GETRLIMIT(2) UNIX Programmer's Manual GETRLIMIT(2) NAME getrlimit, setrlimit - control maximum system resource con- sumption SYNOPSIS #include #include getrlimit(resource, rlp) int resource; struct rlimit *rlp; setrlimit(resource, rlp) int resource; struct rlimit *rlp; DESCRIPTION Limits on the consumption of system resources by the current process and each process it creates may be obtained with the _g_e_t_r_l_i_m_i_t call, and set with the _s_e_t_r_l_i_m_i_t call. The _r_e_s_o_u_r_c_e parameter is one of the following: RLIMIT_CPU the maximum amount of cpu time (in seconds) to be used by each process. RLIMIT_FSIZE the largest size, in bytes, of any single file that may be created. RLIMIT_DATA the maximum size, in bytes, of the data segment for a process; this defines how far a program may extend its break with the _s_b_r_k(2) system call. RLIMIT_STACK the maximum size, in bytes, of the stack segment for a process; this defines how far a program's stack segment may be extended. Stack extension is performed automatically by the system. RLIMIT_CORE the largest size, in bytes, of a _c_o_r_e file that may be created. RLIMIT_RSS the maximum size, in bytes, to which a process's resident set size may grow. This imposes a limit on the amount of physical memory to be given to a process; if memory is tight, the system will prefer to take memory from processes that are exceeding their declared resident set size. Printed 11/26/99 May 13, 1986 1 GETRLIMIT(2) UNIX Programmer's Manual GETRLIMIT(2) A resource limit is specified as a soft limit and a hard limit. When a soft limit is exceeded a process may receive a signal (for example, if the cpu time is exceeded), but it will be allowed to continue execution until it reaches the hard limit (or modifies its resource limit). The _r_l_i_m_i_t structure is used to specify the hard and soft limits on a resource, struct rlimit { int rlim_cur; /* current (soft) limit */ int rlim_max; /* hard limit */ }; Only the super-user may raise the maximum limits. Other users may only alter _r_l_i_m__c_u_r within the range from 0 to _r_l_i_m__m_a_x or (irreversibly) lower _r_l_i_m__m_a_x. An "infinite" value for a limit is defined as RLIM_INFINITY (0x7fffffff). Because this information is stored in the per-process infor- mation, this system call must be executed directly by the shell if it is to affect all future processes created by the shell; _l_i_m_i_t is thus a built-in command to _c_s_h(1). The system refuses to extend the data or stack space when the limits would be exceeded in the normal way: a _b_r_e_a_k call fails if the data space limit is reached. When the stack limit is reached, the process receives a segmentation fault (SIGSEGV); if this signal is not caught by a handler using the signal stack, this signal will kill the process. A file I/O operation that would create a file that is too large will cause a signal SIGXFSZ to be generated; this nor- mally terminates the process, but may be caught. When the soft cpu time limit is exceeded, a signal SIGXCPU is sent to the offending process. RETURN VALUE A 0 return value indicates that the call succeeded, changing or returning the resource limit. A return value of -1 indicates that an error occurred, and an error code is stored in the global location _e_r_r_n_o. ERRORS The possible errors are: [EFAULT] The address specified for _r_l_p is invalid. [EPERM] The limit specified to _s_e_t_r_l_i_m_i_t would have raised the maximum limit value, and the caller is not the super-user. Printed 11/26/99 May 13, 1986 2 GETRLIMIT(2) UNIX Programmer's Manual GETRLIMIT(2) SEE ALSO csh(1), quota(2), sigvec(2), sigstack(2) BUGS There should be _l_i_m_i_t and _u_n_l_i_m_i_t commands in _s_h(1) as well as in _c_s_h. Printed 11/26/99 May 13, 1986 3