Perl ack tool with output parameter and new lines

Question

I use ack very often, but something I have not been able to discover is how to make it add new lines when using the output parameter.

Example

echo 'name=Joe,id=123' | ack '^name=(\w+),id=(\d+)' --output="User name: $1\nUser ID: $2"

I expect

User name: Joe
User ID: 123

but I get

User name: Joe\nUser ID: 123

Anyway to make ack respect the new lines characters in the output?

Thanks

Has nothing to do with `ack`. Pass a newline instead of `\n`. What shell are you asking about? — ikegami, Sep 22 '17 at 19:27

score 3 · Accepted Answer · answered Sep 22 '17 at 19:35

You are passing \n to ack instead of a newline. Replace

--output='User name: $1\nUser ID: $2'

with

--output='User name: $1
User ID: $2'

or

--output="$( printf 'User name: $1\nUser ID: $2' )"

or

--output=$'User name: $1\nUser ID: $2'                   # bash

score 2 · Answer 2 · answered Sep 22 '17 at 19:31

2

You can put arbitrary code into that string via @{[ … ]} interpolation. For some reason a literal "\n" string won't work, but chr 0x0A or $/ does.

Example:

$ echo a b | ack '(\w+)\s+(\w+)' --output '$1@{[ chr 0x0A ]}$2'

Output:

a
b

Note that this kind of functionality is likely to break in the future, see also discussions like https://github.com/beyondgrep/ack2/issues/531

answered Sep 22 '17 at 19:31

amon

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Author of ack here. `@{[ … ]}` is absolutely not going to work in ack 3, currently under development. It's too dangerous. We've severely limited what can be done with `--output`. – Andy Lester Sep 23 '17 at 17:34

Perl ack tool with output parameter and new lines

2 Answers2