NAME
vgrep, vegrep, vfgrep - print lines matching a pattern
SYNOPOSIS
vgrep [ vbind-options ] [ -[[AB] ]num ] [ -[CEFGVBchilnsvwx] ] [ -e ]
pattern | -ffile ] [ names... ]
DESCRIPTION
Vgrep is GNU grep with a patch to access AtFS version objects. Vgrep
searches the files and AtFS version objects listed in the arguments (or
standard input if no names are given, or the name - is given) for lines
containing a match to the given pattern. By default, vgrep prints the
matching lines.
There are three major variants of vgrep, controlled by the following
options.
-G Interpret pattern as a basic regular expression (see below).
This is the default.
-E Interpret pattern as an extended regular expression (see below).
-F Interpret pattern as a list of fixed strings, separated by
newlines, any of which is to be matched.
In addition, two variant programs vegrep and vfgrep are available.
Vegrep is similar (but not identical) to vgrep -E, and is compatible
with the historical Unix egrep. Vfgrep is the same as vgrep -F.
Vgrep understands the standard version binding options of the Shape
toolkit. The names on the command line are replaced by the appropriate
version IDs of the selected version object.
The vbind-options are shapeTools’ standard options for version binding.
A description of these options can be found in the manual page of
vbind(1).
All variants of vgrep understand the following options:
-num Matches will be printed with num lines of leading and trailing
context. However, vgrep will never print any given line more
than once.
-A num Print num lines of trailing context after matching lines.
-B num Print num lines of leading context before matching lines.
-C Equivalent to -2.
-V Print the version number of vgrep to standard error. This
version number should be included in all bug reports (see
below).
-b Print the byte offset within the input file before each line of
output.
-c Suppress normal output; instead print a count of matching lines
for each input file. With the -v option (see below), count non-
matching lines.
-e pattern
Use pattern as the pattern; useful to protect patterns beginning
with -.
-f file
Obtain the pattern from file.
-h Suppress the prefixing of filenames on output when multiple
files are searched.
-i Ignore case distinctions in both the pattern and the input
files.
-L Suppress normal output; instead print the name of each input
file from which no output would normally have been printed.
-l Suppress normal output; instead print the name of each input
file from which output would normally have been printed.
-n Prefix each line of output with the line number within its input
file.
-q Quiet; suppress normal output.
-s Suppress error messages about nonexistent or unreadable files.
-v Invert the sense of matching, to select non-matching lines.
-w Select only those lines containing matches that form whole
words. The test is that the matching substring must either be
at the beginning of the line, or preceded by a non-word
constituent character. Similarly, it must be either at the end
of the line or followed by a non-word constituent character.
Word-constituent characters are letters, digits, and the
underscore.
-x Select only those matches that exactly match the whole line.
REGULAR EXPRESSIONS
A regular expression is a pattern that describes a set of strings.
Regular expressions are constructed analagously to arithmetic
expressions, by using various operators to combine smaller expressions.
Vgrep understands two different versions of regular expression syntax:
‘‘basic’’ and ‘‘extended.’’ In GNU grep, there is no difference in
available functionality using either syntax. In other implementations,
basic regular expressions are less powerful. The following description
applies to extended regular expressions; differences for basic regular
expressions are summarized afterwards.
The fundamental building blocks are the regular expressions that match
a single character. Most characters, including all letters and digits,
are regular expressions that match themselves. Any metacharacter with
special meaning may be quoted by preceding it with a backslash.
A list of characters enclosed by [ and ] matches any single character
in that list; if the first character of the list is the caret ^ then it
matches any character not in the list. For example, the regular
expression [0123456789] matches any single digit. A range of ASCII
characters may be specified by giving the first and last characters,
separated by a hyphen. Finally, certain named classes of characters
are predefined. Their names are self explanatory, and they are
[:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:], [:lower:],
[:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For
example, [[:alnum:]] means [0-9A-Za-z], except the latter form is
dependent upon the ASCII character encoding, whereas the former is
portable. (Note that the brackets in these class names are part of the
symbolic names, and must be included in addition to the brackets
delimiting the bracket list.) Most metacharacters lose their special
meaning inside lists. To include a literal ] place it first in the
list. Similarly, to include a literal ^ place it anywhere but first.
Finally, to include a literal - place it last.
The period . matches any single character. The symbol \w is a synonym
for [[:alnum:]] and \W is a synonym for [^[:alnum]].
The caret ^ and the dollar sign $ are metacharacters that respectively
match the empty string at the beginning and end of a line. The symbols
\< and \> respectively match the empty string at the beginning and end
of a word. The symbol \b matches the empty string at the edge of a
word, and \B matches the empty string provided it’s not at the edge of
a word.
A regular expression matching a single character may be followed by one
of several repetition operators:
? The preceding item is optional and matched at most once.
* The preceding item will be matched zero or more times.
+ The preceding item will be matched one or more times.
{n} The preceding item is matched exactly n times.
{n,} The preceding item is matched n or more times.
{,m} The preceding item is optional and is matched at most m times.
{n,m} The preceding item is matched at least n times, but not more
than m times.
Two regular expressions may be concatenated; the resulting regular
expression matches any string formed by concatenating two substrings
that respectively match the concatenated subexpressions.
Two regular expressions may be joined by the infix operator |; the
resulting regular expression matches any string matching either
subexpression.
Repetition takes precedence over concatenation, which in turn takes
precedence over alternation. A whole subexpression may be enclosed in
parentheses to override these precedence rules.
The backreference \n, where n is a single digit, matches the substring
previously matched by the nth parenthesized subexpression of the
regular expression.
In basic regular expressions the metacharacters ?, +, {, |, (, and )
lose their special meaning; instead use the backslashed versions \?,
\+, \{, \|, \(, and \).
In vegrep the metacharacter { loses its special meaning; instead use
\{.
DIAGNOSTICS
Normally, exit status is 0 if matches were found, and 1 if no matches
were found. (The -v option inverts the sense of the exit status.)
Exit status is 2 if there were syntax errors in the pattern,
inaccessible input files, or other system errors.
EXAMPLES
Grep for ‘‘foo’’ in version 1.43 of smile.c:
vgrep foo smile.c[1.43]
Grep for ‘‘foo’’ in the last version of smile.c (last saved version or
busy file, if available):
vgrep -last foo smile.c
Grep for ‘‘foo’’ in all versions of C files that have been created
since February 14 1993:
vgrep -since 14.2.93 foo \∗.c
Grep for ‘‘foo’’ in all versions carrying the symbolic name
‘‘Release-2.3’’:
vgrep foo \∗[Release-2.3]
SEE ALSO
emacs(1), ed(1), sh(1), vbind(1), atread(3), GNU Emacs Manual
BUGS
Email bug reports to bug-gnu-utils@prep.ai.mit.edu. Be sure to include
the word ‘‘grep’’ somewhere in the ‘‘Subject:’’ field.
Large repetition counts in the {m,n} construct may cause vgrep to use
lots of memory. In addition, certain other obscure regular expressions
require exponential time and space, and may cause vgrep to run out of
memory.
Backreferences are very slow, and may require exponential time.