.\" Copyright (c) 1996 John Birrell <jb@cimlogic.com.au>.
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.\" $FreeBSD$
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.Dd March 15, 2014
.Dt PTHREAD_CREATE 3
.Os
.Sh NAME
.Nm pthread_create
.Nd create a new thread
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_create "pthread_t *thread" "const pthread_attr_t *attr" "void *(*start_routine)(void *)" "void *arg"
.Sh DESCRIPTION
The
.Fn pthread_create
function is used to create a new thread, with attributes specified by
.Fa attr ,
within a process.
If
.Fa attr
is
.Dv NULL ,
the default attributes are used.
If the attributes specified by
.Fa attr
are modified later, the thread's attributes are not affected.
Upon
successful completion
.Fn pthread_create
will store the ID of the created thread in the location specified by
.Fa thread .
.Pp
The thread is created executing
.Fa start_routine
with
.Fa arg
as its sole argument.
If the
.Fa start_routine
returns, the effect is as if there was an implicit call to
.Fn pthread_exit
using the return value of
.Fa start_routine
as the exit status.
Note that the thread in which
.Fn main
was originally invoked differs from this.
When it returns from
.Fn main ,
the effect is as if there was an implicit call to
.Fn exit
using the return value of
.Fn main
as the exit status.
.Pp
Upon thread exit the storage for the thread must be reclaimed by another
thread via a call to
.Fn pthread_join .
Alternatively,
.Fn pthread_detach
may be called on the thread to indicate that the system may automatically
reclaim the thread storage upon exit.
The
.Fn pthread_attr_setdetachstate
function may be used on the
.Fa attr
argument passed to
.Fn pthread_create
in order to achieve the same effect as a call to
.Fn pthread_detach
on the newly created thread.
.Pp
The signal state of the new thread is initialized as:
.Bl -bullet -offset indent
.It
The signal mask is inherited from the creating thread.
.It
The set of signals pending for the new thread is empty.
.El
.Sh RETURN VALUES
If successful, the
.Fn pthread_create
function will return zero.
Otherwise an error number will be returned to
indicate the error.
.Sh ERRORS
The
.Fn pthread_create
function will fail if:
.Bl -tag -width Er
.It Bq Er EAGAIN
The system lacked the necessary resources to create another thread, or
the system-imposed limit on the total number of threads in a process
[PTHREAD_THREADS_MAX] would be exceeded.
.It Bq Er EPERM
The caller does not have appropriate permission to set the required scheduling
parameters or scheduling policy.
.It Bq Er EINVAL
The value specified by
.Fa attr
is invalid.
.El
.Sh SEE ALSO
.Xr fork 2 ,
.Xr pthread_attr 3 ,
.Xr pthread_cancel 3 ,
.Xr pthread_cleanup_pop 3 ,
.Xr pthread_cleanup_push 3 ,
.Xr pthread_exit 3 ,
.Xr pthread_join 3
.Sh STANDARDS
The
.Fn pthread_create
function conforms to
.St -p1003.1-96 .