This command is obsolete and will be removed in the next release.
The vc command copies lines from the standard input to the standard output under control of its arguments and of ''control statements'' encountered in the standard input.
In the
process of performing the copy operation, user-declared keywords may be replaced by their string value when they appear in plain text and/or control
statements.
The copying of lines from the standard input to the standard output is conditional, based on tests (in control statements) of keyword values specified in control statements or as vc
command arguments.
A control statement is a single line beginning with a control character, except as modified by the -t keyletter (see below).
The default control character is colon (:),
except as modified by the -c keyletter (see below).
Input lines beginning with a backslash (\) followed by a control character are not control lines and are copied
to the standard output with the backslash removed.
Lines beginning with a backslash followed by a non-control character are copied in their entirety.
A keyword is composed of alphanumerics; the first must be alphabetic.
A value is any ASCII string that can be created with ed; a numeric
value is an unsigned string of digits.
Keyword values may not contain blanks or tabs.
Replacement of keywords by values is done whenever a keyword surrounded by control characters is encountered on a version control statement.
The -a keyletter (see below) forces replacement
of keywords in all lines of text.
An uninterpreted control character may be included in a value by preceding it with \.
If a literal \ is desired, then it
too must be preceded by \.
The following options are supported:
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-a
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Forces replacement of keywords surrounded by control characters with their assigned value in
all text lines and not just in vc statements.
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-t
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All characters from the beginning of a line up to and including the first tab character are ignored for the purpose of detecting a control statement.
If a control statement is found, all characters up to and including the tab are discarded.
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-cchar
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Specifies a control character to be used in place of the '':'' default.
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-s
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Silences warning messages (not error) that are normally printed on the diagnostic output.
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vc recognizes the following version control statements:
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:dcl keyword[, ..., keyword]
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Declare keywords.
All keywords must be declared.
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:asg keyword=value
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Assign values to keywords.
An asg
statement overrides the assignment for the corresponding keyword on the vc command line and all previous asg statements for that keyword.
Keywords that are declared
but are not assigned values have null values.
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:if condition
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...
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:end
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Skip lines of the standard input.
If the condition is true, all lines between the if statement and the matching end statement are copied to the standard output.
If the condition is false, all intervening
lines are discarded, including control statements.
Note: Intervening if statements and matching end statements are recognized solely for the purpose of maintaining
the proper if-end matching.
The syntax of a condition is:
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<cond>
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::= [ ''not'' ] <or>
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<or>
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::= <and> | <and> ''|'' <or>
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<and>
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::= <exp> | <exp> ''&'' <and>
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<exp>
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::= ''('' <or> '')'' | <value> <op> <value>
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<op>
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::= ''='' | ''!='' | ''<'' | ''>''
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<value>
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::= <arbitrary ASCII string> | <numeric string>
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The available operators and their meanings are:
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=
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equal
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!=
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not equal
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&
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and
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or
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>
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greater than
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<
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less than
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()
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used for logical groupings
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not
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may only occur immediately after the if, and when present, inverts the value of the entire condition
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The > and < operate only on unsigned integer values (for example, : 012 > 12 is false).
All other operators take strings as arguments (for
example, : 012 != 12 is true).
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The precedence of the operators (from highest to lowest) is:
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= != > <
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all of equal precedence
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&
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Parentheses may be used to alter the order of precedence.
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Values must be separated from operators or parentheses by at least one blank or tab.
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::text
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Replace keywords on lines that are copied to the standard output.
The two leading control characters are removed,
and keywords surrounded by control characters in text are replaced by their value before the line is copied to the output file.
This action is independent of the -a keyletter.
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:on
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:off
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Turn on or off keyword replacement on all lines.
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:ctl char
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Change the control character to char.
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:msg message
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Print message on the diagnostic output.
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:err message
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Print message followed by:
ERROR: err statement on line ... (915)
on the diagnostic output.
vc halts execution, and returns an exit code of 1.
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