explain_getpgrp - explain
getpgrp(2) errors
#include <libexplain/getpgrp.h>
const char *explain_getpgrp(pid_t pid);
const char *explain_errno_getpgrp(int errnum, pid_t pid);
void explain_message_getpgrp(char *message, int message_size, pid_t pid);
void explain_message_errno_getpgrp(char *message, int message_size, int errnum,
pid_t pid);
These functions may be used to obtain explanations for errors returned by the
getpgrp(2) system call.
Note: the
getpgrp(2) function has two implementations. The POSIX.1
version has no arguments, while the BSD version has one argument. For
simplicity of implementation, the argument list seen here includes the
pid argument.
The POSIX.1 getpgid() semantics can be obtained by calling getpgrp(0) on BSD
systems, and this is the API for libexplain, even on systems that do not use
the BSD API.
const char *explain_getpgrp(pid_t pid);
The
explain_getpgrp function is used to obtain an explanation of an error
returned by the
getpgrp(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 getpgrp(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:
pid_t result = getpgrp(pid);
if (result < 0)
{
fprintf(stderr, "%s\n", explain_getpgrp(pid));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_getpgrp_or_die(3) function.
const char *explain_errno_getpgrp(int errnum, pid_t pid);
The
explain_errno_getpgrp function is used to obtain an explanation of an
error returned by the
getpgrp(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 getpgrp(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:
pid_t result = getpgrp(pid);
if (result < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_getpgrp(err, pid));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_getpgrp_or_die(3) function.
void explain_message_getpgrp(char *message, int message_size, pid_t pid);
The
explain_message_getpgrp function is used to obtain an explanation of
an error returned by the
getpgrp(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 getpgrp(2) system
call.
Example: This function is intended to be used in a fashion similar to the
following example:
pid_t result = getpgrp(pid);
if (result < 0)
{
char message[3000];
explain_message_getpgrp(message, sizeof(message), pid);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_getpgrp_or_die(3) function.
void explain_message_errno_getpgrp(char *message, int message_size, int errnum,
pid_t pid);
The
explain_message_errno_getpgrp function is used to obtain an
explanation of an error returned by the
getpgrp(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 getpgrp(2) system
call.
Example: This function is intended to be used in a fashion similar to the
following example:
pid_t result = getpgrp(pid);
if (result < 0)
{
int err = errno;
char message[3000];
explain_message_errno_getpgrp(message, sizeof(message), err, pid);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_getpgrp_or_die(3) function.
- getpgrp(2)
- get process group
- explain_getpgrp_or_die(3)
- get process group and report errors
libexplain version 1.3
Copyright (C) 2011 Peter Miller