Section 2: system calls
setfsuid – set user identity used for filesystem checks Synopsis#include <sys/fsuid.h> int setfsuid(uid_t fsuid); DescriptionOn Linux, a process has both a filesystem user ID and an effective user ID. The (Linux-specific) filesystem user ID is used for permissions checking when accessing filesystem objects, while the effective user ID is used for various other kinds of…
setfsuid – set user identity used for filesystem checks Synopsis#include <sys/fsuid.h> int setfsuid(uid_t fsuid); DescriptionOn Linux, a process has both a filesystem user ID and an effective user ID. The (Linux-specific) filesystem user ID is used for permissions checking when accessing filesystem objects, while the effective user ID is used for various other kinds of…
setfsgid – set group identity used for filesystem checks Synopsis#include <sys/fsuid.h> int setfsgid(uid_t fsgid); DescriptionOn Linux, a process has both a filesystem group ID and an effective group ID. The (Linux-specific) filesystem group ID is used for permissions checking when accessing filesystem objects, while the effective group ID is used for some other kinds of…
setfsgid – set group identity used for filesystem checks Synopsis#include <sys/fsuid.h> int setfsgid(uid_t fsgid); DescriptionOn Linux, a process has both a filesystem group ID and an effective group ID. The (Linux-specific) filesystem group ID is used for permissions checking when accessing filesystem objects, while the effective group ID is used for some other kinds of…
seteuid, setegid – set effective user or group ID Synopsis#include <sys/types.h> #include <unistd.h> int seteuid(uid_t euid); int setegid(gid_t egid); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): seteuid(), setegid(): _POSIX_C_SOURCE >= 200112L || /* Glibc versions <= 2.19: */ _BSD_SOURCEDescriptionseteuid() sets the effective user ID of the calling process. Unprivileged processes may only set the effective user ID to the real user ID,…
seteuid, setegid – set effective user or group ID Synopsis#include <sys/types.h> #include <unistd.h> int seteuid(uid_t euid); int setegid(gid_t egid); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): seteuid(), setegid(): _POSIX_C_SOURCE >= 200112L || /* Glibc versions <= 2.19: */ _BSD_SOURCEDescriptionseteuid() sets the effective user ID of the calling process. Unprivileged processes may only set the effective user ID to the real user ID,…
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…
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…
set_tid_address – set pointer to thread ID Synopsis#include <linux/unistd.h> pid_t set_tid_address(int *tidptr);Note: There is no glibc wrapper for this system call; see NOTES. DescriptionFor each thread, the kernel maintains two attributes (addresses) called set_child_tid and clear_child_tid. These two attributes contain the value NULL by default. set_child_tid If a thread is started using clone(2) with the…
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:…
set_mempolicy – set default NUMA memory policy for a thread and its children Synopsis#include <numaif.h> long set_mempolicy(int mode, const unsigned long *nodemask, unsigned long maxnode); Link with -lnuma.Descriptionset_mempolicy() sets the NUMA memory policy of the calling thread, which consists of a policy mode and zero or more nodes, to the values specified by the mode,…
send, sendto, sendmsg – send a message on a socket Synopsis#include <sys/types.h> #include <sys/socket.h> ssize_t send(int sockfd, const void *buf, size_t len, int flags); ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen); ssize_t sendmsg(int sockfd, const struct msghdr *msg, int flags);DescriptionThe system calls send(), sendto(), and sendmsg()…
send, sendto, sendmsg – send a message on a socket Synopsis#include <sys/types.h> #include <sys/socket.h> ssize_t send(int sockfd, const void *buf, size_t len, int flags); ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen); ssize_t sendmsg(int sockfd, const struct msghdr *msg, int flags);DescriptionThe system calls send(), sendto(), and sendmsg()…
sendmmsg – send multiple messages on a socket Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sys/socket.h> int sendmmsg(int sockfd, struct mmsghdr *msgvec, unsigned int vlen, int flags);DescriptionThe sendmmsg() system call is an extension of sendmsg(2) that allows the caller to transmit multiple messages on a socket using a single system call. (This has performance benefits…
sendfile – transfer data between file descriptors Synopsis#include <sys/sendfile.h> ssize_t sendfile(int out_fd, int in_fd, off_t *offset, size_t count); Descriptionsendfile() copies data between one file descriptor and another. Because this copying is done within the kernel, sendfile() is more efficient than the combination of read(2) and write(2), which would require transferring data to and from user…
sendfile – transfer data between file descriptors Synopsis#include <sys/sendfile.h> ssize_t sendfile(int out_fd, int in_fd, off_t *offset, size_t count); Descriptionsendfile() copies data between one file descriptor and another. Because this copying is done within the kernel, sendfile() is more efficient than the combination of read(2) and write(2), which would require transferring data to and from user…
send, sendto, sendmsg – send a message on a socket Synopsis#include <sys/types.h> #include <sys/socket.h> ssize_t send(int sockfd, const void *buf, size_t len, int flags); ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen); ssize_t sendmsg(int sockfd, const struct msghdr *msg, int flags);DescriptionThe system calls send(), sendto(), and sendmsg()…
semop, semtimedop – System V semaphore operations Synopsis#include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> int semop(int semid, struct sembuf *sops, size_t nsops); int semtimedop(int semid, struct sembuf *sops, size_t nsops, const struct timespec *timeout);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): semtimedop(): _GNU_SOURCE DescriptionEach semaphore in a System V semaphore set has the following associated values:…
semop, semtimedop – System V semaphore operations Synopsis#include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> int semop(int semid, struct sembuf *sops, size_t nsops); int semtimedop(int semid, struct sembuf *sops, size_t nsops, const struct timespec *timeout);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): semtimedop(): _GNU_SOURCE DescriptionEach semaphore in a System V semaphore set has the following associated values:…