Section 2: system calls
NAME 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:…
NAME 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 SYNOPSIS Unimplemented system calls. DESCRIPTION These system calls are not implemented in the Linux kernel. RETURN VALUE These system calls always return -1 and set errno to ENOSYS. NOTES…
NAME uname – get name and information about current kernel SYNOPSIS #include <sys/utsname.h> int uname(struct utsname *buf); DESCRIPTION uname() 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…
NAME umount, umount2 – unmount filesystem SYNOPSIS #include <sys/mount.h> int umount(const char *target); int umount2(const char *target, int flags); DESCRIPTION umount() 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…
NAME umount, umount2 – unmount filesystem SYNOPSIS #include <sys/mount.h> int umount(const char *target); int umount2(const char *target, int flags); DESCRIPTION umount() 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…
NAME umask – set file mode creation mask SYNOPSIS #include <sys/types.h> #include <sys/stat.h> mode_t umask(mode_t mask); DESCRIPTION umask() 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),…
NAME 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 DESCRIPTION The getrlimit() and setrlimit() system calls…
NAME 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 SYNOPSIS Unimplemented system calls. DESCRIPTION These system calls are not implemented in the Linux kernel. RETURN VALUE These system calls always return -1 and set errno to ENOSYS. NOTES…
NAME tux – interact with the TUX kernel subsystem SYNOPSIS #include <sys/tuxmodule.h> int tux(unsigned int action, user_req_t *req); DESCRIPTION The 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 =…
NAME 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_SOURCE DESCRIPTION The truncate() and ftruncate() functions…
NAME 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_SOURCE DESCRIPTION The truncate() and ftruncate() functions…
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 times – get process times SYNOPSIS #include <sys/times.h> clock_t times(struct tms *buf); DESCRIPTION times() 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 */…
NAME 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); DESCRIPTION These system calls create and operate on a timer that delivers timer expiration notifications via a file…
NAME 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); DESCRIPTION These system calls create and operate on a timer that delivers timer expiration notifications via a file…
NAME 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); DESCRIPTION These system calls create and operate on a timer that delivers timer expiration notifications via a file…
NAME 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 DESCRIPTION timer_settime() arms or disarms the timer identified…
NAME 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 DESCRIPTION timer_settime() arms or disarms the timer identified…
NAME 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 DESCRIPTION timer_getoverrun() returns the "overrun count" for the timer referred to by timerid. An application can use the overrun count to accurately calculate the number…
NAME 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 DESCRIPTION timer_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….