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CO(1)		    UNIX Programmer's Manual		    CO(1)



[1mNAME
     [0mco - check out RCS revisions

[1mSYNOPSIS
     co [0m[ options ] file ...

[1mDESCRIPTION
     [0m_C_o retrieves revisions from RCS files.  Each file name end-
     ing in `,v' is taken to be an RCS file.  All other files are
     assumed to be working files.  _C_o retrieves a revision from
     each RCS file and stores it into the corresponding working
     file.

     Pairs of RCS files and working files may be specified in 3
     ways (see also the example section).

     1) Both the RCS file and the working file are given. The RCS
     file name is of the form _p_a_t_h_1/_w_o_r_k_f_i_l_e,v and the working
     file name is of the form _p_a_t_h_2/_w_o_r_k_f_i_l_e, where _p_a_t_h_1/ and
     _p_a_t_h_2/ are (possibly different or empty) paths and _w_o_r_k_f_i_l_e
     is a file name.

     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 _p_a_t_h_1/ and the
     suffix `,v'.

     3) Only the working file is given.  Then the name of the RCS
     file is derived from the name of the working file by remov-
     ing _p_a_t_h_2/ and appending the suffix `,v'.

     If the RCS file is omitted or specified without a path, then
     _c_o looks for the RCS file first in the directory ./RCS and
     then in the current directory.

     Revisions of an RCS file may be checked out locked or
     unlocked. Locking a revision prevents overlapping updates. A
     revision checked out for reading or processing (e.g., com-
     piling) need not be locked. A revision checked out for edit-
     ing and later checkin must normally be locked. Locking a
     revision currently locked by another user fails. (A lock may
     be broken with the _r_c_s (1) command.) _C_o with locking
     requires the caller to be on the access list of the RCS
     file, unless he is the owner of the file or the superuser,
     or the access list is empty.  _C_o without locking is not sub-
     ject to accesslist restrictions.

     A revision is selected by number, checkin date/time, author,
     or state. If none of these options are specified, the latest
     revision on the trunk is retrieved.  When the options are
     applied in combination, the latest revision that satisfies
     all of them is retrieved.	The options for date/time,



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     author, and state retrieve a revision on the _s_e_l_e_c_t_e_d
     _b_r_a_n_c_h. The selected branch is either derived from the revi-
     sion number (if given), or is the highest branch on the
     trunk.  A revision number may be attached to one of the
     options [1m-l[0m, [1m-p[0m, [1m-q[0m, or [1m-r[0m.

     A _c_o command applied to an RCS file with no revisions
     creates a zero-length file.  _C_o always performs keyword sub-
     stitution (see below).

     [1m-l[0m[_r_e_v]	locks the checked out revision for the caller.
		If omitted, the checked out revision is not
		locked.  See option [1m-r [0mfor handling of the revi-
		sion number _r_e_v.

     [1m-p[0m[_r_e_v]	prints the retrieved revision on the std. output
		rather than storing it in the working file.  This
		option is useful when _c_o is part of a pipe.

     [1m-q[0m[_r_e_v]	quiet mode; diagnostics are not printed.

     [1m-d[0m_d_a_t_e	retrieves the latest revision on the selected
		branch whose checkin date/time is less than or
		equal to _d_a_t_e.	The date and time may be given in
		free format and are converted to local time.
		Examples of formats for _d_a_t_e:

		_2_2-_A_p_r_i_l-_1_9_8_2, _1_7:_2_0-_C_D_T,
		_2:_2_5 _A_M, _D_e_c. _2_9, _1_9_8_3,
		_T_u_e-_P_D_T, _1_9_8_1, _4_p_m _J_u_l _2_1	  (free format),
		_F_r_i, _A_p_r_i_l _1_6 _1_5:_5_2:_2_5 _E_S_T _1_9_8_2 (output of ctime).

		Most fields in the date and time may be
		defaulted.  _C_o determines the defaults in the
		order year, month, day, hour, minute, and second
		(most to least significant). At least one of
		these fields must be provided. For omitted fields
		that are of higher significance than the highest
		provided field, the current values are assumed.
		For all other omitted fields, the lowest possible
		values are assumed.  For example, the date "20,
		10:30" defaults to 10:30:00 of the 20th of the
		current month and current year.  The date/time
		must be quoted if it contains spaces.

     [1m-r[0m[_r_e_v]	retrieves the latest revision whose number is
		less than or equal to _r_e_v.  If _r_e_v indicates a
		branch rather than a revision, the latest revi-
		sion on that branch is retrieved.  _R_e_v is com-
		posed of one or more numeric or symbolic fields
		separated by `.'. The numeric equivalent of a
		symbolic field is specified with the [1m-n [0moption of



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		the commands _c_i and _r_c_s.

     [1m-s[0m_s_t_a_t_e	retrieves the latest revision on the selected
		branch whose state is set to _s_t_a_t_e.

     [1m-w[0m[_l_o_g_i_n]	retrieves the latest revision on the selected
		branch which was checked in by the user with
		login name _l_o_g_i_n. If the argument _l_o_g_i_n is omit-
		ted, the caller's login is assumed.

     [1m-j[0m_j_o_i_n_l_i_s_t generates a new revision which is the join of the
		revisions on _j_o_i_n_l_i_s_t.	_J_o_i_n_l_i_s_t is a comma-
		separated list of pairs of the form _r_e_v_2:_r_e_v_3,
		where _r_e_v_2 and _r_e_v_3 are (symbolic or numeric)
		revision numbers.  For the initial such pair,
		_r_e_v_1 denotes the revision selected by the options
		[1m-l[0m, ..., [1m-w[0m. For all other pairs, _r_e_v_1 denotes
		the revision generated by the previous pair.
		(Thus, the output of one join becomes the input
		to the next.)

