grep, egrep, fgrep(Global Regular Expression Print) - print lines matching a pattern
SYNOPSIS
grep [OPTIONS] PATTERN [FILE...]
grep [OPTIONS] [-e PATTERN | -f FILE] [FILE...]
Help
# grep --help
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:
-E, --extended-regexp PATTERN is an extended regular expression (ERE)
-F, --fixed-strings PATTERN is a set of newline-separated fixed strings
-G, --basic-regexp PATTERN is a basic regular expression (BRE)
-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 matches
-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 the file name for each match
-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/>
正则
^ 锚定行的开始 如：’^grep’匹配所有以grep开头的行。$ 锚定行的结束 如：‘grep$‘匹配所有以grep结尾的行。. 匹配一个非换行符的字符 如：‘gr.p’匹配gr后接一个任意字符，然后是p。* 匹配零个或多个先前字符 如：’*grep’匹配所有一个或多个空格后紧跟grep的行。.* 一起用代表任意字符。[] 匹配一个指定范围内的字符，如’[Gg]rep’匹配Grep和grep。[^] 匹配一个不在指定范围内的字符，如：’[^A-FH-Z]rep’匹配不包含A-R和T-Z的一个字母开头，紧跟rep的行。\(..\) 标记匹配字符，如’(love)’，love被标记为1。\< 锚定单词的开始，如:’<grep’匹配包含以grep开头的单词的行。\> 锚定单词的结束，如’grep>‘匹配包含以grep结尾的单词的行。x\{m\} 重复字符x，m次，如：‘0{5}‘匹配包含5个o的行。x\{m,\} 重复字符x,至少m次，如：‘o{5,}‘匹配至少有5个o的行。x\{m,n\} 重复字符x，至少m次，不多于n次，如：‘o{5,10}‘匹配5–10个o的行。\w 匹配文字和数字字符，也就是[A-Za-z0-9]，如：‘G\w*p’匹配以G后跟零个或多个文字或数字字符，然后是p。\W \w的反置形式，匹配一个或多个非单词字符，如点号句号等。\b 单词锁定符，如: ‘\bgrep\b’只匹配grep。
示例
# 匹配多个 OR 的关系，`\|` 必须转义
grep 'pattern1\|pattern2' file...
# -E | 不用转义
grep -E 'pattern1|pattern2' file...
# 忽略大小写
grep -i 'fatal\|error\|critical' /var/log/nginx/error.log
# 排除字符
grep -v 'fatal\|error\|critical' /var/log/nginx/error.log
# 查看 OpenStack 配置文件
grep '^[^#]' /etc/nova/nova.conf
grep '^[a-z]' /etc/filebeat/filebeat.yml
grep ERROR -rn *
示例
grep "^#" /etc/denyhosts.conf # 输出以#开头的行内容
grep "^[^#]" /etc/denyhosts.conf # 输出非#开头的行内容
说明
# 打印匹配行的前后10行
$ grep -10 'error' nova.log
或
$ grep -C 10 'error' nova.log
或
$ grep -A 10 -B 10 'error' nova.log
# 打印匹配行的后10行
$ grep -A 10 'error' nova.log
# 打印匹配行的前10行
$ grep -B 10 'error' nova.log
$ grep "被查找的字符串" 文件名
例子：在当前目录里第一级文件夹中寻找包含指定字符串的.in文件
grep "something" */*.in
$ grep –e "正则表达式" 文件名
$ grep –i "被查找的字符串" 文件名
$ grep -c "被查找的字符串" 文件名
$ grep –v "被查找的字符串" 文件名
- 从根目录开始查找所有扩展名为.log的文本文件，并找出包含"ERROR"的行
find / -type f -name "*.log" | xargs grep "ERROR"
- 从当前目录开始查找所有扩展名为.in的文本文件，并找出包含"something"的行
find . -name "*.in" | xargs grep "something"
pgrep
pgrep 是一个命令行工具，用来按照给定的条件查找正在运行的程序的进程ID，它是 procps（或者 procps-ng ）软件包的一部分，示例
pgrep sshd