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Grep and delete lines except the lines with strings
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GREP(1) General Commands Manual GREP(1) NAME
grep, egrep, fgrep - search a file for a pattern SYNOPSIS
grep [ option ] ... expression [ file ] ... egrep [ option ] ... [ expression ] [ file ] ... fgrep [ option ] ... [ strings ] [ file ] DESCRIPTION
Commands of the grep family search the input files (standard input default) for lines matching a pattern. Normally, each line found is copied to the standard output; unless the -h flag is used, the file name is shown if there is more than one input file. Grep patterns are limited regular expressions in the style of ed(1); it uses a compact nondeterministic algorithm. Egrep patterns are full regular expressions; it uses a fast deterministic algorithm that sometimes needs exponential space. Fgrep patterns are fixed strings; it is fast and compact. The following options are recognized. -v All lines but those matching are printed. -c Only a count of matching lines is printed. -l The names of files with matching lines are listed (once) separated by newlines. -n Each line is preceded by its line number in the file. -b Each line is preceded by the block number on which it was found. This is sometimes useful in locating disk block numbers by con- text. -s No output is produced, only status. -h Do not print filename headers with output lines. -y Lower case letters in the pattern will also match upper case letters in the input (grep only). -e expression Same as a simple expression argument, but useful when the expression begins with a -. -f file The regular expression (egrep) or string list (fgrep) is taken from the file. -x (Exact) only lines matched in their entirety are printed (fgrep only). Care should be taken when using the characters $ * [ ^ | ? ' " ( ) and in the expression as they are also meaningful to the Shell. It is safest to enclose the entire expression argument in single quotes ' '. Fgrep searches for lines that contain one of the (newline-separated) strings. Egrep accepts extended regular expressions. In the following description `character' excludes newline: A followed by a single character matches that character. The character ^ ($) matches the beginning (end) of a line. A . matches any character. A single character not otherwise endowed with special meaning matches that character. A string enclosed in brackets [] matches any single character from the string. Ranges of ASCII character codes may be abbreviated as in `a-z0-9'. A ] may occur only as the first character of the string. A literal - must be placed where it can't be mistaken as a range indicator. A regular expression followed by * (+, ?) matches a sequence of 0 or more (1 or more, 0 or 1) matches of the regular expression. Two regular expressions concatenated match a match of the first followed by a match of the second. Two regular expressions separated by | or newline match either a match for the first or a match for the second. A regular expression enclosed in parentheses matches a match for the regular expression. The order of precedence of operators at the same parenthesis level is [] then *+? then concatenation then | and newline. SEE ALSO
ed(1), sed(1), sh(1) DIAGNOSTICS
Exit status is 0 if any matches are found, 1 if none, 2 for syntax errors or inaccessible files. BUGS
Ideally there should be only one grep, but we don't know a single algorithm that spans a wide enough range of space-time tradeoffs. Lines are limited to 256 characters; longer lines are truncated. GREP(1)
