Linux命令详解之 grep
linux 命令详解## 命令名称：grep（global search regular express and print out line）打印匹配的行（内容）类似的命令包括egrep、fgrep、rgrep## 命令用法：grep [选项] 匹配项[PATTERN...][]表示可选参数grep [选项[ [-e 匹配项]... [-f PATTERN]... [FILE...]PATTER
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linux 命令详解
本文主要内容来自Linux man 手册
命令名称：
grep（global search regular express and print out line）打印匹配的行（内容）
类似的命令包括egrep、fgrep、rgrep
命令用法：
grep [选项] 匹配项[PATTERN...] []表示可选参数
grep [选项[ [-e 匹配项]... [-f PATTERN]... [FILE...] PATTERN为正则表达式
命令概述：
grep在指定的文件中搜索包含PATTERN匹配的行。如果不指定文件或指定了“-”，则从标准输入中进行搜
索。 默认情况下，grep打印匹配的行。
此外，grep还有很多演变命令，如egrep、fgrep和rgpre，分别对应grep -E、grep -F和grep -r。
这些变种已经弃用，但他们被提供用作向后兼容。
命令参数：
1.匹配方式的选择
grep正则表达式（BRE、ERE、PCRE）
-E, --extended-regexp
将PATTERN作为扩展的正则表达式（ERE)
-F，--fixed-strings
将PATTERN作为为固定字符串的列表，由换行符分隔，匹配其中任意一个
-G, --basic-regexp
将PATTERN作为基本正则表达式（BRE），该选项为默认设置
-P，--perl-regexp
将PATTERN作为perl兼容正则表达式（PCRE)。
2.匹配控制
-e PATTERN, --regexp=PATTERN
将PATTERN作为匹配项，如果该选项被多次使用或和-f（--file）选项一起使用，匹配所有
的匹配项。该选项可以用来保护以'-'开头的匹配项。
-f FILE，--file=FILE
将FILE中的每行都作为匹配项，如果此选项被多次使用或与-e（--regexp）选项组合使用，搜索所有
给定的匹配项。空文件包含零个匹配项，因此不匹配任何内容
-i，--ignore-case
忽略匹配项的大小写
-v，--invert-match
反向匹配，选择没有匹配上的行
-w，--word-regexp
仅匹配完整单词，匹配的子字符串必须位于行的开头，或者前面有一个非字词字符。类似地，它必须位于
行尾或后面跟非字词组成字符（字词组成字符是字母、数字和下划线）。
-x，--line-regexp
仅选择与整行完全匹配的匹配项。对于正则表达式匹配项，这类似于将匹配项括起来，然后用^和$将其
包围。
-y 和-i作用相同，但已过时
3.通用输出控制
-c，--count
不打印匹配结果，而是打印匹配的行数
--color[=WHEN]，--colour[=WHEN]
将匹配到的字符串、行、上下文行、文件名、行号、字节偏移量和带转义符的分隔符（用于字段和上下文
行组）序列着色，颜色有环境变量GREP_COLORS决定，虽然GREP_COLOR已经过时，但grep依然支持该
环境变量，只不过优先权比GREP_COLORS低。WHEN可以为never、always和auto。相关环境变量介绍
：略。
-L，--files-without-match
不打印正常匹配结果，而是打印没有匹配上的文件的名称，扫描将在第一次匹配时停止。
-l，--files-with-matches
不打印正常匹配结果，而是打印匹配上的输入文件的名称，扫描将在第一次匹配时停止
-m NUM --max-count=NUM
在匹配到NUM行后停止读取文件
-o，--only-matching
仅打印匹配行中（非空的）匹配部分，每个部分在单独的输出行上
-q，--quiet，--silent
不向标准输出打印任何内容，匹配到内容立刻退出，即使检测到错误
-s，--no-messages
当文件不存在或文件不可读取时，不显示错误信息
4.输出行前缀控制
-b，--byte-offset
在每行输出之前，打印输入文件中基于0的字节偏移量。如果指定了-o（--only-matching），则打印
匹配项本身的偏移量
-H，--with-filename
打印每个匹配的文件名，当匹配到多个匹配项时，该选项为默认配置
-h，--no-filename
在输出中不显示文件名，只匹配到单个结果时，默认不显示文件名
--label=LABEL
将标准输入显示为来自文件标签的输入（？？？不理解）
-n，--line-number
显示行号
-T，--initial-tab
使匹配结果中每行的第一个字符位于制表位上，以便制表的对齐看起来显得正常。该选项对一些给输出内
容加前缀的选项很有作用：-H、-n和-b
-u，--unix-byt-offsets
报告Unix样式的字节偏移量，此开关使grep报告字节偏移量，就像文件是Unix样式的文本文件一样，即
去掉CR字符。这将产生与在Unix机器上运行grep相同的结果。除非同时使用-b选项，否则此选项无效，
它对MS-DOS和MS Windows以外的平台没有影响。
-Z，--null
将文件名后面的符号（冒号或回车）改为零字节（ASCII NUL 字符），例如，grep -lZ在每个文件名
后输出一个零字节，而不是通常的换行。此选项使输出明确，甚至如果文件名包含不寻常的字符，如新行。
此选项可与其他命令一起使用，如find -print0、perl-0、sort-z和xargs-0来处理任意文件名，
甚至包含换行符的文件名。
5.上下文行控制
-A NUM，--after-context=NUM
在匹配行之后打印下文的NUM行,连续的匹配组之间用分隔符“--”隔开。和-o或--only-matching选项
一起使用时，该选项没有任何效果，并且会发出警告
-B NUM，--before-context=NUM
在匹配行的前面打印上文的NUM行，,连续的匹配组之间用分隔符“--”隔开。和-o或--only-matching
选项一起使用时，该选项没有任何效果，并且会发出警告
-C NUM，-NUM，--context=NUM
打印匹配行的上下文各NUM行，连续的匹配组之间用分隔符“--”隔开。和-o或--only-matching选项
一起使用时，该选项没有任何效果，并且会发出警告
6.文件及目录的选择
-a，--text
像处理文本一样处理二进制文件，相当于--binary-files=text选项
--binary-files=TYPE
如果文件的前几个字节指示该文件包含二进制数据，则假定文件的类型为TYEP。默认情况下，TYPE为
binary，grep通常只输出一行表示二进制文件匹配的消息，或者因为没有匹配结果而没有输出；如果
TYPE为without-match，则grep不对二进制文件进行匹配，相当于-I选项；如果TYPE为text，grep
