SIMPLE SOLUTIONS

EXPLAIN_OPENAT(3) - man page online | library functions

Explain openat(2) errors.

Chapter
explain_openat(3)                    Library Functions Manual                   explain_openat(3)

NAME explain_openat - explain openat(2) errors
SYNOPSIS #include <libexplain/openat.h> const char *explain_openat(int fildes, const char *pathname, int flags, mode_t mode); const char *explain_errno_openat(int errnum, int fildes, const char *pathname, int flags, mode_t mode); void explain_message_openat(char *message, int message_size, int fildes, const char *path‐ name, int flags, mode_t mode); void explain_message_errno_openat(char *message, int message_size, int errnum, int fildes, const char *pathname, int flags, mode_t mode);
DESCRIPTION These functions may be used to obtain explanations for errors returned by the openat(2) system call. explain_openat const char *explain_openat(int fildes, const char *pathname, int flags, mode_t mode); The explain_openat function is used to obtain an explanation of an error returned by the openat(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 openat(2) system call. pathname The original pathname, exactly as passed to the openat(2) system call. flags The original flags, exactly as passed to the openat(2) system call. mode The original mode, exactly as passed to the openat(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 over‐ written 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 exam‐ ple: int result = openat(fildes, pathname, flags, mode); if (result < 0) { fprintf(stderr, "%s\n", explain_openat(fildes, pathname, flags, mode)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_openat_or_die(3) function. explain_errno_openat const char *explain_errno_openat(int errnum, int fildes, const char *pathname, int flags, mode_t mode); The explain_errno_openat function is used to obtain an explanation of an error returned by the openat(2) system call. The least the message will contain is the value of str‐ error(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 openat(2) system call. pathname The original pathname, exactly as passed to the openat(2) system call. flags The original flags, exactly as passed to the openat(2) system call. mode The original mode, exactly as passed to the openat(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 over‐ written 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 exam‐ ple: int result = openat(fildes, pathname, flags, mode); if (result < 0) { int err = errno; fprintf(stderr, "%s\n", explain_errno_openat(err, fildes, pathname, flags, mode)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_openat_or_die(3) function. explain_message_openat void explain_message_openat(char *message, int message_size, int fildes, const char *path‐ name, int flags, mode_t mode); The explain_message_openat function is used to obtain an explanation of an error returned by the openat(2) system call. The least the message will contain is the value of str‐ error(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 openat(2) system call. pathname The original pathname, exactly as passed to the openat(2) system call. flags The original flags, exactly as passed to the openat(2) system call. mode The original mode, exactly as passed to the openat(2) system call. Example: This function is intended to be used in a fashion similar to the following exam‐ ple: int result = openat(fildes, pathname, flags, mode); if (result < 0) { char message[3000]; explain_message_openat(message, sizeof(message), fildes, pathname, flags, mode); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_openat_or_die(3) function. explain_message_errno_openat void explain_message_errno_openat(char *message, int message_size, int errnum, int fildes, const char *pathname, int flags, mode_t mode); The explain_message_errno_openat function is used to obtain an explanation of an error returned by the openat(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 openat(2) system call. pathname The original pathname, exactly as passed to the openat(2) system call. flags The original flags, exactly as passed to the openat(2) system call. mode The original mode, exactly as passed to the openat(2) system call. Example: This function is intended to be used in a fashion similar to the following exam‐ ple: int result = openat(fildes, pathname, flags, mode); if (result < 0) { int err = errno; char message[3000]; explain_message_errno_openat(message, sizeof(message), err, fildes, pathname, flags, mode); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_openat_or_die(3) function.
SEE ALSO openat(2) open a file relative to a directory file descriptor explain_openat_or_die(3) open a file relative to a directory file descriptor and report errors
explain_openat(3)
This manual Reference Other manuals
explain_openat(3) referred by explain(3) | explain_openat_or_die(3)
refer to explain_openat_or_die(3) | open(2)