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10.2 Signal Concepts

The core file will not be generated if

(a) the process was set-user-ID and the current user is not the owner of the program file,

(b) the process was set-group-ID and the current user is not the group owner of the file,

© the user does not have permission to write in the current working directory,

(d) the file already exists and the user does not have permission to write to it, or

(e) the file is too big (recall the RLIMIT_CORE limit in Section 7.11).

The permissions of the core file (assuming that the file doesn’t already exist) are usually user-read and user-write, although Mac OS X sets only user-read.

NOTE: 上面这段话中的the process was set-user-ID是什么意思?是否是在图4-8中的例子;

SIGKILL 和 SIGTERM的异同

SIGKILL ,This signal is one of the two that can’t be caught or ignored. It provides the system administrator with a sure way to kill any process.

SIGTERM This is the termination signal sent by the kill(1) command by default. Because it can be caught by applications, using SIGTERM gives programs a chance to terminate gracefully by cleaning up before exiting (in contrast to SIGKILL, which can’t be caught or ignored).