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diff --git a/man3p/localtime.3p b/man3p/localtime.3p new file mode 100644 index 000000000..482228755 --- /dev/null +++ b/man3p/localtime.3p @@ -0,0 +1,200 @@ +.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved +.TH "LOCALTIME" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" +.\" localtime +.SH NAME +localtime, localtime_r \- convert a time value to a broken-down local +time +.SH SYNOPSIS +.LP +\fB#include <time.h> +.br +.sp +struct tm *localtime(const time_t *\fP\fItimer\fP\fB); +.br +\fP +.LP +\fBstruct tm *localtime_r(const time_t *restrict\fP \fItimer\fP\fB, +.br +\ \ \ \ \ \ struct tm *restrict\fP \fIresult\fP\fB); \fP +\fB +.br +\fP +.SH DESCRIPTION +.LP +For \fIlocaltime\fP(): The functionality described on this reference +page is aligned with the ISO\ C standard. Any +conflict between the requirements described here and the ISO\ C standard +is unintentional. This volume of +IEEE\ Std\ 1003.1-2001 defers to the ISO\ C standard. +.LP +The \fIlocaltime\fP() function shall convert the time in seconds since +the Epoch pointed to by \fItimer\fP into a broken-down +time, expressed as a local time. The function corrects for the timezone +and any seasonal time adjustments. \ Local timezone +information is used as though \fIlocaltime\fP() calls \fItzset\fP(). +.LP +The relationship between a time in seconds since the Epoch used as +an argument to \fIlocaltime\fP() and the \fBtm\fP structure +(defined in the \fI<time.h>\fP header) is that the result shall be +as specified in the +expression given in the definition of seconds since the Epoch (see +the Base Definitions volume of IEEE\ Std\ 1003.1-2001, +Section 4.14, Seconds Since the Epoch) corrected for timezone and +any seasonal +time adjustments, where the names in the structure and in the expression +correspond. +.LP +The same relationship shall apply for \fIlocaltime_r\fP(). +.LP +The +\fIlocaltime\fP() function need not be reentrant. A function that +is not required to be reentrant is not required to be +thread-safe. +.LP +The \fIasctime\fP(), \fIctime\fP(), \fIgmtime\fP(), and \fIlocaltime\fP() +functions shall return values in one of two static objects: +a broken-down time structure and an array of type \fBchar\fP. Execution +of any of the functions may overwrite the information +returned in either of these objects by any of the other functions. +.LP +The \fIlocaltime_r\fP() function shall convert the time in seconds +since the Epoch pointed to by \fItimer\fP into a broken-down +time stored in the structure to which \fIresult\fP points. The \fIlocaltime_r\fP() +function shall also return a pointer to that +same structure. +.LP +Unlike \fIlocaltime\fP(), the reentrant version is not required to +set \fItzname\fP. +.SH RETURN VALUE +.LP +Upon successful completion, the \fIlocaltime\fP() function shall return +a pointer to the broken-down time structure. If an +error is detected, \fIlocaltime\fP() shall return a null pointer +\ and set \fIerrno\fP to indicate the error. +.LP +Upon successful completion, \fIlocaltime_r\fP() shall return a pointer +to the structure pointed to by the argument \fIresult\fP. +.SH ERRORS +.LP +The \fIlocaltime\fP() function shall fail if: +.TP 7 +.B EOVERFLOW +The result cannot be represented. +.sp +.LP +\fIThe following sections are informative.\fP +.SH EXAMPLES +.SS Getting the Local Date and Time +.LP +The following example uses the \fItime\fP() function to calculate +the time elapsed, in +seconds, since January 1, 1970 0:00 UTC (the Epoch), \fIlocaltime\fP() +to convert that value to a broken-down time, and \fIasctime\fP() to +convert the broken-down time values into a printable string. +.sp +.RS +.nf + +\fB#include <stdio.h> +#include <time.h> +.sp + +int main(void) +{ + time_t result; +.sp + + result = time(NULL); + printf("%s%ju secs since the Epoch\\n", + asctime(localtime(&result)), + (uintmax_t)result); + return(0); +} +\fP +.fi +.RE +.LP +This example writes the current time to \fIstdout\fP in a form like +this: +.sp +.RS +.nf + +\fBWed Jun 26 10:32:15 1996 +835810335 secs since the Epoch +\fP +.fi +.RE +.SS Getting the Modification Time for a File +.LP +The following example gets the modification time for a file. The \fIlocaltime\fP() +function converts the \fBtime_t\fP value of +the last modification date, obtained by a previous call to \fIstat\fP(), +into a \fBtm\fP +structure that contains the year, month, day, and so on. +.sp +.RS +.nf + +\fB#include <time.h> +\&... +struct stat statbuf; +\&... +tm = localtime(&statbuf.st_mtime); +\&... +\fP +.fi +.RE +.SS Timing an Event +.LP +The following example gets the current time, converts it to a string +using \fIlocaltime\fP() and \fIasctime\fP(), and prints it to standard +output using \fIfputs\fP(). It then prints the number of minutes to +an event being timed. +.sp +.RS +.nf + +\fB#include <time.h> +#include <stdio.h> +\&... +time_t now; +int minutes_to_event; +\&... +time(&now); +printf("The time is "); +fputs(asctime(localtime(&now)), stdout); +printf("There are still %d minutes to the event.\\n", + minutes_to_event); +\&... +\fP +.fi +.RE +.SH APPLICATION USAGE +.LP +The \fIlocaltime_r\fP() function is thread-safe and returns values +in a user-supplied buffer instead of possibly using a static +data area that may be overwritten by each call. +.SH RATIONALE +.LP +None. +.SH FUTURE DIRECTIONS +.LP +None. +.SH SEE ALSO +.LP +\fIasctime\fP() , \fIclock\fP() , \fIctime\fP() +, \fIdifftime\fP() , \fIgetdate\fP() , \fIgmtime\fP() , \fImktime\fP() +, \fIstrftime\fP() , \fIstrptime\fP() , \fItime\fP() , \fIutime\fP() +, the +Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<time.h>\fP +.SH COPYRIGHT +Portions of this text are reprinted and reproduced in electronic form +from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology +-- Portable Operating System Interface (POSIX), The Open Group Base +Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of +Electrical and Electronics Engineers, Inc and The Open Group. In the +event of any discrepancy between this version and the original IEEE and +The Open Group Standard, the original IEEE and The Open Group Standard +is the referee document. The original Standard can be obtained online at +http://www.opengroup.org/unix/online.html . |