FreeBSD Manual Pages
explain_dup2(3) Library Functions Manual explain_dup2(3) NAME explain_dup2 - explain dup2(2) errors SYNOPSIS #include <libexplain/dup2.h> const char *explain_dup2(int oldfd, int newfd); const char *explain_errno_dup2(int errnum, int oldfd, int newfd); void explain_message_dup2(char *message, int message_size, int oldfd, int newfd); void explain_message_errno_dup2(char *message, int message_size, int errnum, int oldfd, int newfd); DESCRIPTION These functions may be used to obtain explanations for errors returned by the dup2(2) system call. explain_dup2 const char *explain_dup2(int oldfd, int newfd); The explain_dup2 function is used to obtain an explanation of an error returned by the dup2(2) system call. The least the message will con- tain 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 decoded. This function is intended to be used in a fashion similar to the fol- lowing example: if (dup2(oldfd, newfd) < 0) { fprintf(stderr, "%s\n", explain_dup2(oldfd, newfd)); exit(EXIT_FAILURE); } oldfd The original oldfd, exactly as passed to the dup2(2) system call. newfd The original newfd, exactly as passed to the dup2(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, in- cluding 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_dup2 const char *explain_errno_dup2(int errnum, int oldfd, int newfd); The explain_errno_dup2 function is used to obtain an explanation of an error returned by the dup2(2) system call. The least the message will contain is the value of strerror(errnum), 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 fol- lowing example: if (dup2(oldfd, newfd) < 0) { int err = errno; fprintf(stderr, "%s\n", explain_errno_dup2(err, oldfd, newfd)); exit(EXIT_FAILURE); } 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. oldfd The original oldfd, exactly as passed to the dup2(2) system call. newfd The original newfd, exactly as passed to the dup2(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, in- cluding 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_dup2 void explain_message_dup2(char *message, int message_size, int oldfd, int newfd); The explain_message_dup2 function may be used to obtain an explanation of an error returned by the dup2(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 fol- lowing example: if (dup2(oldfd, newfd) < 0) { char message[3000]; explain_message_dup2(message, sizeof(message), oldfd, newfd); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } 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 re- turned message. oldfd The original oldfd, exactly as passed to the dup2(2) system call. newfd The original newfd, exactly as passed to the dup2(2) system call. explain_message_errno_dup2 void explain_message_errno_dup2(char *message, int message_size, int errnum, int oldfd, int newfd); The explain_message_errno_dup2 function may be used to obtain an expla- nation of an error returned by the dup2(2) system call. The least the message will contain is the value of strerror(errnum), 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 fol- lowing example: if (dup2(oldfd, newfd) < 0) { int err = errno; char message[3000]; explain_message_errno_dup2(message, sizeof(message), err, oldfd, newfd); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } 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 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. oldfd The original oldfd, exactly as passed to the dup2(2) system call. newfd The original newfd, exactly as passed to the dup2(2) system call. SEE ALSO dup2(2) duplicate a file descriptor explain_dup2_or_die(3) duplicate a file descriptor and report errors COPYRIGHT libexplain version 1.3 Copyright (C) 2008 Peter Miller explain_dup2(3)
NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=explain_dup2&sektion=3&manpath=FreeBSD+Ports+15.0.quarterly>