Updated: April 19, 2023 |
Convert calendar time to local time
#include <time.h> char* ctime( const time_t* timer ); char* ctime_r( const time_t* timer, char* buf );
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
The ctime() and ctime_r() functions convert the time pointed to by timer to local time and formats it as a string containing exactly 26 characters in the form:
Tue May 7 10:40:27 2002\n\0
This function: | Is equivalent to calling: |
---|---|
ctime() | asctime( localtime ( timer ) ); |
ctime_r() | asctime_r( localtime ( timer ), buf ) |
The result string for ctime_r() is contained in the buffer pointed to by buf.
All fields have a constant width. The newline character '\n' and NUL character '\0' occupy the last two positions of the string.
Whenever the ctime() or ctime_r() functions are called, the tzset() function is also called.
The calendar time is usually obtained by using the time() function. That time is Coordinated Universal Time (UTC) (formerly known as Greenwich Mean Time (GMT)).
You typically set the time on the computer with the date command to reflect Coordinated Universal Time (UTC), and then use the TZ environment variable or _CS_TIMEZONE configuration string to establish the local time zone. For more information, see Setting the time zone in the Configuring Your Environment chapter of the QNX Neutrino User's Guide.
A pointer to the string containing the formatted local time, or NULL if an error occurs.
ctime() is ANSI, POSIX 1003.1 OB; ctime_r() is POSIX 1003.1 OB. These functions are marked as obsolescent, and may be removed from a future version of the standard.
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | No |
Signal handler | Yes |
Thread | No |
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | No |
Signal handler | Yes |
Thread | Yes |
The asctime() and ctime() functions place their results in a static buffer that's reused for each call to asctime() or ctime().