Section 2: system calls
fcntl – manipulate file descriptor Synopsis#include <unistd.h> #include <fcntl.h> int fcntl(int fd, int cmd, … /* arg */ );Descriptionfcntl() performs one of the operations described below on the open file descriptor fd. The operation is determined by cmd. fcntl() can take an optional third argument. Whether or not this argument is required is determined by…
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,…
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,…
chmod, fchmod, fchmodat – change permissions of a file Synopsis#include <sys/stat.h> int chmod(const char *pathname, mode_t mode); int fchmod(int fd, mode_t mode); #include <fcntl.h> /* Definition of AT_* constants */ #include <sys/stat.h> int fchmodat(int dirfd, const char *pathname, mode_t mode, int flags);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): fchmod(): Since glibc 2.24: _POSIX_C_SOURCE >= 199309L Glibc…
chmod, fchmod, fchmodat – change permissions of a file Synopsis#include <sys/stat.h> int chmod(const char *pathname, mode_t mode); int fchmod(int fd, mode_t mode); #include <fcntl.h> /* Definition of AT_* constants */ #include <sys/stat.h> int fchmodat(int dirfd, const char *pathname, mode_t mode, int flags);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): fchmod(): Since glibc 2.24: _POSIX_C_SOURCE >= 199309L Glibc…
chdir, fchdir – change working directory Synopsis#include <unistd.h> int chdir(const char *path); int fchdir(int fd); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): fchdir(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L || /* Glibc up to and including 2.19: */ _BSD_SOURCEDescriptionchdir() changes the current working directory of the calling process to the directory specified in path. fchdir() is identical to chdir(); the…
afs_syscall, break, fattach, fdetach, ftime, getmsg, getpmsg, gtty, isastream, lock, madvise1, mpx, multiplexer, prof, profil, putmsg, putpmsg, security, stty, tuxcall, ulimit, vserver – unimplemented system calls SynopsisUnimplemented system calls. DescriptionThese system calls are not implemented in the Linux 2.6.22 kernel. Return ValueThese system calls always return -1 and set errno to ENOSYS. NotesNote that ftime(3),…
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…
fanotify_mark – add, remove, or modify an fanotify mark on a filesystem object Synopsis#include <sys/fanotify.h> int fanotify_mark(int fanotify_fd, unsigned int flags, uint64_t mask, int dirfd, const char *pathname);DescriptionFor an overview of the fanotify API, see fanotify(7). fanotify_mark() adds, removes, or modifies an fanotify mark on a filesystem object. The caller must have read permission on…
fanotify_init – create and initialize fanotify group Synopsis#include <fcntl.h> #include <sys/fanotify.h> int fanotify_init(unsigned int flags, unsigned int event_f_flags); DescriptionFor an overview of the fanotify API, see fanotify(7). fanotify_init() initializes a new fanotify group and returns a file descriptor for the event queue associated with the group. The file descriptor is used in calls to fanotify_mark(2)…
fallocate – manipulate file space Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <fcntl.h> int fallocate(int fd, int mode, off_t offset, off_t len);DescriptionThis is a nonportable, Linux-specific system call. For the portable, POSIX.1-specified method of ensuring that space is allocated for a file, see posix_fallocate(3). fallocate() allows the caller to directly manipulate the allocated disk space…
posix_fadvise – predeclare an access pattern for file data Synopsis#include <fcntl.h> int posix_fadvise(int fd, off_t offset, off_t len, int advice);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): posix_fadvise(): _POSIX_C_SOURCE >= 200112LDescriptionPrograms can use posix_fadvise() to announce an intention to access file data in a specific pattern in the future, thus allowing the kernel to perform appropriate optimizations….
posix_fadvise – predeclare an access pattern for file data Synopsis#include <fcntl.h> int posix_fadvise(int fd, off_t offset, off_t len, int advice);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): posix_fadvise(): _POSIX_C_SOURCE >= 200112LDescriptionPrograms can use posix_fadvise() to announce an intention to access file data in a specific pattern in the future, thus allowing the kernel to perform appropriate optimizations….
fadvise64,fadvise64_64 – Give advice about file access Synopsislong fadvise64_64 (int fs, loff_t offset, loff_t len, int advice, int fs, loff_t offset, loff_t len, int advice); long sys_fadvise64 (int fs, loff_t offset, loff_t len, int advice, int fs, loff_t offset, loff_t len, int advice); DescriptionAllows an application to to tell the kernel how it expects to use a file handle, so that the kernel can choose appropriate read-ahead and caching techniques for access to…
access, faccessat, faccessat2 – check user’s permissions for a file Synopsis#include <unistd.h> int access(const char *pathname, int mode); #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h> int faccessat(int dirfd, const char *pathname, int mode, int flags); /* But see C library/kernel differences, below */ int faccessat2(int dirfd, const char *pathname, int mode, int…
access, faccessat, faccessat2 – check user’s permissions for a file Synopsis#include <unistd.h> int access(const char *pathname, int mode); #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h> int faccessat(int dirfd, const char *pathname, int mode, int flags); /* But see C library/kernel differences, below */ int faccessat2(int dirfd, const char *pathname, int mode, int…
exit_group – exit all threads in a process Synopsis#include <linux/unistd.h> void exit_group(int status);DescriptionThis system call is equivalent to _exit(2) except that it terminates not only the calling thread, but all threads in the calling process’s thread group. Return ValueThis system call does not return. VersionsThis call is present since Linux 2.5.35. Conforming ToThis call is…
_exit, _Exit – terminate the calling process Synopsis#include <unistd.h> void _exit(int status); #include <stdlib.h> void _Exit(int status); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): _Exit(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112LDescription_exit() terminates the calling process "immediately". Any open file descriptors belonging to the process are closed. Any children of the process are inherited by init(1) (or by…
execveat – execute program relative to a directory file descriptor Synopsis#include <unistd.h> int execveat(int dirfd, const char *pathname, char *const argv[], char *const envp[], int flags); DescriptionThe execveat() system call executes the program referred to by the combination of dirfd and pathname. It operates in exactly the same way as execve(2), except for the differences…