CTIME(3) Linux Programmer's Manual CTIME(3)
NAME
asctime, ctime, gmtime, localtime, mktime, asctime_r, ctime_r,
gmtime_r, localtime_r - transform date and time to broken-down time or
ASCII
SYNOPSIS
#include <time.h>
char *asctime(const struct tm *tm);
char *asctime_r(const struct tm *tm, char *buf);
char *ctime(const time_t *timep);
char *ctime_r(const time_t *timep, char *buf);
struct tm *gmtime(const time_t *timep);
struct tm *gmtime_r(const time_t *timep, struct tm *result);
struct tm *localtime(const time_t *timep);
struct tm *localtime_r(const time_t *timep, struct tm *result);
time_t mktime(struct tm *tm);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
asctime_r(), ctime_r(), gmtime_r(), localtime_r():
_POSIX_C_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
The ctime(), gmtime() and localtime() functions all take an argument of
data type time_t, which represents calendar time. When interpreted as
an absolute time value, it represents the number of seconds elapsed
since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
The asctime() and mktime() functions both take an argument representing
broken-down time, which is a representation separated into year, month,
day, and so on.
Broken-down time is stored in the structure tm, which is defined in
<time.h> as follows:
struct tm {
int tm_sec; /* Seconds (0-60) */
int tm_min; /* Minutes (0-59) */
int tm_hour; /* Hours (0-23) */
int tm_mday; /* Day of the month (1-31) */
int tm_mon; /* Month (0-11) */
int tm_year; /* Year - 1900 */
int tm_wday; /* Day of the week (0-6, Sunday = 0) */
int tm_yday; /* Day in the year (0-365, 1 Jan = 0) */
int tm_isdst; /* Daylight saving time */
};
The members of the tm structure are:
tm_sec The number of seconds after the minute, normally in the range
0 to 59, but can be up to 60 to allow for leap seconds.
tm_min The number of minutes after the hour, in the range 0 to 59.
tm_hour The number of hours past midnight, in the range 0 to 23.
tm_mday The day of the month, in the range 1 to 31.
tm_mon The number of months since January, in the range 0 to 11.
tm_year The number of years since 1900.
tm_wday The number of days since Sunday, in the range 0 to 6.
tm_yday The number of days since January 1, in the range 0 to 365.
tm_isdst A flag that indicates whether daylight saving time is in
effect at the time described. The value is positive if day-
light saving time is in effect, zero if it is not, and nega-
tive if the information is not available.
The call ctime(t) is equivalent to asctime(localtime(t)). It converts
the calendar time t into a null-terminated string of the form
"Wed Jun 30 21:49:08 1993\n"
,in
The abbreviations for the days of the week are "Sun", "Mon", "Tue",
"Wed", "Thu", "Fri", and "Sat". The abbreviations for the months are
"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct",
"Nov", and "Dec". The return value points to a statically allocated
string which might be overwritten by subsequent calls to any of the
date and time functions. The function also sets the external variables
tzname, timezone, and daylight (see tzset(3)) with information about
the current timezone. The reentrant version ctime_r() does the same,
but stores the string in a user-supplied buffer which should have room
for at least 26 bytes. It need not set tzname, timezone, and daylight.
The gmtime() function converts the calendar time timep to broken-down
time representation, expressed in Coordinated Universal Time (UTC). It
may return NULL when the year does not fit into an integer. The return
value points to a statically allocated struct which might be overwrit-
ten by subsequent calls to any of the date and time functions. The
gmtime_r() function does the same, but stores the data in a user-sup-
plied struct.
The localtime() function converts the calendar time timep to broken-
down time representation, expressed relative to the user's specified
timezone. The function acts as if it called tzset(3) and sets the
external variables tzname with information about the current timezone,
timezone with the difference between Coordinated Universal Time (UTC)
and local standard time in seconds, and daylight to a nonzero value if
daylight savings time rules apply during some part of the year. The
return value points to a statically allocated struct which might be
overwritten by subsequent calls to any of the date and time functions.
The localtime_r() function does the same, but stores the data in a
user-supplied struct. It need not set tzname, timezone, and daylight.
The asctime() function converts the broken-down time value tm into a
null-terminated string with the same format as ctime(). The return
value points to a statically allocated string which might be overwrit-
ten by subsequent calls to any of the date and time functions. The
asctime_r() function does the same, but stores the string in a user-
supplied buffer which should have room for at least 26 bytes.
The mktime() function converts a broken-down time structure, expressed
as local time, to calendar time representation. The function ignores
the values supplied by the caller in the tm_wday and tm_yday fields.