将二进制文件当作文本文件处理，这相当于-a选项，处理二进制数据时，grep可以将非文本字节视为行
终止符，例如，模式“.”（句点）可能不能匹配空字节，因为空字节可能被视为行终止符。警告：grep
--binary-files=text可能输出二进制垃圾，如果输出是终端且终端驱动程序将其中一些文本解释为
命令则可能会产生严重的副作用。
-D ACTION，--devices=ACTION
如果输入文件是一个设备、FIFO或则套接字，使用ACTION去处理它，ACTION默认为read，意味着该文
件将被当作普通文件进行读取。如果ACTION为skip，设备文件被忽略。
-d ACTION，--directories=ACTION
如果输入文件为一个目录，使用ACTION处理它。ACTION默认为read，即将目录作为普通文件处理。如果
ACTION为skip，跳过该目录。如果ACTION为recurse，递归读取目录下的所有文件，并且遵循命令行
符号链接，相当于-r选项
--exclude=GLOB
跳过名称与GLOB匹配的文件（使用通配符匹配），文件名glob可以使用*、？、和[…]作为通配符，并逐
字引用通配符或反斜杠字符。
--exclude-from=FILE
跳过其基名称与从FILE读取的任意文件名通过glob匹配的文件（使用通配符匹配，如--exclude下所述）
--exclude-dir=DIR
从递归搜索中排除与DIR匹配的目录
-I
处理二进制文件，就像它不包含匹配的数据一样，这相当于--binary-files=without-match选项。
--include=GLOB
搜索名称与从GLOB匹配的文件（使用通配符匹配，如--exclude下所述）
-r，--recursive
递归读取目录下的所有文件，并且遵循命令行符号链接。如果没有给定文件操作数，grep将搜索当前工作
目录。该命令相当于-d recurse选项
-R，--dereference-recursive
递归读取目录下所有文件，遵循所有符号链接
7.其他选项
--line-buffered
在输出上使用行缓冲，这可能会导致性能下降
-U，--binary
将文件视为二进制文件，默认情况下，在MS-DOS和MS-Window中，grep通过读取文件前32KB的内容决
定这个文件的类型，如果文件为文本文件，grep从原始文件中删除CR字符（使带有‘^'和’$'的正则表达
式能正常工作），指定-U可以让其对文件进行逐字读取。如果文件为文本文件，每行末尾有CR/LF，这将
造成一些正则表达式失效。该选项对MS-DOS和MS-Windows以外的平台无影响。
-z，--null-data
将输入视为一组行，每个行以零字节（ASCII NUL字符）而不是换行符终止，与-Z或--null选项类似，
此选项可以与sort -z等命令一起使用，以处理任意文件名。
8.通用信息
--help
显示帮助信息
--version
显示版本信息
示例：
1. grep PATTERN…
grep的第一种用法 ，不带任何参数，根据匹配项PATTERN进行匹配。
xiaohui@ubuntu:~/work/grep_learn$ ls | grep .c
grep_test_2.c
grep_test_3.c
grep_test.c
xiaohui@ubuntu:~/work/grep_learn$
通过管道，grep，可以从其他命令的输出中查找匹配项。
2. grep PATTERN… FILE…
grep的第二种用法 ，不带任何参数，根据匹配项进行匹配。
xiaohui@ubuntu:~/work/grep_learn$ cat grep_test.c
iigrep....
learn
text
xiaohui@ubuntu:~/work/grep_learn$ grep text ./grep_test.c
text
xiaohui@ubuntu:~/work/grep_learn$
3. grep -E/-G PATTERN… [FILE…]
由于在grep中，基本正则表达式和扩展正则表达式在使用时的区别在于：在基本正则表达式中，元字符？、+、{、|、(、和)失去了特殊意义，需要使用反斜杠版本\？、+、{、|、(、和\）。如果不加任何匹配方式的选项，默认为-G，即基本正则表达式。
xiaohui@ubuntu:~/work/grep_learn$ cat grep_test_2.c
apple
banana
cat
dog
egg
fire
glof
12
34
56
78
90
xiaohui@ubuntu:~/work/grep_learn$ grep -G [a-g] grep_test_2.c
apple
banana
cat
dog
egg
fire
glof
xiaohui@ubuntu:~/work/grep_learn$ grep -G [1-9] grep_test_2.c
12
34
56
78
90
xiaohui@ubuntu:~/work/grep_learn$
4. grep -F PATTERN… [FILE…]
将PATTERN作为固定字符串形式的匹配项，不识别正则表达式。
xiaohui@ubuntu:~/work/grep_learn$ cat grep_test.c
^abc
abc
efg$
efg
text*
textxx
headxxxxend
headaaaaend
head*end
xiaohui@ubuntu:~/work/grep_learn$ grep ^abc grep_test.c
abc
xiaohui@ubuntu:~/work/grep_learn$ grep -F ^abc grep_test.c
^abc
xiaohui@ubuntu:~/work/grep_learn$ grep efg$ grep_test.c
efg
xiaohui@ubuntu:~/work/grep_learn$ grep -F efg$ grep_test.c
efg$
xiaohui@ubuntu:~/work/grep_learn$ grep text* grep_test.c
text*
textxx
xiaohui@ubuntu:~/work/grep_learn$ grep -F text* grep_test.c
text*
xiaohui@ubuntu:~/work/grep_learn$
5. grep -e PATTERN… [FILE…] 和grep -f FILE… [FILE…]
-e的作用和不加参数时类似，唯一区别是可以保护以‘-’开头的匹配项
xiaohui@ubuntu:~/work/grep_learn$ grep -e -* grep_test.c
^abc
abc
efg$
efg
text*
textxx
headxxxxend
headaaaaend
head*end
-test //-符号标红
test
xiaohui@ubuntu:~/work/grep_learn$ grep -test grep_test.c
grep: invalid option -- 't'
Usage: grep [OPTION]... PATTERN [FILE]...
Try 'grep --help' for more information.
xiaohui@ubuntu:~/work/grep_learn$ grep -e -test grep_test.c
-test
xiaohui@ubuntu:~/work/grep_learn$
-e选项可以多次使用，匹配更多的内容
xiaohui@ubuntu:~/work/grep_learn$ grep -e -test -e test grep_test.c
-test
test
xiaohui@ubuntu:~/work/grep_learn$
-f的作用是将FILE中的每行都作为匹配项，和-e一样可以多次使用
xiaohui@ubuntu:~/work/grep_learn$ grep -f grep_file.c grep_*.c
grep_file.c:test
grep_file.c:text
grep_file.c:head
grep_file.c:end
grep_test_2.c:text_2
grep_test_2.c:test_2
grep_test_3.c:text_3
grep_test_3.c:test_3
grep_test.c:text*
grep_test.c:textxx
grep_test.c:headxxxxend
grep_test.c:headaaaaend
grep_test.c:head*end
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$ cat grep_file.c
test
text
head
end
xiaohui@ubuntu:~/work/grep_learn$ echo [a-b] > grep_file_2.c
xiaohui@ubuntu:~/work/grep_learn$ grep -f grep_file_2.c -f grep_file.c grep_*.c
grep_file_2.c:[a-b]
grep_file.c:test
grep_file.c:text
grep_file.c:head
grep_file.c:end
grep_test_2.c:apple
grep_test_2.c:banana
grep_test_2.c:cat
grep_test_2.c:text_2
grep_test_2.c:test_2
grep_test_3.c:text_3
grep_test_3.c:test_3
grep_test.c:^abc
grep_test.c:abc
grep_test.c:text*
grep_test.c:textxx
grep_test.c:headxxxxend
grep_test.c:headaaaaend
grep_test.c:head*end
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$
-e和-f也可以同时使用，匹配所有匹配项。
xiaohui@ubuntu:~/work/grep_learn$ grep -f grep_file.c -e test grep_test.c
text*
textxx
headxxxxend
headaaaaend
head*end
-test
test
xiaohui@ubuntu:~/work/grep_learn$ cat grep_file.c
test
text
head
end
xiaohui@ubuntu:~/work/grep_learn$
6. grep -i PATTERN… [FILE…]
忽略匹配项PATTERN的大小写
xiaohui@ubuntu:~/work/grep_learn$ grep -i test grep_test.c
TEST
-test
test
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test.c
-test
test
xiaohui@ubuntu:~/work/grep_learn$
7. grep -v PATTERN… [FILE…]
反向匹配
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test.c
-test
test
xiaohui@ubuntu:~/work/grep_learn$ grep -v test grep_test.c
^abc
abc
efg$
efg
text*
textxx
TEXT
TEST
xiaohui@ubuntu:~/work/grep_learn$
8. grep -w PATTERN… [FILE…]
匹配完整的单词，单词前后不能有其他字母或数字，但允许单词前面有非字词符号。
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test_3.c
xxtest
testxx
_test
-test
test_3
test
test_
xxx xxx test-
This is a test file.
xiaohui@ubuntu:~/work/grep_learn$ grep -w test grep_test_3.c
-test
test
xxx xxx test-
This is a test file.
xiaohui@ubuntu:~/work/grep_learn$
9. grep -x PATTERN… [FILE…]
整行匹配
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test_3.c
xxtest
testxx
_test
-test
test_3
test
test_
xxx xxx test-
This is a test file.
xiaohui@ubuntu:~/work/grep_learn$ grep "This is a test file" grep_test_3.c
This is a test file.
xiaohui@ubuntu:~/work/grep_learn$
10. grep -c PATTERN… [FILE…]
打印匹配的行数（不是行号），而不打印匹配内容
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test_3.c
xxtest
testxx
_test
-test
test_3
test test test
test_
xxx xxx test-
This is a test file.
xiaohui@ubuntu:~/work/grep_learn$ grep test -c grep_test_3.c
9
xiaohui@ubuntu:~/work/grep_learn$
11. grep -color[=WHEN] PATTERN… [FILE…]
匹配结果颜色设置，ubuntu默认用红色进行标识
12. grep -L PATTERN… [FILE…]
不打印匹配的内容，打印FILE中没有匹配上的文件
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_*.c
grep_file.c:test
grep_test_2.c:test_2
grep_test_3.c:xxtest
grep_test_3.c:testxx
grep_test_3.c:_test
grep_test_3.c:-test
grep_test_3.c:test_3
grep_test_3.c:test test test
grep_test_3.c:test_
grep_test_3.c:xxx xxx test-
grep_test_3.c:This is a test file.
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_*.c -L
grep_file_2.c
xiaohui@ubuntu:~/work/grep_learn$
13. grep -l PATTERN… [FILE…]
不打印匹配的内容，而是打印FILE中匹配上的文件的名称
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_*.c
grep_file.c:test
grep_test_2.c:test_2
grep_test_3.c:xxtest
grep_test_3.c:testxx
grep_test_3.c:_test
grep_test_3.c:-test
grep_test_3.c:test_3
grep_test_3.c:test test test
grep_test_3.c:test_
grep_test_3.c:xxx xxx test-
grep_test_3.c:This is a test file.
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_*.c -l
grep_file.c
grep_test_2.c
grep_test_3.c
grep_test.c
xiaohui@ubuntu:~/work/grep_learn$
14. grep -m NUM PATTERN… [FILE…]
每个文件最多匹配出NUM行，
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test_3.c -m 5
xxtest
testxx
_test
-test
test_3
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test_3.c
xxtest
testxx
_test
-test
test_3
test test test
test_
xxx xxx test-
This is a test file.
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_*.c -m 3
grep_file.c:test
grep_test_2.c:test_2
grep_test_3.c:xxtest
grep_test_3.c:testxx
grep_test_3.c:_test
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$
15. grep -o PATTERN… [FILE…]
仅打印匹配的内容，而不是匹配的一整行
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test_3.c
xxtest
testxx
_test
-test
test_3
test test test
test_
xxx xxx test-
This is a test file.
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test_3.c -o
test
test
test
test
test
test
test
test
test
test
test
xiaohui@ubuntu:~/work/grep_learn$
16. grep -q PATTERN… [FILE…]
不显示匹配结果，匹配结束立刻退出
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test_3.c
xxtest
testxx
_test
-test
test_3
test test test
test_
xxx xxx test-
This is a test file.
