OSF

NAME

getrlimit, setrlimit − Controls maximum system resource consumption

SYNOPSIS

#include <sys/time.h>
#include <sys/resource.h> int setrlimit(
int resource1,
struct rlimit ∗rlp );
int getrlimit (
int resource1,
struct rlimit ∗rlp );

PARAMETERS

resource1Specifies one of the following values:

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 can be created.

RLIMIT_DATA
The maximum size, in bytes, of the data segment for a process; this defines how far a program can extend its break with the sbrk() function. 

RLIMIT_NOFILE
The maximum number of open file descriptors that the process can have. Any functions that create new file descriptors will fail with errno set to [EMFILE]. 

RLIMIT_ASThe maximum amount of the address space of a process that is defined (in bytes). This resource setting may cause mmap() and malloc() to fail with errno set to [ENOMEM].  Also, the automatic stack growth will fail with the effects described later in this section. 

RLIMIT_STACK
The maximum size, in bytes, of the stack segment for a process; this defines how far a program stack segment can be extended. Stack extension is performed automatically by the system.

RLIMIT_CORE
The largest size, in bytes, of a core file that can be created. 

RLIMIT_RSS
The maximum size, in bytes, to which a process’s resident set size can grow. This imposes a limit on the amount of physical memory to be given to a process; if memory is tight, the system prefers to take memory from processes that are exceeding their declared resident set size.

rlpPoints to the rlimit structure, which contains the current soft and hard limits. For the getrlimit() function, the requested limits are returned in this structure, and for the setrlimit() function, the desired new limits are specified here. 

DESCRIPTION

The getrlimit() function obtains the limits on the consumption of system resources by the current process and each process it creates. The setrlimit() function is used 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 directly by the shell in order to affect all future processes created by the shell; limit is thus a built-in command to the shells. 

The system refuses to extend the data or stack space when the limits would be exceeded in the normal way: a brk() function fails if the data space limit is reached. When the stack limit is reached, the process receives a SIGSEGV signal; if this signal is not caught by a handler using the signal stack, this signal kills the process. A file I/O operation that would create a file that is too large causes a signal SIGXFSZ to be generated; this normally terminates the process, but can be caught. When the soft CPU time limit is exceeded, a signal SIGXCPU is sent to the offending process. 

NOTES

The ulimit() function is implemented in terms of setrlimit().  Therefore, the two interfaces should not be used in the same program.  The result of doing so is undefined. 

RETURN VALUES

Upon successful completion, a value of 0 (zero) is returned.  Otherwise, a value of -1 is returned and errno is set to indicate the error. 

ERRORS

If the getrlimit() or setrlimit() function fails, errno may be set to one of the following values:

[EFAULT]The address specified for the rlp parameter is invalid. 

[EINVAL]The resource1 parameter is not a valid resource. 

[EPERM]The limit specified to the setrlimit() function would have raised the maximum limit value, and the caller does not have appropriate privilege. 

RELATED INFORMATION

Functions: quota(2), setquota(2), sigaction(2), sigstack(2), sigvec(2), ulimit(3)