chmod

chmod [Options]… Mode [,Mode]… file…

chmod -R 755 *.txt ←————- recursive example

read 4

write 2

execute 1

# Permission rwx Binary

7 read, write and execute rwx 111

6 read and write rw- 110

5 read and execute r-x 101

4 read only r– 100

3 write and execute -wx 011

2 write only -w- 010

1 execute only –x 001

0 none — 000