explain_ustat(3) Library Functions Manual explain_ustat(3) NAME explain_ustat - explain ustat(2) errors SYNOPSIS #include <libexplain/ustat.h> const char *explain_ustat(dev_t dev, struct ustat *ubuf); const char *explain_errno_ustat(int errnum, dev_t dev, struct ustat *ubuf); void explain_message_ustat(char *message, int message_size, dev_t dev, struct ustat *ubuf); void explain_message_errno_ustat(char *message, int message_size, int er- rnum, dev_t dev, struct ustat *ubuf); DESCRIPTION These functions may be used to obtain explanations for errors returned by the ustat(2) system call. explain_ustat const char *explain_ustat(dev_t dev, struct ustat *ubuf); The explain_ustat function is used to obtain an explanation of an error re- turned by the ustat(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indi- cate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be de- coded. dev The original dev, exactly as passed to the ustat(2) system call. ubuf The original ubuf, exactly as passed to the ustat(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 ar- gument list. This will be overwritten by the next call to any lib- explain 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: if (ustat(dev, ubuf) < 0) { fprintf(stderr, "%s\n", explain_ustat(dev, ubuf)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_us- tat_or_die(3) function. explain_errno_ustat const char *explain_errno_ustat(int errnum, dev_t dev, struct ustat *ubuf); The explain_errno_ustat function is used to obtain an explanation of an er- ror returned by the ustat(2) system call. The least the message will con- tain 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 ex- plained and this function, because many libc functions will alter the value of errno. dev The original dev, exactly as passed to the ustat(2) system call. ubuf The original ubuf, exactly as passed to the ustat(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 ar- gument list. This will be overwritten by the next call to any lib- explain 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: if (ustat(dev, ubuf) < 0) { int err = errno; fprintf(stderr, "%s\n", explain_errno_ustat(err, dev, ubuf)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_us- tat_or_die(3) function. explain_message_ustat void explain_message_ustat(char *message, int message_size, dev_t dev, struct ustat *ubuf); The explain_message_ustat function is used to obtain an explanation of an error returned by the ustat(2) system call. The least the message will con- tain 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 de- coded. 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. dev The original dev, exactly as passed to the ustat(2) system call. ubuf The original ubuf, exactly as passed to the ustat(2) system call. Example: This function is intended to be used in a fashion similar to the following example: if (ustat(dev, ubuf) < 0) { char message[3000]; explain_message_ustat(message, sizeof(message), dev, ubuf); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_us- tat_or_die(3) function. explain_message_errno_ustat void explain_message_errno_ustat(char *message, int message_size, int er- rnum, dev_t dev, struct ustat *ubuf); The explain_message_errno_ustat function is used to obtain an explanation of an error returned by the ustat(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 ex- plained and this function, because many libc functions will alter the value of errno. dev The original dev, exactly as passed to the ustat(2) system call. ubuf The original ubuf, exactly as passed to the ustat(2) system call. Example: This function is intended to be used in a fashion similar to the following example: if (ustat(dev, ubuf) < 0) { int err = errno; char message[3000]; explain_message_errno_ustat(message, sizeof(message), err, dev, ubuf); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_us- tat_or_die(3) function. SEE ALSO ustat(2) get file system statistics explain_ustat_or_die(3) get file system statistics and report errors COPYRIGHT libexplain version 1.3 Copyright (C) 2009 Peter Miller explain_ustat(3)
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