rlimcur

rlimcur is an informal term used to denote the current, or soft, resource limit of a process as defined by the POSIX resource limit interface. It specifically refers to the rlim_cur field within the resource limit structure used by system calls that manage limits.

In POSIX, resource limits are represented by struct rlimit, which contains two members: rlim_cur and rlim_max. The rlim_cur member encodes the soft limit—the value that the kernel enforces for the corresponding resource during normal operation. The rlim_max member encodes the hard limit, which is the maximum value to which the soft limit can be raised. The type of these fields is rlim_t, typically an unsigned integer large enough to express the limit. A value of RLIM_INFINITY indicates that there is no finite limit, depending on the platform.

The getrlimit and setrlimit system calls retrieve and modify these limits for a given resource. Examples of resources include RLIMIT_CPU (CPU time), RLIMIT_FSIZE (maximum file size), RLIMIT_NOFILE (maximum number of open files), and RLIMIT_AS (address space). In practice, a process can reduce its soft limit, or increase it up to the hard limit; raising the soft limit beyond the hard limit is not permitted. The soft limit can influence behavior such as when the process receives signals or how certain operations are constrained, while the hard limit remains a ceiling that can only be raised by privileged code.

Notes on terminology and portability: rlim_cur is the explicit field name in the standard struct rlimit, and rlimcur is commonly used in documentation and code as a shorthand for the current limit. Implementations and exact behavior can vary slightly across operating systems, but the core concept remains consistent: rlimcur represents the active soft limit that governs resource usage.