sigqueue(3) [osf1 man page]
sigqueue(3) Library Functions Manual sigqueue(3) NAME
sigqueue - Queues a signal and data to a running process LIBRARY
Realtime Library (librt.so, librt.a) SYNOPSIS
#include <signal.h> int sigqueue ( pid_t pid, int signo, const union sigval value); PARAMETERS
pid Specifies the ID of the target process. signo Specifies the signal to be queued. If the signo parameter is 0 (the null signal), error checking is performed but no signal is sent. This can be used to check the validity of the pid parameter. value Specifies the application-defined value to be queued to the receiving process. DESCRIPTION
The sigqueue function causes the signal specified by signo to be sent with the value specified by value to the process specified by pid. The conditions required for a process to have permission to queue a signal to another process are the same as for the kill function. If the call is successful, the signal is queued to the specified process. If the process has the SA_SIGINFO flag enabled for the queued signal, the specified value is delivered to its signal handler as the si_value field of the siginfo parameter. Nonprivileged callers are restricted in the number of signals they can have actively queued. This per-process quota value can be returned with sysconf(_SC_SIGQUEUE_MAX). RETURN VALUES
Upon successful completion, the sigqueue function returns a value of 0 (zero). Otherwise, a value of -1 is returned and errno is set to indicate the error. ERRORS
If sigqueue fails, no signal is sent, and errno is set to one of the following values: [EAGAIN] No resources are available to queue the signal. The process has already queued {SIGQUEUE_MAX} signals that are still pending at the receiver(s), or a system-wide resource limit has been exceeded. [EINVAL] The signo parameter is not a valid signal number. [EINVAL] The signo parameter is SIGKILL, SIGSTOP, SIGTSTP, or SIGCONT, and the pid parameter is 1 (process 1 -- init). [ESRCH] No process can be found corresponding to that specified by the pid parameter. [EPERM] The real or saved user ID does not match the real or effective user ID of the receiving process, the calling process does not have appropriate privilege, or the process is not sending a SIGCONT signal to one of its session's processes. RELATED INFORMATION
Headers: siginfo(5) Functions: kill(2), sigaction(2), sysconf(3) Guide to Realtime Programming delim off sigqueue(3)
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sigqueue(2) System Calls Manual sigqueue(2) NAME
sigqueue() - queue a signal to a process SYNOPSIS
DESCRIPTION
The system call causes the signal specified by signo to be sent with the value specified by value to the process specified by pid. If signo is zero (the null signal), error checking is performed but no signal is actually sent. The null signal can be used to check the validity of pid. The conditions required for a process to have permission to queue a signal to another process are the same as for the system call. The system call returns immediately. If is set for signo at the receiving process (see sigqueue(2)) and if resources are available to queue the signal, the signal will be queued and sent to the receiving process. When the signal is delivered or accepted, the field si_value of the siginfo parameter (see signal(5)) will be set to value. If is not set for signo, then signo, but not necessarily value, will be sent at least once to the receiving process. If the value of pid causes signo to be generated for the sending process, and if signo is not blocked, either signo or at least one pending unblocked signal will be delivered to the sending process before the system call returns. Should any of multiple pending signals in the range to be selected for delivery or acceptance, it will be the lowest numbered one. The selection order between realtime and non-realtime signals, or between multiple pending non-realtime signals, is unspecified. Application Usage Threads Considerations can be used to post signals to another process but can not be used to post signals to a specific thread in another process. If the value of pid causes signo to be generated for the sending process, and if signo is not blocked for the calling thread and if no other thread has signo unblocked or is waiting in a function for signo, either signo or at least one pending unblocked signal will be delivered to the calling thread before the function returns. LWP Considerations Signals can not be posted to specific Lightweight Processes (LWPs) in another process. Security Restrictions Some or all of the actions associated with this system call are subject to compartmental restrictions. See compartments(5) for more infor- mation about compartmentalization on systems that support that feature. Compartmental restrictions can be overridden if the process pos- sesses the privilege (COMMALLOWED). Processes owned by the superuser may not have this privilege. Processes owned by any user may have this privilege, depending on system configuration. Some or all of the actions associated with this system call require one or more privileges. Processes owned by the superuser have many, though not all, privileges. Processes owned by other users may have privilege(s), depending on system configuration. See privileges(5) for more information about privileged access on systems that support fine-grained privileges. RETURN VALUE
Upon successful completion, the specified signal will be queued, and the function returns a value of (zero). Otherwise, a value of is returned, and is set to indicate the error. ERRORS
fails and no signal is sent if any of the following conditions occur: No resources are available to queue the signal. The process has already queued signals that are still pending at the receiver(s), or a systemwide resource limit has been exceeded. The value of the signo argument is an invalid or unsupported signal number. The process does not have the appropriate privilege to send the signal to the receiving process. The process pid does not exist. SEE ALSO
kill(2), sysconf(2), privileges(5), signal(5). sigqueue(2)