OSF

NAME

fork, vfork − Creates a new process

SYNOPSIS

#include <sys/types.h> pid_t fork ( void ); pid_t vfork ( void );

DESCRIPTION

The fork() and vfork() functions create a new process (child process) that is identical to the calling process (parent process).  The child process inherits the following attributes from the parent process:

       •Environment

       •Close-on-exec flags

       •Signal handling settings

       •Set user ID mode bit

       •Set group ID mode bit

       •Trusted state

       •Profiling on/off status

       •Nice value

       •All attached shared libraries

       •Process group ID

       •tty group ID

       •Current directory

       •Root directory

       •File mode creation mask

       •File size limit

       •Attached shared memory segments

       •Attached mapped file segments

       •All mapped regions with the same protection and sharing mode as in the parent process

       •Its own copy of the parent’s open directory streams The child process differs from the parent process in the following ways:

       •The child process has a unique process ID and does not match any active process group ID. 

       •The parent process ID of the child process matches the process ID of the parent. 

       •The child process has its own copy of the parent process’s file descriptors.  However, each of the child’s file descriptors shares a common file pointer with the corresponding file descriptor of the parent process. 

       •All semadj values are cleared. 

       •Process locks, text locks, and data locks are not inherited by the child process. 

       •The child process’s utime(), stime(), cutime(), and cstime() are set to 0 (zero). 

       •Any pending alarms are cleared in the child process. 

       •Any interval timers enabled by the parent process are disabled in the child process. 

       •Any signals pending for the parent process are disabled for the child process.  If a multithreaded process calls the fork() function, the new process contains a replica of the calling thread and its entire address space, possibly including the states of mutexes and other resources.  Consequently, to avoid errors, the child process should only execute operations it knows will not cause deadlock until one of the exec functions is called. 

NOTES

The fork() function is supported for multi-threaded applications.  The vfork() function is supported as a compatibility interface for older BSD system programs, and can be used by compiling with Berkeley Compatibility Library (libbsd.a). The memory sharing semantics of the vfork() function are synonymous with the fork() function. 

AES Support Level:
Full use (fork())

RETURN VALUES

Upon successful completion, the fork() function returns a value of 0 (zero) to the child process and returns the process ID of the child process to the parent process.  If the fork() function fails, a value of -1 is returned to the parent process, no child process is created, and errno is set to indicate the error. 

ERRORS

If the fork() function fails, errno may be set to one of the following values:

[EAGAIN]The system-imposed limit on the total number of processes executing for a single user would be exceeded.  This limit can be exceeded by a process with superuser privilege. 

[ENOMEM]There is not enough space left for this process. 

RELATED INFORMATION

Functions: exec(2), exit(2), getpriority(2), getrusage(2), nice(3), plock(2), ptrace(2), raise(3), semop(2), shmat(2), sigaction(2), sigvec(2), times(3), ulimit(3), umask(2), wait(2)