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test_3.c -q
xiaohui@ubuntu:~/work/grep_learn$
17. grep -s PATTERN… [FILE…]
不显示文件不存在和读取失败的错误信息
xiaohui@ubuntu:~/work/grep_learn$ grep test file.c
grep: file.c: No such file or directory
xiaohui@ubuntu:~/work/grep_learn$ grep test file.c -s
xiaohui@ubuntu:~/work/grep_learn$
xiaohui@ubuntu:~/work/grep_learn$ grep test /root/*
grep: /root/*: Permission denied
xiaohui@ubuntu:~/work/grep_learn$ grep test /root/* -s
xiaohui@ubuntu:~/work/grep_learn$
18. grep -b PATTERN… [FILE…]
打印匹配项基于文件开头的偏移量
19. grep -H PATTERN… [FILE…]
打印匹配项所在文件的文件名，匹配结果多于一个文件时，默认显示文件名。
20. grep -h PATTERN… [FILE…]
不显示文件名，单个文件匹配时，默认不显示文件名
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test_3.c
xxtest
testxx
_test
-test
test_3
test test test
test_
xxx xxx test-
This is a test file.
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test*.c
grep_test_2.c:test_2
grep_test_3.c:xxtest
grep_test_3.c:testxx
grep_test_3.c:_test
grep_test_3.c:-test
grep_test_3.c:test_3
grep_test_3.c:test test test
grep_test_3.c:test_
grep_test_3.c:xxx xxx test-
grep_test_3.c:This is a test file.
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test*.c -h
test_2
xxtest
testxx
_test
-test
test_3
test test test
test_
xxx xxx test-
This is a test file.
-test
test
xiaohui@ubuntu:~/work/grep_learn$
21. grep -n PATTERN… [FILE…]
显示匹配项在文件中的行号
22. grep -T PATTERN… [FILE…]
显示时使用制表符
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test*.c -n -H -b
grep_test_2.c:14:57:test_2
grep_test_3.c:1:0:xxtest
grep_test_3.c:2:7:testxx
grep_test_3.c:3:14:_test
grep_test_3.c:4:20:-test
grep_test_3.c:5:26:test_3
grep_test_3.c:6:33:test test test
grep_test_3.c:7:48:test_
grep_test_3.c:8:54:xxx xxx test-
grep_test_3.c:9:69:This is a test file.
grep_test.c:9:41:-test
grep_test.c:10:47:test
xiaohui@ubuntu:~/work/grep_learn$ grep "test" grep_test*.c -n -H -b -T
grep_test_2.c: 14: 57 :test_2
grep_test_3.c: 1: 0 :xxtest
grep_test_3.c: 2: 7 :testxx
grep_test_3.c: 3: 14 :_test
grep_test_3.c: 4: 20 :-test
grep_test_3.c: 5: 26 :test_3
grep_test_3.c: 6: 33 :test test test
grep_test_3.c: 7: 48 :test_
grep_test_3.c: 8: 54 :xxx xxx test-
grep_test_3.c: 9: 69 :This is a test file.
grep_test.c: 9: 41:-test
grep_test.c: 10: 47:test
xiaohui@ubuntu:~/work/grep_learn$
23. grep -Z PATTERN… [FILE…]
文件名后面的符号改为零字节（ASCII NUL字符）
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test.c -H
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test.c -H -Z
grep_test.c-test
grep_test.ctest
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test* -Z -H -l
grep_test_2.cgrep_test_3.cgrep_test.cxiaohui@ubuntu:~/work/grep_learn$
24. grep -A NUM PATTERN… [FILE…]
将匹配行后面的NUM行也打印出来
xiaohui@ubuntu:~/work/grep_learn$ grep TEST -A 0 grep_test.c
TEST
xiaohui@ubuntu:~/work/grep_learn$ grep TEST -A 1 grep_test.c
TEST
-test
xiaohui@ubuntu:~/work/grep_learn$ grep TEST -A 2 grep_test.c
TEST
-test
test
xiaohui@ubuntu:~/work/grep_learn$ grep TEST -A 3 grep_test.c
TEST
-test
test
xiaohui@ubuntu:~/work/grep_learn$
25. grep -B NUM PATTERN… [FILE…]
将匹配行前面的NUM行也打印出来
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test_2.c -B 0
test_2
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test_2.c -B 1
text_2
test_2
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test_2.c -B 2
90
text_2
test_2
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test_2.c -B -1
grep: -1: invalid context length argument
xiaohui@ubuntu:~/work/grep_learn$
26. grep -C NUM PATTERN… [FILE…]
将匹配行前面和后面的NUM行也打印出来
xiaohui@ubuntu:~/work/grep_learn$ grep TEXT grep_test.c -C 0
TEXT
xiaohui@ubuntu:~/work/grep_learn$ grep TEXT grep_test.c -C 1
textxx
TEXT
TEST
xiaohui@ubuntu:~/work/grep_learn$ grep TEXT grep_test.c -C 2
text*
textxx
TEXT
TEST
-test
xiaohui@ubuntu:~/work/grep_learn$ grep TEXT grep_test.c -C 3
efg
text*
textxx
TEXT
TEST
-test
test
xiaohui@ubuntu:~/work/grep_learn$
27. grep -a PATTERN… [FILE…]
将二进制文件当做文本文件来处理。
下图中hello_grep.out为二进制文件（可执行文件），不加-a参数，grep会提示二进制文件无法进行匹配。
28. grep --binary-files=TYPE PATTERN… [FILE…]
TYPE的值可以为：binary（默认）、without-match、text，binary和without-match的区别是前者使用时会提示二进制文件无法匹配，后者不会提示，–binary-files=text相当于-a选项。
xiaohui@ubuntu:~/work/grep_learn$ grep hello hello_grep.out --binary-files=without-match
xiaohui@ubuntu:~/work/grep_learn$ grep hello hello_grep.out --binary-files=binary
Binary file hello_grep.out matches
xiaohui@ubuntu:~/work/grep_learn$ grep hello hello_grep.out --binary-files=text
h������%�
f�1�I��^H��H���PTI���@H��P@H��&@������fD�?`UH-8`H��H��v�H��t]�8`��f�]�@f.��8`UH��8`H��H��H��H��?H�H��t�H��t
]�8`��]�fD�=Q
uUH���n���]�>
��@� `H�?u���H��t�UH����]�z���UH����@��������@�������]ÐAWAVA��AUATL�% UH�- SI��I��L)�H�H���G���H��t 1��L��L��D��A��H��H9�u�H�[]A\A]A^A_Ðf.���H�H��hello grephello world;0���|D���L:����d��������
zRx
�����*zRx
�$����0FJ
d �?;*3$"D����)A�C
Dd����eB�B�E �B(�H0�H8�M@r8A0A(B BB�����@�@
�@``���o�@@�@ �@
�@
...
