--- name: "explain_opendir" section: "3" platform: "linux" package: "libexplain-dev" version: "1.4.D001-16" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/explain_opendir" --- # explain\_opendir(3) explain opendir(3) errors ## NAME explain\_opendir - explain [opendir(3)](/opendir/3.md) errors ## SYNOPSIS const char \*explain\_opendir(const char \*pathname);\ const char \*explain\_errno\_opendir(int errnum, const char \*pathname); int errnum, const char \*pathname);\ void explain\_message\_opendir(char \*message, int message\_size,\ void explain\_message\_errno\_opendir(char \*message, int message\_size, const char \*pathname); ## DESCRIPTION These functions may be used to explain [*opendir*(3)](/opendir/3.md) errors. ### explain\_opendir const char \*explain\_opendir(const char \*pathname); The explain\_opendir function is used to obtain an explanation of an error returned by the [*opendir*(3)](/opendir/3.md) function. 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 following example: ``` DIR *dp = opendir(pathname); if (!dp) { fprintf(stderr, "%s\n", explain_opendir(pathname)); exit(EXIT_FAILURE); } ``` - *pathname* The original pathname, exactly as passed to the [*opendir*(3)](/opendir/3.md) 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. ### explain\_errno\_opendir const char \*explain\_errno\_opendir(int errnum, const char \*pathname); int errnum, const char \*pathname); The explain\_errno\_opendir function is used to obtain an explanation of an error returned by the [*opendir*(3)](/opendir/3.md) function. 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 following example: ``` DIR *dp = opendir(pathname); if (!dp) { int errnum = errno; const char *message = explain_errno_opendir(errnum, pathname); fprintf(stderr, "%s\n", message); 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*. - *pathname* The original pathname, exactly as passed to the [*opendir*(3)](/opendir/3.md) 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. ### explain\_message\_opendir void explain\_message\_opendir(char \*message, int message\_size, const char \*pathname); The explain\_message\_opendir function is used to obtain an explanation of an error returned by the [*opendir*(3)](/opendir/3.md) function. 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 following example: ``` DIR *dp = opendir(pathname); if (!dp) { char message[3000]; explain_message_opendir(message, sizeof(message), pathname); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } ``` - *message* The location in which to store the returned message. Because a message return buffer has been supplied, this function is thread safe if the buffer is thread safe. - *message\_size* The size in bytes of the location in which to store the returned message. - *pathname* The original pathname, exactly as passed to the [*opendir*(3)](/opendir/3.md) system call. ### explain\_message\_errno\_opendir void explain\_message\_errno\_opendir(char \*message, int message\_size, const char \*pathname); The explain\_message\_errno\_opendir function is used to obtain an explanation of an error returned by the [*opendir*(3)](/opendir/3.md) function. 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 following example: ``` DIR *dp = opendir(pathname); if (!dp); { int err = errno; char message[3000]; explain_message_errno_opendir(message, sizeof(message), err, pathname); fprintf(stderr, '%s\n', message); exit(EXIT_FAILURE); } ``` - *message* The location in which to store the returned message. Because a message return buffer has been supplied, this function is thread safe if the buffer 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*. - *pathname* The original pathname, exactly as passed to the [*opendir*(3)](/opendir/3.md) system call. ## COPYRIGHT libexplain version 1.4\ Copyright (C) 2008 Peter Miller ## AUTHOR Written by Peter Miller \