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diff --git a/gnu/usr.bin/grep/grep.1 b/gnu/usr.bin/grep/grep.1 new file mode 100644 index 0000000..6f5c48a --- /dev/null +++ b/gnu/usr.bin/grep/grep.1 @@ -0,0 +1,410 @@ +.TH GREP 1 "1992 September 10" "GNU Project" +.SH NAME +grep, egrep, fgrep, zgrep \- print lines matching a pattern +.SH SYNOPSIS +.B grep +[\-[AB] num] +[\-HRPS] +[\-CEFGLVabchilnqsvwx] +[\-e expr] +[\-f file] +files... + +.SH DESCRIPTION +.PP +.B Grep +searches the named input +.I files +(or standard input if no files are named, or +the file name +.B \- +is given) +for lines containing a match to the given +.IR pattern . +By default, +.B grep +prints the matching lines. +.PP +There are three major variants of +.BR grep , +controlled by the following options. +.PD 0 +.TP +.B \-G +Interpret +.I pattern +as a basic regular expression (see below). This is the default. +.TP +.B \-E +Interpret +.I pattern +as an extended regular expression (see below). +.TP +.B \-F +Interpret +.I pattern +as a list of fixed strings, separated by newlines, +any of which is to be matched. +.LP +In addition, two variant programs +.B egrep +and +.B fgrep +are available. +.B Egrep +is similar (but not identical) to +.BR "grep\ \-E" , +and is compatible with the historical Unix +.BR egrep . +.B Fgrep +is the same as +.BR "grep\ \-F" . +When called as +.BR zgrep , +the +.BR \-Z +option is assumed. +.PD +.LP +All variants of +.B grep +understand the following options: +.PD 0 +.TP +.BI \- num +Matches will be printed with +.I num +lines of leading and trailing context. However, +.B grep +will never print any given line more than once. +.TP +.BI \-A " num" +Print +.I num +lines of trailing context after matching lines. +.TP +.BI \-B " num" +Print +.I num +lines of leading context before matching lines. +.TP +.B \-C +Equivalent to +.BR \-2 . +.TP +.B \-V +Print the version number of +.B grep +to standard error. This version number should +be included in all bug reports (see below). +.TP +.B \-a +Don't search in binary files. +.TP +.B \-b +Print the byte offset within the input file before +each line of output. +.TP +.B \-c +Suppress normal output; instead print a count of +matching lines for each input file. +With the +.B \-v +option (see below), count non-matching lines. +.TP +.BI \-e " pattern" +Use +.I pattern +as the pattern; useful to protect patterns beginning with +.BR \- . +.TP +.BI \-f " file" +Obtain the pattern from +.IR file . +.TP +.B \-h +Suppress the prefixing of filenames on output +when multiple files are searched. +.TP +.B \-i +Ignore case distinctions in both the +.I pattern +and the input files. +.TP +.B \-L +Suppress normal output; instead print the name +of each input file from which no output would +normally have been printed. +.TP +.B \-l +Suppress normal output; instead print +the name of each input file from which output +would normally have been printed. +.TP +.B \-n +Prefix each line of output with the line number +within its input file. +.TP +.B \-q +Quiet; suppress normal output. +.TP +.B \-s +Suppress error messages about nonexistent or unreadable files. +.TP +.B \-v +Invert the sense of matching, to select non-matching lines. +.TP +.B \-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. +.TP +.B \-x +Select only those matches that exactly match the whole line. + +.PP +Following options are only available if compiled with FTS library: +.PD 0 +.TP +.BI \-H +If the +.I \-R +option is specified, symbolic links on the command line +are followed. (Symbolic links encountered in the tree traversal +are not followed.) +.TP +.BI \-L +If the +.I \-R +option is specified, all symbolic links are followed. +.TP +.BI \-P +If the +.I \-R +option is specified, no symbolic links are followed. +.TP +.BI \-R +Search in the file hierarchies +rooted in the files instead of just the files themselves. + +.LP +Following option is only available if compiled with zlib library: +.PD 0 +.TP +.BI \-Z +If the +.I \-Z +option is specified, the input data will be +decompressed before searching. +.TP +.PD +.SH "REGULAR EXPRESSIONS" +.PP +A regular expression is a pattern that describes a set of strings. +Regular expressions are constructed analogously to arithmetic +expressions, by using various operators to combine smaller expressions. +.PP +.B Grep +understands two different versions of regular expression syntax: +``basic'' and ``extended.'' In +.RB "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. +.PP +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. +.PP +A list of characters enclosed by +.B [ +and +.B ] +matches any single +character in that list; if the first character of the list +is the caret +.B ^ +then it matches any character +.I not +in the list. +For example, the regular expression +.B [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 +.BR [:alnum:] , +.BR [:alpha:] , +.BR [:cntrl:] , +.BR [:digit:] , +.BR [:graph:] , +.BR [:lower:] , +.BR [:print:] , +.BR [:punct:] , +.BR [:space:] , +.BR [:upper:] , +and +.BR [:xdigit:]. +For example, +.B [[:alnum:]] +means +.BR [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 +.B ] +place it first in the list. Similarly, to include a literal +.B ^ +place it anywhere but first. Finally, to include a literal +.B \- +place it last. +.PP +The period +.B . +matches any single character. +The symbol +.B \ew +is a synonym for +.B [[:alnum:]] +and +.B \eW +is a synonym for +.BR [^[:alnum]] . +.PP +The caret +.B ^ +and the dollar sign +.B $ +are metacharacters that respectively match the empty string at the +beginning and end of a line. +The symbols +.B \e< +and +.B \e> +respectively match the empty string at the beginning and end of a word. +The symbol +.B \eb +matches the empty string at the edge of a word, +and +.B \eB +matches the empty string provided it's +.I not +at the edge of a word. +.PP +A regular expression matching a single character may be followed +by one of several repetition operators: +.PD 0 +.TP +.B ? +The preceding item is optional and matched at most once. +.TP +.B * +The preceding item will be matched zero or more times. +.TP +.B + +The preceding item will be matched one or more times. +.TP +.BI { n } +The preceding item is matched exactly +.I n +times. +.TP +.BI { n ,} +The preceding item is matched +.I n +or more times. +.TP +.BI {, m } +The preceding item is optional and is matched at most +.I m +times. +.TP +.BI { n , m } +The preceding item is matched at least +.I n +times, but not more than +.I m +times. +.PD +.PP +Two regular expressions may be concatenated; the resulting +regular expression matches any string formed by concatenating +two substrings that respectively match the concatenated +subexpressions. +.PP +Two regular expressions may be joined by the infix operator +.BR | ; +the resulting regular expression matches any string matching +either subexpression. +.PP +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. +.PP +The backreference +.BI \e n\c +\&, where +.I n +is a single digit, matches the substring +previously matched by the +.IR n th +parenthesized subexpression of the regular expression. +.PP +In basic regular expressions the metacharacters +.BR ? , +.BR + , +.BR { , +.BR | , +.BR ( , +and +.BR ) +lose their special meaning; instead use the backslashed +versions +.BR \e? , +.BR \e+ , +.BR \e{ , +.BR \e| , +.BR \e( , +and +.BR \e) . +.PP +In +.B egrep +the metacharacter +.B { +loses its special meaning; instead use +.BR \e{ . +.SH DIAGNOSTICS +.PP +Normally, exit status is 0 if matches were found, +and 1 if no matches were found. (The +.B \-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. +.SH BUGS +.PP +Email bug reports to +.BR bug-gnu-utils@prep.ai.mit.edu . +Be sure to include the word ``grep'' somewhere in the ``Subject:'' field. +.PP +Large repetition counts in the +.BI { m , n } +construct may cause grep to use lots of memory. +In addition, +certain other obscure regular expressions require exponential time +and space, and may cause +.B grep +to run out of memory. +.PP +Backreferences are very slow, and may require exponential time. |