29. grep -D ACTION PATTERN… [FILE…]
当FILE为设备文件、FIFO或套接字时，使用ACTION去处理它，ACTION默认为read，也可以为skip，前者将该文件作为普通文件处理，后者则跳过读取该文件。
先用mkfifo创建一个fifo件，将test字符串在后台写入：
xiaohui@ubuntu:~/work/grep_learn$ echo test > my_fifo &
[1] 11012
xiaohui@ubuntu:~/work/grep_learn$ grep test my_fifo -D read
test
[1]+ Done echo test > my_fifo
xiaohui@ubuntu:~/work/grep_learn$ echo test > my_fifo &
[1] 11015
xiaohui@ubuntu:~/work/grep_learn$ grep test my_fifo -D skip
xiaohui@ubuntu:~/work/grep_learn$ jobs
[1]+ Broken pipe echo test > my_fifo
xiaohui@ubuntu:~/work/grep_learn$
30. grep -d ACTION PATTERN… [FILE…]
当FILE为目录时，使用ACTION去处理它，ACTION默认为read，也可以为skip或recurse，ACTION为read时，grep将该文件作为普通文件处理，为skip时跳过读取该文件，为recurse时，递归读取所有文件。
xiaohui@ubuntu:~/work/grep_learn$ grep text dir/
grep: dir/: Is a directory
xiaohui@ubuntu:~/work/grep_learn$ grep text dir/ -d read
grep: dir/: Is a directory
xiaohui@ubuntu:~/work/grep_learn$ grep text dir/ -d skip
xiaohui@ubuntu:~/work/grep_learn$ grep text dir/ -d recurse
dir/grep_test.c:text_0
dir/dir1/grep_test.c:text_1
dir/dir2/grep_test.c:text_2
xiaohui@ubuntu:~/work/grep_learn$
31. grep --exclude=GLOB PATTERN… [FILE…]
跳过与GLOB匹配的文件，文件名可以使用通配符
xiaohui@ubuntu:~/work/grep_learn$ grep test --exclude=grep_test_3.c grep_test*.cgrep_test_2.c:test_2
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test*.cgrep_test_2.c:test_2
grep_test_3.c:xxtest
grep_test_3.c:testxx
grep_test_3.c:_test
grep_test_3.c:-test
grep_test_3.c:test_3
grep_test_3.c:test test test
grep_test_3.c:test_
grep_test_3.c:xxx xxx test-
grep_test_3.c:This is a test file.
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$
<
32. grep --exclude-from=FILE PATTERN… [FILE…]
从FILE（要匹配的文件）中排除与FILE（–exclude-from=选项中的FILE）文件内容匹配的文件
grep_test_4.c中有grep_test_3*，所以匹配时排除文件名与grep_test_3*匹配的文件
xiaohui@ubuntu:~/work/grep_learn$ cat grep_test_4.c
xxxx
grep_test_3*
xiaohui@ubuntu:~/work/grep_learn$ grep test --exclude-from=grep_test_4.c grep_test*.c
grep_test_2.c:test_2
grep_test_4.c:grep_test_3*
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$ grep test grep_test*.cgrep_test_2.c:test_2
grep_test_3.c:xxtest
grep_test_3.c:testxx
grep_test_3.c:_test
grep_test_3.c:-test
grep_test_3.c:test_3
grep_test_3.c:test test test
grep_test_3.c:test_
grep_test_3.c:xxx xxx test-
grep_test_3.c:This is a test file.
grep_test_4.c:grep_test_3*
grep_test.c:-test
grep_test.c:test
xiaohui@ubuntu:~/work/grep_learn$
33. grep --exclude-dir=DIR PATTERN… [FILE…]
从FILE（目录文件）中排除目录名/文件名与DIR匹配的文件
xiaohui@ubuntu:~/work/grep_learn$ grep text --exclude-dir=dir ./ -r
./grep_test.c:text*
./grep_test.c:textxx
./grep_file.c:text
./text_0/grep_test.c:text_0
./text_1/grep_test.c:text_0
./grep_test_2.c:text_2
Binary file ./hello_grep.out matches
xiaohui@ubuntu:~/work/grep_learn$ grep text ./ -r
./grep_test.c:text*
./grep_test.c:textxx
./grep_file.c:text
./text_0/grep_test.c:text_0
./text_1/grep_test.c:text_0
./grep_test_2.c:text_2
Binary file ./hello_grep.out matches
./dir/grep_test.c:text_0
./dir/dir1/grep_test.c:text_1
./dir/dir2/grep_test.c:text_2
xiaohui@ubuntu:~/work/grep_learn$
34. grep -I PATTERN… [FILE…]
同–binary-files=without-match，见28.grep --binary-files。
35. grep --include=GLOB PATTERN… [FILE…]
搜索文件名与GLOB匹配的文件（使用通配符匹配）
xiaohui@ubuntu:~/work/grep_learn$ grep test --include=grep_test_2* grep_test_*.c
grep_test_2.c:test_2
xiaohui@ubuntu:~/work/grep_learn$ grep test --include=grep_test_4* grep_test_*.c
grep_test_4.c:grep_test_3*
xiaohui@ubuntu:~/work/grep_learn$
36. grep -r PATTERN… [FILE…]
同-d recurse选项，默认所在当前工作目录，遵循命令行符号链接，见30.grep -d ACTION。
37. grep -R PATTERN… [FILE…]
和-r类似，但遵循所有的符号链接
.
man手册
以下为 grep 命令手册原文：
GREP(1) General Commands Manual GREP(1)
NAME
grep, egrep, fgrep, rgrep - print lines matching a pattern
SYNOPSIS
grep [OPTIONS] PATTERN [FILE...]
grep [OPTIONS] [-e PATTERN]... [-f FILE]... [FILE...]
DESCRIPTION
grep searches the named input FILEs for lines containing a match to the
given PATTERN. If no files are specified, or if the file “-” is given,
grep searches standard input. By default, grep prints the matching
lines.
In addition, the variant programs egrep, fgrep and rgrep are the same
as grep -E, grep -F, and grep -r, respectively. These variants are
deprecated, but are provided for backward compatibility.
OPTIONS
Generic Program Information
--help Output a usage message and exit.
