在没有fork / exec，popen（）和system（）的情况下获取Linux信息

Question

I want to know how to get the following linux system information from C++ without using fork/exec, popen(), and system() :

1. Get the command string (name) that started the process for a given process id.
2. Send a signal to a process
3. Catch and display all the signals my program receives
4. Get the process id(s) for any given process name

Any hints would be appreciated.

Thank you so much for your time!

Answer 1

I believe the info for 1) is contained in /proc/PID/cmdline

If you want the current process you can use /proc/self/ - handy when you don't know pid. I don't know much about C++ but in C you can use open and read syscalls to do it, which avoids forking.

I think a lot of the other answers you can probably do by manipulating /proc entries as well. I beleive /proc/PID/status tells you about signals that have been caught blocked and ignored by the specified PID as well.

edit: Thinking a bit more for 4) you can recursively loop through the pid entries in /proc to look up your given process name - this is only way I can think of without forking (calling "ps" from within code as other suggested requires a fork/exec). Is there a particular reason you are avoiding fork?

Answer 2

1. main function of a process receives that bit
2. kill - ie http://man7.org/linux/man-pages/man2/kill.2.html
3. See 2
4. Tricky.Requires me thinking

Answer 3

1. From main, you may print argv[0]. But that won't help always as the starting program may get replaced by a new due to call to fork/exec.
2. You need to use kill command line program or kill system call
3. Check the man page for sigaction
4. I am assuming you are meaning executable name. You may do the below, may not work on all Unix systems, but should work on Linux.

   ps -ef | grep " program-name" | awk ' { print $2 } '