Open System Services Programmer's Guide
Table 67 Numerical Limits in the POSIX User Thread Model Library
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
4Maximum number of attempts to destroy the
thread-specific data of a thread on termination
_POSIX_DESTRUCTOR_ITERATIONS
_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
1024Maximum number of keys a process can use_POSIX_KEYS_MAX
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
16Maximum 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
4096Minimum number of bytes available for the thread
stack.
_POSIX_STACK_MIN
8Maximum number of streams that one process
can have open at one time
_POSIX_STREAM_MAX
4Maximum number of attempts to destroy the
thread-specific data of a thread on termination
_POSIX_THREAD_DESTRUCTOR_ITERATIONS
128Maximum number of thread-specific data keys
available per process
_POSIX_THREAD_KEYS_MAX
64Maximum number of threads supported per
process
_POSIX_THREAD_THREADS_MAX
3Maximum number of bytes supported for time
zone names
_POSIX_TZNAME_MAX
4Maximum number of attempts to destroy thread's
thread-specific data on termination)
PTHREAD_DESTRUCTOR_ITERATIONS
1024Maximum number of thread-specific data keys
available per process
PTHREAD_KEYS_MAX
384 Using the POSIX User Thread (PUT) Model Library