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1 perry 1 WAIT4
2 !!!WAIT4
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 RETURN VALUE
7 ERRORS
8 NOTE
9 CONFORMING TO
10 SEE ALSO
11 ----
12 !!NAME
13
14
15 wait3, wait4 - wait for process termination, BSD style
16 !!SYNOPSIS
17
18
19 __#define _USE_BSD
20 #include
21 __''status''__, int__ ''options''__,
22 struct rusage *__''rusage''__)
23 pid_t wait4(pid_t__ ''pid''__, int *__''status''__, int__ ''options''__,
24 struct rusage *__''rusage''__)
25 __
26 !!DESCRIPTION
27
28
29 The __wait3__ function suspends execution of the current
30 process until a child has exited, or until a signal is
31 delivered whose action is to terminate the current process
32 or to call a signal handling function. If a child has
33 already exited by the time of the call (a so-called
34 __
35
36
37 The __wait4__ function suspends execution of the current
38 process until a child as specified by the ''pid''
39 argument has exited, or until a signal is delivered whose
40 action is to terminate the current process or to call a
41 signal handling function. If a child as requested by
42 ''pid'' has already exited by the time of the call (a
43 so-called
44 ''
45
46
47 The value of ''pid'' can be one of:
48
49
50
51
52 which means to wait for any child process whose process
53 group ID is equal to the absolute value of
54 ''pid''.
55
56
57 -1
58
59
60 which means to wait for any child process; this is
61 equivalent to calling __wait3__.
62
63
64 0
65
66
67 which means to wait for any child process whose process
68 group ID is equal to that of the calling
69 process.
70
71
72
73
74 which means to wait for the child whose process ID is equal
75 to the value of ''pid''.
76
77
78 The value of ''options'' is a bitwise OR of zero or more
79 of the following constants:
80
81
82 __WNOHANG__
83
84
85 which means to return immediately if no child is there to be
86 waited for.
87
88
89 __WUNTRACED__
90
91
92 which means to also return for children which are stopped,
93 and whose status has not been reported.
94
95
96 If ''status'' is not __NULL__, __wait3__ or
97 __wait4__ store status information in the location
98 pointed to by ''status''.
99
100
101 This status can be evaluated with the following macros
102 (these macros take the stat buffer (an __int__) as an
103 argument -- not a pointer to the buffer!):
104
105
106 __WIFEXITED(__''status''__)__
107
108
109 is non-zero if the child exited normally.
110
111
112 __WEXITSTATUS(__''status''__)__
113
114
115 evaluates to the least significant eight bits of the return
116 code of the child which terminated, which may have been set
117 as the argument to a call to __exit()__ or as the
118 argument for a __return__ statement in the main program.
119 This macro can only be evaluated if __WIFEXITED__
120 returned non-zero.
121
122
123 __WIFSIGNALED(__''status''__)__
124
125
126 returns true if the child process exited because of a signal
127 which was not caught.
128
129
130 __WTERMSIG(__''status''__)__
131
132
133 returns the number of the signal that caused the child
134 process to terminate. This macro can only be evaluated if
135 __WIFSIGNALED__ returned non-zero.
136
137
138 __WIFSTOPPED(__''status''__)__
139
140
141 returns true if the child process which caused the return is
142 currently stopped; this is only possible if the call was
143 done using __WUNTRACED__.
144
145
146 __WSTOPSIG(__''status''__)__
147
148
149 returns the number of the signal which caused the child to
150 stop. This macro can only be evaluated if __WIFSTOPPED__
151 returned non-zero.
152
153
154 If ''rusage'' is not __NULL__, the __struct
155 rusage__ as defined in '''' it
156 points to will be filled with accounting information. See
157 getrusage(2) for details.
158 !!RETURN VALUE
159
160
161 The process ID of the child which exited, -1 on error (in
162 particular, when no unwaited-for child processes of the
163 specified kind exist) or zero if __WNOHANG__ was used and
164 no child was available yet. In the latter two cases
165 ''errno'' will be set appropriately.
166 !!ERRORS
167
168
169 __ECHILD__
170
171
172 No unwaited-for child process as specified does
173 exist.
174
175
176 __ERESTARTSYS__
177
178
179 if __WNOHANG__ was not set and an unblocked signal or a
180 __SIGCHLD__ was caught. This error is returned by the
181 system call. The library interface is not allowed to return
182 __ERESTARTSYS__, but will return
183 __EINTR__.
184 !!NOTE
185
186
187 Including '''' is not required these
188 days, but increases portability. (Indeed,
189 '''' defines the ''rusage''
190 structure with fields of type ''struct timeval'' defined
191 in ''''.)
192 !!CONFORMING TO
193
194
195 SVr4, POSIX.1
196 !!SEE ALSO
197
198
199 signal(2), getrusage(2), wait(2),
200 signal(7)
201 ----
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