For backwards compatibility with older versions of RCS, a bare _t option is ignored.

_T	Set the RCS file's modification time to the new revision's time if the former precedes the latter and there is a new revision; preserve the RCS file's modification time otherwise. If you have locked a revision, ci usually updates the RCS file's modification time to the current time, because the lock is stored in the RCS file and removing the lock requires changing the RCS file. This can create an RCS file newer than the working file in one of two ways: first, ci _M can create a working file with a date before the current time; second, when reverting to the previous revision the RCS file can change while the working file remains unchanged. These two cases can cause excessive recompilation caused by a make(1) dependency of the working file on the RCS file. The _T option inhibits this recompilation by lying about the RCS file's date. Use this option with care; it can suppress recompilation even when a checkin of one working file should affect another working file associated with the same RCS file. For example, suppose the RCS file's time is 01:00, the (changed) working file's time is 02:00, some other copy of the working file has a time of 03:00, and the current time is 04:00. Then ci _d _T sets the RCS file's time to 02:00 instead of the usual 04:00; this causes make(1) to think (incorrectly) that the other copy is newer than the RCS file.
_wlogin	Uses login for the author field of the deposited revision. Useful for lying about the author, and for _k if no author is available.
_V	Print RCS's version number.
_Vn	Emulate RCS version n. See co(1) for details.
_xsuffixes	Specifies the suffixes for RCS files. A nonempty suffix matches any pathname ending in the suffix. An empty suffix matches any pathname of the form RCS/path or path1/RCS/path2. The _x option can specify a list of suffixes separated by /. For example, _x,v/ specifies two suffixes: ,v and the empty suffix. If two or more suffixes are specified, they are tried in order when looking for an RCS file; the first one that works is used for that file. If no RCS file is found but an RCS file can be created, the suffixes are tried in order to determine the new RCS file's name. The default for suffixes is installation-dependent; normally it is ,v/ for hosts like UNIX that permit commas in filenames, and is empty (that is, just the empty suffix) for other hosts.
_zzone	Specifies the date output format in keyword substitution, and specifies the default time zone for date in the _ddate option. The zone should be empty, a numeric UTC offset, or the special string LT for local time. The default is an empty zone, which uses the traditional RCS format of UTC without any time-zone indication and with slashes separating the parts of the date; otherwise, times are output in ISO 8601 format with time zone indication. For example, if local time is January 11, 1990, 8 p.m. Pacific Standard Time, eight hours west of UTC, then the time is output as follows:

Option	Time Output
_z	1990/01/12 04:00:00 (default)
_zLT	1990-01-11 20:00:00_08
_z+05:30	1990-01-12 09:30:00+05:30

The _z option does not affect dates stored in RCS files, which are always UTC.

FILE NAMING

Pairs of RCS files and working files can be specified in three ways. (See also "Examples," next.)

1. Both the RCS file and the working file are given. The RCS pathname is of the form path1/workfileX and the working pathname is of the form path2/workfile where path1/ and path2/ are (possibly different or empty) paths, workfile is a filename, and X is an RCS suffix. If X is empty, path1/ must start with RCS/ or must contain /RCS/.
2. Only the RCS file is given. Then the working file is created in the current directory and its name is derived from the name of the RCS file by removing path1/ and the suffix X.

3. Only the working file is given. Then ci considers each RCS suffix X in turn, looking for an RCS file of the form path2/RCS/workfileX or (if the former is not found and X is nonempty) path2/workfileX.

If the RCS file is specified without a path in one of the first two preceding scenarios, ci looks for the RCS file first in the directory ./RCS and then in the current directory.

ci reports an error if an attempt to open an RCS file fails for an unusual reason, even if the RCS file's pathname is just one of several possibilities. For example, to suppress use of RCS commands in a directory d, create a regular file named d/RCS so that casual attempts to use RCS commands in d fail because d/RCS is not a directory.

EXAMPLES

Suppose ,v is an RCS suffix and the current directory contains a subdirectory RCS with an RCS file io.c,v. Then each of the following commands checks in a copy of io.c into RCS/io.c,v as the latest revision, removing io.c:

ci io.c; ci RCS/io.c,v; ci io.c,v;

ci io.c RCS/io.c,v; ci io.c io.c,v;

ci RCS/io.c,v io.c; ci io.c,v io.c;

Suppose instead that the empty suffix is an RCS suffix and the current directory contains a subdirectory RCS with an RCS file io.c. Then each of the following commands checks in a new revision:

ci io.c; ci RCS/io.c;

ci io.c RCS/io.c;

ci RCS/io.c io.c;

FILE MODES

An RCS file created by ci inherits the read and execute permissions from the working file. If the RCS file exists already, ci preserves its read and execute permissions. ci always turns off all write permissions of RCS files.

FILES

Temporary files are created in the directory containing the working file, and also in the temporary directory. (See TMPDIR under "Environment.") A semaphore file or files are created in the directory containing the RCS file. With a nonempty suffix, the semaphore names begin with the first character of the suffix; therefore, do not specify an suffix whose first character could be that of a working filename. With an empty suffix, the semaphore names end with an underscore (_), so working filenames should not end in _. ci never changes an RCS or working file. Normally, ci unlinks the file and creates a new one; but instead of breaking a chain of one or more symbolic links to an RCS file, it unlinks the destination file instead. Therefore, ci breaks any hard or symbolic links to any working file it changes; and hard links to RCS files are ineffective, but symbolic links to RCS files are preserved.

The effective user must be able to search and write the directory containing the RCS file. Normally, the real user must be able to read the RCS and working files and to search and write the directory containing the working file; however, some older hosts cannot easily switch between real and effective users, so on these hosts the effective user is used for all accesses. The effective user is the same as the real user unless your copies of ci and co have setuid privileges. These privileges yield extra security if the effective user owns all RCS files and directories, and if only the effective user can write RCS directories.

Users can control access to RCS files by setting the permissions of the directory containing the files; only users with write access to the directory can use RCS commands to change its RCS files. For example, in hosts that allow a user to belong to several groups, one can make a group's RCS directories writable to that group only. This approach suffices for informal projects, but it means that any group member can arbitrarily change the group's RCS files, and can even remove them entirely. Hence, more formal projects sometimes distinguish between an RCS administrator, who can change the RCS files at will, and other project members, who can check in new revisions but cannot otherwise change the RCS files.

SETUID USE

To prevent anybody but their RCS administrator from deleting revisions, a set of users can employ setuid privileges as follows: