sigaction.2 (2010 09)

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sigaction(2) sigaction(2)

will not fail with [EINTR] unless otherwise speciﬁed. If the ﬂag is not set,

interruptible functions interrupted by this signal will fail with

errno set

to [EINTR].

SA_SIGINFO If cleared and the signal is caught, the signal-catching function will be

entered as:

void func(int signo); where signo is the only argument to the

signal catching function. In this case the sa_handler member must be used

to describe the signal catching function and the application must not

modify the sa_sigaction member.

SA_SIGINFO is set and the signal is caught, the signal-catching func-

tion will be entered as:

void func(int signo, siginfo_t *info, void *con-

text); where two additional arguments are passed to the signal catching

function. If the second argument is not a null pointer, it will point to an

object of type siginfo_t explaining the reason why the signal was generated;

the third argument can be cast to a pointer to an object of type ucontext_t

to refer to the context of the receiving process or thread that was inter-

rupted when the signal was delivered. In this case the sa_sigaction

member must be used to describe the signal catching function and the

application must not modify the sa_handler member.

The si_signo member of info contains the system-generated signal number.

The si_errno member may contain implementation-dependent additional

error information; if non-zero, it contains an error number identifying the

condition that caused the signal to be generated.

The si_code member contains a code identifying the cause of the signal. If

the value of si_code is less than or equal to 0, then the signal was gen-

erated by a process and si_pid and si_uid respectively indicate the process

ID and the real user ID of the sender. The values of si_pid and si_uid are

otherwise meaningless.

SA_SIGINFO is set in sa_ﬂags , subsequent occurrences of sig generated

by sigqueue() or as a result of any signal-generating function that sup-

ports the speciﬁcation of an application-deﬁned value - when sig is already

pending - will be queued in FIFO order until delivered, and the application

speciﬁed value will be passed to the signal-catching function as the

si_value member of info (See Realtime Signals Extension ). If

SA_SIGINFO is not set in sa_ﬂags , then the disposition of subsequent

occurrences of sig when it is already pending is implementation-deﬁned.

SA_NOCLDWAIT If set, and sig equals SIGCHLD, child processes of the calling process will

not be transformed into zombie processes when they terminate. If the cal-

ling process subsequently waits for its children, and the process has no

unwaited for children that were transformed into zombie processes, it will

block until all of its children terminate, and wait(), wait3(),

waitid(), and waitpid() will fail and set errno to [ECHILD]. Other-

wise, terminating child processes will be transformed into zombie

processes, unless SIGCHLD is set to SIG_IGN.

SA_NODEFER If set and sig is caught, sig will not be added to the process’ signal mask on

entry to the signal handler unless it is included in sa_mask . Otherwise, sig

will always be added to the process’ signal mask on entry to the signal

handler.

If sig is

SIGCHLD and the SA_NOCLDSTOP ﬂag is not set in sa_ﬂags, and the implementation supports

the SIGCHLD signal, then a SIGCHLD signal will be generated for the calling process whenever any of its

child processes stop. If sig is SIGCHLD and the SA_NOCLDSTOP ﬂag is set in sa_ﬂags, then the imple-

mentation will not generate a SIGCHLD signal in this way.

When a signal is caught by a signal-catching function installed by

sigaction(), a new signal mask is

calculated and installed for the duration of the signal-catching function (or until a call to either sig-

procmask() or sigsuspend() is made). This mask is formed by taking the union of the current

2 Hewlett-Packard Company − 2 − HP-UX 11i Version 3: September 2010