re

Overview

re is a command line utility for pattern matching similar to 'grep', but supports capture groups and multiline matches. The syntax of the regular expressions accepted is the same general syntax used by Perl, Python, and other languages. More precisely, it is the syntax accepted by RE2 and described at http://code.google.com/p/re2/wiki/Syntax, except for \C.

Prerequisites

None, binaries are statically linked. If you want to compile from source you need the go toolchain: http://golang.org/doc/install

Installation

• Save the 're' binary to a location in your PATH (i.e. /usr/local/bin/)
• Or compile it yourself go build re.go

Usage

re [options] PATTERN [FILE...]

Options

-d      Delimiter used to seperate capture groups. Default: ", "
-dr     Delimiter used to seperate repeated capture groups. Default: "\n"
-g      Allow . to match newline (Note: This will read the entire input into memory)
-i      Ignore case

Examples

"grep mode"

$ uptime | re "average"
20:19:29 up 119 days, 23:09,  1 user,  load average: 1.66, 1.56, 1.58

Capture group

$ uptime | re "average: (.+)"
1.66, 1.56, 1.58

Named capture groups

$ uptime | re "(?P<1min>\d+\.\d+), (?P<5min>\d+\.\d+), (?P<15min>\d+\.\d+)"
1min=1.66, 5min=1.56, 15min=1.58

Named capture groups with custom delimiter

$ uptime | re -d " -> " "(?P<1min>\d+\.\d+), (?P<5min>\d+\.\d+), (?P<15min>\d+\.\d+)"
1min=1.66 -> 5min=1.56 -> 15min=1.58

Multiline match

$ ifconfig | re -g "(eth\d+).+?inet addr:([\d.]+)"
eth0, IP=10.0.0.100
eth1, IP=10.0.0.101

Substitution

$ uptime | re "s/up/uptime:/"
20:19:29 uptime: 119 days, 23:09,  1 user,  load average: 1.66, 1.56, 1.58

Substitution with capture group

$ uptime | re "s/(up)/\${1}time:/"
20:19:29 uptime: 119 days, 23:09,  1 user,  load average: 1.66, 1.56, 1.58

Substitution with named capture group

$ uptime | re "s/(?P<prefix>up)/\${prefix}time:/"
20:19:29 uptime: 119 days, 23:09,  1 user,  load average: 1.66, 1.56, 1.58