Section 2: system calls
unlink, unlinkat – delete a name and possibly the file it refers to Synopsis#include <unistd.h> int unlink(const char *pathname); #include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h> int unlinkat(int dirfd, const char *pathname, int flags);Feature Test Macro Requirements for glibc (see feature_test_macros(7)): unlinkat(): Since glibc 2.10: _POSIX_C_SOURCE >= 200809L Before glibc 2.10: _ATFILE_SOURCEDescriptionunlink() deletes a…
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…
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…
umount, umount2 – unmount filesystem Synopsis#include <sys/mount.h> int umount(const char *target); int umount2(const char *target, int flags);Descriptionumount() and umount2() remove the attachment of the (topmost) filesystem mounted on target. Appropriate privilege (Linux: the CAP_SYS_ADMIN capability) is required to unmount filesystems. Linux 2.1.116 added the umount2() system call, which, like umount(), unmounts a target, but allows…
umount, umount2 – unmount filesystem Synopsis#include <sys/mount.h> int umount(const char *target); int umount2(const char *target, int flags);Descriptionumount() and umount2() remove the attachment of the (topmost) filesystem mounted on target. Appropriate privilege (Linux: the CAP_SYS_ADMIN capability) is required to unmount filesystems. Linux 2.1.116 added the umount2() system call, which, like umount(), unmounts a target, but allows…
umask – set file mode creation mask Synopsis#include <sys/types.h> #include <sys/stat.h> mode_t umask(mode_t mask); Descriptionumask() sets the calling process’s file mode creation mask (umask) to mask & 0777 (i.e., only the file permission bits of mask are used), and returns the previous value of the mask. The umask is used by open(2), mkdir(2), and other…
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…
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…
tux – interact with the TUX kernel subsystem Synopsis#include <sys/tuxmodule.h> int tux (unsigned int action, user_req_t * req);DescriptionThe tux() system call calls the kernel to perform an action on behalf of the currently executing user-space TUX module. action can be one of: enum tux_actions { TUX_ACTION_STARTUP = 1, TUX_ACTION_SHUTDOWN = 2, TUX_ACTION_STARTTHREAD = 3, TUX_ACTION_STOPTHREAD…
truncate, ftruncate – truncate a file to a specified length Synopsis#include <unistd.h> #include <sys/types.h> int truncate(const char *path, off_t length); int ftruncate(int fd, off_t length); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): truncate(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L || /* Glibc versions <= 2.19: */ _BSD_SOURCE ftruncate(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.3.5: */ _POSIX_C_SOURCE >= 200112L || /* Glibc versions <= 2.19: */ _BSD_SOURCEDescriptionThe truncate() and ftruncate() functions cause the regular file…
truncate, ftruncate – truncate a file to a specified length Synopsis#include <unistd.h> #include <sys/types.h> int truncate(const char *path, off_t length); int ftruncate(int fd, off_t length); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): truncate(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L || /* Glibc versions <= 2.19: */ _BSD_SOURCE ftruncate(): _XOPEN_SOURCE >= 500 || /* Since glibc 2.3.5: */ _POSIX_C_SOURCE >= 200112L || /* Glibc versions <= 2.19: */ _BSD_SOURCEDescriptionThe truncate() and ftruncate() functions cause the regular file…
tkill, tgkill – send a signal to a thread Synopsisint tkill(int tid, int sig); int tgkill(int tgid, int tid, int sig);Note: There is no glibc wrapper for tkill(); see NOTES. Descriptiontgkill() sends the signal sig to the thread with the thread ID tid in the thread group tgid. (By contrast, kill(2) can be used to…
times – get process times Synopsis#include <sys/times.h> clock_t times(struct tms *buf); Descriptiontimes() stores the current process times in the struct tms that buf points to. The struct tms is as defined in <sys/times.h>: struct tms { clock_t tms_utime; /* user time */ clock_t tms_stime; /* system time */ clock_t tms_cutime; /* user time of children */ clock_t tms_cstime; /* system time of children */ }; The tms_utime…
timerfd_create, timerfd_settime, timerfd_gettime – timers that notify via file descriptors Synopsis#include <sys/timerfd.h> int timerfd_create(int clockid, int flags); int timerfd_settime(int fd, int flags, const struct itimerspec *new_value, struct itimerspec *old_value); int timerfd_gettime(int fd, struct itimerspec *curr_value);DescriptionThese system calls create and operate on a timer that delivers timer expiration notifications via a file descriptor. They provide an…
timerfd_create, timerfd_settime, timerfd_gettime – timers that notify via file descriptors Synopsis#include <sys/timerfd.h> int timerfd_create(int clockid, int flags); int timerfd_settime(int fd, int flags, const struct itimerspec *new_value, struct itimerspec *old_value); int timerfd_gettime(int fd, struct itimerspec *curr_value);DescriptionThese system calls create and operate on a timer that delivers timer expiration notifications via a file descriptor. They provide an…
timerfd_create, timerfd_settime, timerfd_gettime – timers that notify via file descriptors Synopsis#include <sys/timerfd.h> int timerfd_create(int clockid, int flags); int timerfd_settime(int fd, int flags, const struct itimerspec *new_value, struct itimerspec *old_value); int timerfd_gettime(int fd, struct itimerspec *curr_value);DescriptionThese system calls create and operate on a timer that delivers timer expiration notifications via a file descriptor. They provide an…
timer_settime, timer_gettime – arm/disarm and fetch state of POSIX per-process timer Synopsis#include <time.h> int timer_settime(timer_t timerid, int flags, const struct itimerspec *new_value, struct itimerspec *old_value); int timer_gettime(timer_t timerid, struct itimerspec *curr_value);Link with -lrt. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): timer_settime(), timer_gettime(): _POSIX_C_SOURCE >= 199309L Descriptiontimer_settime() arms or disarms the timer identified by timerid. The new_value…
timer_settime, timer_gettime – arm/disarm and fetch state of POSIX per-process timer Synopsis#include <time.h> int timer_settime(timer_t timerid, int flags, const struct itimerspec *new_value, struct itimerspec *old_value); int timer_gettime(timer_t timerid, struct itimerspec *curr_value);Link with -lrt. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): timer_settime(), timer_gettime(): _POSIX_C_SOURCE >= 199309L Descriptiontimer_settime() arms or disarms the timer identified by timerid. The new_value…
timer_getoverrun – get overrun count for a POSIX per-process timer Synopsis#include <time.h> int timer_getoverrun(timer_t timerid);Link with -lrt. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): timer_getoverrun(): _POSIX_C_SOURCE >= 199309L Descriptiontimer_getoverrun() returns the "overrun count" for the timer referred to by timerid. An application can use the overrun count to accurately calculate the number of timer expirations that…
timer_delete – delete a POSIX per-process timer Synopsis#include <time.h> int timer_delete(timer_t timerid);Link with -lrt. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): timer_delete(): _POSIX_C_SOURCE >= 199309L Descriptiontimer_delete() deletes the timer whose ID is given in timerid. If the timer was armed at the time of this call, it is disarmed before being deleted. The treatment of any…