--- name: "explain_fclose" section: "3" platform: "linux" package: "libexplain-dev" version: "1.4.D001-16" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/explain_fclose" --- # explain\_fclose(3) explain fclose(3) errors ## NAME explain\_fclose - explain [fclose(3)](/fclose/3.md) errors ## SYNOPSIS \#include \\ const char \*explain\_fclose(FILE \*fp);\ const char \*explain\_errno\_fclose(int errnum, FILE \*fp);\ void explain\_message\_fclose(char \*message, int message\_size, FILE \*fp);\ void explain\_message\_errno\_fclose(char \*message, int message\_size, int errnum, FILE \*fp); ## DESCRIPTION These functions may be used to obtain explanations of [*fclose*(3)](/fclose/3.md) errors. ### explain\_fclose const char \*explain\_fclose(FILE \* fp); The explain\_fclose function is used to obtain an explanation of an error returned by the [*fclose*(3)](/fclose/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: ``` if (fclose(fp)) { fprintf(stderr, "%s\n", explain_fclose(fp)); exit(EXIT_FAILURE); } ``` - *fp* The original fp, exactly as passed to the [*fclose*(3)](/fclose/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. **Note:** This function may be of little diagnostic value, because libc may have destroyed any useful context, leaving nothing for libexplain to work with (this is true of glibc in particular). For files that are open for writing, you will obtain more useful information by first calling [*fflush*(3)](/fflush/3.md), as in the following example ``` if (fflush(fp)) { fprintf(stderr, "%s\n", explain_fflush(fp)); exit(EXIT_FAILURE); } if (fclose(fp)) { fprintf(stderr, "%s\n", explain_fclose(fp)); exit(EXIT_FAILURE); } ``` ### explain\_errno\_fclose const char \*explain\_errno\_fclose(int errnum, FILE \* fp); The explain\_errno\_fclose function is used to obtain an explanation of an error returned by the [*fclose*(3)](/fclose/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: ``` if (fclose(fp)) { int err = errno; fprintf(stderr, "%s\n", explain_errno_fclose(err, fp)); 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*. - *fp* The original fp, exactly as passed to the [*fclose*(3)](/fclose/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. **Note:** This function may be of little diagnostic value, because libc may have destroyed any useful context, leaving nothing for libexplain to work with (this is true of glibc in particular). For files that are open for writing, you will obtain more useful information by first calling [*fflush*(3)](/fflush/3.md), as in the following example ``` if (fflush(fp)) { int err = errno; fprintf(stderr, "%s\n", explain_errno_fflush(err, fp)); exit(EXIT_FAILURE); } if (fclose(fp)) { int err = errno; fprintf(stderr, "%s\n", explain_errno_fclose(err, fp)); exit(EXIT_FAILURE); } ``` ### explain\_message\_fclose void explain\_message\_fclose(char \*message, int message\_size, FILE \*fp); The explain\_message\_fclose function is used to obtain an explanation of an error returned by the [*fclose*(3)](/fclose/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: ``` if (fclose(fp)) { char message[3000]; explain_message_fclose(message, sizeof(message), fp); 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. - *message\_size* The size in bytes of the location in which to store the returned message. - *fp* The original fp, exactly as passed to the *[fclose(3)](/fclose/3.md)* system call. **Note:** This function may be of little diagnostic value, because libc may have destroyed any useful context, leaving nothing for libexplain to work with (this is true of glibc in particular). For files that are open for writing, you will obtain more useful information by first calling [*fflush*(3)](/fflush/3.md), as in the following example ``` if (fflush(fp)) { char message[3000]; explain_message_fflush(message, sizeof(message), fp); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } if (fclose(fp)) { char message[3000]; explain_message_fclose(message, sizeof(message), fp); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } ``` ### explain\_message\_errno\_fclose void explain\_message\_errno\_fclose(char \*message, int message\_size, int errnum, FILE \*fp); The explain\_message\_errno\_fclose function is used to obtain an explanation of an error returned by the [*fclose*(3)](/fclose/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 exameple: ``` if (fclose(fp)) { int err = errno; char message[3000]; explain_message_errno_fclose(message, sizeof(message), err, fp); 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. - *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*. - *fp* The original fp, exactly as passed to the [*fclose*(3)](/fclose/3.md) system call. **Note:** This function may be of little diagnostic value, because libc may have destroyed any useful context, leaving nothing for libexplain to work with (this is true of glibc in particular). For files that are open for writing, you will obtain more useful information by first calling [*fflush*(3)](/fflush/3.md), as in the following example ``` if (fflush(fp)) { int err = errno; char message[3000]; explain_message_errno_fflush(message, sizeof(message), err, fp); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } if (fclose(fp)) { int err = errno; char message[3000]; explain_message_errno_fclose(message, sizeof(message), err, fp); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } ``` ## COPYRIGHT libexplain version 1.4\ Copyright (C) 2008 Peter Miller ## AUTHOR Written by Peter Miller \