explain_ungetc(3) Library Functions Manual explain_ungetc(3) NAME explain_ungetc - explain ungetc(3) errors SYNOPSIS #include <libexplain/ungetc.h> const char *explain_ungetc(int c, FILE *fp); const char *explain_errno_ungetc(int errnum, int c, FILE *fp); void explain_message_ungetc(char *message, int message_size, int c, FILE *fp); void explain_message_errno_ungetc(char *message, int message_size, int er- rnum, int c, FILE *fp); DESCRIPTION These functions may be used to obtain explanations for errors returned by the ungetc(3) system call. explain_ungetc const char *explain_ungetc(int c, FILE *fp); The explain_ungetc function is used to obtain an explanation of an error returned by the ungetc(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 de- coded. c The original c, exactly as passed to the ungetc(3) system call. fp The original fp, exactly as passed to the ungetc(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 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 (ungetc(c, fp) < 0) { fprintf(stderr, "%s\n", explain_ungetc(c, fp)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the ex- plain_ungetc_or_die(3) function. explain_errno_ungetc const char *explain_errno_ungetc(int errnum, int c, FILE *fp); The explain_errno_ungetc function is used to obtain an explanation of an error returned by the ungetc(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much bet- ter, 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. c The original c, exactly as passed to the ungetc(3) system call. fp The original fp, exactly as passed to the ungetc(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 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 (ungetc(c, fp) < 0) { int err = errno; fprintf(stderr, "%s\n", explain_errno_ungetc(err, c, fp)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the ex- plain_ungetc_or_die(3) function. explain_message_ungetc void explain_message_ungetc(char *message, int message_size, int c, FILE *fp); The explain_message_ungetc function is used to obtain an explanation of an error returned by the ungetc(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much bet- ter, 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. c The original c, exactly as passed to the ungetc(3) system call. fp The original fp, exactly as passed to the ungetc(3) system call. Example: This function is intended to be used in a fashion similar to the following example: if (ungetc(c, fp) < 0) { char message[3000]; explain_message_ungetc(message, sizeof(message), c, fp); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the ex- plain_ungetc_or_die(3) function. explain_message_errno_ungetc void explain_message_errno_ungetc(char *message, int message_size, int er- rnum, int c, FILE *fp); The explain_message_errno_ungetc function is used to obtain an explanation of an error returned by the ungetc(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. 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. c The original c, exactly as passed to the ungetc(3) system call. fp The original fp, exactly as passed to the ungetc(3) system call. Example: This function is intended to be used in a fashion similar to the following example: if (ungetc(c, fp) < 0) { int err = errno; char message[3000]; explain_message_errno_ungetc(message, sizeof(message), err, c, fp); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the ex- plain_ungetc_or_die(3) function. SEE ALSO ungetc(3) push a character back to a stream explain_ungetc_or_die(3) push a character back to a stream and report errors COPYRIGHT libexplain version 1.3 Copyright (C) 2010 Peter Miller explain_ungetc(3)
NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT
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