grep

# grep
## 使用帮助
```shell
Usage: grep [OPTION]... PATTERN [FILE]...
Search for PATTERN in each FILE or standard input.
PATTERN is, by default, a basic regular expression (BRE).
Example: grep -i 'hello world' menu.h main.c

Regexp selection and interpretation: 正则表达式
  -E, --extended-regexp     PATTERN is an extended regular expression (ERE)/posix扩展正则表达式，实际并非BRE的扩展不完全兼容
  -F, --fixed-strings       PATTERN is a set of newline-separated fixed strings
  -G, --basic-regexp        PATTERN is a basic regular expression (BRE)/posix标准正则表达式
  -P, --perl-regexp         PATTERN is a Perl regular expression/比较强大的perl正则表达式
  -e, --regexp=PATTERN      use PATTERN for matching/正则表达式
  -f, --file=FILE           obtain PATTERN from FILE/从文件中读取正则表达式
  -i, --ignore-case         ignore case distinctions/忽略大小写
  -w, --word-regexp         force PATTERN to match only whole words/整词匹配
  -x, --line-regexp         force PATTERN to match only whole lines/整行匹配
  -z, --null-data           a data line ends in 0 byte, not newline/没太用明白，如果匹配到关键字所有内容都会输出，但是会高亮关键字，也许某些情况下可以用来高亮结果的输出。

Miscellaneous:
  -s, --no-messages         suppress error messages/关闭错误输出
  -v, --invert-match        select non-matching lines/输出不匹配关键字的行
  -V, --version             display version information and exit
      --help                display this help text and exit

Output control:
  -m, --max-count=NUM       stop after NUM matches/限制输出结果数，可以避免瀑布式输出
  -b, --byte-offset         print the byte offset with output lines/输出每一行的偏移量？没太理解作用
  -n, --line-number         print line number with output lines/输出匹配结果的行号
      --line-buffered       flush output on every line
  -H, --with-filename       print the file name for each match/在每个结果前增加文件名，目录递归查找时
  -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 containing no match
  -l, --files-with-matches  print only names of FILEs containing matches
  -c, --count               print only a count of matching 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
      --group-separator=SEP use SEP as a group separator
      --no-group-separator  use empty string as a group separator
      --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)
  -u, --unix-byte-offsets   report offsets as if CRs were not there
                            (MSDOS/Windows)

'egrep' means 'grep -E'.  'fgrep' means 'grep -F'.
Direct invocation as either 'egrep' or 'fgrep' is deprecated.
When FILE is -, read standard input.  With no FILE, read . if a command-line
-r is given, - otherwise.  If fewer than two FILEs are given, 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: bug-grep@gnu.org
GNU Grep home page: <http://www.gnu.org/software/grep/>
General help using GNU software: <http://www.gnu.org/gethelp/>
```

## 示例
### 输出文件中的IP地址
```
masscan -p22 10.20.0.0/24 -oX ip.xml
grep -ioP '((2(5[0-5]|[0-4]\d))|[0-1]?\d{1,2})(\.((2(5[0-5]|[0-4]\d))|[0-1]?\d{1,2})){3}' ip.xml
```