wait3.2 (2010 09)

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wait3(2) wait3(2)

NAME

wait3(), wait4() - wait for child process to change state

SYNOPSIS

#include <sys/wait.h>

pid_t wait3 (int *stat_loc, int options, struct rusage *resource_usage);

pid_t wait4 (pid_t pid, int *stat_loc, int options,

struct rusage *resource_usage);

DESCRIPTION

The wait3() and wait4() functions allow the calling process to obtain various status information for

a caller’s child process based on the options speciﬁed. If status information is available for two or more

child processes, the order of which process to report status on is not deﬁned.

The

wait4() function is similar to wait3()

, except that wait4() waits for a speciﬁc child as indi-

cated by the pid parameter.

Note that the following call

wait3(stat_loc, options, resource_usage);

is equivalent to the call:

waitpid((pid_t)-1, stat_loc, options);

Note that the following call

wait4(pid, stat_loc, options, resource_usage);

is equivalent to the call:

waitpid(pid, stat_loc, options);

In both of the previous prototypes, on successful completion, if the resource_usage argument to

wait3()

or wait4() is not a null pointer, the rusage structure that the resource_usage argument points to is

ﬁlled in for the child process identiﬁed by the return value.

The pid argument speciﬁes a child process for which status is requested. The following rules deﬁne

which status information is returned:

• If pid is equal to (pid_t ) −1, status is requested for any child process.

• If pid is greater than 0, it speciﬁes the process ID of a single child process for which status is

requested.

• If pid is 0, status is requested for any child process whose process group ID is equal to that of the

calling process.

• If pid is less than (pid_t ) −1, status is requested for any child process whose process group ID is

equal to the absolute value of pid.

The stat_loc argument is the address where status about the speciﬁed child process is placed.

The options argument is constructed from the bitwise-inclusive OR of zero or more of the following ﬂags

deﬁned in the

<sys/wait.h> header ﬁle:

WCONTINUED The status of any continued child process speciﬁed by pid that has not been

reported since it continued is reported to the requesting process.

WNOHANG The wait3() and wait4() functions will not suspend execution of the calling

process if status is not immediately available for one of the child processes

speciﬁed by pid .

WNOWAIT This causes the wait not to be registered. This means that the registered process

that is being waited on, can be waited on again with identical results, provided

that the status of the child does not change in the meantime.

WUNTRACED The status of any child processes speciﬁed by pid that are stopped and whose

status has not yet been reported since they stopped, will also be reported to the

requesting process.

The resource_usage argument points to the resource utilization structure.

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (2 pages)

PAGE 1
wait3(2) wait3(2) NAME wait3(), wait4() - wait for child process to change state SYNOPSIS #include pid_t wait3 (int *stat_loc, int options, struct rusage *resource_usage); pid_t wait4 (pid_t pid, int *stat_loc, int options, struct rusage *resource_usage); DESCRIPTION The wait3() and wait4() functions allow the calling process to obtain various status information for a caller’s child process based on the options specified.
PAGE 2
wait3(2) wait3(2) APPLICATION USAGE Threads Considerations In a multi-threaded application, only the calling thread is suspended by wait3() and wait4(). The wait3() and wait4() functions will not return until all threads in the process have reached the desired state. For example, wait3() and wait4() will not return until all threads have terminated. If the WUNTRACED or WCONTINUED options are specified, wait3() and wait4() will not return until all threads have stopped or continued respectively.