Section 2: system calls
getgroups, setgroups – get/set list of supplementary group IDs Synopsis#include <sys/types.h> #include <unistd.h> int getgroups(int size, gid_t list[]); #include <grp.h> int setgroups(size_t size, const gid_t *list); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): setgroups(): Since glibc 2.19: _DEFAULT_SOURCE Glibc 2.19 and earlier: _BSD_SOURCE Descriptiongetgroups() returns the supplementary group IDs of the calling process in…
getgid, getegid – get group identity Synopsis#include <unistd.h> #include <sys/types.h> gid_t getgid(void); gid_t getegid(void); Descriptiongetgid() returns the real group ID of the calling process. getegid() returns the effective group ID of the calling process. ErrorsThese functions are always successful. Conforming ToPOSIX.1-2001, POSIX.1-2008, 4.3BSD. NotesThe original Linux getgid() and getegid() system calls supported only 16-bit group…
getgid, getegid – get group identity Synopsis#include <unistd.h> #include <sys/types.h> gid_t getgid(void); gid_t getegid(void); Descriptiongetgid() returns the real group ID of the calling process. getegid() returns the effective group ID of the calling process. ErrorsThese functions are always successful. Conforming ToPOSIX.1-2001, POSIX.1-2008, 4.3BSD. NotesThe original Linux getgid() and getegid() system calls supported only 16-bit group…
getuid, geteuid – get user identity Synopsis#include <unistd.h> #include <sys/types.h> uid_t getuid(void); uid_t geteuid(void); Descriptiongetuid() returns the real user ID of the calling process. geteuid() returns the effective user ID of the calling process. ErrorsThese functions are always successful. Conforming ToPOSIX.1-2001, POSIX.1-2008, 4.3BSD. NotesHistoryIn UNIX V6 the getuid() call returned (euid << 8) + uid….
getuid, geteuid – get user identity Synopsis#include <unistd.h> #include <sys/types.h> uid_t getuid(void); uid_t geteuid(void); Descriptiongetuid() returns the real user ID of the calling process. geteuid() returns the effective user ID of the calling process. ErrorsThese functions are always successful. Conforming ToPOSIX.1-2001, POSIX.1-2008, 4.3BSD. NotesHistoryIn UNIX V6 the getuid() call returned (euid << 8) + uid….
getgid, getegid – get group identity Synopsis#include <unistd.h> #include <sys/types.h> gid_t getgid(void); gid_t getegid(void); Descriptiongetgid() returns the real group ID of the calling process. getegid() returns the effective group ID of the calling process. ErrorsThese functions are always successful. Conforming ToPOSIX.1-2001, POSIX.1-2008, 4.3BSD. NotesThe original Linux getgid() and getegid() system calls supported only 16-bit group…
getgid, getegid – get group identity Synopsis#include <unistd.h> #include <sys/types.h> gid_t getgid(void); gid_t getegid(void); Descriptiongetgid() returns the real group ID of the calling process. getegid() returns the effective group ID of the calling process. ErrorsThese functions are always successful. Conforming ToPOSIX.1-2001, POSIX.1-2008, 4.3BSD. NotesThe original Linux getgid() and getegid() system calls supported only 16-bit group…
getdtablesize – get file descriptor table size Synopsis#include <unistd.h> int getdtablesize(void); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): getdtablesize(): Since glibc 2.12: /* Glibc since 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || ! (_POSIX_C_SOURCE >= 200112L) Before glibc 2.12: _BSD_SOURCE || _XOPEN_SOURCE >= 500Descriptiongetdtablesize() returns the maximum number of files a process can…
getdomainname, setdomainname – get/set NIS domain name Synopsis#include <unistd.h> int getdomainname(char *name, size_t len); int setdomainname(const char *name, size_t len); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): getdomainname(), setdomainname(): 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)DescriptionThese…
getdents, getdents64 – get directory entries Synopsislong getdents(unsigned int fd, struct linux_dirent *dirp, unsigned int count); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <dirent.h> ssize_t getdents64(int fd, void *dirp, size_t count);Note: There is no glibc wrapper for getdents(); see NOTES. DescriptionThese are not the interfaces you are interested in. Look at readdir(3) for the POSIX-conforming…
