Some omit full descriptions (for sake of conciseness as an exam reference).
| Function | Parameters | Return value | Details | Library |
|---|---|---|---|---|
fork |
() |
0 (child); child’s PID (parent) | Memory space is copy-on-write. | unistd.h |
exec_ |
depends (see details) | -1 (only if error) | See equivalent exec code |
unistd.h |
exit |
(int status) |
Status | stdlib.h | |
wait |
(int *wstatus) |
Status | Last 8 bits = exit status = WEXITSTATUS(status) |
unistd.h |
waitpid |
(pid_t pid, int *wstatus, int options) |
Status | PID $\leq 0$: wait for any child. Options: see wait options |
unistd.h |
getpid |
() |
PID of calling process | unistd.h |
List: execl("/bin/ls", "ls", "-l", "-R", "-a", NULL);
Vector: char* arr[] = {"ls", "-l", "-R", "-a", NULL}; execv("/bin/ls", arr);
PATH environment variable, i.e. mimics shell: char *cmd = "ls"; execvp(cmd, arr);
Others: lp, le, ve, lpe, vpe
WNOHANG: return immediately if no child has exited.
WEXITED, WSTOPPED, WCONTINUED: wait for children that have been (exited/stopped/continued).
| Function | Parameters | Return value | Details |
|---|---|---|---|
open |
(char *path, int flags) |
-1 (error); fd (success) | path can be either absolute or relative (to current working directory of process). flags: O_RDONLY, O_WRONLY, O_RDWR | O_CREAT | O_TRUNC. |
close |
(int fd) |
-1 (error); 0 (success) | if fd is the last to refer to the underlying open file, the resources associated with the open file description are freed. |
read |
(int fd, void *buf, size_t count) |
-1 (error); bytes read (success) | |
write |
(int fd, const void *buf, size_t count) |
-1 (error); bytes written (success) | |
lseek |
(int fd, off_t offset, int whence) |
-1 (error); offset bytes from start address (success) | |
dup2 |
(int oldfd, int newfd) |
-1 (error); new fd (success) | allocates a new fd referring to the same open-file description (system-wide open-file table) as the oldfd |
pipe |
(int fd[]) |
-1 (error); 0 (success) | fd[0] read end, fd[1] write end. For input redirection. |
| Function | Parameters | Return value | Details |
|---|---|---|---|
signal |
(int signum, sighandler_t handler) |
SIG_ERR (error); previous value of handler (success) |
signal handler provided must be of the signature void handler(int signo) |
sigaction |
(int signum, sigaction *sa, NULL) |
-1 (error); 0 (success) | Simplified parameters. sa.sa_sigaction must be set to the handler with params (int signo, siginfo_t *info, void *ucontext). |
| Function | Parameters | Return value | Details |
|---|---|---|---|
shmget |
(key, size_t size, shmflg) |
-1 (error); valid shared memory identifier (success) | key=IPC_PRIVATE. size rounded up to nearest page size. IPC_CREAT to create a new region. |
shmat |
(shmid, NULL, 0) |
-1 (error); void*address of shared memory segment (success) |
Simplified parameters. |
shmdt |
(void * shmaddr) |
-1 (error); 0 (success) | Detaches the shared memory segment located at the address. |
shmctl |
(shmid, cmd, shmid_ds * buf) |
-1 (error); 0 (success for void cmds) | shmctl(id, IPC_RMID, 0) to destroy a shm segment |