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getrlimit(2) System Calls Manual getrlimit(2) NAME getrlimit, setrlimit - Controls maximum system resource consumption SYNOPSIS #include <sys/resource.h> int getrlimit( int resource1, struct rlimit *rlp); int setrlimit( int resource1, const struct rlimit *rlp); [Digital] The following declaration of the setrlimit() function does not conform to current standards and is supported only for backward compatibility: int setrlimit( int resource1, struct rlimit *rlp); [Digital] Application developers may want to specify an #include statement for <sys/time.h> before the one for <sys/resource.h> if pro- grams are being developed for multiple platforms. The additional #in- clude statement is not required on DIGITAL UNIX systems or by ISO or X/Open standards, but may be required on other vendors' systems that conform to these standards. STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: getrlimit(), setrlimit(): XPG4-UNIX Refer to the standards(5) reference page for more information about in- dustry standards and associated tags. PARAMETERS Specifies one of the following values: The maximum size, in bytes, of the total memory available to a process. Exceeding this limit causes the brk(), malloc(), mmap(), and sbrk() functions to fail with errno set to [ENOMEM]. Also, the automatic stack growth will fail with the effects described under RLIMIT_STACK. The largest size, in bytes, of a core file that can be created. A limit of 0 (zero) prevents the process from creating a core file. If a process exceeds this limit, any remain- ing data to be written to the core file is lost. The maximum amount of CPU time (in seconds) to be used by a process. If the process exceeds this limit, the system sends the SIGXCPU signal to the process. The maximum size, in bytes, of a process's data segment. Exceeding this limit causes the brk(), malloc(), mmap(), and sbrk() functions to fail with errno set to [ENOMEM]. The maximum size, in bytes, of any single file that can be created. A limit of 0 (zero) prevents the process from creating a file. If a write or truncate operation would cause this limit to be exceeded, the system generates the SIGXFSZ signal. If the process is blocking, catching, or ignoring SIGXFSZ, continued attempts to increase the size of a file from end-of-file to beyond the limit will fail with errno set to [EFBIG]. The maximum number of open file descriptors that the process can have. Any functions that attempt to create new file descriptors when the maximum hard limit has been reached will fail with errno set to [EMFILE]. [Digital] The default maximum is 4096 file descriptors. The maximum can be 64K file descriptors when a process has enabled support for greater than 4096 open file descriptors. [Digi- tal] The maximum size, in bytes, to which a process's resident set size can grow. This value imposes a limit on the amount of physical memory to be given to a process. If memory is in short supply, the system prefers to take memory from processes that are exceeding their declared resident set size. The maximum size, in bytes, of a process's stack. The system will not auto- matically grow the stack beyond this limit. If this limit is exceeded, SIGSEGV is generated for the process. If the process is blocking or ignoring SIGSEGV, or is catching SIGSEGV and has not made arrangements to use an alternate stack, the disposition of SIGSEGV is set to SIG_DFL before it is generated. Points to the rlimit structure, which contains the current soft and hard limits. For the getrlimit() function, the requested limits are returned in this structure; for the setrlimit() function, the desired new limits are specified here. DESCRIPTION The getrlimit() function obtains the limits on the consumption of sys- tem resources by the current process and each process it creates. You use the setrlimit() function to set these resources. Each resource limit is specified as either a soft limit or a hard limit. When a soft limit is exceeded (for example, if the CPU time is exceeded), a process can receive a signal until it reaches the hard limit or until it modifies its resource limit. The rlimit structure is used to specify the hard and soft limits on a resource, as defined in the sys/resource.h header file. The calling process must have superuser privilege in order to raise the maximum limits. An unprivileged process can alter the rlim_cur field of the rlimit structure within the range from 0 (zero) to rlim_max or can (irreversibly) lower rlim_max. An infinite value for a limit is defined as RLIM_INFINITY. Because this information is stored in the per-process information, and inherited by fork(), the setrlimit() function should be executed di- rectly by the shell in order to affect all future processes created by the shell. Thus, limit is a built-in command to the shells. NOTES The ulimit() function is implemented in terms of setrlimit(). There- fore, the two interfaces should not be used in the same program. The result of doing so is undefined. [Digital] When compiled in the X/Open UNIX environment, calls to the setrlimit() function are internally renamed by prepending _E to the function name. When you are debugging a module that includes the setr- limit() function and for which _XOPEN_SOURCE_EXTENDED has been defined, use _Esetrlimit to refer to the setrlimit() call. See standards(5) for further information. RETURN VALUES Upon successful completion, these functions return a value of 0 (zero). Otherwise, the functions return a value of -1 and set errno to indicate the error. ERRORS If the getrlimit() or setrlimit() function fails, errno might be set to one of the following values: [Digital] The address specified for the rlp parameter is invalid. An invalid resource was specified, or the new rlim_cur specified in a setrlimit() call exceeds the new rlim_max specified in that same call. The limit specified to the setrlimit() function would have raised the maximum limit value, and the calling process does not have appropriate privilege. RELATED INFORMATION Functions: quotactl(2), setsysinfo(2), sigaction(2), sigstack(2), sigvec(2) Routines: ulimit(3) Standards: standards(5) delim off getrlimit(2)