Tutorail: www.digitalocean.com/community/t…
Man page: man7.org/linux/man-p…
GNU Grep: www.gnu.org/software/gr…
man grep
grep "reg" filename
-r/-R 未指定文件时，递归的搜索指定文件夹下的所有文件
-r, --recursive
Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option.
-R, --dereference-recursive
Read all files under each directory, recursively. Follow all symbolic links, unlike -r.
-i 不区分大小写
-i, --ignore-case
gnore case distinctions in patterns and input data, so that characters that differ only in case match each other.
-c 计算匹配的行数
-c, --count
Suppress normal output; instead print a count of **matching lines** for each input file. With the -v, --invert-match option
(see above), count non-matching lines.
-v 打印不匹配的行(invert)
-v, --invert-match
Invert the sense of matching, to select non-matching lines.
-n 打印行号
-n, --line-number
Prefix each line of output with the 1-based line number within its input file.
-w 精准匹配单词
-w, --word-regexp
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. This option has no effect if -x is also specified.
-A/-B/-C 打印上下文
-A NUM, --after-context=NUM
Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between
contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given.
-B NUM, --before-context=NUM
Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between
contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given.
-C NUM, -NUM, --context=NUM
Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches.
With the -o or --only-matching option, this has no effect and a warning is given.
Regular Expressions
-E, --extended-regexp
Interpret PATTERNS as extended regular expressions (EREs, see below).
-F, --fixed-strings
Interpret PATTERNS as fixed strings, not regular expressions.
-G, --basic-regexp
Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default.
-P, --perl-regexp
Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features.
Extended Regular Expressions
- grouping
- alternation
