Section 2: system calls
NAME sigpending, rt_sigpending – examine pending signals SYNOPSIS #include <signal.h> int sigpending(sigset_t *set); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): sigpending(): _POSIX_C_SOURCE DESCRIPTION sigpending() returns the set of signals that are pending for delivery to the calling thread (i.e., the signals which have been raised while blocked). The mask of pending signals is returned…
NAME signalfd – create a file descriptor for accepting signals SYNOPSIS #include <sys/signalfd.h> int signalfd(int fd, const sigset_t *mask, int flags); DESCRIPTION signalfd() 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…
NAME signalfd – create a file descriptor for accepting signals SYNOPSIS #include <sys/signalfd.h> int signalfd(int fd, const sigset_t *mask, int flags); DESCRIPTION signalfd() 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…
NAME signal – ANSI C signal handling SYNOPSIS #include <signal.h> typedef void (*sighandler_t)(int); sighandler_t signal(int signum, sighandler_t handler); DESCRIPTION WARNING: 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…
NAME 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_SOURCE DESCRIPTION sigaltstack() allows a thread to define a new alternate signal stack and/or retrieve the state of an existing alternate signal stack….
NAME 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 DESCRIPTION The sigaction() system call is used to change the action taken by a process on receipt of…
NAME shutdown – shut down part of a full-duplex connection SYNOPSIS #include <sys/socket.h> int shutdown(int sockfd, int how); DESCRIPTION The 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…
NAME shmat, shmdt – System V shared memory operations SYNOPSIS #include <sys/shm.h> #include <sys/types.h> void *shmat(int shmid, const void *shmaddr, int shmflg); int shmdt(const void *shmaddr); DESCRIPTION shmat() 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…
NAME 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); DESCRIPTION shmget() 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…
NAME shmat, shmdt – System V shared memory operations SYNOPSIS #include <sys/shm.h> #include <sys/types.h> void *shmat(int shmid, const void *shmaddr, int shmflg); int shmdt(const void *shmaddr); DESCRIPTION shmat() 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…
NAME 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); DESCRIPTION shmctl() 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…
NAME shmat, shmdt – System V shared memory operations SYNOPSIS #include <sys/shm.h> #include <sys/types.h> void *shmat(int shmid, const void *shmaddr, int shmflg); int shmdt(const void *shmaddr); DESCRIPTION shmat() 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…
NAME sgetmask, ssetmask – manipulation of signal mask (obsolete) SYNOPSIS long sgetmask(void); long ssetmask(long newmask); Note: There are no glibc wrappers for these system calls; see NOTES. DESCRIPTION These 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…
NAME 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 setup – setup devices and filesystems, mount root filesystem SYNOPSIS #include <unistd.h> int setup(void); DESCRIPTION setup() 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…
NAME setuid – set user identity SYNOPSIS #include <sys/types.h> #include <unistd.h> int setuid(uid_t uid); DESCRIPTION setuid() 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,…
NAME setuid – set user identity SYNOPSIS #include <sys/types.h> #include <unistd.h> int setuid(uid_t uid); DESCRIPTION setuid() 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,…
NAME 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 DESCRIPTION The functions gettimeofday() and settimeofday() can get and set…
NAME getsockopt, setsockopt – get and set options on sockets SYNOPSIS #include <sys/socket.h> #include <sys/types.h> /* See NOTES */ 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); DESCRIPTION getsockopt() and setsockopt() manipulate options for the socket referred to by the…
NAME setsid – creates a session and sets the process group ID SYNOPSIS #include <sys/types.h> #include <unistd.h> pid_t setsid(void); DESCRIPTION setsid() 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…