'\" te
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.TH pthread_once 3C "23 Mar 2005" "SunOS 5.11" "Standard C Library Functions"
.SH NAME
pthread_once \- initialize dynamic package
.SH SYNOPSIS
.LP
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR... -lpthread [ \fIlibrary\fR... ]

#include <pthread.h> 
\fBpthread_once_t\fR \fIonce_control\fR = \fBPTHREAD_ONCE_INIT\fR;

\fBint\fR \fBpthread_once\fR(\fBpthread_once_t *\fR\fIonce_control\fR,
     \fBvoid (*\fR\fIinit_routine\fR)(\fBvoid\fR));
.fi

.SH DESCRIPTION
.sp
.LP
If any thread in a process with a \fIonce_control\fR parameter makes a call to
\fBpthread_once()\fR, the first call will summon the \fBinit_routine()\fR, but
subsequent calls will not. The \fIonce_control\fR parameter determines whether
the associated initialization routine has been called. The \fBinit_routine()\fR
is complete upon return of \fBpthread_once()\fR.
.sp
.LP
\fBpthread_once()\fR is not a cancellation point; however, if the function
\fBinit_routine()\fR is a cancellation point and is canceled, the effect on
\fIonce_control\fR is the same as if \fBpthread_once()\fR had never been
called.
.sp
.LP
The constant \fBPTHREAD_ONCE_INIT\fR is defined in the \fB<pthread.h>\fR
header.
.sp
.LP
If \fIonce_control\fR has automatic storage duration or is not initialized by
\fBPTHREAD_ONCE_INIT\fR, the behavior of \fBpthread_once()\fR is undefined.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBpthread_once()\fR returns \fB0\fR. Otherwise, an
error number is returned to indicate the error.
.SH ERRORS
.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR \fR
.ad
.RS 11n
.rt  
\fIonce_control\fR or  \fIinit_routine\fR is \fINULL\fR.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityStandard
_
MT-LevelMT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBattributes\fR(5), \fBstandards\fR(5)
.SH NOTES
.sp
.LP
Solaris threads do not offer this functionality.