NAME [Toc] [Back]
co - check out RCS revisions
SYNOPSIS [Toc] [Back]
co [options] file ...
DESCRIPTION [Toc] [Back]
co retrieves revisions from RCS files. Each file name ending in ,v is
taken to be an RCS file. All other files are assumed to be working
files. co retrieves a revision from each RCS file and stores it in
the corresponding working file (see also rcsintro(5)).
Revisions of an RCS file can be checked out locked or unlocked.
Locking a revision prevents overlapping updates. A revision checked
out for reading or processing (e.g., compiling) need not be locked. A
revision checked out for editing and later checked in must normally be
locked. Locking a revision currently locked by another user fails (a
lock can be broken with the rcs command, but poses inherent risks when
independent changes are being made simultaneously (see rcs(1)). co
with locking requires the caller to be on the access list of the RCS
file unless: he is the owner of the file, a user with appropriate
privileges, or the access list is empty. co without locking is not
subject to access list restrictions.
A revision is selected by number, check-in 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, author, and state retrieve a revision on the
selected branch. The selected branch is either derived from the
revision number (if given), or is the highest branch on the trunk. A
revision number can be attached to the options -l, -p, -q, or -r.
The 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 permission (for locking) in the
directory that contains the RCS file.
The working file inherits the read and execute permissions from the
RCS file. In addition, the owner write permission is turned on,
unless the file is checked out unlocked and locking is set to strict
If a file with the name of the working file exists already and has
write permission, co aborts the check out if -q is given, or asks
whether to abort if -q is not given. If the existing working file is
not writable, it is deleted before the check out.
A number of temporary files are created. A semaphore file is created
in the directory of the RCS file to prevent simultaneous update.
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A co command applied to an RCS file with no revisions creates a zerolength
file. co always performs keyword substitution (see below).
Options [Toc] [Back]
-l[rev] Locks the checked out revision for the caller. If
omitted, the checked out revision is not locked. See
option -r for handling of the revision number rev.
-p[rev] Prints the retrieved revision on the standard output
rather than storing it in the working file. This
option is useful when co is part of a pipe.
-q[rev] Quiet mode; diagnostics are not printed.
-ddate Retrieves the latest revision on the selected branch
whose check in date/time is less than or equal to date.
The date and time may be given in free format and are
converted to local time. Examples of formats for date:
Tue-PDT, 1981, 4pm Jul 21 (free format)
Fri April 16 15:52:25 EST 1982 (output of ctime(3C))
4/21/86 10:30am (format: mm/dd/yy hh:mm:ss)
Most fields in the date and time can be defaulted. co
determines the defaults in the order year, month, day,
hour, minute, and second (from most- to leastsignificant).
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. Date/time
fields can be delimited by spaces or commas. If spaces
are used, the string must be surrounded by double
For 2-digit year input (yy) without the presence of the
century field, the following interpretation is taken:
[70-99, 00-69 (1970-1999, 2000-2069)].
-r[rev] Retrieves the latest revision whose number is less than
or equal to rev. If rev indicates a branch rather than
a revision, the latest revision on that branch is
retrieved. rev is composed of one or more numeric or
symbolic fields separated by .. The numeric equivalent
of a symbolic field is specified with the ci -n and rcs
-n commands (see ci(1) and rcs(1)).
-sstate Retrieves the latest revision on the selected branch
whose state is set to state.
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-w[login] Retrieves the latest revision on the selected branch
that was checked in by the user with login name login.
If the argument login is omitted, the caller's login is
-jjoinlist Generates a new revision that is the result of the
joining of the revisions on joinlist. joinlist is a
comma-separated list of pairs of the form rev2:rev3,
where rev2 and rev3 are (symbolic or numeric) revision
numbers. For the initial pair, rev1 denotes the
revision selected by the options -l, ..., -w. For all
other pairs, rev1 denotes the revision generated by the
previous pair. (Thus, the output of one join becomes
the input to the next.)
For each pair, co joins revisions rev1 and rev3 with
respect to rev2. This means that all changes that
transform rev2 into rev1 are applied to a copy of rev3.
This is particularly useful if rev1 and rev3 are the
ends of two branches that have rev2 as a common
ancestor. If rev1 < rev2 < rev3 on the same branch,
joining generates a new revision that is similar to
rev3, but with all changes that lead from rev1 to rev2
undone. If changes from rev2 to rev1 overlap with
changes from rev2 to rev3, co prints a warning and
includes the overlapping sections, delimited as
For the initial pair, rev2 can 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 -l option is present, the
initial rev1 is locked.
Keyword Substitution [Toc] [Back]
Strings of the form $keyword$ and $keyword:...$ embedded in the text
are replaced with strings of the form $keyword: value $, where keyword
and value are pairs listed below. Keywords may be embedded in literal
strings or comments to identify a revision.
Initially, the user enters strings of the form $keyword$. On check
out, co replaces these strings with strings of the form
$keyword: value $. If a revision containing strings of the latter
form is checked back in, the value fields are replaced during the next
checkout. Thus, the keyword values are automatically updated on
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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 revision
(empty if not locked).
$Log$ The log message supplied during checkin, preceded 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 $Log:...$. This is useful
for accumulating a complete change log in a source
$Revision$ The revision number assigned to the revision.
$Source$ The full pathname of the RCS file.
$State$ The state assigned to the revision with rcs -s or ci
Access Control Lists (ACLs) [Toc] [Back]
Optional ACL entries should not be added to RCS files because they
might be deleted.
DIAGNOSTICS [Toc] [Back]
The 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 if unsuccessful.
EXAMPLES [Toc] [Back]
Assume the current directory contains a subdirectory named RCS with an
RCS file named io.c,v. Each of the following commands retrieves the
latest revision from RCS/io.c,v and stores it into io.c:
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
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Check out version 1.1 of RCS file foo.c,v:
co -r1.1 foo.c,v
Check out version 1.1 of RCS file foo.c,v to the standard output:
co -p1.1 foo.c,v
Check out the version of file foo.c,v that existed on September 18,
co -d"09/18/92" foo.c,v
WARNINGS [Toc] [Back]
The co command generates the working file name by removing the ,v from
the end of the RCS file name. If the given RCS file name is too long
for the file system on which the RCS file should reside, co terminates
with an error message.
There is no way to suppress the expansion of keywords, except by
writing them differently. In nroff and troff, this is done by
embedding the null-character \& into the keyword.
The -d option gets confused in some circumstances, and accepts no date
The -j option does not work for files containing lines consisting of a
RCS is designed to be used with text files only. Attempting to use
RCS with non-text (binary) files results in data corruption.
AUTHOR [Toc] [Back]
co was developed by Walter F. Tichy.
SEE ALSO [Toc] [Back]
ci(1), ident(1), rcs(1), rcsdiff(1), rcsmerge(1), rlog(1), rcsfile(4),
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