Geek Stuff (Linux) - Show Chmod Numerical Permissions

During Linux installations of EPM, setting and validating the correct security on folders and files can be a challenge. The chmod command is used to set security access, while chown sets the ownership's. As you might now chmod has two modes of reading and applying security access: Symbolic and Octal mode.


Default is Symbolic mode, which is represented by a Reference, Operator and Mode. Octal mode simplifies the usage and is represented by three (digits) Numerical values.

Below a default output of an "ls -a" command in bash:

total 0 -rw-r----- 1 www-data www-data 0 Sep  4 23:16 global.dir -rw-r----- 1 www-data www-data 0 Sep  4 23:16 global.pag -rw-r----- 1 www-data www-data 0 Sep  4 23:16 ip.dir -rw-r----- 1 www-data www-data 0 Sep  4 23:16 ip.pag

As you can see access rights is represented in symbolic mode (-rw-r-----). Sometime is it helpful to additionally show the octal representation. However the "ls" command and many others do not support this. Below a script that takes the "ls" command input and adds the numerical representation of the security.

ls -la | awk '{k=0;for(i=0;i<=8;i++)k+=((substr($1,i+2,1)~/[rwx]/) \              *2^(8-i));if(k)printf("%0o ",k);print}'

Output of this script will look similar to (notice the 3 digits at the start of each row):

total 0 640 -rw-r----- 1 www-data www-data 0 Sep  4 23:16 global.dir 640 -rw-r----- 1 www-data www-data 0 Sep  4 23:16 global.pag 640 -rw-r----- 1 www-data www-data 0 Sep  4 23:16 ip.dir 640 -rw-r----- 1 www-data www-data 0 Sep  4 23:16 ip.pag

Enjoy this script!


sources:  https://en.wikipedia.org/wiki/Chmod