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| .TH BSD_SIGNAL 3 2019-03-06 "" "Linux Programmer's Manual" |
| .SH NAME |
| bsd_signal \- signal handling with BSD semantics |
| .SH SYNOPSIS |
| .B #include <signal.h> |
| .PP |
| .B typedef void (*sighandler_t)(int); |
| .PP |
| .BI "sighandler_t bsd_signal(int " signum ", sighandler_t " handler ); |
| .PP |
| .in -4n |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .in |
| .PP |
| .ad l |
| .BR bsd_signal (): |
| .RS 4 |
| Since glibc 2.26: |
| _XOPEN_SOURCE >= 500 |
| .\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED |
| && ! (_POSIX_C_SOURCE\ >=\ 200809L) |
| .br |
| Glibc 2.25 and earlier: |
| _XOPEN_SOURCE |
| .RE |
| .ad b |
| .SH DESCRIPTION |
| The |
| .BR bsd_signal () |
| function takes the same arguments, and performs the same task, as |
| .BR signal (2). |
| .PP |
| The difference between the two is that |
| .BR bsd_signal () |
| is guaranteed to provide reliable signal semantics, that is: |
| a) the disposition of the signal is not reset to the default |
| when the handler is invoked; |
| b) delivery of further instances of the signal is blocked while |
| the signal handler is executing; and |
| c) if the handler interrupts a blocking system call, |
| then the system call is automatically restarted. |
| A portable application cannot rely on |
| .BR signal (2) |
| to provide these guarantees. |
| .SH RETURN VALUE |
| The |
| .BR bsd_signal () |
| function returns the previous value of the signal handler, or |
| .B SIG_ERR |
| on error. |
| .SH ERRORS |
| As for |
| .BR signal (2). |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .TS |
| allbox; |
| lb lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR bsd_signal () |
| T} Thread safety MT-Safe |
| .TE |
| .SH CONFORMING TO |
| 4.2BSD, POSIX.1-2001. |
| POSIX.1-2008 removes the specification of |
| .BR bsd_signal (), |
| recommending the use of |
| .BR sigaction (2) |
| instead. |
| .SH NOTES |
| Use of |
| .BR bsd_signal () |
| should be avoided; use |
| .BR sigaction (2) |
| instead. |
| .PP |
| On modern Linux systems, |
| .BR bsd_signal () |
| and |
| .BR signal (2) |
| are equivalent. |
| But on older systems, |
| .BR signal (2) |
| provided unreliable signal semantics; see |
| .BR signal (2) |
| for details. |
| .PP |
| The use of |
| .I sighandler_t |
| is a GNU extension; |
| this type is defined only if the |
| .B _GNU_SOURCE |
| feature test macro is defined. |
| .SH SEE ALSO |
| .BR sigaction (2), |
| .BR signal (2), |
| .BR sysv_signal (3), |
| .BR signal (7) |