The value specified in the tm_isdst field informs mktime() whether or
not daylight saving time (DST) is in effect for the time supplied in
the tm structure: a positive value means DST is in effect; zero means
that DST is not in effect; and a negative value means that mktime()
should (use timezone information and system databases to) attempt to
determine whether DST is in effect at the specified time.
The mktime() function modifies the fields of the tm structure as fol-
lows: tm_wday and tm_yday are set to values determined from the con-
tents of the other fields; if structure members are outside their valid
interval, they will be normalized (so that, for example, 40 October is
changed into 9 November); tm_isdst is set (regardless of its initial
value) to a positive value or to 0, respectively, to indicate whether
DST is or is not in effect at the specified time. Calling mktime()
also sets the external variable tzname with information about the cur-
rent timezone.
If the specified broken-down time cannot be represented as calendar
time (seconds since the Epoch), mktime() returns (time_t) -1 and does
not alter the members of the broken-down time structure.
RETURN VALUE
On success, gmtime() and localtime() return a pointer to a struct tm.
On success, gmtime_r() and localtime_r() return the address of the
structure pointed to by result.
On success, asctime() and ctime() return a pointer to a string.
On success, asctime_r() and ctime_r() return a pointer to the string
pointed to by buf.
On success, mktime() returns the calendar time (seconds since the
Epoch), expressed as a value of type time_t.
On error, mktime() returns the value (time_t) -1. The remaining func-
tions return NULL on error. On error, errno is set to indicate the
cause of the error.
ERRORS
EOVERFLOW
The result cannot be represented.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
+---------------+---------------+---------------------------------+
|Interface | Attribute | Value |
+---------------+---------------+---------------------------------+
|asctime() | Thread safety | MT-Unsafe race:asctime locale |
+---------------+---------------+---------------------------------+
|asctime_r() | Thread safety | MT-Safe locale |
+---------------+---------------+---------------------------------+
|ctime() | Thread safety | MT-Unsafe race:tmbuf |
| | | race:asctime env locale |
+---------------+---------------+---------------------------------+
|ctime_r(), | Thread safety | MT-Safe env locale |
|gmtime_r(), | | |
|localtime_r(), | | |
|mktime() | | |
+---------------+---------------+---------------------------------+
|gmtime(), | Thread safety | MT-Unsafe race:tmbuf env locale |
|localtime() | | |
+---------------+---------------+---------------------------------+
CONFORMING TO
POSIX.1-2001. C89 and C99 specify asctime(), ctime(), gmtime(), local-
time(), and mktime(). POSIX.1-2008 marks asctime(), asctime_r(),
ctime(), and ctime_r() as obsolete, recommending the use of strftime(3)
instead.
NOTES
The four functions asctime(), ctime(), gmtime() and localtime() return
a pointer to static data and hence are not thread-safe. The thread-
safe versions, asctime_r(), ctime_r(), gmtime_r() and localtime_r(),
are specified by SUSv2.
POSIX.1-2001 says: "The asctime(), ctime(), gmtime(), and localtime()
functions shall return values in one of two static objects: a broken-
down time structure and an array of type char. Execution of any of the
functions may overwrite the information returned in either of these
objects by any of the other functions." This can occur in the glibc
implementation.
In many implementations, including glibc, a 0 in tm_mday is interpreted
as meaning the last day of the preceding month.
The glibc version of struct tm has additional fields
const char *tm_zone; /* Timezone abbreviation */
defined when _BSD_SOURCE was set before including <time.h>. This is a
BSD extension, present in 4.3BSD-Reno.
According to POSIX.1-2004, localtime() is required to behave as though
tzset(3) was called, while localtime_r() does not have this require-
ment. For portable code, tzset(3) should be called before local-
time_r().
SEE ALSO
date(1), gettimeofday(2), time(2), utime(2), clock(3), difftime(3),
strftime(3), strptime(3), timegm(3), tzset(3), time(7)
COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2017-09-15 CTIME(3)
SCALAR(1) Git Manual SCALAR(1)
NAME
scalar - A tool for managing large Git repositories
SYNOPSIS
scalar clone [--single-branch] [--branch <main-branch>] [--full-clone]
[--[no-]src] <url> [<enlistment>]
scalar list
scalar register [<enlistment>]
scalar unregister [<enlistment>]
scalar run ( all | config | commit-graph | fetch | loose-objects | pack-files ) [<enlistment>]
scalar reconfigure [ --all | <enlistment> ]
scalar diagnose [<enlistment>]
scalar delete <enlistment>
DESCRIPTION
Scalar is a repository management tool that optimizes Git for use in
large repositories. Scalar improves performance by configuring advanced
Git settings, maintaining repositories in the background, and helping
to reduce data sent across the network.
