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vfgrep

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.