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| .TH SIGVEC 3 2021-03-22 "Linux" "Linux Programmer's Manual" |
| .SH NAME |
| sigvec, sigblock, sigsetmask, siggetmask, sigmask \- BSD signal API |
| .SH SYNOPSIS |
| .nf |
| .B #include <signal.h> |
| .PP |
| .BI "int sigvec(int " sig ", const struct sigvec *" vec ", struct sigvec *" ovec ); |
| .PP |
| .BI "int sigmask(int " signum ); |
| .PP |
| .BI "int sigblock(int " mask ); |
| .BI "int sigsetmask(int " mask ); |
| .B int siggetmask(void); |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| All functions shown above: |
| .nf |
| Since glibc 2.19: |
| _DEFAULT_SOURCE |
| Glibc 2.19 and earlier: |
| _BSD_SOURCE |
| .fi |
| .SH DESCRIPTION |
| These functions are provided in glibc as a compatibility interface |
| for programs that make use of the historical BSD signal API. |
| This API is obsolete: new applications should use the POSIX signal API |
| .RB ( sigaction (2), |
| .BR sigprocmask (2), |
| etc.). |
| .PP |
| The |
| .BR sigvec () |
| function sets and/or gets the disposition of the signal |
| .I sig |
| (like the POSIX |
| .BR sigaction (2)). |
| If |
| .I vec |
| is not NULL, it points to a |
| .I sigvec |
| structure that defines the new disposition for |
| .IR sig . |
| If |
| .I ovec |
| is not NULL, it points to a |
| .I sigvec |
| structure that is used to return the previous disposition of |
| .IR sig . |
| To obtain the current disposition of |
| .I sig |
| without changing it, specify NULL for |
| .IR vec , |
| and a non-null pointer for |
| .IR ovec . |
| .PP |
| The dispositions for |
| .B SIGKILL |
| and |
| .B SIGSTOP |
| cannot be changed. |
| .PP |
| The |
| .I sigvec |
| structure has the following form: |
| .PP |
| .in +4n |
| .EX |
| struct sigvec { |
| void (*sv_handler)(int); /* Signal disposition */ |
| int sv_mask; /* Signals to be blocked in handler */ |
| int sv_flags; /* Flags */ |
| }; |
| .EE |
| .in |
| .PP |
| The |
| .I sv_handler |
| field specifies the disposition of the signal, and is either: |
| the address of a signal handler function; |
| .BR SIG_DFL , |
| meaning the default disposition applies for the signal; or |
| .BR SIG_IGN , |
| meaning that the signal is ignored. |
| .PP |
| If |
| .I sv_handler |
| specifies the address of a signal handler, then |
| .I sv_mask |
| specifies a mask of signals that are to be blocked while |
| the handler is executing. |
| In addition, the signal for which the handler is invoked is |
| also blocked. |
| Attempts to block |
| .B SIGKILL |
| or |
| .B SIGSTOP |
| are silently ignored. |
| .PP |
| If |
| .I sv_handler |
| specifies the address of a signal handler, then the |
| .I sv_flags |
| field specifies flags controlling what happens when the handler is called. |
| This field may contain zero or more of the following flags: |
| .TP |
| .B SV_INTERRUPT |
| If the signal handler interrupts a blocking system call, |
| then upon return from the handler the system call s not be restarted: |
| instead it fails with the error |
| .BR EINTR . |
| If this flag is not specified, then system calls are restarted |
| by default. |
| .TP |
| .B SV_RESETHAND |
| Reset the disposition of the signal to the default |
| before calling the signal handler. |
| If this flag is not specified, then the handler remains established |
| until explicitly removed by a later call to |
| .BR sigvec () |
| or until the process performs an |
| .BR execve (2). |
| .TP |
| .B SV_ONSTACK |
| Handle the signal on the alternate signal stack |
| (historically established under BSD using the obsolete |
| .BR sigstack () |
| function; the POSIX replacement is |
| .BR sigaltstack (2)). |
| .PP |
| The |
| .BR sigmask () |
| macro constructs and returns a "signal mask" for |
| .IR signum . |
| For example, we can initialize the |
| .I vec.sv_mask |
| field given to |
| .BR sigvec () |
| using code such as the following: |
| .PP |
| .in +4n |
| .EX |
| vec.sv_mask = sigmask(SIGQUIT) | sigmask(SIGABRT); |
| /* Block SIGQUIT and SIGABRT during |
| handler execution */ |
| .EE |
| .in |
| .PP |
| The |
| .BR sigblock () |
| function adds the signals in |
| .I mask |
| to the process's signal mask |
| (like POSIX |
| .IR sigprocmask(SIG_BLOCK) ), |
| and returns the process's previous signal mask. |
| Attempts to block |
| .B SIGKILL |
| or |
| .B SIGSTOP |
| are silently ignored. |
| .PP |
| The |
| .BR sigsetmask () |
| function sets the process's signal mask to the value given in |
| .I mask |
| (like POSIX |
| .IR sigprocmask(SIG_SETMASK) ), |
| and returns the process's previous signal mask. |
| .PP |
| The |
| .BR siggetmask () |
| function returns the process's current signal mask. |
| This call is equivalent to |
| .IR sigblock(0) . |
| .SH RETURN VALUE |
| The |
| .BR sigvec () |
| function returns 0 on success; on error, it returns \-1 and sets |
| .I errno |
| to indicate the error. |
| .PP |
| The |
| .BR sigblock () |
| and |
| .BR sigsetmask () |
| functions return the previous signal mask. |
| .PP |
| The |
| .BR sigmask () |
| macro returns the signal mask for |
| .IR signum . |
| .SH ERRORS |
| See the ERRORS under |
| .BR sigaction (2) |
| and |
| .BR sigprocmask (2). |
| .SH VERSIONS |
| Starting with version 2.21, the GNU C library no longer exports the |
| .BR sigvec () |
| function as part of the ABI. |
| (To ensure backward compatibility, |
| the glibc symbol versioning scheme continues to export the interface |
| to binaries linked against older versions of the library.) |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR sigvec (), |
| .BR sigmask (), |
| .BR sigblock (), |
| .BR sigsetmask (), |
| .BR siggetmask () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| All of these functions were in |
| 4.3BSD, except |
| .BR siggetmask (), |
| whose origin is unclear. |
| These functions are obsolete: do not use them in new programs. |
| .SH NOTES |
| On 4.3BSD, the |
| .BR signal () |
| function provided reliable semantics (as when calling |
| .BR sigvec () |
| with |
| .I vec.sv_mask |
| equal to 0). |
| On System V, |
| .BR signal () |
| provides unreliable semantics. |
| POSIX.1 leaves these aspects of |
| .BR signal () |
| unspecified. |
| See |
| .BR signal (2) |
| for further details. |
| .PP |
| In order to wait for a signal, |
| BSD and System V both provided a function named |
| .BR sigpause (3), |
| but this function has a different argument on the two systems. |
| See |
| .BR sigpause (3) |
| for details. |
| .SH SEE ALSO |
| .BR kill (2), |
| .BR pause (2), |
| .BR sigaction (2), |
| .BR signal (2), |
| .BR sigprocmask (2), |
| .BR raise (3), |
| .BR sigpause (3), |
| .BR sigset (3), |
| .BR signal (7) |