--- name: "explain_fchdir" section: "3" platform: "linux" package: "libexplain-dev" version: "1.4.D001-16" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/explain_fchdir" --- # explain\_fchdir(3) explain fchdir(2) errors ## NAME explain\_fchdir - explain [fchdir(2)](/fchdir/2.md) errors ## SYNOPSIS \#include \\ const char \*explain\_fchdir(int fildes);\ void explain\_message\_fchdir(char \*message, int message\_size, int fildes);\ const char \*explain\_errno\_fchdir(int errnum, int fildes);\ void explain\_message\_errno\_fchdir(char \*message, int message\_size, int errnum, int fildes); ## DESCRIPTION These functions may be used to obtain explanations for [*fchdir*(2)](/fchdir/2.md) errors. ### explain\_fchdir const char \*explain\_fchdir(int fildes); The explain\_fchdir function is used to obtain an explanation of an error returned by the [*fchdir*(2)](/fchdir/2.md) 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 following example: ``` if (fchdir(fildes) < 0) { fprintf(stderr, '%s0, explain_fchdir(fildes)); exit(EXIT_FAILURE); } ``` - *fildes* The original fildes, exactly as passed to the [*fchdir*(2)](/fchdir/2.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\_fchdir const char \*explain\_errno\_fchdir(int errnum, int fildes); The explain\_errno\_fchdir function is used to obtain an explanation of an error returned by the [*fchdir*(2)](/fchdir/2.md) 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 following example: ``` if (fchdir(fildes) < 0) { int err = errno; fprintf(stderr, '%s0, explain_errno_fchdir(err, fildes)); 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*. - *fildes* The original fildes, exactly as passed to the [*fchdir*(2)](/fchdir/2.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\_fchdir void explain\_message\_fchdir(char \*message, int message\_size, int fildes); The explain\_message\_fchdir function is used to obtain an explanation of an error returned by the [*fchdir*(2)](/fchdir/2.md) 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 following example: ``` if (fchdir(fildes) < 0) { char message[3000]; explain_message_fchdir(message, sizeof(message), fildes); fprintf(stderr, '%s0, 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. - *message\_size* The size in bytes of the location in which to store the returned message. - *fildes* The original fildes, exactly as passed to the [*fchdir*(2)](/fchdir/2.md) system call. ### explain\_message\_errno\_fchdir void explain\_message\_errno\_fchdir(char \*message, int message\_size, int errnum, int fildes); The explain\_message\_errno\_fchdir function is used to obtain an explanation of an error returned by the [*fchdir*(2)](/fchdir/2.md) 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 following example: ``` if (fchdir(fildes) < 0) { int err = errno; char message[3000]; explain_message_errno_fchdir(message, sizeof(message), err, fildes); fprintf(stderr, '%s0, 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. - *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*. - *fildes* The original fildes, exactly as passed to the [*fchdir*(2)](/fchdir/2.md) system call. ## COPYRIGHT libexplain version 1.4\ Copyright (C) 2008 Peter Miller ## AUTHOR Written by Peter Miller \