plucky (3) explain_setpriority.3.gz

Provided by: libexplain-dev_1.4.D001-16_amd64 bug

NAME

       explain_setpriority - explain setpriority(2) errors

SYNOPSIS

       #include <libexplain/setpriority.h>
       const char *explain_setpriority(int which, int who, int prio);
       const char *explain_errno_setpriority(int errnum, int which, int who, int prio);
       void explain_message_setpriority(char *message, int message_size, int which, int who, int prio);
       void explain_message_errno_setpriority(char *message, int message_size, int errnum, int which, int who,
       int prio);

DESCRIPTION

       These functions may be used to obtain explanations for errors returned by the setpriority(2) system call.

   explain_setpriority
       const char *explain_setpriority(int which, int who, int prio);

       The explain_setpriority function  is  used  to  obtain  an  explanation  of  an  error  returned  by  the
       setpriority(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.

       which   The original which, exactly as passed to the setpriority(2) system call.

       who     The original who, exactly as passed to the setpriority(2) system call.

       prio    The original prio, exactly as passed to the setpriority(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 (setpriority(which, who, prio) < 0)
              {
                  fprintf(stderr, "%s\n", explain_setpriority(which, who, prio));
                  exit(EXIT_FAILURE);
              }

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

   explain_errno_setpriority
       const char *explain_errno_setpriority(int errnum, int which, int who, int prio);

       The  explain_errno_setpriority  function  is  used  to  obtain an explanation of an error returned by the
       setpriority(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.

       which   The original which, exactly as passed to the setpriority(2) system call.

       who     The original who, exactly as passed to the setpriority(2) system call.

       prio    The original prio, exactly as passed to the setpriority(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 (setpriority(which, who, prio) < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_setpriority(err, which, who, prio));
                  exit(EXIT_FAILURE);
              }

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

   explain_message_setpriority
       void explain_message_setpriority(char *message, int message_size, int which, int who, int prio);

       The explain_message_setpriority function is used to obtain an explanation of an  error  returned  by  the
       setpriority(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.

       which   The original which, exactly as passed to the setpriority(2) system call.

       who     The original who, exactly as passed to the setpriority(2) system call.

       prio    The original prio, exactly as passed to the setpriority(2) system call.

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

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

   explain_message_errno_setpriority
       void explain_message_errno_setpriority(char *message, int message_size, int errnum, int which, int who,
       int prio);

       The explain_message_errno_setpriority function is used to obtain an explanation of an error  returned  by
       the  setpriority(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.

       which   The original which, exactly as passed to the setpriority(2) system call.

       who     The original who, exactly as passed to the setpriority(2) system call.

       prio    The original prio, exactly as passed to the setpriority(2) system call.

       Example: This function is intended to be used in a fashion similar to the following example:
              if (setpriority(which, who, prio) < 0)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_setpriority(message, sizeof(message), err, which, who, prio);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

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

SEE ALSO

       setpriority(2)
               set program scheduling priority

       explain_setpriority_or_die(3)
               set program scheduling priority and report errors

       libexplain version 1.4
       Copyright (C) 2013 Peter Miller

                                                                                          explain_setpriority(3)