-V, --version
Output the version number of grep and exit.
Matcher Selection
-E, --extended-regexp
Interpret PATTERN as an extended regular expression (ERE, see
below).
-F, --fixed-strings
Interpret PATTERN as a list of fixed strings (instead of regular
expressions), separated by newlines, any of which is to be
matched.
-G, --basic-regexp
Interpret PATTERN as a basic regular expression (BRE, see
below). This is the default.
-P, --perl-regexp
Interpret the pattern as a Perl-compatible regular expression
(PCRE). This is highly experimental and grep -P may warn of
unimplemented features.
Matching Control
-e PATTERN, --regexp=PATTERN
Use PATTERN as the pattern. If this option is used multiple
times or is combined with the -f (--file) option, search for all
patterns given. This option can be used to protect a pattern
beginning with “-”.
-f FILE, --file=FILE
Obtain patterns from FILE, one per line. If this option is used
multiple times or is combined with the -e (--regexp) option,
search for all patterns given. The empty file contains zero
patterns, and therefore matches nothing.
-i, --ignore-case
Ignore case distinctions in both the PATTERN and the input
files.
-v, --invert-match
Invert the sense of matching, to select non-matching lines.
-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.
-x, --line-regexp
Select only those matches that exactly match the whole line.
For a regular expression pattern, this is like parenthesizing
the pattern and then surrounding it with ^ and $.
-y Obsolete synonym for -i.
General Output Control
-c, --count
Suppress normal output; instead print a count of matching lines
for each input file. With the -v, --invert-match option (see
below), count non-matching lines.
--color[=WHEN], --colour[=WHEN]
Surround the matched (non-empty) strings, matching lines,
context lines, file names, line numbers, byte offsets, and
separators (for fields and groups of context lines) with escape
sequences to display them in color on the terminal. The colors
are defined by the environment variable GREP_COLORS. The
deprecated environment variable GREP_COLOR is still supported,
but its setting does not have priority. WHEN is never, always,
or auto.
-L, --files-without-match
Suppress normal output; instead print the name of each input
file from which no output would normally have been printed. The
scanning will stop on the first match.
-l, --files-with-matches
Suppress normal output; instead print the name of each input
file from which output would normally have been printed. The
scanning will stop on the first match.
-m NUM, --max-count=NUM
Stop reading a file after NUM matching lines. If the input is
standard input from a regular file, and NUM matching lines are
output, grep ensures that the standard input is positioned to
just after the last matching line before exiting, regardless of
the presence of trailing context lines. This enables a calling
process to resume a search. When grep stops after NUM matching
lines, it outputs any trailing context lines. When the -c or
--count option is also used, grep does not output a count
greater than NUM. When the -v or --invert-match option is also
used, grep stops after outputting NUM non-matching lines.
-o, --only-matching
Print only the matched (non-empty) parts of a matching line,
with each such part on a separate output line.
-q, --quiet, --silent
Quiet; do not write anything to standard output. Exit
immediately with zero status if any match is found, even if an
error was detected. Also see the -s or --no-messages option.
-s, --no-messages
Suppress error messages about nonexistent or unreadable files.
Output Line Prefix Control
-b, --byte-offset
Print the 0-based byte offset within the input file before each
line of output. If -o (--only-matching) is specified, print the
offset of the matching part itself.
-H, --with-filename
Print the file name for each match. This is the default when
there is more than one file to search.
-h, --no-filename
Suppress the prefixing of file names on output. This is the
default when there is only one file (or only standard input) to
search.
--label=LABEL
Display input actually coming from standard input as input
coming from file LABEL. This is especially useful when
implementing tools like zgrep, e.g., gzip -cd foo.gz | grep
--label=foo -H something. See also the -H option.
-n, --line-number
Prefix each line of output with the 1-based line number within
its input file.
-T, --initial-tab
Make sure that the first character of actual line content lies
on a tab stop, so that the alignment of tabs looks normal. This
is useful with options that prefix their output to the actual
content: -H,-n, and -b. In order to improve the probability
that lines from a single file will all start at the same column,
this also causes the line number and byte offset (if present) to
be printed in a minimum size field width.
-u, --unix-byte-offsets
Report Unix-style byte offsets. This switch causes grep to
report byte offsets as if the file were a Unix-style text file,
i.e., with CR characters stripped off. This will produce
results identical to running grep on a Unix machine. This
option has no effect unless -b option is also used; it has no
effect on platforms other than MS-DOS and MS-Windows.
-Z, --null
Output a zero byte (the ASCII NUL character) instead of the
character that normally follows a file name. For example, grep
-lZ outputs a zero byte after each file name instead of the
usual newline. This option makes the output unambiguous, even
in the presence of file names containing unusual characters like
newlines. This option can be used with commands like find
-print0, perl -0, sort -z, and xargs -0 to process arbitrary
file names, even those that contain newline characters.
Context Line Control
-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.
File and Directory Selection
-a, --text
Process a binary file as if it were text; this is equivalent to
the --binary-files=text option.
--binary-files=TYPE
If the first few bytes of a file indicate that the file contains
binary data, assume that the file is of type TYPE. By default,
TYPE is binary, and grep normally outputs either a one-line
message saying that a binary file matches, or no message if
there is no match. If TYPE is without-match, grep assumes that
a binary file does not match; this is equivalent to the -I
option. If TYPE is text, grep processes a binary file as if it
were text; this is equivalent to the -a option. When processing
binary data, grep may treat non-text bytes as line terminators;
for example, the pattern '.' (period) might not match a null
byte, as the null byte might be treated as a line terminator.
Warning: grep --binary-files=text might output binary garbage,
which can have nasty side effects if the output is a terminal
and if the terminal driver interprets some of it as commands.
-D ACTION, --devices=ACTION
If an input file is a device, FIFO or socket, use ACTION to
process it. By default, ACTION is read, which means that
devices are read just as if they were ordinary files. If ACTION
is skip, devices are silently skipped.
-d ACTION, --directories=ACTION
If an input file is a directory, use ACTION to process it. By
default, ACTION is read, i.e., read directories just as if they
were ordinary files. If ACTION is skip, silently skip
directories. If ACTION is recurse, read all files under each
directory, recursively, following symbolic links only if they
are on the command line. This is equivalent to the -r option.
