to last string seperated by / from a line.

(\d\d\d\d/\d\d/\d\d/[-_\.\w\d]*?)

Match an 8 digit number, followed by anything consiting of - _ . letters or numbers, finally followed by a ?

Thanks Smiling Dragon;
Now i have this question

If i have a list of directories, for example:

/fs/pas/2007/4/6/2634210/admdat/examin
/fs/pas/2007/4/6/2634210/admdat2/stat
/fs/pas/2007/4/6/2634210/admdat3/data
/fs/pas/2007/4/6/2634210/im_2/0b.dcm

Now; my questions are:
1. How to use RE to extract the last file such as "examin and stat,..."?

2. How to use RE to extract the parent directory for the last file. such as "amdat, amdat2, im_2,..."?

3. How to use RE to extract the date in the middle "2007/4/6"?

Any answer for this question?

Code:

perl -nle'm|([^/]*)$| and print $1' input
perl -nle'm|([^/]*)/[^/]*$| and print $1' input
perl -nle'm|/([^/]*/){2}(([^/]*/){2}[^/]*)| and print $2' input

Or just:

Code:

perl -F\/ -anle'print $F[-1]' input
perl -F\/ -anle'print $F[-2]' input
perl -F\/ -anle'print join "/", @F[3..5]' input