Yrurtj

egrep "foo|bar" *.txt

or

grep "foo|bar" *.txt

grep -E "foo|bar" *.txt

selectively citing the man page of gnu-grep:

   -E, --extended-regexp

          Interpret PATTERN as an extended regular expression (ERE, see below).  (-E is specified by POSIX.)



Matching Control

   -e PATTERN, --regexp=PATTERN

          Use PATTERN as the pattern.  This can be used to specify multiple search patterns, or to protect  a  pattern

          beginning with a hyphen (-).  (-e is specified by POSIX.)

(...)

   grep understands two different versions of regular expression syntax: “basic” and “extended.”  In  GNU grep,  there

   is  no  difference  in  available  functionality  using  either  syntax.   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.

In the beginning I didn't read further, so I didn't recognize the subtle differences:

Basic vs Extended Regular Expressions

   In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead  use  the

   backslashed versions ?, +, {, |, (, and ).

I always used egrep and needlessly parens, because I learned from examples. Now I learned something new. :)

Like TC1 said, -F seems to be usable option:

$> cat text

some text

foo

another text

bar

end of file



$> patterns="foo

bar" 



$> grep -F "${patterns}" text

foo

bar

Firstly, you need to use quotes for special characters. Second, even so, grep will not understand alternation directly; you would need to use egrep, or (with GNU grep only) grep -E.

egrep 'foo|bar' *.txt

(The parentheses are unnecessary unless the alternation is part of a larger regex.)

If you don't need regular expressions, it's much faster to use fgrep or grep -F with multiple -e parameters, like this:

fgrep -efoo -ebar *.txt

fgrep (alternatively grep -F) is much faster than regular grep because it searches for fixed strings instead of regular expressions.

You can try the below command to get the result:

egrep 'rose.*lotus|lotus.*rose' some_file

I had access logs where the dates were stupidly formatted: [30/Jun/2013:08:00:45 +0200]

But I needed to display it as: 30/Jun/2013 08:00:45

The problem is that using "OR" in my grep statement, I was receiving the two match expressions on two separate lines.

Here is the solution:

grep -in myURL_of_interest  *access.log  | 

grep -Eo '(b[[:digit:]]{2}/[[:upper:]][[:lower:]]{2}/[[:digit:]]{4}|[[:digit:]]{2}:[[:digit:]]{2}:[[:digit:]]{2}b)'   

| paste - - -d" " > MyAccess.log

I hope it helps :)

A cheap and cheerful way to grep for multiple patterns:

$ echo "foo" > ewq ; echo "bar" >> ewq ; grep -H -f ewq *.txt ; rm ewq

Pipe (|) is a special shell character, so it either needs to be escaped (|) or quoted as per manual (man bash):

Quoting is used to remove the special meaning of certain characters or words to the shell. It can be used to disable special treatment for special characters, to prevent reserved words from being recognized as such, and to prevent parameter expansion.

Enclosing characters in double quotes preserves the literal value of all characters within the quotes

A non-quoted backslash () is the escape character.

See: Which characters need to be escaped in Bash?

Here are few examples (using tools not mentioned yet):

• 
  

  Using ripgrep:

  
  
  
  
  
  • rg "foo|bar" *.txt
  
  
  • rg -e foo -e bar *.txt
  
  
  
  


• 
  

  Using git grep:

  
  
  
  
  
  • 
    

    git grep --no-index -e foo --or -e bar

    
    
    

    ^{Note: It also supports Boolean expressions such as --and, --or and --not.}

    
    
  
  
  
  

For AND operation per line, see: How to run grep with multiple AND patterns?

For AND operation per file, see: How to check all of multiple strings or regexes exist in a file?

This works for me

root@gateway:/home/sshuser# aws ec2 describe-instances --instance-ids i-2db0459d |grep 'STATE|TAG'



**STATE**   80      stopped



**STATE**REASON     Client.UserInitiatedShutdown    Client.UserInitiatedShutdown: User initiated shutdown



**TAGS**    Name    Magento-Testing root@gateway:/home/sshuser#

There are multiple ways to do so.

1. grep 'foo|bar' *.txt


2. egrep 'foo|bar' *.txt


3. find . -maxdepth 1 -type f -name "*.txt" | xargs grep 'foo|bar'


4. find . -maxdepth 1 -type f -name "*.txt" | xargs egrep 'foo|bar'

3rd and 4th option will grep only in the files and avoid directories having .txt in their names.

So, as per your use-case you can use any of the option mentioned above.

Thanks!!

TL;DR: if you want to do more things after matching one of the multiple patterns, enclose them as in (pattern1|pattern2)

No one has mentioned searching for any one of multiple patterns followed by more patterns, so I figured I'd throw it out here:

example: I want to find all the places where a variable that contains the name 'date' is defined as a String or int. (i.e., "int date =" or "String date ="):

grep '.' -rne '(int|String) [a-zA-Z_]*date[a-zA-Z_]* ='