--exclude=GLOB
Skip files whose base name matches GLOB (using wildcard
matching). A file-name glob can use *, ?, and [...] as
wildcards, and \ to quote a wildcard or backslash character
literally.
--exclude-from=FILE
Skip files whose base name matches any of the file-name globs
read from FILE (using wildcard matching as described under
--exclude).
--exclude-dir=DIR
Exclude directories matching the pattern DIR from recursive
searches.
-I Process a binary file as if it did not contain matching data;
this is equivalent to the --binary-files=without-match option.
--include=GLOB
Search only files whose base name matches GLOB (using wildcard
matching as described under --exclude).
-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.
Other Options
--line-buffered
Use line buffering on output. This can cause a performance
penalty.
-U, --binary
Treat the file(s) as binary. By default, under MS-DOS and MS-
Windows, grep guesses the file type by looking at the contents
of the first 32KB read from the file. If grep decides the file
is a text file, it strips the CR characters from the original
file contents (to make regular expressions with ^ and $ work
correctly). Specifying -U overrules this guesswork, causing all
files to be read and passed to the matching mechanism verbatim;
if the file is a text file with CR/LF pairs at the end of each
line, this will cause some regular expressions to fail. This
option has no effect on platforms other than MS-DOS and MS-
Windows.
-z, --null-data
Treat the input as a set of lines, each terminated by a zero
byte (the ASCII NUL character) instead of a newline. Like the
-Z or --null option, this option can be used with commands like
sort -z to process arbitrary file names.
REGULAR EXPRESSIONS
A regular expression is a pattern that describes a set of strings.
Regular expressions are constructed analogously to arithmetic
expressions, by using various operators to combine smaller expressions.
grep understands three different versions of regular expression syntax:
“basic” (BRE), “extended” (ERE) and “perl” (PCRE). In GNU grep, there
is no difference in available functionality between basic and extended
syntaxes. In other implementations, basic regular expressions are less
powerful. The following description applies to extended regular
expressions; differences for basic regular expressions are summarized
afterwards. Perl-compatible regular expressions give additional
functionality, and are documented in pcresyntax(3) and pcrepattern(3),
but work only if PCRE is available in the system.
The fundamental building blocks are the regular expressions that match
a single character. Most characters, including all letters and digits,
are regular expressions that match themselves. Any meta-character with
special meaning may be quoted by preceding it with a backslash.
The period . matches any single character.
Character Classes and Bracket Expressions
A bracket expression is a list of characters enclosed by [ and ]. It
matches any single character in that list; if the first character of
the list is the caret ^ then it matches any character not in the list.
For example, the regular expression [0123456789] matches any single
digit.
Within a bracket expression, a range expression consists of two
characters separated by a hyphen. It matches any single character that
sorts between the two characters, inclusive, using the locale's
collating sequence and character set. For example, in the default C
locale, [a-d] is equivalent to [abcd]. Many locales sort characters in
dictionary order, and in these locales [a-d] is typically not
equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example.
To obtain the traditional interpretation of bracket expressions, you
can use the C locale by setting the LC_ALL environment variable to the
value C.
Finally, certain named classes of characters are predefined within
bracket expressions, as follows. Their names are self explanatory, and
they are [:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:],
[:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:].
For example, [[:alnum:]] means the character class of numbers and
letters in the current locale. In the C locale and ASCII character set
encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in
these class names are part of the symbolic names, and must be included
in addition to the brackets delimiting the bracket expression.) Most
meta-characters lose their special meaning inside bracket expressions.
To include a literal ] place it first in the list. Similarly, to
include a literal ^ place it anywhere but first. Finally, to include a
literal - place it last.
Anchoring
The caret ^ and the dollar sign $ are meta-characters that respectively
match the empty string at the beginning and end of a line.
The Backslash Character and Special Expressions
The symbols \< and \> respectively match the empty string at the
beginning and end of a word. The symbol \b matches the empty string at
the edge of a word, and \B matches the empty string provided it's not
at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and
\W is a synonym for [^_[:alnum:]].
Repetition
A regular expression may be followed by one of several repetition
operators:
? The preceding item is optional and matched at most once.
* The preceding item will be matched zero or more times.
+ The preceding item will be matched one or more times.
{n} The preceding item is matched exactly n times.
{n,} The preceding item is matched n or more times.
{,m} The preceding item is matched at most m times. This is a GNU
extension.
{n,m} The preceding item is matched at least n times, but not more
than m times.
Two regular expressions may be concatenated; the resulting regular
expression matches any string formed by concatenating two substrings
that respectively match the concatenated expressions.
Alternation
Two regular expressions may be joined by the infix operator |; the
resulting regular expression matches any string matching either
alternate expression.
Precedence
Repetition takes precedence over concatenation, which in turn takes
precedence over alternation. A whole expression may be enclosed in
parentheses to override these precedence rules and form a
subexpression.
Back References and Subexpressions
The back-reference \n, where n is a single digit, matches the substring
previously matched by the nth parenthesized subexpression of the
regular expression.
Basic vs Extended Regular Expressions
In basic regular expressions the meta-characters ?, +, {, |, (, and )
lose their special meaning; instead use the backslashed versions \?,
\+, \{, \|, \(, and \).
ENVIRONMENT VARIABLES
The behavior of grep is affected by the following environment
variables.
The locale for category LC_foo is specified by examining the three
environment variables LC_ALL, LC_foo, LANG, in that order. The first
of these variables that is set specifies the locale. For example, if
LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian
Portuguese locale is used for the LC_MESSAGES category. The C locale
is used if none of these environment variables are set, if the locale
catalog is not installed, or if grep was not compiled with national
language support (NLS).
GREP_OPTIONS
This variable specifies default options to be placed in front of
any explicit options. As this causes problems when writing
portable scripts, this feature will be removed in a future
Concatenation
release of grep, and grep warns if it is used. Please use an
alias or script instead.
GREP_COLOR
This variable specifies the color used to highlight matched
(non-empty) text. It is deprecated in favor of GREP_COLORS, but
still supported. The mt, ms, and mc capabilities of GREP_COLORS
have priority over it. It can only specify the color used to
highlight the matching non-empty text in any matching line (a
selected line when the -v command-line option is omitted, or a
context line when -v is specified). The default is 01;31, which
means a bold red foreground text on the terminal's default
background.
