Free Unix Permissions calculator with clear step-by-step results.
Each permission class is a three-bit field where read is 4, write is 2 and execute is 1, so summing the bits per class gives the familiar three octal digits. The complementary umask is what a process would need so that newly created files default to this mode.
Octal digit per class
Digit = 4 if read + 2 if write + 1 if execute
Umask
Umask = 777 - the resulting octal mode, digit by digit
Permission changes on shared or production systems can create security exposures or break running services. Review changes carefully and prefer least privilege.
It grants the right to traverse into the directory and access entries by name. Read without execute lets you list names but not stat or open them.
Any user on the system can modify or replace the file. On a shared host that is a straightforward path to privilege escalation or data tampering.