Detailed explanation of grep command

grep is a powerful text search tool that uses regular expressions to search text and prints matching lines. Common syntax of grep command: [grep [-acinv] [--color=auto] 'Search string' filename].

grep

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grep is a powerful Text search tool that uses regular expressions to search for text and prints matching lines.

Common syntax:

[root@www ~]# grep [-acinv] [--color=auto] '搜寻字符串' filename

Options and parameters:

• -a: Search binary files as text files

• -c: Count the number of times 'search string' is found

• -i: Ignore the difference in case, so the case is considered the same

• -n: Output line number

• -v: Reverse selection, that is, display the line without 'search string' content

• --color=auto: You can add color to the found keyword part

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Example:

Take out the lines where root appears in /etc/passwd

# grep root /etc/passwd
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin
或
# cat /etc/passwd | grep root 
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin

Take out the lines where root appears in/etc/passwd, and display these at the same time Line number in /etc/passwd

# grep -n root /etc/passwd
1:root:x:0:0:root:/root:/bin/bash
30:operator:x:11:0:operator:/root:/sbin/nologin

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