查找需求，grep是一个很好的命令，现针对grep 的使用方法，总结如下。
一、grep help 命令
grep --help 可以查看详细的说明文档。
Usage: grep [OPTION]... PATTERN [FILE]...
Search for PATTERN in each FILE.
Example: grep -i 'hello world' menu.h main.c
grep --help
Usage: grep [OPTION]... PATTERN [FILE]...
Search for PATTERN in each FILE.
Example: grep -i 'hello world' menu.h main.c
Pattern selection and interpretation:
-E, --extended-regexp PATTERN is an extended regular expression
-F, --fixed-strings PATTERN is a set of newline-separated strings
-G, --basic-regexp PATTERN is a basic regular expression (default)
-P, --perl-regexp PATTERN is a Perl regular expression
-e, --regexp=PATTERN use PATTERN for matching
-f, --file=FILE obtain PATTERN from FILE
-i, --ignore-case ignore case distinctions
-w, --word-regexp force PATTERN to match only whole words
-x, --line-regexp force PATTERN to match only whole lines
-z, --null-data a data line ends in 0 byte, not newline
Miscellaneous:
-s, --no-messages suppress error messages
-v, --invert-match select non-matching lines
-V, --version display version information and exit
--help display this help text and exit
Output control:
-m, --max-count=NUM stop after NUM selected lines
-b, --byte-offset print the byte offset with output lines
-n, --line-number print line number with output lines
--line-buffered flush output on every line
-H, --with-filename print file name with output lines
-h, --no-filename suppress the file name prefix on output
--label=LABEL use LABEL as the standard input file name prefix
-o, --only-matching show only the part of a line matching PATTERN
-q, --quiet, --silent suppress all normal output
--binary-files=TYPE assume that binary files are TYPE;
TYPE is 'binary', 'text', or 'without-match'
-a, --text equivalent to --binary-files=text
-I equivalent to --binary-files=without-match
-d, --directories=ACTION how to handle directories;
ACTION is 'read', 'recurse', or 'skip'
-D, --devices=ACTION how to handle devices, FIFOs and sockets;
ACTION is 'read' or 'skip'
-r, --recursive like --directories=recurse
-R, --dereference-recursive likewise, but follow all symlinks
--include=FILE_PATTERN search only files that match FILE_PATTERN
--exclude=FILE_PATTERN skip files and directories matching FILE_PATTERN
--exclude-from=FILE skip files matching any file pattern from FILE
--exclude-dir=PATTERN directories that match PATTERN will be skipped.
-L, --files-without-match print only names of FILEs with no selected lines
-l, --files-with-matches print only names of FILEs with selected lines
-c, --count print only a count of selected lines per FILE
-T, --initial-tab make tabs line up (if needed)
-Z, --null print 0 byte after FILE name
Context control:
-B, --before-context=NUM print NUM lines of leading context
-A, --after-context=NUM print NUM lines of trailing context
-C, --context=NUM print NUM lines of output context
-NUM same as --context=NUM
--color[=WHEN],
--colour[=WHEN] use markers to highlight the matching strings;
WHEN is 'always', 'never', or 'auto'
-U, --binary do not strip CR characters at EOL (MSDOS/Windows)
When FILE is '-', read standard input. With no FILE, read '.' if
recursive, '-' otherwise. With fewer than two FILEs, assume -h.
Exit status is 0 if any line is selected, 1 otherwise;
if any error occurs and -q is not given, the exit status is 2.
Report bugs to: [email protected]
GNU grep home page: <http://www.gnu.org/software/grep/>
General help using GNU software: <http://www.gnu.org/gethelp/>针对上述help 文件，不一一进行说明了，只针对常用的option 举例。
二、经常使用的option
（一）.在特定目录或者特定文件搜索某个string,比如搜索"def"这个string.
1.如果文件不是很多，可以直接使用
grep -nr "def" .
grep -nr def .
./test_dir/test.txt:2:def
./test.c:2:def
./test.txt:2:def
./include/test.py:2:def
./include/test.txt:2:def
./.git/test.git:1:abdc cef def2.如果是文件较多，搜索比较慢，这个时候就需要配合一些option 进行了。
ls -al
total 28
drwxrwxr-x 5 xa00084 xa00084 4096 Sep 29 11:11 .
drwxr-xr-x 4 xa00084 xa00084 4096 Sep 29 10:57 ..
drwxrwxr-x 2 xa00084 xa00084 4096 Sep 29 11:12 .git
drwxr-xr-x 2 xa00084 xa00084 4096 Sep 29 11:11 include
-rwxr--r-- 1 xa00084 xa00084 8 Sep 29 10:58 test.c
drwxr-xr-x 2 xa00084 xa00084 4096 Sep 29 11:11 test_dir
-rwxr--r-- 1 xa00084 xa00084 34 Sep 29 11:02 test.txt比如，有上面的目录结构，我们需要排除.git 和 test_dir 这2个目录，
带有特殊符合比如. 的目录名字，需要用“” 。其他可以使用“”也可以不使用“”。
grep -nr "def" . --exclude-dir=".git" --exclude-dir=test_dir
./test.c:2:def
./test.txt:2:def
./include/test.py:2:def
./include/test.txt:2:def3.排除某些文件类型
grep -nr "def" . --exclude="*.git" --exclude="*.py"
./test_dir/test.txt:2:def
./test.c:2:def
./test.txt:2:def
./include/test.txt:2:def4.只包含某一类文件
grep -nr "def" . --include="*.c" --include=*.txt
./test_dir/test.txt:2:def
./test.c:2:def
./test.txt:2:def
./include/test.txt:2:def暂是更新到这里，后续再继续更新。