NAME

getrlimit(), setrlimit() − control maximum resource consumption

SYNOPSIS

#include <sys/resource.h>

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

int setrlimit(int resource, const struct rlimit *rlp);

DESCRIPTION

Limits on the consumption of a variety of  resources by   the   calling  process  may  be  obtained  with getrlimit() and set with setrlimit(). 

Each  call  to  either getrlimit() or setrlimit() identifies  a  specific resource to be operated upon as well as a resource limit.  A  resource  limit  is represented  by  an rlimit structure.  The rlim_cur member specifies the current or soft limit  and  the rlim_max member specifies the maximum or hard limit.  Soft limits may be changed by a process to any value that  is  less  than  or equal to the hard limit.  A process may (irreversibly) lower its hard  limit  to any  value that is greater than or equal to the soft limit.  Only a process with  appropriate  privileges can  raise  a hard limit.  Both hard and soft limits can be changed  in  a  single  call  to setrlimit() subject to the constraints described above. 

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.  Specifying RLIM_INFINITY as any resource limit value on  a  successful  call  to setrlimit() inhibits enforcement of that resource limit. 

The following resources are defined:

RLIMIT_CORE This is the maximum size of a  core file in bytes that may be created by a  process.  A limit of 0  will prevent the creation of a core file.  If this limit is exceeded, the writing of a core file  will terminate at this size. 

RLIMIT_CPU This is the maximum amount of CPU time in seconds used by a process.  If this limit is exceeded, SIGXCPU is generated for the process.  If the process is blocking, catching or ignoring SIGXCPU, the behaviour is unspecified. 

RLIMIT_DATA This is the maximum size of a process’ data segment in bytes.  If this limit is exceeded, the brk(), malloc(), and sbrk() functions will fail with errno set to ENOMEM. 

RLIMIT_FSIZE This is the maximum size of a file in bytes that may be created by a process.  A limit of 0 will prevent the  creation of a file.  If a write or truncate operation would cause this limit to be exceeded, SIGXFSZ is generated for the process.  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. 

RLIMIT_NOFILE This is a number one greater than the maximum value that the system may assign to a newly-created descriptor.  If this limit is exceeded, functions that allocate new file descriptors may fail with errno set to EMFILE.  This limit constrains the number of file descriptors that a process may allocate. 

RLIMIT_STACK This is the maximum size of a process’ stack in bytes.  The implementation will not automatically 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 will  be set to SIG_DFL before it is generated. 

RLIMIT_AS This is the maximum size of a process’ total available memory, in bytes.  If this limit is exceeded, the brk(), malloc(), mmap(), and sbrk() functions will fail with errno set to ENOMEM.  In addition, the automatic stack growth will fail with the effects outlined above. 

RETURN VALUE

Upon successful completion, getrlimit() and setrlimit() return 0.  Otherwise, these functions return -1 and set errno to indicate the error. 

ERRORS

The getrlimit() and setrlimit() functions will fail if:

[EINVAL] An invalid resource was specified; or in a setrlimit() call, the new rlim_cur exceeds the new rlim_max.

[EPERM] The limit specified to setrlimit() would have raised the maximum limit value, and the calling process does not have appropriate privileges. 

The setrlimit() function may fail if:

[EINVAL] The limit specified cannot be lowered because current usage is already higher than the limit. 

SEE ALSO

brk(), exec, fork(), getdtablesize(), malloc(), open(), sigaltstack(), sysconf(), ulimit(), <stropts.h>, <sys/resource.h>. 

CHANGE HISTORY

First released in Issue 4, Version 2. 

HP−UX EXTENSIONS

DESCRIPTION

The resource parameter selects the system resource limits to be set or retrieved.  The possible values for resource are defined in <sys/resource.h>.  Currently, only the following values are supported:

RLIMIT_NOFILE The maximum number of files a process can have open.  The soft limit for this resource is the same as the value returned by sysconf(_SC_OPEN_MAX). 

RLIMIT_OPEN_MAX Defined to be the same as RLIMIT_NOFILE. 

The rlp argument points to an object of type struct rlimit, which is defined in <sys/resource.h>, and includes the following members:

int rlim_cur      Current (soft) limit
int rlim_max      Hard limit

For getrlimit(), the system stores the two limits on the specified resource in the structure to which rlp points. 

For setrlimit(), the system reads new values for the two limits on the specified resource from the structure to which rlp points. 

ERRORS

If the getrlimit() or setlimit() system call fails, errno (see errno (2)) is set to one of the following values:

[EFAULT] The address specified for rlp is invalid.  Reliable detection of this error is implementation dependent. 

If setrlimit() fails it may set errno (see errno(2)) to one of the following values:

[EINVAL] The rlp argument specified a hard or soft limit higher than the current hard limit value, and the caller does not have the appropriate privileges. 

[EINVAL] A user with appropriate privileges has attempted to raise rlp−>rlim_cur or rlp−>rlim_max to a value greater than the system is capable of supporting. 

[EINVAL] The value of rlp−>rlim_cur is less than the number of file descriptors the process already has allocated. 

[EINVAL] The value of rlp−>rlim_max is less than the current soft limit. 

WARNINGS

The maximum size of a file returned by getrlimit() is in terms of bytes.  The maximum size of a file returned by ulimit (see ulimit(2)) with UL_GETFSIZE is in terms of blocks of size 512 bytes.  The value returned by ulimit with UL_GETFSIZE may thus have to be rounded down to a multiple of 512. 

AUTHOR

getrlimit() and setrlimit() were developed by HP, AT&T, and the University of California, Berkeley. 

SEE ALSO

getrlimit64(2), setrlimit64(2), sysconf(2), ulimit(2). 

Hewlett-Packard Company  —  HP-UX Release 10.20:  July 1996