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explain_fsetpos(3) Library Functions Manual explain_fsetpos(3) NAME explain_fsetpos - explain fsetpos(3) errors SYNOPSIS #include <libexplain/fsetpos.h> const char *explain_fsetpos(FILE *fp, fpos_t *pos); const char *explain_errno_fsetpos(int errnum, FILE *fp, fpos_t *pos); void explain_message_fsetpos(char *message, int message_size, FILE *fp, fpos_t *pos); void explain_message_errno_fsetpos(char *message, int message_size, int errnum, FILE *fp, fpos_t *pos); DESCRIPTION These functions may be used to obtain explanations for errors returned by the fsetpos(3) system call. explain_fsetpos const char *explain_fsetpos(FILE *fp, fpos_t *pos); The explain_fsetpos function is used to obtain an explanation of an er- ror returned by the fsetpos(3) 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. fp The original fp, exactly as passed to the fsetpos(3) system call. pos The original pos, exactly as passed to the fsetpos(3) 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: if (fsetpos(fp, pos) < 0) { fprintf(stderr, "%s\n", explain_fsetpos(fp, pos)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_fset- pos_or_die(3) function. explain_errno_fsetpos const char *explain_errno_fsetpos(int errnum, FILE *fp, fpos_t *pos); The explain_errno_fsetpos function is used to obtain an explanation of an error returned by the fsetpos(3) 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. fp The original fp, exactly as passed to the fsetpos(3) system call. pos The original pos, exactly as passed to the fsetpos(3) 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: if (fsetpos(fp, pos) < 0) { int err = errno; fprintf(stderr, "%s\n", explain_errno_fsetpos(err, fp, pos)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_fset- pos_or_die(3) function. explain_message_fsetpos void explain_message_fsetpos(char *message, int message_size, FILE *fp, fpos_t *pos); The explain_message_fsetpos function is used to obtain an explanation of an error returned by the fsetpos(3) 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 suit- able message return buffer is supplied, this function is thread safe. message_size The size in bytes of the location in which to store the re- turned message. fp The original fp, exactly as passed to the fsetpos(3) system call. pos The original pos, exactly as passed to the fsetpos(3) system call. Example: This function is intended to be used in a fashion similar to the following example: if (fsetpos(fp, pos) < 0) { char message[3000]; explain_message_fsetpos(message, sizeof(message), fp, pos); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_fset- pos_or_die(3) function. explain_message_errno_fsetpos void explain_message_errno_fsetpos(char *message, int message_size, int errnum, FILE *fp, fpos_t *pos); The explain_message_errno_fsetpos function is used to obtain an expla- nation of an error returned by the fsetpos(3) 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 de- tail. message The location in which to store the returned message. If a suit- able message return buffer is supplied, this function is thread safe. message_size The size in bytes of the location in which to store the re- turned 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. fp The original fp, exactly as passed to the fsetpos(3) system call. pos The original pos, exactly as passed to the fsetpos(3) system call. Example: This function is intended to be used in a fashion similar to the following example: if (fsetpos(fp, pos) < 0) { int err = errno; char message[3000]; explain_message_errno_fsetpos(message, sizeof(message), err, fp, pos); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_fset- pos_or_die(3) function. SEE ALSO fsetpos(3) reposition a stream explain_fsetpos_or_die(3) reposition a stream and report errors COPYRIGHT libexplain version 1.3 Copyright (C) 2010 Peter Miller explain_fsetpos(3)
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