1explain_getpgid(3)         Library Functions Manual         explain_getpgid(3)
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NAME

6       explain_getpgid - explain getpgid(2) errors
7

SYNOPSIS

9       #include <libexplain/getpgid.h>
10       const char *explain_getpgid(pid_t pid);
11       const char *explain_errno_getpgid(int errnum, pid_t pid);
12       void explain_message_getpgid(char *message, int message_size, pid_t
13       pid);
14       void explain_message_errno_getpgid(char *message, int message_size, int
15       errnum, pid_t pid);
16

DESCRIPTION

18       These  functions may be used to obtain explanations for errors returned
19       by the getpgid(2) system call.
20
21   explain_getpgid
22       const char *explain_getpgid(pid_t pid);
23
24       The explain_getpgid function is used to obtain  an  explanation  of  an
25       error  returned  by  the  getpgid(2) system call. The least the message
26       will contain is the value of strerror(errno), but usually  it  will  do
27       much better, and indicate the underlying cause in more detail.
28
29       The  errno global variable will be used to obtain the error value to be
30       decoded.
31
32       pid     The original pid, exactly as passed to  the  getpgid(2)  system
33               call.
34
35       Returns:
36               The message explaining the error. This message buffer is shared
37               by all libexplain functions which do not  supply  a  buffer  in
38               their argument list.  This will be overwritten by the next call
39               to any libexplain function which shares this buffer,  including
40               other threads.
41
42       Note: This function is not thread safe, because it shares a return buf‐
43       fer across all threads, and many other functions in this library.
44
45       Example: This function is intended to be used in a fashion  similar  to
46       the following example:
47              pid_t result = getpgid(pid);
48              if (result < 0)
49              {
50                  fprintf(stderr, "%s\n", explain_getpgid(pid));
51                  exit(EXIT_FAILURE);
52              }
53
54       The   above   code   example   is   available   pre-packaged   as   the
55       explain_getpgid_or_die(3) function.
56
57   explain_errno_getpgid
58       const char *explain_errno_getpgid(int errnum, pid_t pid);
59
60       The explain_errno_getpgid function is used to obtain an explanation  of
61       an  error returned by the getpgid(2) system call. The least the message
62       will contain is the value of strerror(errno), but usually  it  will  do
63       much better, and indicate the underlying cause in more detail.
64
65       errnum  The  error value to be decoded, usually obtained from the errno
66               global variable just before this function is  called.  This  is
67               necessary  if you need to call any code between the system call
68               to be explained and this function, because many libc  functions
69               will alter the value of errno.
70
71       pid     The  original  pid,  exactly as passed to the getpgid(2) system
72               call.
73
74       Returns:
75               The message explaining the error. This message buffer is shared
76               by  all  libexplain  functions  which do not supply a buffer in
77               their argument list.  This will be overwritten by the next call
78               to  any libexplain function which shares this buffer, including
79               other threads.
80
81       Note: This function is not thread safe, because it shares a return buf‐
82       fer across all threads, and many other functions in this library.
83
84       Example:  This  function is intended to be used in a fashion similar to
85       the following example:
86              pid_t result = getpgid(pid);
87              if (result < 0)
88              {
89                  int err = errno;
90                  fprintf(stderr, "%s\n", explain_errno_getpgid(err, pid));
91                  exit(EXIT_FAILURE);
92              }
93
94       The   above   code   example   is   available   pre-packaged   as   the
95       explain_getpgid_or_die(3) function.
96
97   explain_message_getpgid
98       void explain_message_getpgid(char *message, int message_size, pid_t
99       pid);
100
101       The explain_message_getpgid function is used to obtain  an  explanation
102       of  an error returned by the getpgid(2) system call. The least the mes‐
103       sage will contain is the value of strerror(errno), but usually it  will
104       do much better, and indicate the underlying cause in more detail.
105
106       The  errno global variable will be used to obtain the error value to be
107       decoded.
108
109       message The location in which to store the returned message. If a suit‐
110               able message return buffer is supplied, this function is thread
111               safe.
112
113       message_size
114               The size in bytes  of  the  location  in  which  to  store  the
115               returned message.
116
117       pid     The  original  pid,  exactly as passed to the getpgid(2) system
118               call.
119
120       Example: This function is intended to be used in a fashion  similar  to
121       the following example:
122              pid_t result = getpgid(pid);
123              if (result < 0)
124              {
125                  char message[3000];
126                  explain_message_getpgid(message, sizeof(message), pid);
127                  fprintf(stderr, "%s\n", message);
128                  exit(EXIT_FAILURE);
129              }
130
131       The   above   code   example   is   available   pre-packaged   as   the
132       explain_getpgid_or_die(3) function.
133
134   explain_message_errno_getpgid
135       void explain_message_errno_getpgid(char *message, int message_size, int
136       errnum, pid_t pid);
137
138       The  explain_message_errno_getpgid function is used to obtain an expla‐
139       nation of an error returned by the getpgid(2) system  call.  The  least
140       the  message  will contain is the value of strerror(errno), but usually
141       it will do much better, and  indicate  the  underlying  cause  in  more
142       detail.
143
144       message The location in which to store the returned message. If a suit‐
145               able message return buffer is supplied, this function is thread
146               safe.
147
148       message_size
149               The  size  in  bytes  of  the  location  in  which to store the
150               returned message.
151
152       errnum  The error value to be decoded, usually obtained from the  errno
153               global  variable  just  before this function is called. This is
154               necessary if you need to call any code between the system  call
155               to  be explained and this function, because many libc functions
156               will alter the value of errno.
157
158       pid     The original pid, exactly as passed to  the  getpgid(2)  system
159               call.
160
161       Example:  This  function is intended to be used in a fashion similar to
162       the following example:
163              pid_t result = getpgid(pid);
164              if (result < 0)
165              {
166                  int err = errno;
167                  char message[3000];
168                  explain_message_errno_getpgid(message, sizeof(message), err,
169                  pid);
170                  fprintf(stderr, "%s\n", message);
171                  exit(EXIT_FAILURE);
172              }
173
174       The   above   code   example   is   available   pre-packaged   as   the
175       explain_getpgid_or_die(3) function.
176

SEE ALSO

178       getpgid(2)
179               get process group
180
181       explain_getpgid_or_die(3)
182               get process group and report errors
183
185       libexplain version 1.4
186       Copyright (C) 2011 Peter Miller
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189
190                                                            explain_getpgid(3)
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