Section 2: system calls
semget – get a System V semaphore set identifier Synopsis#include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h>int semget(key_t key, int nsems, int semflg); DescriptionThe semget() system call returns the System V semaphore set identifier associated with the argument key. It may be used either to obtain the identifier of a previously created semaphore set (when semflg is…
semctl – System V semaphore control operations Synopsis#include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> int semctl(int semid, int semnum, int cmd, …);Descriptionsemctl() performs the control operation specified by cmd on the System V semaphore set identified by semid, or on the semnum-th semaphore of that set. (The semaphores in a set are numbered starting at 0.)…
select, pselect – synchronous I/O multiplexing SynopsisSee select(2) DescriptionThe select() and pselect() system calls are used to efficiently monitor multiple file descriptors, to see if any of them is, or becomes, "ready"; that is, to see whether I/O becomes possible, or an "exceptional condition" has occurred on any of the file descriptors. This page provides…
afs_syscall, break, fattach, fdetach, ftime, getmsg, getpmsg, gtty, isastream, lock, madvise1, mpx, prof, profil, putmsg, putpmsg, security, stty, tuxcall, ulimit, vserver – unimplemented system calls SynopsisUnimplemented system calls. DescriptionThese system calls are not implemented in the Linux kernel. Return ValueThese system calls always return -1 and set errno to ENOSYS. NotesNote that ftime(3), profil(3), and…
seccomp – operate on Secure Computing state of the process Synopsis#include <linux/seccomp.h> #include <linux/filter.h> #include <linux/audit.h> #include <linux/signal.h> #include <sys/ptrace.h> int seccomp(unsigned int operation, unsigned int flags, void *args);DescriptionThe seccomp() system call operates on the Secure Computing (seccomp) state of the calling process. Currently, Linux supports the following operation values: SECCOMP_SET_MODE_STRICT The only system calls…
sched_yield – yield the processor Synopsis#include <sched.h> int sched_yield(void); Descriptionsched_yield() causes the calling thread to relinquish the CPU. The thread is moved to the end of the queue for its static priority and a new thread gets to run. Return ValueOn success, sched_yield() returns 0. On error, -1 is returned, and errno is set appropriately….
sched_setscheduler, sched_getscheduler – set and get scheduling policy/parameters Synopsis#include <sched.h> int sched_setscheduler(pid_t pid, int policy, const struct sched_param *param); int sched_getscheduler(pid_t pid);DescriptionThe sched_setscheduler() system call sets both the scheduling policy and parameters for the thread whose ID is specified in pid. If pid equals zero, the scheduling policy and parameters of the calling thread will…
sched_setparam, sched_getparam – set and get scheduling parameters Synopsis#include <sched.h> int sched_setparam(pid_t pid, const struct sched_param *param); int sched_getparam(pid_t pid, struct sched_param *param); struct sched_param { … int sched_priority; … }; Descriptionsched_setparam() sets the scheduling parameters associated with the scheduling policy for the thread whose thread ID is specified in pid. If pid is zero,…
sched_setattr, sched_getattr – set and get scheduling policy and attributes Synopsis#include <sched.h> int sched_setattr(pid_t pid, struct sched_attr *attr, unsigned int flags); int sched_getattr(pid_t pid, struct sched_attr *attr, unsigned int size, unsigned int flags);Descriptionsched_setattr()The sched_setattr() system call sets the scheduling policy and associated attributes for the thread whose ID is specified in pid. If pid equals…
sched_setaffinity, sched_getaffinity – set and get a thread’s CPU affinity mask Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sched.h> int sched_setaffinity(pid_t pid, size_t cpusetsize, const cpu_set_t *mask); int sched_getaffinity(pid_t pid, size_t cpusetsize, cpu_set_t *mask);DescriptionA thread’s CPU affinity mask determines the set of CPUs on which it is eligible to run. On a multiprocessor system, setting…
sched_rr_get_interval – get the SCHED_RR interval for the named process Synopsis#include <sched.h> int sched_rr_get_interval(pid_t pid, struct timespec *tp); Descriptionsched_rr_get_interval() writes into the timespec structure pointed to by tp the round-robin time quantum for the process identified by pid. The specified process should be running under the SCHED_RR scheduling policy. The timespec structure has the following…
