Substring from a file

Question

I need to extract coincidence lines from a file with a regular expression:

This is the content of file:

netbios-ns      137/tcp                         # NETBIOS Name Service
netbios-ns      137/udp
hkp             11371/tcp                       # OpenPGP HTTP Keyserver
hkp             11371/udp                       # OpenPGP HTTP Keyserver
bprd            13720/tcp                       # VERITAS NetBackup
bprd            13720/udp
vopied          13783/udp

I need to filter using 137 with grep :

grep -n -e "137" file

The output must be:

netbios-ns      137/tcp                         # NETBIOS Name Service
netbios-ns      137/udp

Answer 1

If you always have preceding whitespace and a trailing slash then:

$ grep " 137/" file
netbios-ns 137/tcp # NETBIOS Name Service
netbios-ns 137/udp

Or more robust, check for non-digits either side:

$ grep "[^[:digit:]]137[^[:digit:]]" file
netbios-ns 137/tcp # NETBIOS Name Service
netbios-ns 137/udp

Answer 2

使用grep的单词边界： grep '\\<137\\>' file