NAME
explain_wait4 - explain wait4(2) errors
SYNOPSIS
#include <libexplain/wait4.h>
const char *explain_wait4(int pid, int *status, int options, struct
rusage *rusage);
const char *explain_errno_wait4(int errnum, int pid, int *status, int
options, struct rusage *rusage);
void explain_message_wait4(char *message, int message_size, int pid,
int *status, int options, struct rusage *rusage);
void explain_message_errno_wait4(char *message, int message_size, int
errnum, int pid, int *status, int options, struct rusage *rusage);
DESCRIPTION
These functions may be used to obtain explanations for errors returned
by the wait4(2) system call.
explain_wait4
const char *explain_wait4(int pid, int *status, int options, struct
rusage *rusage);
The explain_wait4 function is used to obtain an explanation of an error
returned by the wait4(2) system call. The least the message will
contain is the value of strerror(errno), but usually it will do much
better, and indicate the underlying cause in more detail.
The errno global variable will be used to obtain the error value to be
decoded.
This function is intended to be used in a fashion similar to the
following example:
if (wait4(pid, status, options, rusage) < 0)
{
fprintf(stderr, "%s\n", explain_wait4(pid, status, options, rusage));
exit(EXIT_FAILURE);
}
pid The original pid, exactly as passed to the wait4(2) system
call.
status The original status, exactly as passed to the wait4(2) system
call.
options The original options, exactly as passed to the wait4(2) system
call.
rusage The original rusage, exactly as passed to the wait4(2) system
call.
Returns:
The message explaining the error. This message buffer is
shared by all libexplain functions which do not supply a buffer
in their argument list. This will be overwritten by the next
call to any libexplain function which shares this buffer,
including other threads.
Note: This function is not thread safe, because it shares a return
buffer across all threads, and many other functions in this library.
explain_errno_wait4
const char *explain_errno_wait4(int errnum, int pid, int *status, int
options, struct rusage *rusage);
The explain_errno_wait4 function is used to obtain an explanation of an
error returned by the wait4(2) system call. The least the message will
contain is the value of strerror(errnum), but usually it will do much
better, and indicate the underlying cause in more detail.
This function is intended to be used in a fashion similar to the
following example:
if (wait4(pid, status, options, rusage) < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_wait4(err,
pid, status, options, rusage));
exit(EXIT_FAILURE);
}
errnum The error value to be decoded, usually obtained from the errno
global variable just before this function is called. This is
necessary if you need to call any code between the system call
to be explained and this function, because many libc functions
will alter the value of errno.
pid The original pid, exactly as passed to the wait4(2) system
call.
status The original status, exactly as passed to the wait4(2) system
call.
options The original options, exactly as passed to the wait4(2) system
call.
rusage The original rusage, exactly as passed to the wait4(2) system
call.
Returns:
The message explaining the error. This message buffer is
shared by all libexplain functions which do not supply a buffer
in their argument list. This will be overwritten by the next
call to any libexplain function which shares this buffer,
including other threads.
Note: This function is not thread safe, because it shares a return
buffer across all threads, and many other functions in this library.
explain_message_wait4
void explain_message_wait4(char *message, int message_size, int pid,
int *status, int options, struct rusage *rusage);
The explain_message_wait4 function may be used to obtain an
explanation of an error returned by the wait4(2) system call. The
least the message will contain is the value of strerror(errno), but
usually it will do much better, and indicate the underlying cause in
more detail.
The errno global variable will be used to obtain the error value to be
decoded.
This function is intended to be used in a fashion similar to the
following example:
if (wait4(pid, status, options, rusage) < 0)
{
char message[3000];
explain_message_wait4(message, sizeof(message),
pid, status, options, rusage);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
message The location in which to store the returned message. If a
suitable message return buffer is supplied, this function is
thread safe.
message_size
The size in bytes of the location in which to store the
returned message.
pid The original pid, exactly as passed to the wait4(2) system
call.
status The original status, exactly as passed to the wait4(2) system
call.
options The original options, exactly as passed to the wait4(2) system
call.
rusage The original rusage, exactly as passed to the wait4(2) system
call.
explain_message_errno_wait4
void explain_message_errno_wait4(char *message, int message_size, int
errnum, int pid, int *status, int options, struct rusage *rusage);
The explain_message_errno_wait4 function may be used to obtain an
explanation of an error returned by the wait4(2) system call. The
least the message will contain is the value of strerror(errnum), but
usually it will do much better, and indicate the underlying cause in
more detail.
This function is intended to be used in a fashion similar to the
following example:
if (wait4(pid, status, options, rusage) < 0)
{
int err = errno;
char message[3000];
explain_message_errno_wait4(message, sizeof(message), err,
pid, status, options, rusage);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
message The location in which to store the returned message. If a
suitable message return buffer is supplied, this function is
thread safe.
message_size
The size in bytes of the location in which to store the
returned message.
errnum The error value to be decoded, usually obtained from the errno
global variable just before this function is called. This is
necessary if you need to call any code between the system call
to be explained and this function, because many libc functions
will alter the value of errno.
pid The original pid, exactly as passed to the wait4(2) system
call.
status The original status, exactly as passed to the wait4(2) system
call.
options The original options, exactly as passed to the wait4(2) system
call.
rusage The original rusage, exactly as passed to the wait4(2) system
call.
SEE ALSO
wait4(2)
wait for process to change state
explain_wait4_or_die(3)
wait for process to change state and report errors
COPYRIGHT
libexplain version 0.19
Copyright (C) 2008 Peter Miller
explain_wait4(3)