POSIX Processes API

Creating processes

fork

// Returns new Process ID in parent
// Returns 0 in child
int fork(void);

• Create a process that is an exact copy of the current one

• Called once returned twice

waitpid

int waitpid(int pid, int *status, int options);

• Attempt to get exit status of child

• pid: process ID of child
• status: will contain exit value or signal if crashed
• options:
  • 0 -> wait for child to terminate
  • WNOHANG -> do not wait for terminate
• Returns process ID or -1 on error

Deleting Processes

exit

void exit(int status);

• have the current process exit

• status: shows up in encoded format if waitpid is called
• status of 0 is success, non-zero is error

Kill

int kill(int pid, int sig);

• Sends signal sig to pid

Running Programs

execve

int execve (char *prog, char **argv, char **envp)

• Replaces the current running program with a new one prog

• prog: full pathname of the program to run
• argv: argument vector that is passed to main of prog
• envp: environment variables

int execvp(char *prog, char **argv);

int execlp(char *prog, char *arg, …);