Unix file permissions
Unix file permissions unix.com
umask Wikipedia
0 - none (i.e. all permissions specified are preserved) 1 - execute only 2 - write only 3 - write and execute 4 - read only 5 - read and execute 6 - read and write 7 - read, write and execute (i.e. no permissions are preserved)
[read, write, execute] for [user, group, other]
umask
660
770
symbolic
rw-rw----
rwxrwx---
The Evolution of the Unix Time-sharing System Denis Ritchie, cm.bell-labs.com
The Unix Heritage Society minnie.tuhs.org
tuXfiles tuxfiles.org
nixCraft: Linux Tips, Hacks, Tutorials, And Ideas In Blog Format cyberciti.biz
Scripting
Perl
perlrun - how to execute the Perl interpreter perldoc.perl.org