explain_getpgid(3)

NAME
explain_getpgid - explain getpgid(2) errors

SYNOPSIS
#include <libexplain/getpgid.h>

const char *explain_getpgid(pid_t pid);
const char *explain_errno_getpgid(int errnum, pid_t pid);
void explain_message_getpgid(char *message, int message_size, pid_t pid);
void explain_message_errno_getpgid(char *message, int message_size, int errnum, pid_t pid);

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

  explain_getpgid
const char *explain_getpgid(pid_t pid);

The explain_getpgid function is used to obtain an explanation of an error returned by the getpgid(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 getpgid(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 = getpgid(pid);
    if (result < 0)
    {
    fprintf(stderr, "%s\n", explain_getpgid(pid));
        exit(EXIT_FAILURE);
    }

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

  explain_errno_getpgid
const char *explain_errno_getpgid(int errnum, pid_t pid);

The explain_errno_getpgid function is used to obtain an explanation of an error returned by the getpgid(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 getpgid(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 = getpgid(pid);
    if (result < 0)
    {
        int err = errno;
    fprintf(stderr, "%s\n", explain_errno_getpgid(err, pid));
        exit(EXIT_FAILURE);
    }

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

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

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

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

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

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

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

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

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

SEE ALSO

getpgid(2)
    get process group

explain_getpgid_or_die(3)
    get process group and report errors

COPYRIGHT
libexplain version 1.4
Copyright (C) 2011 Peter Miller