Linux常用命令之grep命令用法详解

1.官方简介

grep是linux的常用命令，用于对文件和文本执行重复搜索任务的Unix工具，可以通过grep命令指定特定搜索条件来搜索文件及其内容以获取有用的信息。

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.cRegexp 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 newlineMiscellaneous: -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 exitOutput 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 nameContext 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.orgGNU Grep home page: <http://www.gnu.org/software/grep/>General help using GNU software: http://www.gnu.org/gethelp/

我平时也是简单的查看一个用户数据，用于简单的数据校对，最近突然接到分析后台日志的需求，才发现grep用处还是不少的。

比如我们后台日志相当大，要是直接从服务器直接拉取，耗时长占用带宽，所以方案就是直接使用 grep关键字重定向到新的文件中，从14G直接到12M,然后再数据清洗和分析。

2.实战介绍

2.1使用grep命令对多文件中多种文本查询

note :使用egrep命令，可使用扩展的正则表达式

1.多文件

grep ’pattern’ file1 file2

2.多文本 ， 关系是OR

egrep ’pattern1|pattern2’ *.py grep -e pattern1 -e pattern2 *.py grep -E ’pattern1|pattern2’ *.doc

例如下面对 对文件中 存在关键字 wordA or wordB进行提取:

grep ’wordA|wordB’ *.pygrep -E ’wordA|wordB’ *.docgrep -e wordA -e wordB *.pyegrep 'wordA|wordB' *.c

3.多文本关系是 AND

这里我并没有看到 直接能用的【option】,只能加一层管道符|。

例如：

grep -e pattern1 *.py |grep -e pattern2

2.2完全匹配关键词 -w

grep -w ’warning|error|critical’ /home/logs

2.3使用-i参数忽略大小写，?color高亮显示匹配结果

egrep -wi --color ’warning|error|critical’ /home/logs

2.4递归查找

egrep -Rwi --color ’warning|error’ /home/logs/

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