sched_setscheduler, sched_getscheduler – set and get scheduling policy/parameters Synopsis#include <sched.h> int sched_setscheduler(pid_t pid, int policy, const struct sched_param *param); int sched_getscheduler(pid_t pid);DescriptionThe sched_setscheduler() system call sets both the scheduling policy and parameters for the thread whose ID is specified in pid. If pid equals zero, the scheduling policy and parameters of the calling thread will…
sched_setparam, sched_getparam – set and get scheduling parameters Synopsis#include <sched.h> int sched_setparam(pid_t pid, const struct sched_param *param); int sched_getparam(pid_t pid, struct sched_param *param); struct sched_param { … int sched_priority; … }; Descriptionsched_setparam() sets the scheduling parameters associated with the scheduling policy for the thread whose thread ID is specified in pid. If pid is zero,…
sched_setattr, sched_getattr – set and get scheduling policy and attributes Synopsis#include <sched.h> int sched_setattr(pid_t pid, struct sched_attr *attr, unsigned int flags); int sched_getattr(pid_t pid, struct sched_attr *attr, unsigned int size, unsigned int flags);Descriptionsched_setattr()The sched_setattr() system call sets the scheduling policy and associated attributes for the thread whose ID is specified in pid. If pid equals…
sched_setaffinity, sched_getaffinity – set and get a thread’s CPU affinity mask Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sched.h> int sched_setaffinity(pid_t pid, size_t cpusetsize, const cpu_set_t *mask); int sched_getaffinity(pid_t pid, size_t cpusetsize, cpu_set_t *mask);DescriptionA thread’s CPU affinity mask determines the set of CPUs on which it is eligible to run. On a multiprocessor system, setting…
sched_get_priority_max, sched_get_priority_min – get static priority range Synopsis#include <sched.h> int sched_get_priority_max(int policy); int sched_get_priority_min(int policy); Descriptionsched_get_priority_max() returns the maximum priority value that can be used with the scheduling algorithm identified by policy. sched_get_priority_min() returns the minimum priority value that can be used with the scheduling algorithm identified by policy. Supported policy values are SCHED_FIFO, SCHED_RR,…
sched_get_priority_max, sched_get_priority_min – get static priority range Synopsis#include <sched.h> int sched_get_priority_max(int policy); int sched_get_priority_min(int policy); Descriptionsched_get_priority_max() returns the maximum priority value that can be used with the scheduling algorithm identified by policy. sched_get_priority_min() returns the minimum priority value that can be used with the scheduling algorithm identified by policy. Supported policy values are SCHED_FIFO, SCHED_RR,…
brk, sbrk – change data segment size Synopsis#include <unistd.h> int brk(void *addr); void *sbrk(intptr_t increment); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): brk(), sbrk(): Since glibc 2.19: _DEFAULT_SOURCE || (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200112L)From glibc 2.12 to 2.19: _BSD_SOURCE || _SVID_SOURCE || (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200112L)Before glibc 2.12: _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500Descriptionbrk() and sbrk()…
s390_sthyi – emulate STHYI instruction Synopsis#include <asm/unistd.h> int s390_sthyi(unsigned long function_code, void *resp_buffer, uint64_t *return_code, unsigned long flags);DescriptionThe s390_sthyi() system call emulates the STHYI (Store Hypervisor Information) instruction. It provides hardware resource information for the machine and its virtualization levels. This includes CPU type and capacity, as well as the machine model and other metrics….
s390_runtime_instr – enable/disable s390 CPU run-time instrumentation Synopsis#include <asm/runtime_instr.h> int s390_runtime_instr(int command, int signum);DescriptionThe s390_runtime_instr() system call starts or stops CPU run-time instrumentation for the calling thread. The command argument controls whether run-time instrumentation is started (S390_RUNTIME_INSTR_START, 1) or stopped (S390_RUNTIME_INSTR_STOP, 2) for the calling thread. The signum argument specifies the number of a real-time…