getrlimit() — Get current or maximum resource consumption

Standards

Standards / Extensions C or C++ Dependencies

XPG4.2
Single UNIX Specification, Version 3

 both  

Format

#define _XOPEN_SOURCE_EXTENDED 1
#include <sys/resource.h>

int getrlimit(int resource, struct rlimit *rlp);

General description

The getrlimit() function gets resource limits for the calling process. A resource limit is a pair of values; one specifying the current (soft) limit, the other a maximum (hard) limit.

The value RLIM_INFINITY defined in sys/resource.h, is considered to be larger than any other limit value. If a call to getrlimit() returns RLIM_INFINITY for a resource, it means the implementation does not enforce limits on that resource.

The resource argument specifies which resource to get the hard and/or soft limits for, and may be one of the following values:
RLIMIT_CORE
The maximum size of a dump of memory (in bytes) allowed for the process. A value of 0 (zero) prevents file creation. Dump file creation will stop at this limit.
RLIMIT_CPU
The maximum amount of CPU time (in seconds) allowed for the process. If the limit is exceeded, a SIGXCPU signal is sent to the process and the process is granted a small CPU time extension to allow for signal generation and delivery. If the extension is used up, the process is terminated with a SIGKILL signal.
RLIMIT_DATA
The maximum size of the break value for the process, in bytes. In this implementation, this resource always has a hard and soft limit value of RLIM_INFINITY.
RLIMIT_FSIZE
The maximum file size (in bytes) allowed for the process. A value of 0 (zero) prevents file creation. If the size is exceeded, a SIGXFSZ signal is sent to the process. If the process is blocking, catching, or ignoring SIGXFSZ, continued attempts to increase the size of a file beyond the limit will fail with an errno of EFBIG.
RLIMIT_MEMLIMIT
The maximum amount of usable storage above the 2 gigabyte bar (in 1 megabyte segments) that can be allocated.
RLIMIT_NOFILE
The maximum number of open file descriptors allowed for the process. This number is one greater than the maximum value that may be assigned to a newly created descriptor. (That is, it is one-based.) Any function that attempts to create a new file descriptor beyond the limit will fail with an EMFILE errno.
RLIMIT_STACK
The maximum size of the stack for a process, in bytes. Note that in z/OS® UNIX services, the stack is a per-thread resource. In this implementation, this resource always has a hard and soft limit value of RLIM_INFINITY. A call to setrlimit() to set this resource to any value other than RLIM_INFINITY will fail with an errno of EINVAL.
RLIMIT_AS
The maximum address space size for the process, in bytes. If the limit is exceeded, malloc() and mmap() functions will fail with an errno of ENOMEM. Automatic stack growth will also fail.
The rlp argument points to a rlimit structure. This structure contains the following members:
rlim_cur
The current (soft) limit
rlim_max
The maximum (hard) limit
See the <sys/resource.h> header for more detail.

The resource limit values are propagated across exec and fork.

Special behavior for z/OS UNIX System Services: An exception exists for exec processing in conjunction with daemon support. If a daemon process invokes exec and it had previously invoked setuid() before exec, the RLIMIT_CPU, RLIMIT_AS, RLIMIT_CORE, RLIMIT_FSIZE, and RLIMIT_NOFILE limit values are set based on the limit values specified in the kernel parmlib member BPXPRMxx.

For processes which are not the only process within an address space, the RLIMIT_CPU and RLIMIT_AS limits are shared with all the processes within the address space. For RLIMIT_CPU, when the soft limit is exceeded, action will be taken on the first process within the address space. If the action is termination, all processes within the address space will be terminated.

In addition to the RLIMIT_CORE limit values, the dump file defaults are set by SYSMDUMP defaults. Refer to z/OS MVS Initialization and Tuning Reference for information on setting up SYSMDUMP defaults using the IEADMR00 parmlib member.

Dumps of memory are taken in 4160 byte increments. Therefore, RLIMIT_CORE values affect the size of memory dumps in 4160 byte increments. For example, if the RLIMIT_CORE soft limit value is 4000, the dump will contain no data. If the RLIMIT_CORE soft limit value is 8000, the maximum size of a memory dump is 4160 bytes.

Large file support for z/OS UNIX files: Large z/OS UNIX files are supported automatically for AMODE 64 C/C++ applications. AMODE 31 C/C++ applications must be compiled with the option LANGLVL(LONGLONG) and define the _LARGE_FILES feature test macro before any headers are included to enable this function to operate on z/OS UNIX files that are larger than 2 GB in size. File size and offset fields are enlarged to 63 bits in width. Therefore, any other function operating on the file is required to define the _LARGE_FILES feature test macro as well.

Returned value

If successful, getrlimit() returns 0.

If unsuccessful, getrlimit() returns -1 and sets errno to one of the following values:
Error Code
Description
EINVAL
A non-valid resource was specified.

Related information

Parent topic: Library functions