NAME

       explain_setpgid - explain setpgid(2) errors

SYNOPSIS

       #include <libexplain/setpgid.h>
       const char *explain_setpgid(pid_t pid, pid_t pgid);
       const char *explain_errno_setpgid(int errnum, pid_t pid, pid_t pgid);
       void explain_message_setpgid(char *message, int message_size, pid_t pid, pid_t pgid);
       void explain_message_errno_setpgid(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  setpgid(2)
       system call.

   explain_setpgid
       const char *explain_setpgid(pid_t pid, pid_t pgid);

       The  explain_setpgid function is used to obtain an explanation of an error returned by the
       setpgid(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 setpgid(2) system call.

       pgid    The original pgid, exactly as passed to the setpgid(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 (setpgid(pid, pgid) < 0)
              {
                  fprintf(stderr, "%s\n", explain_setpgid(pid, pgid));
                  exit(EXIT_FAILURE);
              }

       The  above  code  example  is  available  pre-packaged  as  the  explain_setpgid_or_die(3)
       function.

   explain_errno_setpgid
       const char *explain_errno_setpgid(int errnum, pid_t pid, pid_t pgid);

       The explain_errno_setpgid function is used to obtain an explanation of an  error  returned
       by  the  setpgid(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 setpgid(2) system call.

       pgid    The original pgid, exactly as passed to the setpgid(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 (setpgid(pid, pgid) < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_setpgid(err, pid, pgid));
                  exit(EXIT_FAILURE);
              }

       The  above  code  example  is  available  pre-packaged  as  the  explain_setpgid_or_die(3)
       function.

   explain_message_setpgid
       void explain_message_setpgid(char *message, int message_size, pid_t pid, pid_t pgid);

       The explain_message_setpgid function is used to obtain an explanation of an error returned
       by  the  setpgid(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 setpgid(2) system call.

       pgid    The original pgid, exactly as passed to the setpgid(2) system call.

       Example: This function is intended to be used  in  a  fashion  similar  to  the  following
       example:
              if (setpgid(pid, pgid) < 0)
              {
                  char message[3000];
                  explain_message_setpgid(message, sizeof(message), pid, pgid);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The  above  code  example  is  available  pre-packaged  as  the  explain_setpgid_or_die(3)
       function.

   explain_message_errno_setpgid
       void explain_message_errno_setpgid(char *message, int message_size, int errnum, pid_t pid,
       pid_t pgid);

       The  explain_message_errno_setpgid  function  is used to obtain an explanation of an error
       returned by the setpgid(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 setpgid(2) system call.

       pgid    The original pgid, exactly as passed to the setpgid(2) system call.

       Example: This function is intended to be used  in  a  fashion  similar  to  the  following
       example:
              if (setpgid(pid, pgid) < 0)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_setpgid(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_setpgid_or_die(3)
       function.

SEE ALSO

       setpgid(2)
               set process group

       explain_setpgid_or_die(3)
               set process group and report errors

COPYRIGHT

       libexplain version 1.4
       Copyright (C) 2011 Peter Miller

                                                                               explain_setpgid(3)