		For each pair, _c_o joins revisions _r_e_v_1 and _r_e_v_3
		with respect to _r_e_v_2.  This means that all
		changes that transform _r_e_v_2 into _r_e_v_1 are applied
		to a copy of _r_e_v_3.  This is particularly useful
		if _r_e_v_1 and _r_e_v_3 are the ends of two branches
		that have _r_e_v_2 as a common ancestor. If _r_e_v_1 <
		_r_e_v_2 < _r_e_v_3 on the same branch, joining generates
		a new revision which is like _r_e_v_3, but with all
		changes that lead from _r_e_v_1 to _r_e_v_2 undone.  If
		changes from _r_e_v_2 to _r_e_v_1 overlap with changes
		from _r_e_v_2 to _r_e_v_3, _c_o prints a warning and
		includes the overlapping sections, delimited by
		the lines <<<<<<< _r_e_v_1, =======, and
		>>>>>>> _r_e_v_3.

		For the initial pair, _r_e_v_2 may be omitted. The
		default is the common ancestor.  If any of the
		arguments indicate branches, the latest revisions
		on those branches are assumed. If the option [1m-l
		[0mis present, the initial _r_e_v_1 is locked.

[1mKEYWORD SUBSTITUTION
     [0mStrings of the form $_k_e_y_w_o_r_d$ and $_k_e_y_w_o_r_d:...$ embedded in
     the text are replaced with strings of the form
     $_k_e_y_w_o_r_d: _v_a_l_u_e $, where _k_e_y_w_o_r_d and _v_a_l_u_e are pairs listed
     below.  Keywords may be embedded in literal strings or com-
     ments to identify a revision.

     Initially, the user enters strings of the form $_k_e_y_w_o_r_d$.
     On checkout, _c_o replaces these strings with strings of the
     form $_k_e_y_w_o_r_d: _v_a_l_u_e $. If a revision containing strings of



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     the latter form is checked back in, the value fields will be
     replaced during the next checkout.  Thus, the keyword values
     are automatically updated on checkout.

     Keywords and their corresponding values:

     $Author$	  The login name of the user who checked in the
		  revision.

     $Date$	  The date and time the revision was checked in.

     $Header$	  A standard header containing the RCS file name,
		  the revision number, the date, the author, and
		  the state.

     $Locker$	  The login name of the user who locked the revi-
		  sion (empty if not locked).

     $Log$	  The log message supplied during checkin, pre-
		  ceded by a header containing the RCS file name,
		  the revision number, the author, and the date.
		  Existing log messages are NOT replaced.
		  Instead, the new log message is inserted after
		  $_L_o_g:...$.  This is useful for accumulating a
		  complete change log in a source file.

     $Revision$   The revision number assigned to the revision.

     $Source$	  The full pathname of the RCS file.

     $State$	  The state assigned to the revision with _r_c_s -_s
		  or _c_i -_s.

[1mDIAGNOSTICS
     [0mThe RCS file name, the working file name, and the revision
     number retrieved are written to the diagnostic output.  The
     exit status always refers to the last file checked out, and
     is 0 if the operation was successful, 1 otherwise.

[1mEXAMPLES
     [0mSuppose the current directory contains a subdirectory `RCS'
     with an RCS file `io.c,v'. Then all of the following com-
     mands retrieve the latest revision from `RCS/io.c,v' and
     store it into `io.c'.

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

[1mFILE MODES
     [0mThe working file inherits the read and execute permissions
     from the RCS file. In addition, the owner write permission



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     is turned on, unless the file is checked out unlocked and
     locking is set to _s_t_r_i_c_t (see _r_c_s (1)).

     If a file with the name of the working file exists already
     and has write permission, _c_o aborts the checkout if [1m-q [0mis
     given, or asks whether to abort if [1m-q [0mis not given. If the
     existing working file is not writable, it is deleted before
     the checkout.

[1mFILES
     [0mThe caller of the command must have write permission in the
     working directory, read permission for the RCS file, and
     either read permission (for reading) or read/write permis-
     sion (for locking) in the directory which contains the RCS
     file.

     A number of temporary files are created.  A semaphore file
     is created in the directory of the RCS file to prevent
     simultaneous update.

[1mIDENTIFICATION
     [0mAuthor: Walter F. Tichy, Purdue University, West Lafayette,
     IN, 47907.
     Revision Number: 1.2 ; Release Date: 88/10/19 .
     Copyright (C) 1982 by Walter F. Tichy.

[1mSEE ALSO
     [0mci (1), ident(1), rcs (1), rcsdiff (1), rcsintro (1),
     rcsmerge (1), rlog (1), rcsfile (5), sccstorcs (8).
     Walter F. Tichy, "Design, Implementation, and Evaluation of
     a Revision Control System," in _P_r_o_c_e_e_d_i_n_g_s _o_f _t_h_e _6_t_h _I_n_t_e_r_-
     _n_a_t_i_o_n_a_l _C_o_n_f_e_r_e_n_c_e _o_n _S_o_f_t_w_a_r_e _E_n_g_i_n_e_e_r_i_n_g, IEEE, Tokyo,
     Sept. 1982.

[1mLIMITATIONS
     [0mThe option [1m-d [0mgets confused in some circumstances, and
     accepts no date before 1970.  There is no way to suppress
     the expansion of keywords, except by writing them dif-
     ferently. In nroff and troff, this is done by embedding the
     null-character `\&' into the keyword.

[1mBUGS
     [0mThe option [1m-j [0mdoes not work for files that contain lines
     with a single `.'.











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