The Linux Manuals (man pages) document is an important part of Linux documents. Linux Manuals are organized as several sections. Each section has a group of commands for a specific area in Linux usage, administration or development.
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…
eventfd – create a file descriptor for event notification Synopsis#include <sys/eventfd.h> int eventfd(unsigned int initval, int flags); Descriptioneventfd() creates an "eventfd object" that can be used as an event wait/notify mechanism by user-space applications, and by the kernel to notify user-space applications of events. The object contains an unsigned 64-bit integer (uint64_t) counter that is…
eventfd – create a file descriptor for event notification Synopsis#include <sys/eventfd.h> int eventfd(unsigned int initval, int flags); Descriptioneventfd() creates an "eventfd object" that can be used as an event wait/notify mechanism by user-space applications, and by the kernel to notify user-space applications of events. The object contains an unsigned 64-bit integer (uint64_t) counter that is…
epoll_wait, epoll_pwait – wait for an I/O event on an epoll file descriptor Synopsis#include <sys/epoll.h> int epoll_wait(int epfd, struct epoll_event *events, int maxevents, int timeout); int epoll_pwait(int epfd, struct epoll_event *events, int maxevents, int timeout, const sigset_t *sigmask);DescriptionThe epoll_wait() system call waits for events on the epoll(7) instance referred to by the file descriptor epfd….
epoll_wait, epoll_pwait – wait for an I/O event on an epoll file descriptor Synopsis#include <sys/epoll.h> int epoll_wait(int epfd, struct epoll_event *events, int maxevents, int timeout); int epoll_pwait(int epfd, struct epoll_event *events, int maxevents, int timeout, const sigset_t *sigmask);DescriptionThe epoll_wait() system call waits for events on the epoll(7) instance referred to by the file descriptor epfd….
epoll_ctl – control interface for an epoll file descriptor Synopsis#include <sys/epoll.h> int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event); DescriptionThis system call is used to add, modify, or remove entries in the interest list of the epoll(7) instance referred to by the file descriptor epfd. It requests that the operation op be performed…
epoll_create, epoll_create1 – open an epoll file descriptor Synopsis#include <sys/epoll.h> int epoll_create(int size); int epoll_create1(int flags);Descriptionepoll_create() creates a new epoll(7) instance. Since Linux 2.6.8, the size argument is ignored, but must be greater than zero; see NOTES. epoll_create() returns a file descriptor referring to the new epoll instance. This file descriptor is used for all…
epoll_create, epoll_create1 – open an epoll file descriptor Synopsis#include <sys/epoll.h> int epoll_create(int size); int epoll_create1(int flags);Descriptionepoll_create() creates a new epoll(7) instance. Since Linux 2.6.8, the size argument is ignored, but must be greater than zero; see NOTES. epoll_create() returns a file descriptor referring to the new epoll instance. This file descriptor is used for all…
dup, dup2, dup3 – duplicate a file descriptor Synopsis#include <unistd.h> int dup(int oldfd); int dup2(int oldfd, int newfd); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <fcntl.h> /* Obtain O_* constant definitions */ #include <unistd.h> int dup3(int oldfd, int newfd, int flags);DescriptionThe dup() system call creates a copy of the file descriptor oldfd, using the lowest-numbered…
dup, dup2, dup3 – duplicate a file descriptor Synopsis#include <unistd.h> int dup(int oldfd); int dup2(int oldfd, int newfd); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <fcntl.h> /* Obtain O_* constant definitions */ #include <unistd.h> int dup3(int oldfd, int newfd, int flags);DescriptionThe dup() system call creates a copy of the file descriptor oldfd, using the lowest-numbered…
delete_module – unload a kernel module Synopsisint delete_module(const char *name, int flags);Note: No declaration of this system call is provided in glibc headers; see NOTES. DescriptionThe delete_module() system call attempts to remove the unused loadable module entry identified by name. If the module has an exit function, then that function is executed before unloading the…
create_module – create a loadable module entry Synopsis#include <linux/module.h> caddr_t create_module(const char *name, size_t size);Note: No declaration of this system call is provided in glibc headers; see NOTES. DescriptionNote: This system call is present only in kernels before Linux 2.6. create_module() attempts to create a loadable module entry and reserve the kernel memory that will…
open, openat, creat – open and possibly create a file Synopsis#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> int open(const char *pathname, int flags); int open(const char *pathname, int flags, mode_t mode); int creat(const char *pathname, mode_t mode); int openat(int dirfd, const char *pathname, int flags); int openat(int dirfd, const char *pathname, int flags, mode_t mode); /*…
copy_file_range – Copy a range of data from one file to another Synopsis#define _GNU_SOURCE #include <unistd.h> ssize_t copy_file_range(int fd_in, loff_t *off_in, int fd_out, loff_t *off_out, size_t len, unsigned int flags);DescriptionThe copy_file_range() system call performs an in-kernel copy between two file descriptors without the additional cost of transferring data from the kernel to user space and…