Section 2: system calls
NAME timer_create – create a POSIX per-process timer SYNOPSIS #include <signal.h> #include <time.h> int timer_create(clockid_t clockid, struct sigevent *sevp, timer_t *timerid); Link with -lrt. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): timer_create(): _POSIX_C_SOURCE >= 199309L DESCRIPTION timer_create() creates a new per-process interval timer. The ID of the new timer is returned in the buffer pointed to…
NAME time – get time in seconds SYNOPSIS #include <time.h> time_t time(time_t *tloc); DESCRIPTION time() returns the time as the number of seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC). If tloc is non-NULL, the return value is also stored in the memory pointed to by tloc. RETURN VALUE On success, the value of time…
NAME tkill, tgkill – send a signal to a thread SYNOPSIS int tkill(int tid, int sig); int tgkill(int tgid, int tid, int sig); Note: There is no glibc wrapper for tkill(); see NOTES. DESCRIPTION tgkill() sends the signal sig to the thread with the thread ID tid in the thread group tgid. (By contrast, kill(2)…
NAME tee – duplicating pipe content SYNOPSIS #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <fcntl.h> ssize_t tee(int fd_in, int fd_out, size_t len, unsigned int flags); DESCRIPTION tee() duplicates up to len bytes of data from the pipe referred to by the file descriptor fd_in to the pipe referred to by the file descriptor fd_out. It…
NAME syslog, klogctl – read and/or clear kernel message ring buffer; set console_loglevel SYNOPSIS int syslog(int type, char *bufp, int len); /* No wrapper provided in glibc */ /* The glibc interface */ #include <sys/klog.h> int klogctl(int type, char *bufp, int len); DESCRIPTION Note: Probably, you are looking for the C library function syslog(), which…
NAME sysinfo – return system information SYNOPSIS #include <sys/sysinfo.h> int sysinfo(struct sysinfo *info); DESCRIPTION sysinfo() returns certain statistics on memory and swap usage, as well as the load average. Until Linux 2.3.16, sysinfo() returned information in the following structure: struct sysinfo { long uptime; /* Seconds since boot */ unsigned long loads[3]; /* 1, 5, and 15 minute load averages */…
NAME sysfs – get filesystem type information SYNOPSIS int sysfs(int option, const char *fsname); int sysfs(int option, unsigned int fs_index, char *buf); int sysfs(int option); DESCRIPTION Note: if you are looking for information about the sysfs filesystem that is normally mounted at /sys, see sysfs(5). The (obsolete) sysfs() system call returns information about the filesystem…
NAME sysctl – read/write system parameters SYNOPSIS #include <linux/sysctl.h> #include <unistd.h> int _sysctl(struct __sysctl_args *args); DESCRIPTION This system call no longer exists on current kernels! See NOTES. The _sysctl() call reads and/or writes kernel parameters. For example, the hostname, or the maximum number of open files. The argument has the form struct __sysctl_args { int *name; /* integer…
NAME syscalls – Linux system calls SYNOPSIS Linux system calls. DESCRIPTION The system call is the fundamental interface between an application and the Linux kernel. System calls and library wrapper functions System calls are generally not invoked directly, but rather via wrapper functions in glibc (or perhaps some other library). For details of direct invocation…
NAME syscall – indirect system call SYNOPSIS #include <sys/syscall.h> /* For SYS_xxx definitions */ #include <unistd.h> long syscall(long number, …); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): syscall(): Since glibc 2.19: _DEFAULT_SOURCE Before glibc 2.19: _BSD_SOURCE || _SVID_SOURCE DESCRIPTION syscall() is a small library function that invokes the system call whose assembly language interface…
NAME sync, syncfs – commit filesystem caches to disk SYNOPSIS #include <unistd.h> void sync(void); int syncfs(int fd); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): sync(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE syncfs(): _GNU_SOURCE DESCRIPTION sync() causes all pending modifications to filesystem metadata and cached file data to be written to the underlying filesystems. syncfs()…
NAME sync_file_range – sync a file segment with disk SYNOPSIS #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <fcntl.h> int sync_file_range(int fd, off64_t offset, off64_t nbytes, unsigned int flags); DESCRIPTION sync_file_range() permits fine control when synchronizing the open file referred to by the file descriptor fd with disk. offset is the starting byte of the file…
NAME sync_file_range – sync a file segment with disk SYNOPSIS #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <fcntl.h> int sync_file_range(int fd, off64_t offset, off64_t nbytes, unsigned int flags); DESCRIPTION sync_file_range() permits fine control when synchronizing the open file referred to by the file descriptor fd with disk. offset is the starting byte of the file…
NAME sync, syncfs – commit filesystem caches to disk SYNOPSIS #include <unistd.h> void sync(void); int syncfs(int fd); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): sync(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE syncfs(): _GNU_SOURCE DESCRIPTION sync() causes all pending modifications to filesystem metadata and cached file data to be written to the underlying filesystems. syncfs()…
NAME symlink, symlinkat – make a new name for a file SYNOPSIS #include <unistd.h> int symlink(const char *target, const char *linkpath); #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h> int symlinkat(const char *target, int newdirfd, const char *linkpath); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): symlink(): _XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200112L || /* Glibc versions <= 2.19: */ _BSD_SOURCE symlinkat():…
NAME symlink, symlinkat – make a new name for a file SYNOPSIS #include <unistd.h> int symlink(const char *target, const char *linkpath); #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h> int symlinkat(const char *target, int newdirfd, const char *linkpath); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): symlink(): _XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200112L || /* Glibc versions <= 2.19: */ _BSD_SOURCE symlinkat():…
NAME swapon, swapoff – start/stop swapping to file/device SYNOPSIS #include <unistd.h> #include <sys/swap.h> int swapon(const char *path, int swapflags); int swapoff(const char *path); DESCRIPTION swapon() sets the swap area to the file or block device specified by path. swapoff() stops swapping to the file or block device specified by path. If the SWAP_FLAG_PREFER flag is…
NAME swapon, swapoff – start/stop swapping to file/device SYNOPSIS #include <unistd.h> #include <sys/swap.h> int swapon(const char *path, int swapflags); int swapoff(const char *path); DESCRIPTION swapon() sets the swap area to the file or block device specified by path. swapoff() stops swapping to the file or block device specified by path. If the SWAP_FLAG_PREFER flag is…
NAME swapcontext – Swap out old context with new context SYNOPSIS int sys_swapcontext (struct ucontext *old_ctx, struct ucontext *new_ctx, int r5, int r6, int r7, int r8, struct pt_regs *regs); DESCRIPTION swapcontext swaps out context old_ctx with new context new_ctx. The int r# values have no place in the system call functionality. The regs value indicates the current user register values from the user…
NAME subpage_prot – define a subpage protection for an address range SYNOPSIS int subpage_prot(unsigned long addr, unsigned long len, uint32_t *map); Note: There is no glibc wrapper for this system call; see NOTES. DESCRIPTION The PowerPC-specific subpage_prot() system call provides the facility to control the access permissions on individual 4 kB subpages on systems configured…