umask - default chmod for directories and files.

UNIX determines directory modes by subracting your umask from the octal
number 777. If your umask is 027, your default directory mode is 750.
To find corresponding file permissions, subtract your umask from 666.
If your umask is 022, your default file modes will be 644.

$umask = 000
filemode 666
diremode 777

Typical umask Values:

  +-----------------------------------------------+
  | umask |  file             |  directory        |
  |       |                   |                   |
  | 077   |  600 (rw-------)  |  700 (rwx------)  |
  | 067   |  600 (rw-------)  |  710 (rwx--x---)  |
  | 066   |  600 (rw-------)  |  711 (rwx--x--x)  |
  | 027   |  640 (rw-r-----)  |  750 (rwxr-xr-x)  |
  | 022   |  644 (rw-r--r--)  |  755 (rwxr-xr-x)  |
  | 000   |  666 (rw-rw-rw-)  |  777 (rwxrwxrwx)  |
  +-----------------------------------------------+