explain_pread_or_die(3) [debian man page]
explain_pread_or_die(3) Library Functions Manual explain_pread_or_die(3) NAME
explain_pread_or_die - seek and read from a file descriptor and report errors SYNOPSIS
#include <libexplain/pread.h> ssize_t explain_pread_or_die(int fildes, void *data, size_t data_size, off_t offset); ssize_t explain_pread_on_error(int fildes, void *data, size_t data_size, off_t offset)) DESCRIPTION
The explain_pread_or_die function is used to call the pread(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_pread(3) function, and then the process terminates by calling exit(EXIT_FAILURE). The explain_pread_on_error function is used to call the pread(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_pread(3) function, but still returns to the caller. fildes The fildes, exactly as to be passed to the pread(2) system call. data The data, exactly as to be passed to the pread(2) system call. data_size The data_size, exactly as to be passed to the pread(2) system call. offset The offset, exactly as to be passed to the pread(2) system call. RETURN VALUE
The explain_pread_or_die function only returns on success, see pread(2) for more information. On failure, prints an explanation and exits, it does not return. The explain_pread_on_error function always returns the value return by the wrapped pread(2) system call. EXAMPLE
The explain_pread_or_die function is intended to be used in a fashion similar to the following example: ssize_t result = explain_pread_or_die(fildes, data, data_size, offset); SEE ALSO
pread(2) read from a file descriptor at a given offset explain_pread(3) explain pread(2) errors exit(2) terminate the calling process COPYRIGHT
libexplain version 0.52 Copyright (C) 2009 Peter Miller explain_pread_or_die(3)
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explain_pwrite(3) Library Functions Manual explain_pwrite(3) NAME
explain_pwrite - explain pwrite(2) errors SYNOPSIS
#include <libexplain/pwrite.h> const char *explain_pwrite(int fildes, const void *data, size_t data_size, off_t offset); const char *explain_errno_pwrite(int errnum, int fildes, const void *data, size_t data_size, off_t offset); void explain_message_pwrite(char *message, int message_size, int fildes, const void *data, size_t data_size, off_t offset); void explain_message_errno_pwrite(char *message, int message_size, int errnum, int fildes, const void *data, size_t data_size, off_t off- set); DESCRIPTION
These functions may be used to obtain explanations for errors returned by the pwrite(2) system call. explain_pwrite const char *explain_pwrite(int fildes, const void *data, size_t data_size, off_t offset); The explain_pwrite function is used to obtain an explanation of an error returned by the pwrite(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 pwrite(2) system call. data The original data, exactly as passed to the pwrite(2) system call. data_size The original data_size, exactly as passed to the pwrite(2) system call. offset The original offset, exactly as passed to the pwrite(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 = pwrite(fildes, data, data_size, offset); if (result < 0) { fprintf(stderr, "%s ", explain_pwrite(fildes, data, data_size, offset)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_pwrite_or_die(3) function. explain_errno_pwrite const char *explain_errno_pwrite(int errnum, int fildes, const void *data, size_t data_size, off_t offset); The explain_errno_pwrite function is used to obtain an explanation of an error returned by the pwrite(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 neces- sary 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 pwrite(2) system call. data The original data, exactly as passed to the pwrite(2) system call. data_size The original data_size, exactly as passed to the pwrite(2) system call. offset The original offset, exactly as passed to the pwrite(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 = pwrite(fildes, data, data_size, offset); if (result < 0) { int err = errno; fprintf(stderr, "%s ", explain_errno_pwrite(err, fildes, data, data_size, offset)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_pwrite_or_die(3) function. explain_message_pwrite void explain_message_pwrite(char *message, int message_size, int fildes, const void *data, size_t data_size, off_t offset); The explain_message_pwrite function is used to obtain an explanation of an error returned by the pwrite(2) system call. The least the mes- sage 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 pwrite(2) system call. data The original data, exactly as passed to the pwrite(2) system call. data_size The original data_size, exactly as passed to the pwrite(2) system call. offset The original offset, exactly as passed to the pwrite(2) system call. Example: This function is intended to be used in a fashion similar to the following example: ssize_t result = pwrite(fildes, data, data_size, offset); if (result < 0) { char message[3000]; explain_message_pwrite(message, sizeof(message), fildes, data, data_size, offset); fprintf(stderr, "%s ", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_pwrite_or_die(3) function. explain_message_errno_pwrite void explain_message_errno_pwrite(char *message, int message_size, int errnum, int fildes, const void *data, size_t data_size, off_t off- set); The explain_message_errno_pwrite function is used to obtain an explanation of an error returned by the pwrite(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 neces- sary 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 pwrite(2) system call. data The original data, exactly as passed to the pwrite(2) system call. data_size The original data_size, exactly as passed to the pwrite(2) system call. offset The original offset, exactly as passed to the pwrite(2) system call. Example: This function is intended to be used in a fashion similar to the following example: ssize_t result = pwrite(fildes, data, data_size, offset); if (result < 0) { int err = errno; char message[3000]; explain_message_errno_pwrite(message, sizeof(message), err, fildes, data, data_size, offset); fprintf(stderr, "%s ", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_pwrite_or_die(3) function. SEE ALSO
pwrite(2) read from or write to a file descriptor at a given offset explain_pwrite_or_die(3) read from or write to a file descriptor at a given offset and report errors COPYRIGHT
libexplain version 0.52 Copyright (C) 2009 Peter Miller explain_pwrite(3)