Section 2: system calls
msgrcv, msgsnd – System V message queue operations Synopsis#include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg); ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg);DescriptionThe msgsnd() and msgrcv() system calls are used to send messages to, and receive messages from, a System V message queue….
msgget – get a System V message queue identifier Synopsis#include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> int msgget(key_t key, int msgflg);DescriptionThe msgget() system call returns the System V message queue identifier associated with the value of the key argument. It may be used either to obtain the identifier of a previously created message queue (when msgflg…
msgctl – System V message control operations Synopsis#include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> int msgctl(int msqid, int cmd, struct msqid_ds *buf);Descriptionmsgctl() performs the control operation specified by cmd on the System V message queue with identifier msqid. The msqid_ds data structure is defined in <sys/msg.h> as follows: struct msqid_ds { struct ipc_perm msg_perm; /* Ownership and permissions */…
mremap – remap a virtual memory address Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sys/mman.h> void *mremap(void *old_address, size_t old_size, size_t new_size, int flags, … /* void *new_address */);Descriptionmremap() expands (or shrinks) an existing memory mapping, potentially moving it at the same time (controlled by the flags argument and the available virtual address space). old_address…
mq_unlink – remove a message queue Synopsis#include <mqueue.h> int mq_unlink(const char *name);Link with -lrt. Descriptionmq_unlink() removes the specified message queue name. The message queue name is removed immediately. The queue itself is destroyed once any other processes that have the queue open close their descriptors referring to the queue. Return ValueOn success mq_unlink() returns 0;…
mq_send, mq_timedsend – send a message to a message queue Synopsis#include <mqueue.h> int mq_send(mqd_t mqdes, const char *msg_ptr, size_t msg_len, unsigned int msg_prio); #include <time.h> #include <mqueue.h> int mq_timedsend(mqd_t mqdes, const char *msg_ptr, size_t msg_len, unsigned int msg_prio, const struct timespec *abs_timeout);Link with -lrt. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): mq_timedsend(): _POSIX_C_SOURCE >= 200112LDescriptionmq_send() adds…
mq_receive, mq_timedreceive – receive a message from a message queue Synopsis#include <mqueue.h> ssize_t mq_receive(mqd_t mqdes, char *msg_ptr, size_t msg_len, unsigned int *msg_prio); #include <time.h> #include <mqueue.h> ssize_t mq_timedreceive(mqd_t mqdes, char *msg_ptr, size_t msg_len, unsigned int *msg_prio, const struct timespec *abs_timeout);Link with -lrt. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): mq_timedreceive(): _POSIX_C_SOURCE >= 200112LDescriptionmq_receive() removes the oldest…
mq_open – open a message queue Synopsis#include <fcntl.h> /* For O_* constants */ #include <sys/stat.h> /* For mode constants */ #include <mqueue.h> mqd_t mq_open(const char *name, int oflag); mqd_t mq_open(const char *name, int oflag, mode_t mode, struct mq_attr *attr);Link with -lrt. Descriptionmq_open() creates a new POSIX message queue or opens an existing queue. The queue…
mq_notify – register for notification when a message is available Synopsis#include <mqueue.h> int mq_notify(mqd_t mqdes, const struct sigevent *sevp);Link with -lrt. Descriptionmq_notify() allows the calling process to register or unregister for delivery of an asynchronous notification when a new message arrives on the empty message queue referred to by the message queue descriptor mqdes. The…
mq_getsetattr – get/set message queue attributes Synopsis#include <sys/types.h> #include <mqueue.h> int mq_getsetattr(mqd_t mqdes, const struct mq_attr *newattr, struct mq_attr *oldattr);Note: There is no glibc wrapper for this system call; see NOTES. DescriptionDo not use this system call. This is the low-level system call used to implement mq_getattr(3) and mq_setattr(3). For an explanation of how this…
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…
mprotect, pkey_mprotect – set protection on a region of memory Synopsis#include <sys/mman.h> int mprotect(void *addr, size_t len, int prot); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sys/mman.h> int pkey_mprotect(void *addr, size_t len, int prot, int pkey);Descriptionmprotect() changes the access protections for the calling process’s memory pages containing any part of the address range in the…
move_pages – move individual pages of a process to another node Synopsis#include <numaif.h> long move_pages(int pid, unsigned long count, void **pages, const int *nodes, int *status, int flags);Link with -lnuma. Descriptionmove_pages() moves the specified pages of the process pid to the memory nodes specified by nodes. The result of the move is reflected in status….
mount – mount filesystem Synopsis#include <sys/mount.h> int mount(const char *source, const char *target, const char *filesystemtype, unsigned long mountflags, const void *data);Descriptionmount() attaches the filesystem specified by source (which is often a pathname referring to a device, but can also be the pathname of a directory or file, or a dummy string) to the location…
modify_ldt – get or set a per-process LDT entry Synopsis#include <sys/types.h> int modify_ldt(int func, void *ptr, unsigned long bytecount);Note: There is no glibc wrapper for this system call; see NOTES. Descriptionmodify_ldt() reads or writes the local descriptor table (LDT) for a process. The LDT is an array of segment descriptors that can be referenced by…
mmap2 – map files or devices into memory Synopsis#include <sys/mman.h> void *mmap2(void *addr, size_t length, int prot, int flags, int fd, off_t pgoffset);DescriptionThis is probably not the system call that you are interested in; instead, see mmap(2), which describes the glibc wrapper function that invokes this system call. The mmap2() system call provides the same…
mlock, mlock2, munlock, mlockall, munlockall – lock and unlock memory Synopsis#include <sys/mman.h> int mlock(const void *addr, size_t len); int mlock2(const void *addr, size_t len, int flags); int munlock(const void *addr, size_t len); int mlockall(int flags); int munlockall(void);Descriptionmlock(), mlock2(), and mlockall() lock part or all of the calling process’s virtual address space into RAM, preventing that…
mlock, mlock2, munlock, mlockall, munlockall – lock and unlock memory Synopsis#include <sys/mman.h> int mlock(const void *addr, size_t len); int mlock2(const void *addr, size_t len, int flags); int munlock(const void *addr, size_t len); int mlockall(int flags); int munlockall(void);Descriptionmlock(), mlock2(), and mlockall() lock part or all of the calling process’s virtual address space into RAM, preventing that…
mlock, mlock2, munlock, mlockall, munlockall – lock and unlock memory Synopsis#include <sys/mman.h> int mlock(const void *addr, size_t len); int mlock2(const void *addr, size_t len, int flags); int munlock(const void *addr, size_t len); int mlockall(int flags); int munlockall(void);Descriptionmlock(), mlock2(), and mlockall() lock part or all of the calling process’s virtual address space into RAM, preventing that…
mknod, mknodat – create a special or ordinary file Synopsis#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> int mknod(const char *pathname, mode_t mode, dev_t dev); #include <fcntl.h> /* Definition of AT_* constants */ #include <sys/stat.h> int mknodat(int dirfd, const char *pathname, mode_t mode, dev_t dev);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): mknod(): _XOPEN_SOURCE >= 500 || /* Since…