GREP_COLORS
Specifies the colors and other attributes used to highlight
various parts of the output. Its value is a colon-separated
list of capabilities that defaults to
ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv
and ne boolean capabilities omitted (i.e., false). Supported
capabilities are as follows.
sl= SGR substring for whole selected lines (i.e., matching
lines when the -v command-line option is omitted, or non-
matching lines when -v is specified). If however the
boolean rv capability and the -v command-line option are
both specified, it applies to context matching lines
instead. The default is empty (i.e., the terminal's
default color pair).
cx= SGR substring for whole context lines (i.e., non-matching
lines when the -v command-line option is omitted, or
matching lines when -v is specified). If however the
boolean rv capability and the -v command-line option are
both specified, it applies to selected non-matching lines
instead. The default is empty (i.e., the terminal's
default color pair).
rv Boolean value that reverses (swaps) the meanings of the
sl= and cx= capabilities when the -v command-line option
is specified. The default is false (i.e., the capability
is omitted).
mt=01;31
SGR substring for matching non-empty text in any matching
line (i.e., a selected line when the -v command-line
option is omitted, or a context line when -v is
specified). Setting this is equivalent to setting both
ms= and mc= at once to the same value. The default is a
bold red text foreground over the current line
background.
ms=01;31
SGR substring for matching non-empty text in a selected
line. (This is only used when the -v command-line option
is omitted.) The effect of the sl= (or cx= if rv)
capability remains active when this kicks in. The
default is a bold red text foreground over the current
line background.
mc=01;31
SGR substring for matching non-empty text in a context
line. (This is only used when the -v command-line option
is specified.) The effect of the cx= (or sl= if rv)
capability remains active when this kicks in. The
default is a bold red text foreground over the current
line background.
fn=35 SGR substring for file names prefixing any content line.
The default is a magenta text foreground over the
terminal's default background.
ln=32 SGR substring for line numbers prefixing any content
line. The default is a green text foreground over the
terminal's default background.
bn=32 SGR substring for byte offsets prefixing any content
line. The default is a green text foreground over the
terminal's default background.
se=36 SGR substring for separators that are inserted between
selected line fields (:), between context line fields,
(-), and between groups of adjacent lines when nonzero
context is specified (--). The default is a cyan text
foreground over the terminal's default background.
ne Boolean value that prevents clearing to the end of line
using Erase in Line (EL) to Right (\33[K) each time a
colorized item ends. This is needed on terminals on
which EL is not supported. It is otherwise useful on
terminals for which the back_color_erase (bce) boolean
terminfo capability does not apply, when the chosen
highlight colors do not affect the background, or when EL
is too slow or causes too much flicker. The default is
false (i.e., the capability is omitted).
Note that boolean capabilities have no =... part. They are
omitted (i.e., false) by default and become true when specified.
See the Select Graphic Rendition (SGR) section in the
documentation of the text terminal that is used for permitted
values and their meaning as character attributes. These
substring values are integers in decimal representation and can
be concatenated with semicolons. grep takes care of assembling
the result into a complete SGR sequence (\33[...m). Common
values to concatenate include 1 for bold, 4 for underline, 5 for
blink, 7 for inverse, 39 for default foreground color, 30 to 37
for foreground colors, 90 to 97 for 16-color mode foreground
colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes
foreground colors, 49 for default background color, 40 to 47 for
background colors, 100 to 107 for 16-color mode background
colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes
background colors.
LC_ALL, LC_COLLATE, LANG
These variables specify the locale for the LC_COLLATE category,
which determines the collating sequence used to interpret range
expressions like [a-z].
LC_ALL, LC_CTYPE, LANG
These variables specify the locale for the LC_CTYPE category,
which determines the type of characters, e.g., which characters
are whitespace.
LC_ALL, LC_MESSAGES, LANG
These variables specify the locale for the LC_MESSAGES category,
which determines the language that grep uses for messages. The
default C locale uses American English messages.
POSIXLY_CORRECT
These variables specify the locale for the LC_MESSAGES category,
which determines the language that grep uses for messages. The
default C locale uses American English messages.
POSIXLY_CORRECT
If set, grep behaves as POSIX requires; otherwise, grep behaves
more like other GNU programs. POSIX requires that options that
follow file names must be treated as file names; by default,
such options are permuted to the front of the operand list and
are treated as options. Also, POSIX requires that unrecognized
options be diagnosed as “illegal”, but since they are not really
against the law the default is to diagnose them as “invalid”.
POSIXLY_CORRECT also disables _N_GNU_nonoption_argv_flags_,
described below.
_N_GNU_nonoption_argv_flags_
(Here N is grep's numeric process ID.) If the ith character of
this environment variable's value is 1, do not consider the ith
operand of grep to be an option, even if it appears to be one.
A shell can put this variable in the environment for each
command it runs, specifying which operands are the results of
file name wildcard expansion and therefore should not be treated
as options. This behavior is available only with the GNU C
library, and only when POSIXLY_CORRECT is not set.
EXIT STATUS
Normally the exit status is 0 if a line is selected, 1 if no lines were
selected, and 2 if an error occurred. However, if the -q or --quiet or
--silent is used and a line is selected, the exit status is 0 even if
an error occurred.
COPYRIGHT
Copyright 1998-2000, 2002, 2005-2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is
NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE.
BUGS
Reporting Bugs
Email bug reports to the bug-reporting address ⟨bug-grep@gnu.org⟩. An
email archive ⟨http://lists.gnu.org/mailman/listinfo/bug-grep⟩ and a
bug tracker ⟨http://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep⟩ are
available.
Known Bugs
Large repetition counts in the {n,m} construct may cause grep to use
lots of memory. In addition, certain other obscure regular expressions
require exponential time and space, and may cause grep to run out of
memory.
Back-references are very slow, and may require exponential time.
SEE ALSO
Regular Manual Pages
awk(1), cmp(1), diff(1), find(1), gzip(1), perl(1), sed(1), sort(1),
xargs(1), zgrep(1), read(2), pcre(3), pcresyntax(3), pcrepattern(3),
terminfo(5), glob(7), regex(7).
POSIX Programmer's Manual Page
grep(1p).
Full Documentation
A complete manual ⟨http://www.gnu.org/software/grep/manual/⟩ is
available. If the info and grep programs are properly installed at
your site, the command
info grep
should give you access to the complete manual.
NOTES
This man page is maintained only fitfully; the full documentation is
often more up-to-date.
User Commands GNU grep 2.25 GREP(1)
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