Linux Manuals session 2

getsid – get session ID Synopsis#include <sys/types.h> #include <unistd.h> pid_t getsid(pid_t pid); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): getsid(): _XOPEN_SOURCE >= 500     || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809LDescriptiongetsid(0) returns the session ID of the calling process. getsid() returns the session ID of the process with process ID pid. If pid is 0, getsid() returns the session ID of…

getrusage – get resource usage Synopsis#include <sys/time.h> #include <sys/resource.h> int getrusage(int who, struct rusage *usage); Descriptiongetrusage() returns resource usage measures for who, which can be one of the following: RUSAGE_SELF Return resource usage statistics for the calling process, which is the sum of resources used by all threads in the process. RUSAGE_CHILDREN Return resource usage…

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…

getresuid, getresgid – get real, effective and saved user/group IDs Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <unistd.h> int getresuid(uid_t *ruid, uid_t *euid, uid_t *suid); int getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid); Descriptiongetresuid() returns the real UID, the effective UID, and the saved set-user-ID of the calling process, in the arguments ruid, euid, and suid,…

getresuid, getresgid – get real, effective and saved user/group IDs Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <unistd.h> int getresuid(uid_t *ruid, uid_t *euid, uid_t *suid); int getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid); Descriptiongetresuid() returns the real UID, the effective UID, and the saved set-user-ID of the calling process, in the arguments ruid, euid, and suid,…

getresuid, getresgid – get real, effective and saved user/group IDs Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <unistd.h> int getresuid(uid_t *ruid, uid_t *euid, uid_t *suid); int getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid); Descriptiongetresuid() returns the real UID, the effective UID, and the saved set-user-ID of the calling process, in the arguments ruid, euid, and suid,…

getresuid, getresgid – get real, effective and saved user/group IDs Synopsis#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <unistd.h> int getresuid(uid_t *ruid, uid_t *euid, uid_t *suid); int getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid); Descriptiongetresuid() returns the real UID, the effective UID, and the saved set-user-ID of the calling process, in the arguments ruid, euid, and suid,…

getrandom – obtain a series of random bytes Synopsis#include <sys/random.h> ssize_t getrandom(void *buf, size_t buflen, unsigned int flags); DescriptionThe getrandom() system call fills the buffer pointed to by buf with up to buflen random bytes. These bytes can be used to seed user-space random number generators or for cryptographic purposes. By default, getrandom() draws entropy…

getpriority, setpriority – get/set program scheduling priority Synopsis#include <sys/time.h> #include <sys/resource.h> int getpriority(int which, id_t who); int setpriority(int which, id_t who, int prio); DescriptionThe scheduling priority of the process, process group, or user, as indicated by which and who is obtained with the getpriority() call and set with the setpriority() call. The process attribute dealt…

getpid, getppid – get process identification Synopsis#include <sys/types.h> #include <unistd.h> pid_t getpid(void); pid_t getppid(void); Descriptiongetpid() returns the process ID (PID) of the calling process. (This is often used by routines that generate unique temporary filenames.) getppid() returns the process ID of the parent of the calling process. This will be either the ID of the…

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…

setpgid, getpgid, setpgrp, getpgrp – set/get process group Synopsis#include <sys/types.h> #include <unistd.h> int setpgid(pid_t pid, pid_t pgid); pid_t getpgid(pid_t pid); pid_t getpgrp(void); /* POSIX.1 version */ pid_t getpgrp(pid_t pid); /* BSD version */ int setpgrp(void); /* System V version */ int setpgrp(pid_t pid, pid_t pgid); /* BSD version */ Feature Test Macro Requirements for glibc…

setpgid, getpgid, setpgrp, getpgrp – set/get process group Synopsis#include <sys/types.h> #include <unistd.h> int setpgid(pid_t pid, pid_t pgid); pid_t getpgid(pid_t pid); pid_t getpgrp(void); /* POSIX.1 version */ pid_t getpgrp(pid_t pid); /* BSD version */ int setpgrp(void); /* System V version */ int setpgrp(pid_t pid, pid_t pgid); /* BSD version */ Feature Test Macro Requirements for glibc…

getpeername – get name of connected peer socket Synopsis#include <sys/socket.h> int getpeername(int sockfd, struct sockaddr *addr, socklen_t *addrlen); Descriptiongetpeername() returns the address of the peer connected to the socket sockfd, in the buffer pointed to by addr. The addrlen argument should be initialized to indicate the amount of space pointed to by addr. On return…

getpagesize – get memory page size Synopsis#include <unistd.h> int getpagesize(void); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): getpagesize(): Since glibc 2.19: _DEFAULT_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)From glibc 2.12 to 2.19: _BSD_SOURCE || ! (_POSIX_C_SOURCE >= 200112L)Before glibc 2.12: _BSD_SOURCE || _XOPEN_SOURCE >= 500DescriptionThe function getpagesize() returns the number of bytes in a memory page, where "page" is a fixed-length…

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…

getitimer, setitimer – get or set value of an interval timer Synopsis#include <sys/time.h> int getitimer(int which, struct itimerval *curr_value); int setitimer(int which, const struct itimerval *new_value, struct itimerval *old_value);DescriptionThese system calls provide access to interval timers, that is, timers that initially expire at some point in the future, and (optionally) at regular intervals after that….

gethostname, sethostname – get/set hostname Synopsis#include <unistd.h> int gethostname(char *name, size_t len); int sethostname(const char *name, size_t len); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): gethostname(): Since glibc 2.12: _BSD_SOURCE || _XOPEN_SOURCE >= 500 || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200112L sethostname(): Since glibc 2.21: _DEFAULT_SOURCE In glibc 2.19 and 2.20: _DEFAULT_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)…

gethostid, sethostid – get or set the unique identifier of the current host Synopsis#include <unistd.h> long gethostid(void); int sethostid(long hostid); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): gethostid(): _BSD_SOURCE || _XOPEN_SOURCE >= 500 sethostid(): 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 ||…

getgroups, setgroups – get/set list of supplementary group IDs Synopsis#include <sys/types.h> #include <unistd.h> int getgroups(int size, gid_t list[]); #include <grp.h> int setgroups(size_t size, const gid_t *list); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): setgroups():     Since glibc 2.19:         _DEFAULT_SOURCE     Glibc 2.19 and earlier:         _BSD_SOURCE Descriptiongetgroups() returns the supplementary group IDs of the calling process in…