Linux Manuals session 2

select, pselect, FD_CLR, FD_ISSET, FD_SET, FD_ZERO – synchronous I/O multiplexing Synopsis#include <sys/select.h> int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout); void FD_CLR(int fd, fd_set *set); int FD_ISSET(int fd, fd_set *set); void FD_SET(int fd, fd_set *set); void FD_ZERO(fd_set *set); int pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout,…

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…

process_vm_readv, process_vm_writev – transfer data between process address spaces Synopsis#include <sys/uio.h> ssize_t process_vm_readv(pid_t pid, const struct iovec *local_iov, unsigned long liovcnt, const struct iovec *remote_iov, unsigned long riovcnt, unsigned long flags); ssize_t process_vm_writev(pid_t pid, const struct iovec *local_iov, unsigned long liovcnt, const struct iovec *remote_iov, unsigned long riovcnt, unsigned long flags);Feature Test Macro Requirements for…

process_vm_readv, process_vm_writev – transfer data between process address spaces Synopsis#include <sys/uio.h> ssize_t process_vm_readv(pid_t pid, const struct iovec *local_iov, unsigned long liovcnt, const struct iovec *remote_iov, unsigned long riovcnt, unsigned long flags); ssize_t process_vm_writev(pid_t pid, const struct iovec *local_iov, unsigned long liovcnt, const struct iovec *remote_iov, unsigned long riovcnt, unsigned long flags);Feature Test Macro Requirements for…

getrlimit, setrlimit, prlimit – get/set resource limits Synopsis#include <sys/time.h> #include <sys/resource.h> int getrlimit(int resource, struct rlimit *rlim); int setrlimit(int resource, const struct rlimit *rlim); int prlimit(pid_t pid, int resource, const struct rlimit *new_limit, struct rlimit *old_limit); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): prlimit(): _GNU_SOURCE DescriptionThe getrlimit() and setrlimit() system calls get and set…

getrlimit, setrlimit, prlimit – get/set resource limits Synopsis#include <sys/time.h> #include <sys/resource.h> int getrlimit(int resource, struct rlimit *rlim); int setrlimit(int resource, const struct rlimit *rlim); int prlimit(pid_t pid, int resource, const struct rlimit *new_limit, struct rlimit *old_limit); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): prlimit(): _GNU_SOURCE DescriptionThe getrlimit() and setrlimit() system calls get and set…

readv, writev, preadv, pwritev, preadv2, pwritev2 – read or write data into multiple buffers Synopsis#include <sys/uio.h> ssize_t readv(int fd, const struct iovec *iov, int iovcnt); ssize_t writev(int fd, const struct iovec *iov, int iovcnt); ssize_t preadv(int fd, const struct iovec *iov, int iovcnt, off_t offset); ssize_t pwritev(int fd, const struct iovec *iov, int iovcnt, off_t…

readv, writev, preadv, pwritev, preadv2, pwritev2 – read or write data into multiple buffers Synopsis#include <sys/uio.h> ssize_t readv(int fd, const struct iovec *iov, int iovcnt); ssize_t writev(int fd, const struct iovec *iov, int iovcnt); ssize_t preadv(int fd, const struct iovec *iov, int iovcnt, off_t offset); ssize_t pwritev(int fd, const struct iovec *iov, int iovcnt, off_t…

pread, pwrite – read from or write to a file descriptor at a given offset Synopsis#include <unistd.h> ssize_t pread(int fd, void *buf, size_t count, off_t offset); ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): pread(), pwrite(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809LDescriptionpread() reads…

pread, pwrite – read from or write to a file descriptor at a given offset Synopsis#include <unistd.h> ssize_t pread(int fd, void *buf, size_t count, off_t offset); ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): pread(), pwrite(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809LDescriptionpread() reads…

prctl – operations on a process or thread Synopsis#include <sys/prctl.h> int prctl(int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5);Descriptionprctl() manipulates various aspects of the behavior of the calling thread or process. Note that careless use of some prctl() operations can confuse the user-space run-time environment, so these operations should…

poll, ppoll – wait for some event on a file descriptor Synopsis#include <poll.h> int poll(struct pollfd *fds, nfds_t nfds, int timeout); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <signal.h> #include <poll.h> int ppoll(struct pollfd *fds, nfds_t nfds, const struct timespec *tmo_p, const sigset_t *sigmask);Descriptionpoll() performs a similar task to select(2): it waits for one of…

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….

poll, ppoll – wait for some event on a file descriptor Synopsis#include <poll.h> int poll(struct pollfd *fds, nfds_t nfds, int timeout); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <signal.h> #include <poll.h> int ppoll(struct pollfd *fds, nfds_t nfds, const struct timespec *tmo_p, const sigset_t *sigmask);Descriptionpoll() performs a similar task to select(2): it waits for one of…

mprotect, pkey_mprotect – set protection on a region of memory Synopsis#include <sys/mman.h> int mprotect(void *addr, size_t len, int prot); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sys/mman.h> int pkey_mprotect(void *addr, size_t len, int prot, int pkey);Descriptionmprotect() changes the access protections for the calling process’s memory pages containing any part of the address range in the…

pkey_alloc, pkey_free – allocate or free a protection key Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sys/mman.h> int pkey_alloc(unsigned int flags, unsigned int access_rights); int pkey_free(int pkey);Descriptionpkey_alloc() allocates a protection key (pkey) and allows it to be passed to pkey_mprotect(2). The pkey_alloc() flags is reserved for future use and currently must always be specified as…

pkey_alloc, pkey_free – allocate or free a protection key Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <sys/mman.h> int pkey_alloc(unsigned int flags, unsigned int access_rights); int pkey_free(int pkey);Descriptionpkey_alloc() allocates a protection key (pkey) and allows it to be passed to pkey_mprotect(2). The pkey_alloc() flags is reserved for future use and currently must always be specified as…

pivot_root – change the root mount Synopsisint pivot_root(const char *new_root, const char *put_old); Note: There is no glibc wrapper for this system call; see NOTES. Descriptionpivot_root() changes the root mount in the mount namespace of the calling process. More precisely, it moves the root mount to the directory put_old and makes new_root the new root…

pipe, pipe2 – create pipe Synopsis#include <unistd.h> /* On Alpha, IA-64, MIPS, SuperH, and SPARC/SPARC64; see NOTES */ struct fd_pair { long fd[2]; }; struct fd_pair pipe(); /* On all other architectures */ int pipe(int pipefd[2]); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <fcntl.h> /* Obtain O_* constant definitions */ #include <unistd.h> int pipe2(int pipefd[2],…

pidfd_send_signal – send a signal to a process specified by a file descriptor Synopsis#include <signal.h> int pidfd_send_signal(int pidfd, int sig, siginfo_t *info, unsigned int flags);DescriptionThe pidfd_send_signal() system call sends the signal sig to the target process referred to by pidfd, a PID file descriptor that refers to a process. If the info argument points to…