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.\" Copyright (c) 1983, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd September 23, 2025
.Dt PSIGNAL 3
.Os
.Sh NAME
.Nm psignal ,
.Nm psiginfo ,
.Nm strsignal ,
.Nm sys_siglist ,
.Nm sys_signame ,
.Nm sig2str ,
.Nm str2sig
.Nd system signal messages
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In signal.h
.Ft void
.Fn psignal "int sig" "const char *s"
.Ft void
.Fn psiginfo "const siginfo_t *si" "const char *s"
.Vt extern const char * const sys_siglist[] ;
.Vt extern const char * const sys_signame[] ;
.In string.h
.Ft "char *"
.Fn strsignal "int sig"
.Ft int
.Fn sig2str "int signum" "char *str"
.Ft int
.Fn str2sig "char *str" "int *pnum"
.Sh DESCRIPTION
The
.Fn psignal
and
.Fn strsignal
functions locate the descriptive message
string for a signal number.
.Pp
The
.Fn strsignal
function accepts a signal number argument
.Fa sig
and returns a pointer to the corresponding message string.
.Pp
The
.Fn psignal
function accepts a signal number argument
.Fa sig
and writes it to the standard error.
If the argument
.Fa s
is
.Pf non- Dv NULL
and does not point to the null character,
.Fa s
is written to the standard error file descriptor
prior to the message string,
immediately followed by a colon and a space.
If the signal number is not recognized
.Pq Xr sigaction 2 ,
the string
.Dq "Unknown signal"
is produced.
.Pp
The
.Fn psiginfo
function is similar to
.Fn psignal ,
except that the signal number information is taken from the
.Fa si
argument which is a
.Vt siginfo_t
structure.
.Pp
The message strings can be accessed directly
through the external array
.Va sys_siglist ,
indexed by recognized signal numbers.
The external array
.Va sys_signame
is used similarly and
contains short, upper-case abbreviations for signals
which are useful for recognizing signal names
in user input.
The defined variable
.Dv NSIG
contains a count of the strings in
.Va sys_siglist
and
.Va sys_signame .
.Pp
The
.Fn sig2str
function translates the signal number
.Fa signum
to the signal name, without the
.Dq SIG
prefix, and stores it at the location specified by
.Fa str ,
which should be large enough to hold the name and the terminating
.Dv NUL
byte.
The symbol
.Dv SIG2STR_MAX
gives the maximum size in bytes required.
.Pp
The
.Fn str2sig
function translates the signal name
.Fa str
to a signal number and stores it in the location referenced by
.Fa pnum .
The name in
.Fa str
can be either the name of the signal, with or without the
.Dq SIG
prefix, or a decimal number.
.Sh RETURN VALUES
The
.Fn sig2str
and
.Fn str2sig
return 0 on success and -1 on translation failure.
In the latter case the memory to store the translation result is left intact.
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr perror 3 ,
.Xr strerror 3
.Sh STANDARDS
The
.Fn psignal
and
.Fn psiginfo
functions are defined by
.St -p1003.1-2008
, while the
.Fn sig2str
and
.Fn str2sig
functions are defined by
.St -p1003.1-2024 .
.Sh HISTORY
The
.Fn psignal
function appeared in
.Bx 4.2 .
The
.Fn psiginfo
function appeared in
.Fx 14.3 ,
.Nx 6.0 ,
and
.Dx 4.1 .
The
.Fn sig2str
and
.Fn str2sig
functions appeared in
.Fx 15.0 .
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