Advanced Programming in the UNIX® Environment

ptg10805159

Section 2.5 Limits 43

Name of limit Description nameargument

ARG_MAX maximum length, in bytes, of arguments to theexec_SC_ARG_MAX

functions

ATEXIT_MAX maximum number of functions that can be _SC_ATEXIT_MAX

registered with theatexitfunction

CHILD_MAX maximum number of processes per real user ID _SC_CHILD_MAX

clock ticks/second number of clock ticks per second _SC_CLK_TCK

COLL_WEIGHTS_MAX maximum number of weights that can be assigned _SC_COLL_WEIGHTS_MAX

to an entry of theLC_COLLATEorder keyword

in the locale definition file

DELAYTIMER_MAX maximum number of timer expiration overruns _SC_DELAYTIMER_MAX

HOST_NAME_MAX maximum length of a host name as returned by _SC_HOST_NAME_MAX

gethostname

IOV_MAX maximum number ofiovecstructures that can be _SC_IOV_MAX

used withreadvorwritev

LINE_MAX maximum length of a utility’s input line _SC_LINE_MAX

LOGIN_NAME_MAX maximum length of a login name _SC_LOGIN_NAME_MAX

NGROUPS_MAX maximum number of simultaneous supplementary _SC_NGROUPS_MAX

process group IDs per process

OPEN_MAX one morethan the maximum value assigned to a _SC_OPEN_MAX

newly created file descriptor

PAGESIZE system memory page size, in bytes _SC_PAGESIZE

PAGE_SIZE system memory page size, in bytes _SC_PAGE_SIZE

RE_DUP_MAX number of repeated occurrences of a basic regular _SC_RE_DUP_MAX

expression permitted by theregexecand

regcompfunctions when using the interval

notation\{m,n\}

RTSIG_MAX maximum number of real-time signals reserved for _SC_RTSIG_MAX

application use

SEM_NSEMS_MAX maximum number of semaphores a process can use _SC_SEM_NSEMS_MAX

at one time

SEM_VALUE_MAX maximum value of a semaphore _SC_SEM_VALUE_MAX

SIGQUEUE_MAX maximum number of signals that can be queued for _SC_SIGQUEUE_MAX

aprocess

STREAM_MAX maximum number of standardI/O streams per _SC_STREAM_MAX

process at any given time; if defined, it must

have the same value asFOPEN_MAX

SYMLOOP_MAX number of symbolic links that can be traversed _SC_SYMLOOP_MAX

during pathname resolution

TIMER_MAX maximum number of timers per process _SC_TIMER_MAX

TTY_NAME_MAX length of a terminal device name, including the _SC_TTY_NAME_MAX

terminating null

TZNAME_MAX maximum number of bytes for a time zone name _SC_TZNAME_MAX

Figure 2.11 Limits andnamearguments tosysconf

4. Thereferenced file for_PC_PATH_MAXmust be a directory.The value returned
   is the maximum length of a relative pathname when the specified directory is
   the working directory.(Unfortunately,this isn’t the real maximum length of an
   absolute pathname, which is what we want to know.We’ll return to this
   problem in Section 2.5.5.)