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What is signal behavior in the fork. Should all signals are inherited in fork If not then which one and why?
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POSIX specifies that fork can be called safely from signal handlers; it is required to be an async-signal-safe function.
There are 31 standard signals, numbered 1-31. Each signal is named as " SIG " followed by a suffix. Starting from version 2.2, the Linux kernel supports 33 different real-time signals.
The SIGCHLD signal is the only signal that the z/TPF system sends to a process. When a child process created by the tpf_fork function ends, the z/TPF system: Sends a SIGCHLD signal to the parent process to indicate that the child process has ended.
The common communication channel between user space program and kernel is given by the system calls.
At least under Linux, signal handlers themselves are inherited but not the pending signals.
Quoting the Linux fork(2) man page:
fork() creates a child process that differs from the parent process only in its PID and PPID, and in the fact that resource utilizations are set to 0. File locks and pending signals are not inherited.
This makes sense since the signals belong to the (parent) process. The newly created process is (mostly) a copy of the current process so signal handlers are preserved.
Although not directly related, the exec()-type call that often follows a fork() will destroy all signal handlers since a brand new executable is being loaded into the process (overwriting the functions currently servicing signals).
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