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.