explain_gethostname_or_die(3) [debian man page]
explain_gethostname_or_die(3) Library Functions Manual explain_gethostname_or_die(3) NAME
explain_gethostname_or_die - get/set hostname and report errors SYNOPSIS
#include <libexplain/gethostname.h> void explain_gethostname_or_die(char *data, size_t data_size); intexplain_gethostname_on_error(char *data, size_t data_size); DESCRIPTION
The explain_gethostname_or_die function is used to call the gethostname(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_gethostname(3) function, and then the process terminates by calling exit(EXIT_FAILURE). The explain_gethostname_on_error function is used to call the gethostname(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_gethostname(3) function, but still returns to the caller. data The data, exactly as to be passed to the gethostname(2) system call. data_size The data_size, exactly as to be passed to the gethostname(2) system call. RETURN VALUE
The explain_gethostname_or_die function only returns on success, see gethostname(2) for more information. On failure, prints an explanation and exits, it does not return. The explain_gethostname_on_error function always returns the value return by the wrapped gethostname(2) system call. EXAMPLE
The explain_gethostname_or_die function is intended to be used in a fashion similar to the following example: explain_gethostname_or_die(data, data_size); SEE ALSO
gethostname(2) get/set hostname explain_gethostname(3) explain gethostname(2) errors exit(2) terminate the calling process COPYRIGHT
libexplain version 0.52 Copyright (C) 2009 Peter Miller explain_gethostname_or_die(3)
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explain_gethostname(3) Library Functions Manual explain_gethostname(3) NAME
explain_gethostname - explain gethostname(2) errors SYNOPSIS
#include <libexplain/gethostname.h> const char *explain_gethostname(char *data, size_t data_size); const char *explain_errno_gethostname(int errnum, char *data, size_t data_size); void explain_message_gethostname(char *message, int message_size, char *data, size_t data_size); void explain_message_errno_gethostname(char *message, int message_size, int errnum, char *data, size_t data_size); DESCRIPTION
These functions may be used to obtain explanations for errors returned by the gethostname(2) system call. explain_gethostname const char *explain_gethostname(char *data, size_t data_size); The explain_gethostname function is used to obtain an explanation of an error returned by the gethostname(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. This function is intended to be used in a fashion similar to the following example: if (gethostname(data, data_size) < 0) { fprintf(stderr, "%s ", explain_gethostname(data, data_size)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_gethostname_or_die(3) function. data The original data, exactly as passed to the gethostname(2) system call. data_size The original data_size, exactly as passed to the gethostname(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. explain_errno_gethostname const char *explain_errno_gethostname(int errnum, char *data, size_t data_size); The explain_errno_gethostname function is used to obtain an explanation of an error returned by the gethostname(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. This function is intended to be used in a fashion similar to the following example: if (gethostname(data, data_size) < 0) { int err = errno; fprintf(stderr, "%s ", explain_errno_gethostname(err, data, data_size)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_gethostname_or_die(3) function. 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. data The original data, exactly as passed to the gethostname(2) system call. data_size The original data_size, exactly as passed to the gethostname(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. explain_message_gethostname void explain_message_gethostname(char *message, int message_size, char *data, size_t data_size); The explain_message_gethostname function is used to obtain an explanation of an error returned by the gethostname(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. This function is intended to be used in a fashion similar to the following example: if (gethostname(data, data_size) < 0) { char message[3000]; explain_message_gethostname(message, sizeof(message), data, data_size); fprintf(stderr, "%s ", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_gethostname_or_die(3) function. 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. data The original data, exactly as passed to the gethostname(2) system call. data_size The original data_size, exactly as passed to the gethostname(2) system call. explain_message_errno_gethostname void explain_message_errno_gethostname(char *message, int message_size, int errnum, char *data, size_t data_size); The explain_message_errno_gethostname function is used to obtain an explanation of an error returned by the gethostname(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. This function is intended to be used in a fashion similar to the following example: if (gethostname(data, data_size) < 0) { int err = errno; char message[3000]; explain_message_errno_gethostname(message, sizeof(message), err, data, data_size); fprintf(stderr, "%s ", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_gethostname_or_die(3) function. 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. data The original data, exactly as passed to the gethostname(2) system call. data_size The original data_size, exactly as passed to the gethostname(2) system call. SEE ALSO
gethostname(2) get/set hostname explain_gethostname_or_die(3) get/set hostname and report errors COPYRIGHT
libexplain version 0.52 Copyright (C) 2009 Peter Miller explain_gethostname(3)