grep egrep multiple-strings

Suppose I have several strings: str1 and str2 and str3.

• How to find lines that have all the strings?
• How to find lines that can have any of them?
• And how to find lines that have str1 and either of str2 and str3 [but not both?]?

This looks like three questions. The easiest way to put these sorts of expressions together is with multiple pipes. There's no shame in that, particularly because a regular expression (using egrep) would be ungainly since you seem to imply you want order independence.

So, in order,

1. grep str1 | grep str2 | grep str3

2. egrep '(str1|str2|str3)'

3. grep str1 | egrep '(str2|str3)'

you can do the "and" form in an order independent way using egrep, but I think you'll find it easier to remember to do order independent ands using piped greps and order independent or's using regular expressions.

You can't reasonably do the "all" or "this plus either of those" cases because grep doesn't support lookahead. Use Perl. For the "any" case, it's egrep '(str1|str2|str3)' file.

The unreasonable way to do the "all" case is:

egrep '(str1.*str2.*str3|str3.*str1.*str2|str2.*str1.*str3|str1.*str3.*str2)' file

i.e. you build out the permutations. This is, of course, a ridiculous thing to do.

For the "this plus either of those", similarly:

egrep '(str1.*(str2|str3)|(str2|str3).*str1)' file

grep -E --color "string1|string2|string3...."

for example to find whether our system using AMD(svm) or Intel(vmx) processor and if it is 64bit(lm) lm stands for long mode- that means 64bit...

command example:

grep -E --color "lm|svm|vmx" /proc/cpuinfo

-E is must to find multiple strings

Personally, I do this in perl rather than trying to cobble together something with grep.

For instance, for the first one:

while (<FILE>)
{
   next if ! m/pattern1/;
   next if ! m/pattern2/;
   next if ! m/pattern3/;

   print $_;
}