explain_readv(3)

NAME
explain_readv - explain readv(2) errors

SYNOPSIS
#include <libexplain/readv.h>

const char *explain_readv(int fildes, const struct iovec *iov, int iovcnt);
const char *explain_errno_readv(int errnum, int fildes, const struct iovec *iov, int iovcnt);
void explain_message_readv(char *message, int message_size, int fildes, const struct iovec *iov, int iovcnt);
void explain_message_errno_readv(char *message, int message_size, int errnum, int fildes, const struct iovec *iov, int iovcnt);

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

  explain_readv
const char *explain_readv(int fildes, const struct iovec *iov, int iovcnt);

The explain_readv function is used to obtain an explanation of an error returned by the readv(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.

fildes
    The original fildes, exactly as passed to the readv(2) system call.

iov The original iov, exactly as passed to the readv(2) system call.

iovcnt
    The original iovcnt, exactly as passed to the readv(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:
    ssize_t result = readv(fildes, iov, iovcnt);
    if (result < 0)
    {
    fprintf(stderr, "%s\n", explain_readv(fildes, iov, iovcnt));
        exit(EXIT_FAILURE);
    }

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

  explain_errno_readv
const char *explain_errno_readv(int errnum, int fildes, const struct iovec *iov, int iovcnt);

The explain_errno_readv function is used to obtain an explanation of an error returned by the readv(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.

fildes
    The original fildes, exactly as passed to the readv(2) system call.

iov The original iov, exactly as passed to the readv(2) system call.

iovcnt
    The original iovcnt, exactly as passed to the readv(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:
    ssize_t result = readv(fildes, iov, iovcnt);
    if (result < 0)
    {
        int err = errno;
    fprintf(stderr, "%s\n", explain_errno_readv(err, fildes, iov, iovcnt));
        exit(EXIT_FAILURE);
    }

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

  explain_message_readv
void explain_message_readv(char *message, int message_size, int fildes, const struct iovec *iov, int iovcnt);

The explain_message_readv function is used to obtain an explanation of an error returned by the readv(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.

fildes
    The original fildes, exactly as passed to the readv(2) system call.

iov The original iov, exactly as passed to the readv(2) system call.

iovcnt
    The original iovcnt, exactly as passed to the readv(2) system call.

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

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

  explain_message_errno_readv
void explain_message_errno_readv(char *message, int message_size, int errnum, int fildes, const struct iovec *iov, int iovcnt);

The explain_message_errno_readv function is used to obtain an explanation of an error returned by the readv(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.

fildes
    The original fildes, exactly as passed to the readv(2) system call.

iov The original iov, exactly as passed to the readv(2) system call.

iovcnt
    The original iovcnt, exactly as passed to the readv(2) system call.

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

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

SEE ALSO

readv(2)
    read data into multiple buffers

explain_readv_or_die(3)
    read data into multiple buffers and report errors

COPYRIGHT
libexplain version 1.2
Copyright (C) 2009 Peter Miller