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1.1 root 1: .TH FORK 2
2: .SH NAME
3: fork \- create a new process
4: .SH SYNOPSIS
5: .B int fork (\|)
6: .SH DESCRIPTION
7: .I Fork\^
8: causes creation of a new process.
9: The new process (child process) is an
10: exact copy of the calling process (parent process).
11: This means the child process inherits the following attributes from the parent
12: process:
13: .PP
14: .PD 0
15: .RS 0.5i
16: .PP
17: environment
18: .PP
19: close-on-exec flag (see
20: .IR exec (2))
21: .PP
22: signal handling settings (i.e.,
23: .SM
24: .BR SIG_DFL ", " SIG_ING ,
25: function address)
26: .PP
27: set-user-\s-1ID\s+1 mode bit
28: .PP
29: set-group-\s-1ID\s+1 mode bit
30: .PP
31: profiling on/off status
32: .PP
33: nice value (see
34: .IR nice (2))
35: .PP
36: all attached shared memory segments (see
37: .IR shmop (2))
38: .PP
39: process group
40: .SM ID
41: .PP
42: tty group
43: .SM ID
44: (see
45: .IR exit (2)
46: and
47: .IR signal (2))
48: .PP
49: trace flag (see
50: .IR ptrace "(2) request 0)"
51: .PP
52: time left until an alarm clock signal (see
53: .IR alarm (2))
54: .PP
55: current working directory
56: .PP
57: root directory
58: .PP
59: file mode creation mask (see
60: .IR umask (2))
61: .PP
62: file size limit (see
63: .IR ulimit (2))
64: .RE
65: .PD
66: .PP
67: The child process differs from the parent process in the following ways:
68: .IP
69: The child process has a unique process
70: .SM ID\*S.
71: .IP
72: The child process has a different parent process
73: .SM ID
74: (i.e., the
75: process
76: .SM ID
77: of the parent process).
78: .IP
79: The child process has its own copy of the parent's file descriptors.
80: Each of the child's file descriptors shares a common file pointer with the
81: corresponding file descriptor of the parent.
82: .IP
83: All semadj values are cleared (see
84: .IR semop (2)).
85: .IP
86: Process locks, text locks and data locks are not inherited by the child (see
87: .IR plock (2)).
88: .IP
89: The child process's
90: .IR utime , " stime" , " cutime" ,
91: and
92: .I cstime\^
93: are set to 0.
94: The time left until an alarm clock signal is reset to 0.
95: .PP
96: .I Fork\^
97: will fail and no child process will be created if one or more of the
98: following are true:
99: .sp
100: .TP 15
101: \s-1\%[EAGAIN]\s+1
102: The system-imposed limit on the total number of processes under execution
103: would be exceeded.
104: .TP
105: \s-1\%[EAGAIN]\s+1
106: The system-imposed limit on the total number of processes under execution
107: by a single user would be exceeded.
108: .SH RETURN VALUE
109: Upon successful completion,
110: .I fork\^
111: returns a value of 0 to the child process and returns the process
112: .SM ID
113: of the
114: child process to the parent process.
115: Otherwise, a value of \-1 is
116: returned to the parent process, no child process is created, and
117: .I errno\^
118: is set to indicate the error.
119: .SH NOTES
120: This manual page replaces the 4.2BSD manual page.
121: .SH "SEE ALSO"
122: exec(2), nice(2), plock(2), ptrace(2), semop(2), shmop(2), signal(2), times(2), ulimit(2), umask(2), wait(2).
123: .\" @(#)fork.2 6.2 of 9/6/83
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