Section 2: system calls
link, linkat – make a new name for a file Synopsis#include <unistd.h> int link(const char *oldpath, const char *newpath); #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h> int linkat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath, int flags);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): linkat(): Since glibc 2.10: _POSIX_C_SOURCE >= 200809L Before…
link, linkat – make a new name for a file Synopsis#include <unistd.h> int link(const char *oldpath, const char *newpath); #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h> int linkat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath, int flags);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): linkat(): Since glibc 2.10: _POSIX_C_SOURCE >= 200809L Before…
getxattr, lgetxattr, fgetxattr – retrieve an extended attribute value Synopsis#include <sys/types.h> #include <sys/xattr.h> ssize_t getxattr(const char *path, const char *name, void *value, size_t size); ssize_t lgetxattr(const char *path, const char *name, void *value, size_t size); ssize_t fgetxattr(int fd, const char *name, void *value, size_t size);DescriptionExtended attributes are name:value pairs associated with inodes (files, directories, symbolic links, etc.). They are extensions to the normal…
chown, fchown, lchown, fchownat – change ownership of a file Synopsis#include <unistd.h> int chown(const char *pathname, uid_t owner, gid_t group); int fchown(int fd, uid_t owner, gid_t group); int lchown(const char *pathname, uid_t owner, gid_t group); #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h> int fchownat(int dirfd, const char *pathname, uid_t owner, gid_t group,…
chown, fchown, lchown, fchownat – change ownership of a file Synopsis#include <unistd.h> int chown(const char *pathname, uid_t owner, gid_t group); int fchown(int fd, uid_t owner, gid_t group); int lchown(const char *pathname, uid_t owner, gid_t group); #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h> int fchownat(int dirfd, const char *pathname, uid_t owner, gid_t group,…
killpg – send signal to a process group Synopsis#include <signal.h> int killpg(int pgrp, int sig); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): killpg(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCEDescriptionkillpg() sends the signal sig to the process group pgrp. See signal(7) for a list of signals. If pgrp is 0, killpg() sends the signal to…
kill – send signal to a process Synopsis#include <sys/types.h> #include <signal.h> int kill(pid_t pid, int sig);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): kill(): _POSIX_C_SOURCE DescriptionThe kill() system call can be used to send any signal to any process group or process. If pid is positive, then signal sig is sent to the process with…
keyctl – manipulate the kernel’s key management facility Synopsis#include <sys/types.h> #include <keyutils.h> long keyctl(int operation, …); /* For direct call via syscall(2): */ #include <asm/unistd.h> #include <linux/keyctl.h> #include <unistd.h> long syscall(__NR_keyctl, int operation, __kernel_ulong_t arg2, __kernel_ulong_t arg3, __kernel_ulong_t arg4, __kernel_ulong_t arg5);No glibc wrapper is provided for this system call; see NOTES. Descriptionkeyctl() allows user-space programs…
kexec_load, kexec_file_load – load a new kernel for later execution Synopsis#include <linux/kexec.h> long kexec_load(unsigned long entry, unsigned long nr_segments, struct kexec_segment *segments, unsigned long flags); long kexec_file_load(int kernel_fd, int initrd_fd, unsigned long cmdline_len, const char *cmdline, unsigned long flags);Note: There are no glibc wrappers for these system calls; see NOTES. DescriptionThe kexec_load() system call loads…
kexec_load, kexec_file_load – load a new kernel for later execution Synopsis#include <linux/kexec.h> long kexec_load(unsigned long entry, unsigned long nr_segments, struct kexec_segment *segments, unsigned long flags); long kexec_file_load(int kernel_fd, int initrd_fd, unsigned long cmdline_len, const char *cmdline, unsigned long flags);Note: There are no glibc wrappers for these system calls; see NOTES. DescriptionThe kexec_load() system call loads…
kcmp – compare two processes to determine if they share a kernel resource Synopsis#include <linux/kcmp.h> int kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1, unsigned long idx2);Note: There is no glibc wrapper for this system call; see NOTES. DescriptionThe kcmp() system call can be used to check whether the two processes identified by pid1…
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…
ipc – System V IPC system calls Synopsisint ipc(unsigned int call, int first, int second, int third, void *ptr, long fifth);Descriptionipc() is a common kernel entry point for the System V IPC calls for messages, semaphores, and shared memory. call determines which IPC function to invoke; the other arguments are passed through to the appropriate…
ioprio_get, ioprio_set – get/set I/O scheduling class and priority Synopsisint ioprio_get(int which, int who); int ioprio_set(int which, int who, int ioprio);Note: There are no glibc wrappers for these system calls; see NOTES. DescriptionThe ioprio_get() and ioprio_set() system calls get and set the I/O scheduling class and priority of one or more threads. The which and…
ioprio_get, ioprio_set – get/set I/O scheduling class and priority Synopsisint ioprio_get(int which, int who); int ioprio_set(int which, int who, int ioprio);Note: There are no glibc wrappers for these system calls; see NOTES. DescriptionThe ioprio_get() and ioprio_set() system calls get and set the I/O scheduling class and priority of one or more threads. The which and…
iopl – change I/O privilege level Synopsis#include <sys/io.h> int iopl(int level); Descriptioniopl() changes the I/O privilege level of the calling thread, as specified by the two least significant bits in level. The I/O privilege level for a normal thread is 0. Permissions are inherited from parents to children. This call is deprecated, is significantly slower…
ioperm – set port input/output permissions Synopsis#include <sys/io.h> /* for glibc */ int ioperm(unsigned long from, unsigned long num, int turn_on); Descriptionioperm() sets the port access permission bits for the calling thread for num bits starting from port address from. If turn_on is nonzero, then permission for the specified bits is enabled; otherwise it is…
ioctl_userfaultfd – create a file descriptor for handling page faults in user space Synopsis#include <sys/ioctl.h> int ioctl(int fd, int cmd, …);DescriptionVarious ioctl(2) operations can be performed on a userfaultfd object (created by a call to userfaultfd(2)) using calls of the form: ioctl(fd, cmd, argp); In the above, fd is a file descriptor referring to a…
ioctl_tty – ioctls for terminals and serial lines Synopsis#include <termios.h> int ioctl(int fd, int cmd, …); DescriptionThe ioctl(2) call for terminals and serial ports accepts many possible command arguments. Most require a third argument, of varying type, here called argp or arg. Use of ioctl makes for nonportable programs. Use the POSIX interface described in…
ioctl_ns – ioctl() operations for Linux namespaces DescriptionDiscovering namespace relationshipsThe following ioctl(2) operations are provided to allow discovery of namespace relationships (see user_namespaces(7) and pid_namespaces(7)). The form of the calls is: new_fd = ioctl(fd, request); In each case, fd refers to a /proc/[pid]/ns/* file. Both operations return a new file descriptor on success. NS_GET_USERNS (since…