getdents, getdents64 – get directory entries Synopsislong getdents(unsigned int fd, struct linux_dirent *dirp, unsigned int count); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <dirent.h> ssize_t getdents64(int fd, void *dirp, size_t count);Note: There is no glibc wrapper for getdents(); see NOTES. DescriptionThese are not the interfaces you are interested in. Look at readdir(3) for the POSIX-conforming…
getcwd, getwd, get_current_dir_name – get current working directory Synopsis#include <unistd.h> char *getcwd(char *buf, size_t size); char *getwd(char *buf); char *get_current_dir_name(void);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): get_current_dir_name(): _GNU_SOURCE getwd(): Since glibc 2.12: (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L) || /* Glibc since 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCEBefore glibc 2.12: _BSD_SOURCE…
getcpu – determine CPU and NUMA node on which the calling thread is running Synopsis#include <linux/getcpu.h> int getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache);DescriptionThe getcpu() system call identifies the processor and node on which the calling thread or process is currently running and writes them into the integers pointed to by the cpu and node…
getcontext, setcontext – get or set the user context Synopsis#include <ucontext.h> int getcontext(ucontext_t *ucp); int setcontext(const ucontext_t *ucp); DescriptionIn a System V-like environment, one has the two types mcontext_t and ucontext_t defined in <ucontext.h> and the four functions getcontext(), setcontext(), makecontext(3), and swapcontext(3) that allow user-level context switching between multiple threads of control within a…
get_thread_area, set_thread_area – manipulate thread-local storage information Synopsis#include <linux/unistd.h> #if defined __i386__ || defined __x86_64__ # include <asm/ldt.h> int get_thread_area(struct user_desc *u_info); int set_thread_area(struct user_desc *u_info); #elif defined __m68k__ int get_thread_area(void); int set_thread_area(unsigned long tp); #elif defined __mips__ int set_thread_area(unsigned long addr); #endifNote: There are no glibc wrappers for these system calls; see NOTES. DescriptionThese…
get_robust_list, set_robust_list – get/set list of robust futexes Synopsis#include <linux/futex.h> #include <sys/types.h> #include <syscall.h> long get_robust_list(int pid, struct robust_list_head **head_ptr, size_t *len_ptr); long set_robust_list(struct robust_list_head *head, size_t len);Note: There are no glibc wrappers for these system calls; see NOTES. DescriptionThese system calls deal with per-thread robust futex lists. These lists are managed in user space:…
get_mempolicy – retrieve NUMA memory policy for a thread Synopsis#include <numaif.h> long get_mempolicy(int *mode, unsigned long *nodemask, unsigned long maxnode, void *addr, unsigned long flags); Link with -lnuma.Descriptionget_mempolicy() retrieves the NUMA policy of the calling thread or of a memory address, depending on the setting of flags. A NUMA machine has different memory controllers with…
get_kernel_syms – retrieve exported kernel and module symbols Synopsis#include <linux/module.h> int get_kernel_syms(struct kernel_sym *table);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. If table is NULL, get_kernel_syms() returns the number of symbols available for query. Otherwise, it fills…
futimesat – change timestamps of a file relative to a directory file descriptor Synopsis#include <fcntl.h> /* Definition of AT_* constants */ #include <sys/time.h> int futimesat(int dirfd, const char *pathname, const struct timeval times[2]);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): futimesat(): _GNU_SOURCE DescriptionThis system call is obsolete. Use utimensat(2) instead. The futimesat() system call operates…
futex – fast user-space locking Synopsis#include <linux/futex.h> #include <stdint.h> #include <sys/time.h> long futex(uint32_t *uaddr, int futex_op, uint32_t val, const struct timespec *timeout, /* or: uint32_t val2 */ uint32_t *uaddr2, uint32_t val3);Note: There is no glibc wrapper for this system call; see NOTES. DescriptionThe futex() system call provides a method for waiting until a certain condition…