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fork(2) [v7 man page]

FORK(2) 							System Calls Manual							   FORK(2)

NAME
fork - spawn new process SYNOPSIS
fork( ) DESCRIPTION
Fork is the only way new processes are created. The new process's core image is a copy of that of the caller of fork. The only distinc- tion is the fact that the value returned in the old (parent) process contains the process ID of the new (child) process, while the value returned in the child is 0. Process ID's range from 1 to 30,000. This process ID is used by wait(2). Files open before the fork are shared, and have a common read-write pointer. In particular, this is the way that standard input and output files are passed and also how pipes are set up. SEE ALSO
wait(2), exec(2) DIAGNOSTICS
Returns -1 and fails to create a process if: there is inadequate swap space, the user is not super-user and has too many processes, or the system's process table is full. Only the super-user can take the last process-table slot. ASSEMBLER
(fork = 2.) sys fork (new process return) (old process return, new process ID in r0) The return locations in the old and new process differ by one word. The C-bit is set in the old process if a new process could not be cre- ated. FORK(2)

Check Out this Related Man Page

FORK(3F)																  FORK(3F)

NAME
fork - create a copy of this process SYNOPSIS
integer function fork() DESCRIPTION
Fork creates a copy of the calling process. The only distinction between the 2 processes is that the value returned to one of them (referred to as the `parent' process) will be the process id of the copy. The copy is usually referred to as the `child' process. The value returned to the `child' process will be zero. All logical units open for writing are flushed before the fork to avoid duplication of the contents of I/O buffers in the external file(s). If the returned value is negative, it indicates an error and will be the negation of the system error code. See perror(3F). A corresponding exec routine has not been provided because there is no satisfactory way to retain open logical units across the exec. How- ever, the usual function of fork/exec can be performed using system(3F). FILES
/usr/lib/libU77.a SEE ALSO
fork(2), wait(3F), kill(3F), system(3F), perror(3F) 4.2 Berkeley Distribution May 27, 1986 FORK(3F)
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