RLIMITFSIZE

RLIMIT_FSIZE is a per-process resource limit that controls the maximum size to which a file can be created or grown by that process. The limit is expressed in bytes and is stored as a pair in struct rlimit: a soft limit (rlim_cur) and a hard limit (rlim_max).

The limit applies to operations that increase a file’s size, such as write and ftruncate. If a write would enlarge a file beyond rlim_cur, the kernel prevents the operation and returns an error, typically errno EFBIG (File too large).

Interfaces and data structures: The limits are retrieved and changed with getrlimit and setrlimit using the resource RLIMIT_FSIZE. The struct rlimit contains rlim_cur and rlim_max, both of type rlim_t. A value of RLIM_INFINITY means no limit.

Usage and behavior: The soft limit (rlim_cur) can be increased by the process up to the hard limit (rlim_max) using setrlimit. Raising beyond the hard limit generally requires appropriate privileges, such as root access. The hard limit represents the ceiling that cannot be exceeded without special permissions. The soft limit can also be lowered.

Inheritance and environment: Limits are inherited by child processes after fork and persist across execve calls. In modern environments such as containers, RLIMIT_FSIZE may be further constrained by cgroups or security policies, which can override or supplement per-process limits.

See also: RLIMIT_AS, RLIMIT_CPU, getrlimit, setrlimit.