Open System Services Programmer's Guide

Threads Portability
Standard POSIX Threads follow the POSIX threads Standard document. Using thread functions
whose names end with _np (non-portable) decreases the portability of a program, because these
functions are extensions to the standard. Using the jacket routines provided by HP also reduces
portability of a threaded application; see “Jacket Routines” (page 333) for more information about
the jacket routines.
Numerical Limits in Standard POSIX Threads
Table 57 lists numerical limits imposed by the standard implementation. The symbolic constants
listed in the table are defined in limits.h with the values shown in the table. These symbolic
constants refer to the most restrictive value for each feature.
Table 57 Numerical Limits in Standard POSIX Threads
ValueDescriptionSymbolic Constant
4096Maximum length of the arguments for one of the
exec functions, in bytes, including environment
data
_POSIX_ARG_MAX
6Maximum number of simultaneous processes for
one real user ID
_POSIX_CHILD_MAX
_POSIX_OPEN_MAXMaximum number of descriptors that a process can
examine
_POSIX_FD_SETSIZE
_POSIX_PIPE_BUFMaximum number of bytes that can be buffered on
a socket for sending or receiving
_POSIX_HIWAT
8Maximum value of a file’s link count_POSIX_LINK_MAX
255Maximum number of bytes in a terminal canonical
input queue
_POSIX_MAX_CANON
255Maximum number of bytes for which space will be
available in a terminal input queue
_POSIX_MAX_INPUT
14Maximum number of bytes in a filename_POSIX_NAME_MAX
0Maximum number of simultaneous supplementary
group IDs for one process
_POSIX_NGROUPS_MAX
256Maximum number of files that one process can have
open at one time
_POSIX_OPEN_MAX
255Maximum number of bytes in a pathname_POSIX_PATH_MAX
512Maximum number of bytes that can be written
atomically when writing to a pipe
_POSIX_PIPE_BUF
1Maximum number of connections that can be
queued on a socket
_POSIX_QLIMIT_
32,767Maximum value that can be stored in an object of
type ssize_t
_POSIX_SSIZE_MAX
8Maximum number of streams that one process can
have open at one time
_POSIX_STREAM_MAX
3Maximum number of bytes supported for time zone
names
_POSIX_TZNAME_MAX
Standard POSIX Threads 327