--- name: "explain_gettimeofday" section: "3" platform: "linux" package: "libexplain-dev" version: "1.4.D001-16" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/explain_gettimeofday" --- # explain\_gettimeofday(3) explain gettimeofday(2) errors ## NAME explain\_gettimeofday - explain [gettimeofday(2)](/gettimeofday/2.md) errors ## SYNOPSIS \#include \ const char \*explain\_gettimeofday(struct timeval \*tv, struct timezone \*tz);\ const char \*explain\_errno\_gettimeofday(int errnum, struct timeval \*tv, struct timezone \*tz);\ void explain\_message\_gettimeofday(char \*message, int message\_size, struct timeval \*tv, struct timezone \*tz);\ void explain\_message\_errno\_gettimeofday(char \*message, int message\_size, int errnum, struct timeval \*tv, struct timezone \*tz); ## DESCRIPTION These functions may be used to obtain explanations for errors returned by the [*gettimeofday*(2)](/gettimeofday/2.md) system call. ### explain\_gettimeofday const char \*explain\_gettimeofday(struct timeval \*tv, struct timezone \*tz); The **explain\_gettimeofday** function is used to obtain an explanation of an error returned by the [*gettimeofday*(2)](/gettimeofday/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 (gettimeofday(tv, tz) < 0) { fprintf(stderr, "%s\n", explain_gettimeofday(tv, tz)); exit(EXIT_FAILURE); } ``` - *tv* The original tv, exactly as passed to the [*gettimeofday*(2)](/gettimeofday/2.md) system call. - *tz* The original tz, exactly as passed to the [*gettimeofday*(2)](/gettimeofday/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\_gettimeofday const char \*explain\_errno\_gettimeofday(int errnum, struct timeval \*tv, struct timezone \*tz); The **explain\_errno\_gettimeofday** function is used to obtain an explanation of an error returned by the [*gettimeofday*(2)](/gettimeofday/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 (gettimeofday(tv, tz) < 0) { int err = errno; fprintf(stderr, "%s\n", explain_errno_gettimeofday(err, tv, tz)); 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*. - *tv* The original tv, exactly as passed to the [*gettimeofday*(2)](/gettimeofday/2.md) system call. - *tz* The original tz, exactly as passed to the [*gettimeofday*(2)](/gettimeofday/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\_gettimeofday void explain\_message\_gettimeofday(char \*message, int message\_size, struct timeval \*tv, struct timezone \*tz); The **explain\_message\_gettimeofday** function may be used to obtain an explanation of an error returned by the [*gettimeofday*(2)](/gettimeofday/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 (gettimeofday(tv, tz) < 0) { char message[3000]; explain_message_gettimeofday(message, sizeof(message), tv, tz); 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 returned message. - *tv* The original tv, exactly as passed to the [*gettimeofday*(2)](/gettimeofday/2.md) system call. - *tz* The original tz, exactly as passed to the [*gettimeofday*(2)](/gettimeofday/2.md) system call. ### explain\_message\_errno\_gettimeofday void explain\_message\_errno\_gettimeofday(char \*message, int message\_size, int errnum, struct timeval \*tv, struct timezone \*tz); The **explain\_message\_errno\_gettimeofday** function may be used to obtain an explanation of an error returned by the [*gettimeofday*(2)](/gettimeofday/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 (gettimeofday(tv, tz) < 0) { int err = errno; char message[3000]; explain_message_errno_gettimeofday(message, sizeof(message), err, tv, tz); 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 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*. - *tv* The original tv, exactly as passed to the [*gettimeofday*(2)](/gettimeofday/2.md) system call. - *tz* The original tz, exactly as passed to the [*gettimeofday*(2)](/gettimeofday/2.md) system call. ## SEE ALSO - [*gettimeofday*(2)](/gettimeofday/2.md) get time - [*explain\_gettimeofday\_or\_die*(3)](/explain_gettimeofday_or_die/3.md) get time and report errors ## COPYRIGHT libexplain version 1.4\ Copyright (C) 2008 Peter Miller