An important Scalar concept is the enlistment: this is the top-level
directory of the project. It usually contains the subdirectory src/
which is a Git worktree. This encourages the separation between tracked
files (inside src/) and untracked files, such as build artifacts
(outside src/). When registering an existing Git worktree with Scalar
whose name is not src, the enlistment will be identical to the
worktree.
The scalar command implements various subcommands, and different
options depending on the subcommand. With the exception of clone, list
and reconfigure --all, all subcommands expect to be run in an
enlistment.
The following options can be specified before the subcommand:
-C <directory>
Before running the subcommand, change the working directory. This
option imitates the same option of git(1).
-c <key>=<value>
For the duration of running the specified subcommand, configure
this setting. This option imitates the same option of git(1).
COMMANDS
Clone
clone [<options>] <url> [<enlistment>]
Clones the specified repository, similar to git-clone(1). By
default, only commit and tree objects are cloned. Once finished,
the worktree is located at <enlistment>/src.
The sparse-checkout feature is enabled (except when run with
--full-clone) and the only files present are those in the top-level
directory. Use git sparse-checkout set to expand the set of
directories you want to see, or git sparse-checkout disable to
expand to all files (see git-sparse-checkout(1) for more details).
You can explore the subdirectories outside your sparse-checkout by
using git ls-tree HEAD[:<directory>].
-b <name>, --branch <name>
Instead of checking out the branch pointed to by the cloned
repository's HEAD, check out the <name> branch instead.
--[no-]single-branch
Clone only the history leading to the tip of a single branch,
either specified by the --branch option or the primary branch
remote's HEAD points at.
Further fetches into the resulting repository will only update the
remote-tracking branch for the branch this option was used for the
initial cloning. If the HEAD at the remote did not point at any
branch when --single-branch clone was made, no remote-tracking
branch is created.
--[no-]src
By default, scalar clone places the cloned repository within a
<entlistment>/src directory. Use --no-src to place the cloned
repository directly in the <enlistment> directory.
--[no-]full-clone
A sparse-checkout is initialized by default. This behavior can be
turned off via --full-clone.
List
list
List enlistments that are currently registered by Scalar. This
subcommand does not need to be run inside an enlistment.
Register
register [<enlistment>]
Adds the enlistment's repository to the list of registered
repositories and starts background maintenance. If <enlistment> is
not provided, then the enlistment associated with the current
working directory is registered.
Note: when this subcommand is called in a worktree that is called
src/, its parent directory is considered to be the Scalar
enlistment. If the worktree is not called src/, it itself will be
considered to be the Scalar enlistment.
Unregister
unregister [<enlistment>]
Remove the specified repository from the list of repositories
registered with Scalar and stop the scheduled background
maintenance.
Run
scalar run ( all | config | commit-graph | fetch | loose-objects |
pack-files ) [<enlistment>]
Run the given maintenance task (or all tasks, if all was
specified). Except for all and config, this subcommand simply hands
off to git-maintenance(1) (mapping fetch to prefetch and pack-files
to incremental-repack).
These tasks are run automatically as part of the scheduled
maintenance, as soon as the repository is registered with Scalar.
It should therefore not be necessary to run this subcommand
manually.
The config task is specific to Scalar and configures all those
opinionated default settings that make Git work more efficiently
with large repositories. As this task is run as part of scalar
clone automatically, explicit invocations of this task are rarely
needed.
Reconfigure
After a Scalar upgrade, or when the configuration of a Scalar
enlistment was somehow corrupted or changed by mistake, this subcommand
allows to reconfigure the enlistment.
With the --all option, all enlistments currently registered with Scalar
will be reconfigured. Use this option after each Scalar upgrade.
Diagnose
diagnose [<enlistment>]
When reporting issues with Scalar, it is often helpful to provide
the information gathered by this command, including logs and
certain statistics describing the data shape of the current
enlistment.
The output of this command is a .zip file that is written into a
directory adjacent to the worktree in the src directory.
Delete
delete <enlistment>
This subcommand lets you delete an existing Scalar enlistment from
your local file system, unregistering the repository.
SEE ALSO
git-clone(1), git-maintenance(1).
GIT
Part of the git(1) suite
Git 2.43.5 05/31/2024 SCALAR(1)
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