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.\"     @(#)psignal.3	8.2 (Berkeley) 2/27/95
.\" $FreeBSD: src/lib/libc/gen/psignal.3,v 1.10.2.5 2003/03/15 15:11:05 trhodes Exp $
.\" $DragonFly: src/lib/libc/gen/psignal.3,v 1.5 2007/10/19 20:28:09 swildner Exp $
.\"
.Dd February 27, 1995
.Dt PSIGNAL 3
.Os
.Sh NAME
.Nm psignal ,
.Nm strsignal ,
.Nm sys_siglist ,
.Nm sys_signame ,
.Nm sys_nsig
.Nd system signal messages
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In signal.h
.Ft void
.Fn psignal "unsigned sig" "const char *s"
.Vt extern const char * const sys_siglist[] ;
.Vt extern const char * const sys_signame[] ;
.Vt extern const int sys_nsig ;
.In string.h
.Ft "char *"
.Fn strsignal "int sig"
.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 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, lower-case abbreviations for signals
which are useful for recognizing signal names
in user input.
The external variable
.Va sys_nsig
contains a count of the strings in
.Va sys_siglist
and
.Va sys_signame .
Note that the defined variable
.Dv NSIG
will typically be the same as
.Va sys_nsig ,
but might be different due to newer or older kernels and newer or
older libc libraries.  For maximum portability you must use
.Va sys_nsig
to limit-check the above arrays.  Additionally, you should check
for
.Dv NULL
array entries and generate a generic signal name in those cases.
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr perror 3 ,
.Xr strerror 3
.Sh HISTORY
The
.Fn psignal
function appeared in
.Bx 4.2 .