Difference between EACCES and EPERM

问题

What is the difference between EACCES and EPERM exactly? EPERM is described here as "not super user", but I would usually associate that with EACCES. In fact, I can't recall ever seeing an EPERM in real life.

回答1:

EACCES is almost always used when the system call was passed a path that was inaccessible by the current user.

EPERM is used in various other situations where you need to be root to perform an action, e.g.

• kill() on a process that you don't own
• link() on a directory
• reboot()

回答2:

According to Linux programmers, learn the difference between EACCES and EPERM already! - A Random Dev's Rants...

• EACCES "Permission denied" should be used to mean that the user doesn't have sufficient privileges to do the action. The root user, or another user with sufficient user/group permissions should be able to do the action.
• EPERM "Operation not permitted" should be used to mean the action is not possible or safe in general, regardless of whether the user is root or not. Examples would be:
  • chmoding a file on a FAT filesystem (the filesystem doesn't support permission bits)
• Note that a lot of Linux code returns EPERM when it should really return EACCES.

回答3:

The Linux capabilities(7) figure into execve(2) so that if the exec'ing process lacks the correct inheritance/bounding-set/ambient to set the file-capabilities:

"If the process did not obtain the full set of file permitted capabilities, then execve(2) fails with the error EPERM."

来源：https://stackoverflow.com/questions/35023667/difference-between-eacces-and-eperm