Question

Consider the following example, where grep is used to search in binary mode:

$ echo "test blabla test ertytey" | grep -ao tes
tes
tes

I can add a ‘dot’ in the search pattern, to “match any character” and show the next character after the match:

$ echo "test blabla test ertytey" | grep -ao tes.
test 
test 

… or more dots, to match subsequent characters:

$ echo "test blabla test ertytey" | grep -ao tes...
test b
test e

 

Let’s say now I want to match a number of characters (say 30, no: 3) after the match; and I read from man grep: {n} The preceding item is matched exactly n times.. So I try:

$ echo "test blabla test ertytey" | grep -ao tes.{3}
$

… nothing happens;

$ echo "test blabla test ertytey" | grep -ao tes.\{3\}
$

… nothing happens;

$ echo "test blabla test ertytey" | grep -ao tes[.]\{3\}
$

… nothing happens;

$ echo "test blabla test ertytey" | grep -ao tes\[.\]\{3\}
$

… nothing happens.

 

Any ideas what would the correct syntax be to match “any character” (dot) a given number of times in grep’s binary mode?

Many thanks in advance for any answers,
Cheers!

 

EDIT: as @aix’ answer points out, initially I made a mistake of specifying 30 characters to search for, whereas the string in the example is not long enough 🙂 Have now changed it to the more reasonable count of 3 🙂

Answer 1

First of all, {30} matches exactly thirty characters, and your string isn’t long enough.

Secondly, your grep might require the -E flag to enable the extended syntax (mine does).

The following works for me:

$ echo "test blabla test ertytey" | grep -aoE 'tes.{20}'
test blabla test ertyte