Provided by: explain_0.52.D002-1_amd64 
NAME
explain_setpgrp - explain setpgrp(2) errors
SYNOPSIS
#include <libexplain/setpgrp.h>
const char *explain_setpgrp(pid_t pid, pid_t pgid);
const char *explain_errno_setpgrp(int errnum, pid_t pid, pid_t pgid);
void explain_message_setpgrp(char *message, int message_size, pid_t pid, pid_t pgid);
void explain_message_errno_setpgrp(char *message, int message_size, int errnum, pid_t pid,
pid_t pgid);
DESCRIPTION
These functions may be used to obtain explanations for errors returned by the setpgrp(2)
system call.
Note: the setpgrp(2) function has two implementations. The System V version has no
arguments, while the BSD version has two arguments. For simplicity of implementation, the
argument list seen here includes the pid and pgid arguments.
The System V getpgid() semantics can be obtained by calling setpgrp(0, 0) on systems with
the BSD version, and this is the API for libexplain, even on systems that do not use the
BSD API.
explain_setpgrp
const char *explain_setpgrp(pid_t pid, pid_t pgid);
The explain_setpgrp function is used to obtain an explanation of an error returned by the
setpgrp(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.
pid The original pid, exactly as passed to the setpgrp(2) system call.
pgid The original pgid, exactly as passed to the setpgrp(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.
Example: This function is intended to be used in a fashion similar to the following
example:
if (setpgrp(pid, pgid) < 0)
{
fprintf(stderr, "%s\n", explain_setpgrp(pid, pgid));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_setpgrp_or_die(3)
function.
explain_errno_setpgrp
const char *explain_errno_setpgrp(int errnum, pid_t pid, pid_t pgid);
The explain_errno_setpgrp function is used to obtain an explanation of an error returned
by the setpgrp(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.
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 setpgrp(2) system call.
pgid The original pgid, exactly as passed to the setpgrp(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.
Example: This function is intended to be used in a fashion similar to the following
example:
if (setpgrp(pid, pgid) < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_setpgrp(err, pid, pgid));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_setpgrp_or_die(3)
function.
explain_message_setpgrp
void explain_message_setpgrp(char *message, int message_size, pid_t pid, pid_t pgid);
The explain_message_setpgrp function is used to obtain an explanation of an error returned
by the setpgrp(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.
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 setpgrp(2) system call.
pgid The original pgid, exactly as passed to the setpgrp(2) system call.
Example: This function is intended to be used in a fashion similar to the following
example:
if (setpgrp(pid, pgid) < 0)
{
char message[3000];
explain_message_setpgrp(message, sizeof(message), pid, pgid);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_setpgrp_or_die(3)
function.
explain_message_errno_setpgrp
void explain_message_errno_setpgrp(char *message, int message_size, int errnum, pid_t pid,
pid_t pgid);
The explain_message_errno_setpgrp function is used to obtain an explanation of an error
returned by the setpgrp(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.
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 setpgrp(2) system call.
pgid The original pgid, exactly as passed to the setpgrp(2) system call.
Example: This function is intended to be used in a fashion similar to the following
example:
if (setpgrp(pid, pgid) < 0)
{
int err = errno;
char message[3000];
explain_message_errno_setpgrp(message, sizeof(message), err, pid, pgid);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_setpgrp_or_die(3)
function.
SEE ALSO
setpgrp(2)
set process group
explain_setpgrp_or_die(3)
set process group and report errors
COPYRIGHT
libexplain version 0.52
Copyright (C) 2011 Peter Miller
explain_setpgrp(3)