Section 2: system calls
openat2 – open and possibly create a file (extended) Synopsis#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <linux/openat2.h> long openat2(int dirfd, const char *pathname, struct open_how *how, size_t size);Note: There is no glibc wrapper for this system call; see NOTES. DescriptionThe openat2() system call is an extension of openat(2) and provides a superset of its functionality….
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); /*…
name_to_handle_at, open_by_handle_at – obtain handle for a pathname and open file via a handle Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> int name_to_handle_at(int dirfd, const char *pathname, struct file_handle *handle, int *mount_id, int flags); int open_by_handle_at(int mount_fd, struct file_handle *handle, int flags);DescriptionThe name_to_handle_at() and open_by_handle_at() system calls split the functionality…
uname – get name and information about current kernel Synopsis#include <sys/utsname.h> int uname(struct utsname *buf); Descriptionuname() returns system information in the structure pointed to by buf. The utsname struct is defined in <sys/utsname.h>: struct utsname { char sysname[]; /* Operating system name (e.g., "Linux") */ char nodename[]; /* Name within "some implementation-defined network" */ char release[]; /* Operating system release (e.g., "2.6.28") */ char version[]; /* Operating system version */ char…
stat, fstat, lstat, fstatat – get file status Synopsis#include <sys/types.h> #include <sys/stat.h> #include <unistd.h> int stat(const char *pathname, struct stat *statbuf); int fstat(int fd, struct stat *statbuf); int lstat(const char *pathname, struct stat *statbuf); #include <fcntl.h> /* Definition of AT_* constants */ #include <sys/stat.h> int fstatat(int dirfd, const char *pathname, struct stat *statbuf, int flags);Feature…
uname – get name and information about current kernel Synopsis#include <sys/utsname.h> int uname(struct utsname *buf); Descriptionuname() returns system information in the structure pointed to by buf. The utsname struct is defined in <sys/utsname.h>: struct utsname { char sysname[]; /* Operating system name (e.g., "Linux") */ char nodename[]; /* Name within "some implementation-defined network" */ char release[]; /* Operating system release (e.g., "2.6.28") */ char version[]; /* Operating system version */ char…
stat, fstat, lstat, fstatat – get file status Synopsis#include <sys/types.h> #include <sys/stat.h> #include <unistd.h> int stat(const char *pathname, struct stat *statbuf); int fstat(int fd, struct stat *statbuf); int lstat(const char *pathname, struct stat *statbuf); #include <fcntl.h> /* Definition of AT_* constants */ #include <sys/stat.h> int fstatat(int dirfd, const char *pathname, struct stat *statbuf, int flags);Feature…
stat, fstat, lstat, fstatat – get file status Synopsis#include <sys/types.h> #include <sys/stat.h> #include <unistd.h> int stat(const char *pathname, struct stat *statbuf); int fstat(int fd, struct stat *statbuf); int lstat(const char *pathname, struct stat *statbuf); #include <fcntl.h> /* Definition of AT_* constants */ #include <sys/stat.h> int fstatat(int dirfd, const char *pathname, struct stat *statbuf, int flags);Feature…
nice – change process priority Synopsis#include <unistd.h> int nice(int inc); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): nice(): _XOPEN_SOURCE || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE Descriptionnice() adds inc to the nice value for the calling thread. (A higher nice value means a lower priority.) The range of the nice value is +19 (low priority)…
nfsservctl – syscall interface to kernel nfs daemon Synopsis#include <linux/nfsd/syscall.h> long nfsservctl(int cmd, struct nfsctl_arg *argp, union nfsctl_res *resp);DescriptionNote: Since Linux 3.1, this system call no longer exists. It has been replaced by a set of files in the nfsd filesystem; see nfsd(7). /* * These are the commands understood by nfsctl(). */ #define NFSCTL_SVC 0…
stat, fstat, lstat, fstatat – get file status Synopsis#include <sys/types.h> #include <sys/stat.h> #include <unistd.h> int stat(const char *pathname, struct stat *statbuf); int fstat(int fd, struct stat *statbuf); int lstat(const char *pathname, struct stat *statbuf); #include <fcntl.h> /* Definition of AT_* constants */ #include <sys/stat.h> int fstatat(int dirfd, const char *pathname, struct stat *statbuf, int flags);Feature…
nanosleep – high-resolution sleep Synopsis#include <time.h> int nanosleep(const struct timespec *req, struct timespec *rem); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): nanosleep(): _POSIX_C_SOURCE >= 199309L Descriptionnanosleep() suspends the execution of the calling thread until either at least the time specified in *req has elapsed, or the delivery of a signal that triggers the invocation of a…
name_to_handle_at, open_by_handle_at – obtain handle for a pathname and open file via a handle Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> int name_to_handle_at(int dirfd, const char *pathname, struct file_handle *handle, int *mount_id, int flags); int open_by_handle_at(int mount_fd, struct file_handle *handle, int flags);DescriptionThe name_to_handle_at() and open_by_handle_at() system calls split the functionality…
mmap, munmap – map or unmap files or devices into memory Synopsis#include <sys/mman.h> void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset); int munmap(void *addr, size_t length);See NOTES for information on feature test macro requirements. Descriptionmmap() creates a new mapping in the virtual address space of the calling process. The starting…
mlock, mlock2, munlock, mlockall, munlockall – lock and unlock memory Synopsis#include <sys/mman.h> int mlock(const void *addr, size_t len); int mlock2(const void *addr, size_t len, int flags); int munlock(const void *addr, size_t len); int mlockall(int flags); int munlockall(void);Descriptionmlock(), mlock2(), and mlockall() lock part or all of the calling process’s virtual address space into RAM, preventing that…
mlock, mlock2, munlock, mlockall, munlockall – lock and unlock memory Synopsis#include <sys/mman.h> int mlock(const void *addr, size_t len); int mlock2(const void *addr, size_t len, int flags); int munlock(const void *addr, size_t len); int mlockall(int flags); int munlockall(void);Descriptionmlock(), mlock2(), and mlockall() lock part or all of the calling process’s virtual address space into RAM, preventing that…
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),…
msync – synchronize a file with a memory map Synopsis#include <sys/mman.h> int msync(void *addr, size_t length, int flags); Descriptionmsync() flushes changes made to the in-core copy of a file that was mapped into memory using mmap(2) back to the filesystem. Without use of this call, there is no guarantee that changes are written back before…
msgrcv, msgsnd – System V message queue operations Synopsis#include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg); ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg);DescriptionThe msgsnd() and msgrcv() system calls are used to send messages to, and receive messages from, a System V message queue….
msgrcv, msgsnd – System V message queue operations Synopsis#include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg); ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg);DescriptionThe msgsnd() and msgrcv() system calls are used to send messages to, and receive messages from, a System V message queue….