I want to count the number of interfaces that have some specific configuration in my router. I want to use the most basic tools found in linux (so dont have to assume anything else is installed) and I want to use as less commands as possible.<\/p>\n\n\n\n
So this is my config:<\/p>\n\n\n\n
frr version 7.5\nfrr defaults traditional\nhostname R2\nlog syslog informational\nno ipv6 forwarding\nservice integrated-vtysh-config\n!\ninterface ens6\n ip router isis ISIS \n isis circuit-type level-2-only\n isis network point-to-point\n!\ninterface lo1\n ip router isis ISIS \n isis passive\n!\ninterface ens7\n ip router isis ISIS \n isis circuit-type level-2-only\n isis network point-to-point\n!\ninterface lo2\n ip router isis ISIS \n isis passive\n!\nmpls ldp\n router-id 172.20.15.2\n !\n address-family ipv4\n discovery transport-address 172.20.15.2\n !\n interface ens6\n !\n interface ens7\n !\n exit-address-family\n !\n!\nrouter isis ISIS \n net 49.0001.1720.2001.5002.00\n!\nline vty\n!\n<\/code><\/pre>\n\n\n\nAnd I want to count the number of interfaces that have “isis network point-to-point” regardless of any other config.<\/p>\n\n\n\n
In this example, we have just two interfaces.<\/p>\n\n\n\n
interface ens6\n ip router isis ISIS \n isis circuit-type level-2-only\n isis network point-to-point\n\ninterface ens7\n ip router isis ISIS \n isis circuit-type level-2-only\n isis network point-to-point\n<\/code><\/pre>\n\n\n\nThe pseudo-pattern should be something like:<\/p>\n\n\n\n
^interface ens.*point-to-point$<\/code><\/pre>\n\n\n\nSo something that starts with “interface ens”, it can have anything after that and then it ends with “point-to-point”<\/p>\n\n\n\n
Ideally I want to use just “grep” and it is a standard and common tool<\/p>\n\n\n\n
But grep mainly works in one line each time. And my pattern covers multiple lines.<\/p>\n\n\n\n
So I searched for some help and found this<\/a> that uses “perl compatible regular expressions” (PCRE). I have no idea about perl but let’s give it a go:<\/p>\n\n\n\n$ grep -Pz '(?s)interface ens.*point-to-point\\n' r5.txt<\/em><\/strong>\nfrr version 7.5\nfrr defaults traditional\nhostname R2\nlog syslog informational\nno ipv6 forwarding\nservice integrated-vtysh-config\n!\ninterface ens6\n ip router isis ISIS <\/strong>\n isis circuit-type level-2-only\n isis network point-to-point<\/strong>\n!\ninterface lo1\n ip router isis ISIS \n isis passive\n!<\/strong>\ninterface ens7\n ip router isis ISIS \n isis circuit-type level-2-only\n isis network point-to-point<\/strong>\n!\ninterface lo2\n ip router isis ISIS \n isis passive\n!\nmpls ldp\n router-id 172.20.15.2\n !\n address-family ipv4\n discovery transport-address 172.20.15.2\n !\n interface ens6\n !\n interface ens7\n !\n exit-address-family\n !\n!\nrouter isis ISIS \n net 49.0001.1720.2001.5002.00\n!\nline vty\n!\n<\/code><\/pre>\n\n\n\nLet’s explain the parameters provided to grep so far:<\/p>\n\n\n\n
- -P: Use perl compatible regular expressions (PCRE).<\/li>
- -z: Treat the input as a set of lines, each terminated by a zero byte instead of a newline. i.e. grep treats the input as a one big line.<\/li>
- (?s): activate PCRE_DOTALL, which means that ‘.’ matches any character or newline.<\/li><\/ul>\n\n\n\n
But if I count, we dont have the expected answer of 2:<\/p>\n\n\n\n
$ grep -Pzc '(?s)interface ens.*point-to-point\\n' r5.txt\n1\n<\/code><\/pre>\n\n\n\nThe “z” parameter is treating the file as a single line so for grep, there is one match only. The initial command shows in bold just one block.<\/p>\n\n\n\n
We notice that the pattern is matching “interface lo1” and that is not what we want, it should be ignored.<\/p>\n\n\n\n
