Grep of three swordsmen in text processing

grep：Global search REgular expression and Print out the line

effect ： Text search tools , According to the user specified “ Pattern ” Match the target text line by line ; Print the matched lines

Pattern ： Filter conditions written by regular expression characters and text characters

Format ：

grep [OPTIONS] PATTERN [FILE...]

Common options ：

• -color=auto         Color the matched text
• -m #        matching # Stop after
• -V           Display not pattern Matched rows , Take the opposite
• -i            Ignore character case
• -n           Display the matched line number
• -c           Count the number of rows matched
• -o           Show only strings that match
• -q           silent mode , Do not output any information
• -A #          after, after # That's ok
• -B #          before, front # That's ok
• -C #          context, Before and after # That's ok
• -e           Implement logic between multiple options or Relationship , Such as grep -e ‘cat’ -e ‘dog’ file
• -w           Match the whole word
• -E          Use ERE, amount to egrep
• -F           Regular expressions are not supported , amount to fgrep
• -f file       Process according to the schema file
• -r           Recursive directory , But don't handle soft links
• -R          Recursive directory , But dealing with soft links

Example ： Take the same line of two files

[19:33:09 [email protected] data]#cat f1.txt 
a
b
1
c
[19:33:24 [email protected] data]#cat f2.txt 
b
e
f
c
1
2
[19:33:28 [email protected] data]#grep -f f1.txt f2.txt 
b
c