Section 2: system calls
readv, writev, preadv, pwritev, preadv2, pwritev2 – read or write data into multiple buffers Synopsis#include <sys/uio.h> ssize_t readv(int fd, const struct iovec *iov, int iovcnt); ssize_t writev(int fd, const struct iovec *iov, int iovcnt); ssize_t preadv(int fd, const struct iovec *iov, int iovcnt, off_t offset); ssize_t pwritev(int fd, const struct iovec *iov, int iovcnt, off_t…
wait, waitpid, waitid – wait for process to change state Synopsis#include <sys/types.h> #include <sys/wait.h> pid_t wait(int *wstatus); pid_t waitpid(pid_t pid, int *wstatus, int options); int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options); /* This is the glibc and POSIX interface; see NOTES for information on the raw system call. */ Feature Test Macro Requirements for glibc (see…
wait, waitpid, waitid – wait for process to change state Synopsis#include <sys/types.h> #include <sys/wait.h> pid_t wait(int *wstatus); pid_t waitpid(pid_t pid, int *wstatus, int options); int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options); /* This is the glibc and POSIX interface; see NOTES for information on the raw system call. */ Feature Test Macro Requirements for glibc (see…
wait3, wait4 – wait for process to change state, BSD style Synopsis#include <sys/types.h> #include <sys/time.h> #include <sys/resource.h> #include <sys/wait.h> pid_t wait3(int *wstatus, int options, struct rusage *rusage); pid_t wait4(pid_t pid, int *wstatus, int options, struct rusage *rusage);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): wait3(): Since glibc 2.26: _DEFAULT_SOURCE || (_XOPEN_SOURCE >= 500 && ! (_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)) From glibc…
wait3, wait4 – wait for process to change state, BSD style Synopsis#include <sys/types.h> #include <sys/time.h> #include <sys/resource.h> #include <sys/wait.h> pid_t wait3(int *wstatus, int options, struct rusage *rusage); pid_t wait4(pid_t pid, int *wstatus, int options, struct rusage *rusage);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): wait3(): Since glibc 2.26: _DEFAULT_SOURCE || (_XOPEN_SOURCE >= 500 && ! (_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)) From glibc…
wait, waitpid, waitid – wait for process to change state Synopsis#include <sys/types.h> #include <sys/wait.h> pid_t wait(int *wstatus); pid_t waitpid(pid_t pid, int *wstatus, int options); int waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options); /* This is the glibc and POSIX interface; see NOTES for information on the raw system call. */ Feature Test Macro Requirements for glibc (see…
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…
vmsplice – splice user pages to/from a pipe Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <fcntl.h> #include <sys/uio.h> ssize_t vmsplice(int fd, const struct iovec *iov, unsigned long nr_segs, unsigned int flags);DescriptionIf fd is opened for writing, the vmsplice() system call maps nr_segs ranges of user memory described by iov into a pipe. If fd is…
vm86old, vm86 – enter virtual 8086 mode Synopsis#include <sys/vm86.h> int vm86old(struct vm86_struct *info); int vm86(unsigned long fn, struct vm86plus_struct *v86); DescriptionThe system call vm86() was introduced in Linux 0.97p2. In Linux 2.1.15 and 2.0.28, it was renamed to vm86old(), and a new vm86() was introduced. The definition of struct vm86_struct was changed in 1.1.8 and…
vm86old, vm86 – enter virtual 8086 mode Synopsis#include <sys/vm86.h> int vm86old(struct vm86_struct *info); int vm86(unsigned long fn, struct vm86plus_struct *v86); DescriptionThe system call vm86() was introduced in Linux 0.97p2. In Linux 2.1.15 and 2.0.28, it was renamed to vm86old(), and a new vm86() was introduced. The definition of struct vm86_struct was changed in 1.1.8 and…
vhangup – virtually hangup the current terminal Synopsis#include <unistd.h> int vhangup(void); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): vhangup(): Since glibc 2.21: _DEFAULT_SOURCE In glibc 2.19 and 2.20: _DEFAULT_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500) Up to and including glibc 2.19: _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)Descriptionvhangup() simulates a hangup on the current terminal. This call arranges…
vfork – create a child process and block parent Synopsis#include <sys/types.h> #include <unistd.h> pid_t vfork(void); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): vfork(): Since glibc 2.12: (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L) || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCEBefore glibc 2.12: _BSD_SOURCE || _XOPEN_SOURCE >= 500DescriptionStandard description(From POSIX.1) The vfork()…
utime, utimes – change file last access and modification times Synopsis#include <sys/types.h> #include <utime.h> int utime(const char *filename, const struct utimbuf *times); #include <sys/time.h> int utimes(const char *filename, const struct timeval times[2]);DescriptionNote: modern applications may prefer to use the interfaces described in utimensat(2). The utime() system call changes the access and modification times of the…
utimensat, futimens – change file timestamps with nanosecond precision Synopsis#include <fcntl.h> /* Definition of AT_* constants */ #include <sys/stat.h> int utimensat(int dirfd, const char *pathname, const struct timespec times[2], int flags); int futimens(int fd, const struct timespec times[2]);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): utimensat(): Since glibc 2.10: _POSIX_C_SOURCE >= 200809L Before glibc 2.10: _ATFILE_SOURCE futimens():…
utime, utimes – change file last access and modification times Synopsis#include <sys/types.h> #include <utime.h> int utime(const char *filename, const struct utimbuf *times); #include <sys/time.h> int utimes(const char *filename, const struct timeval times[2]);DescriptionNote: modern applications may prefer to use the interfaces described in utimensat(2). The utime() system call changes the access and modification times of the…
ustat – get filesystem statistics Synopsis#include <sys/types.h> #include <unistd.h> /* libc[45] */ #include <ustat.h> /* glibc2 */ int ustat(dev_t dev, struct ustat *ubuf);Descriptionustat() returns information about a mounted filesystem. dev is a device number identifying a device containing a mounted filesystem. ubuf is a pointer to a ustat structure that contains the following members: daddr_t…
userfaultfd – create a file descriptor for handling page faults in user space Synopsis#include <sys/types.h> #include <linux/userfaultfd.h> int userfaultfd(int flags);Note: There is no glibc wrapper for this system call; see NOTES. Descriptionuserfaultfd() creates a new userfaultfd object that can be used for delegation of page-fault handling to a user-space application, and returns a file descriptor…
uselib – load shared library Synopsis#include <unistd.h> int uselib(const char *library); Note: No declaration of this system call is provided in glibc headers; see NOTES. DescriptionThe system call uselib() serves to load a shared library to be used by the calling process. It is given a pathname. The address where to load is found in…
unshare – disassociate parts of the process execution context Synopsis#define _GNU_SOURCE #include <sched.h> int unshare(int flags);Descriptionunshare() allows a process (or thread) to disassociate parts of its execution context that are currently being shared with other processes (or threads). Part of the execution context, such as the mount namespace, is shared implicitly when a new process…
unlink, unlinkat – delete a name and possibly the file it refers to Synopsis#include <unistd.h> int unlink(const char *pathname); #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h> int unlinkat(int dirfd, const char *pathname, int flags);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): unlinkat(): Since glibc 2.10: _POSIX_C_SOURCE >= 200809L Before glibc 2.10: _ATFILE_SOURCEDescriptionunlink() deletes a…