So our pattern should match the smallest string. So we want a non-greedy matching regex. So searching again, found this<\/a>. It seems for Perl regex, we need to use ? <\/strong>after *<\/strong><\/p>\n\n\n\n$ grep -Pz '(?s)interface ens.*?<\/strong>point-to-point\\n' r5.txt\nfrr version 7.5\nfrr defaults traditiona\nhostname R2\nlog syslog informational\nno ipv6 forwarding\nservice integrated-vtysh-config\n!\ninterface ens6<\/strong>\n ip router isis ISIS \n isis circuit-type level-2-only\n isis network point-to-point<\/strong>\n!\ninterface lo1\n ip router isis ISIS \n isis passive\n!\ninterface ens7<\/strong>\n ip router isis ISIS \n isis circuit-type level-2-only\n isis network point-to-point<\/strong>\n!\ninterface lo2\n ip router isis ISIS \n isis passive\n!\nmpls ldp\n router-id 172.20.15.2\n !\n address-family ipv4\n discovery transport-address 172.20.15.2\n !\n interface ens6\n !\n interface ens7\n !\n exit-address-family\n !\n!\nrouter isis ISIS \n net 49.0001.1720.2001.5002.00\n!\nline vty\n!\n\n<\/code><\/pre>\n\n\n\nSo now, we can see two blocks highlighted. So now let’s print only the matched strings using -o<\/strong>:<\/p>\n\n\n\n$ grep -Pzo '(?s)interface ens.*?point-to-point\\n' r5.txt\ninterface ens6\n ip router isis ISIS \n isis circuit-type level-2-only\n isis network point-to-point\ninterface ens7\n ip router isis ISIS \n isis circuit-type level-2-only\n isis network point-to-point\n<\/code><\/pre>\n\n\n\nSo this looks correct but still counting (-c) doesnt work properly because -z is treating the entry as one big line.<\/p>\n\n\n\n
I haven’t been able to find the solution with just one command so at the end, I have to pipe another grep. The initial grep matches the pattern, so the second one should just count a specific pattern like “point”. It should be that simple:<\/p>\n\n\n\n
$ grep -Pzo '(?s)interface ens.*?point-to-point\\n' r5.txt | grep point\ngrep: (standard input): binary file matches\n<\/code><\/pre>\n\n\n\nWeird, I thought this was pure text but seems the ouput of the first grep has some binary data:<\/p>\n\n\n\n
$ grep -Pzo '(?s)interface ens.*?point-to-point\\n' r5.txt > r55.txt\n$ vim r55.txt\ninterface ens6\n ip router isis ISIS\n isis circuit-type level-2-only\n isis network point-to-point\n^@<\/strong>interface ens7\n ip router isis ISIS \n isis circuit-type level-2-only\n isis network point-to-point\n^@<\/strong>\n<\/code><\/pre>\n\n\n\nBut we can tell grep to read binary data too using -a as per this blog<\/a> and then count.<\/p>\n\n\n\n$ grep -Pzo '(?s)interface ens.*?point-to-point\\n' r5.txt | grep -a point\n isis network point-to-point\n isis network point-to-point\n$ grep -Pzo '(?s)interface ens.*?point-to-point\\n' r5.txt | grep -ac point\n2\n<\/code><\/pre>\n\n\n\nFunny enough, if I just want to count, I dont need -a:<\/p>\n\n\n\n
$ grep -Pzo '(?s)interface ens.*?point-to-point\\n' r5.txt | grep -c point\n2\n<\/code><\/pre>\n\n\n\nSo not sure if this is the best solution but it took me a bit to find it. It seems to work:<\/p>\n\n\n\n
grep -Pzo ‘(?s)interface ens.*?point-to-point\\n’ r5.txt | grep -ac point<\/strong><\/p>\n\n\n\n<\/p>\n","protected":false},"excerpt":{"rendered":"
I want to count the number of interfaces that have some specific configuration in my router. I want to use the most basic tools found in linux (so dont have to assume anything else is installed) and I want to use as less commands as possible. So this is my config: And I want to … Continue reading “grep multiline”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-669","post","type-post","status-publish","format-standard","hentry","category-unix"],"_links":{"self":[{"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/posts\/669","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/comments?post=669"}],"version-history":[{"count":1,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/posts\/669\/revisions"}],"predecessor-version":[{"id":670,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/posts\/669\/revisions\/670"}],"wp:attachment":[{"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/media?parent=669"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/categories?post=669"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.thomarite.uk\/index.php\/wp-json\/wp\/v2\/tags?post=669"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}