signalfd – create a file descriptor for accepting signals Synopsis#include <sys/signalfd.h> int signalfd(int fd, const sigset_t *mask, int flags); Descriptionsignalfd() creates a file descriptor that can be used to accept signals targeted at the caller. This provides an alternative to the use of a signal handler or sigwaitinfo(2), and has the advantage that the file…
signalfd – create a file descriptor for accepting signals Synopsis#include <sys/signalfd.h> int signalfd(int fd, const sigset_t *mask, int flags); Descriptionsignalfd() creates a file descriptor that can be used to accept signals targeted at the caller. This provides an alternative to the use of a signal handler or sigwaitinfo(2), and has the advantage that the file…
signal – ANSI C signal handling Synopsis#include <signal.h> typedef void (*sighandler_t)(int); sighandler_t signal(int signum, sighandler_t handler); DescriptionWARNING: the behavior of signal() varies across UNIX versions, and has also varied historically across different versions of Linux. Avoid its use: use sigaction(2) instead. See Portability below. signal() sets the disposition of the signal signum to handler, which…
sigaltstack – set and/or get signal stack context Synopsis#include <signal.h> int sigaltstack(const stack_t *ss, stack_t *old_ss); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): sigaltstack(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L || /* Glibc versions <= 2.19: */ _BSD_SOURCEDescriptionsigaltstack() allows a thread to define a new alternate signal stack and/or retrieve the state of an existing alternate signal stack. An alternate signal stack…
sigaction, rt_sigaction – examine and change a signal action Synopsis#include <signal.h> int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): sigaction(): _POSIX_C_SOURCE siginfo_t: _POSIX_C_SOURCE >= 199309L DescriptionThe sigaction() system call is used to change the action taken by a process on receipt of a specific signal. (See…
shutdown – shut down part of a full-duplex connection Synopsis#include <sys/socket.h> int shutdown(int sockfd, int how); DescriptionThe shutdown() call causes all or part of a full-duplex connection on the socket associated with sockfd to be shut down. If how is SHUT_RD, further receptions will be disallowed. If how is SHUT_WR, further transmissions will be disallowed….
shmat, shmdt – System V shared memory operations Synopsis#include <sys/types.h> #include <sys/shm.h> void *shmat(int shmid, const void *shmaddr, int shmflg); int shmdt(const void *shmaddr);Descriptionshmat()shmat() attaches the System V shared memory segment identified by shmid to the address space of the calling process. The attaching address is specified by shmaddr with one of the following criteria:…
shmget – allocates a System V shared memory segment Synopsis#include <sys/ipc.h> #include <sys/shm.h> int shmget(key_t key, size_t size, int shmflg); Descriptionshmget() returns the identifier of the System V shared memory segment associated with the value of the argument key. It may be used either to obtain the identifier of a previously created shared memory segment…
shmat, shmdt – System V shared memory operations Synopsis#include <sys/types.h> #include <sys/shm.h> void *shmat(int shmid, const void *shmaddr, int shmflg); int shmdt(const void *shmaddr);Descriptionshmat()shmat() attaches the System V shared memory segment identified by shmid to the address space of the calling process. The attaching address is specified by shmaddr with one of the following criteria:…
shmctl – System V shared memory control Synopsis#include <sys/ipc.h> #include <sys/shm.h> int shmctl(int shmid, int cmd, struct shmid_ds *buf); Descriptionshmctl() performs the control operation specified by cmd on the System V shared memory segment whose identifier is given in shmid. The buf argument is a pointer to a shmid_ds structure, defined in <sys/shm.h> as follows:…
shmat, shmdt – System V shared memory operations Synopsis#include <sys/types.h> #include <sys/shm.h> void *shmat(int shmid, const void *shmaddr, int shmflg); int shmdt(const void *shmaddr);Descriptionshmat()shmat() attaches the System V shared memory segment identified by shmid to the address space of the calling process. The attaching address is specified by shmaddr with one of the following criteria:…
sgetmask, ssetmask – manipulation of signal mask (obsolete) Synopsislong sgetmask(void); long ssetmask(long newmask); Note: There are no glibc wrappers for these system calls; see NOTES. DescriptionThese system calls are obsolete. Do not use them; use sigprocmask(2) instead. sgetmask() returns the signal mask of the calling process. ssetmask() sets the signal mask of the calling process…
setxattr, lsetxattr, fsetxattr – set an extended attribute value Synopsis#include <sys/types.h> #include <sys/xattr.h> int setxattr(const char *path, const char *name, const void *value, size_t size, int flags); int lsetxattr(const char *path, const char *name, const void *value, size_t size, int flags); int fsetxattr(int fd, const char *name, const void *value, size_t size, int flags);DescriptionExtended attributes are name:value pairs associated with inodes (files, directories,…
setup – setup devices and filesystems, mount root filesystem Synopsis#include <unistd.h> int setup(void); Descriptionsetup() is called once from within linux/init/main.c. It calls initialization functions for devices and filesystems configured into the kernel and then mounts the root filesystem. No user process may call setup(). Any user process, even a process with superuser permission, will receive…
setuid – set user identity Synopsis#include <sys/types.h> #include <unistd.h> int setuid(uid_t uid); Descriptionsetuid() sets the effective user ID of the calling process. If the calling process is privileged (more precisely: if the process has the CAP_SETUID capability in its user namespace), the real UID and saved set-user-ID are also set. Under Linux, setuid() is implemented…
setuid – set user identity Synopsis#include <sys/types.h> #include <unistd.h> int setuid(uid_t uid); Descriptionsetuid() sets the effective user ID of the calling process. If the calling process is privileged (more precisely: if the process has the CAP_SETUID capability in its user namespace), the real UID and saved set-user-ID are also set. Under Linux, setuid() is implemented…
gettimeofday, settimeofday – get / set time Synopsis#include <sys/time.h> int gettimeofday(struct timeval *tv, struct timezone *tz); int settimeofday(const struct timeval *tv, const struct timezone *tz);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): settimeofday(): Since glibc 2.19: _DEFAULT_SOURCE Glibc 2.19 and earlier: _BSD_SOURCE DescriptionThe functions gettimeofday() and settimeofday() can get and set the time as well…
getsockopt, setsockopt – get and set options on sockets Synopsis#include <sys/types.h> /* See NOTES */ #include <sys/socket.h> int getsockopt(int sockfd, int level, int optname, void *optval, socklen_t *optlen); int setsockopt(int sockfd, int level, int optname, const void *optval, socklen_t optlen);Descriptiongetsockopt() and setsockopt() manipulate options for the socket referred to by the file descriptor sockfd. Options…
setsid – creates a session and sets the process group ID Synopsis#include <sys/types.h> #include <unistd.h> pid_t setsid(void); Descriptionsetsid() creates a new session if the calling process is not a process group leader. The calling process is the leader of the new session (i.e., its session ID is made the same as its process ID). The…
getrlimit, setrlimit, prlimit – get/set resource limits Synopsis#include <sys/time.h> #include <sys/resource.h> int getrlimit(int resource, struct rlimit *rlim); int setrlimit(int resource, const struct rlimit *rlim); int prlimit(pid_t pid, int resource, const struct rlimit *new_limit, struct rlimit *old_limit); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): prlimit(): _GNU_SOURCE DescriptionThe getrlimit() and setrlimit() system calls get and set…