How to add path in the head of original ENV['path']

Ruby
1

As we know, commands below can add new path in the tail of original
ENV[‘path’](i.e. /path_old:/path_new)

ENV[‘PATH’] += “:/path_new”

If I want the new path added in the head of original ENV[‘path’](i.e.
/path_new:/path_old), is there quick way simlilar as “+=”?

Certainly commands below works, just want to know whether simplified
command similiar with “+=”.

ENV[‘PATH’] = ‘/path_new’ + ‘:’ + ‘/path_old’

2

Subject: How to add path in the head of original ENV[‘path’]
Date: gio 16 gen 14 07:13:00 +0100

Quoting Previn L. ([email protected]):

If I want the new path added in the head of original ENV[‘path’](i.e.
/path_new:/path_old), is there quick way simlilar as “+=”?

ENV[‘PATH’].prepend(’/path_new:’)

ENV[‘PATH’] is a string, which can be manipulated like any other
string.

Carlo

3

It would be
ENV[‘PATH’] = ‘/newpath’ + ENV[‘PATH’]
and it is as easy as it can get. Not aware about any method like +=.

4

Arun kant sharma wrote in post #1133323:

It would be
ENV[‘PATH’] = ‘/newpath’ + ENV[‘PATH’]
and it is as easy as it can get. Not aware about any method like +=.

I know, thank you. :slight_smile:

5

Carlo E. Prelz wrote in post #1133313:

Subject: How to add path in the head of original ENV[‘path’]
Date: gio 16 gen 14 07:13:00 +0100

Quoting Previn L. ([email protected]):

If I want the new path added in the head of original ENV[‘path’](i.e.
/path_new:/path_old), is there quick way simlilar as “+=”?

ENV[‘PATH’].prepend(’/path_new:’)

ENV[‘PATH’] is a string, which can be manipulated like any other
string.

Carlo

This is just I want, thank you.

6

Carlo E. Prelz wrote in post #1133313:

Subject: How to add path in the head of original ENV[‘path’]
Date: gio 16 gen 14 07:13:00 +0100

Quoting Previn L. ([email protected]):

If I want the new path added in the head of original ENV[‘path’](i.e.
/path_new:/path_old), is there quick way simlilar as “+=”?

ENV[‘PATH’].prepend(’/path_new:’)

ENV[‘PATH’] is a string, which can be manipulated like any other
string.

Carlo

======

  1. ruby 1.9.2-p320
    ======
    Sorry, it reports error below when use “prepend”, the ruby version used
    is 1.9.2-p320 .

undefined method `prepend’ for “/path_old”:String (NoMethodError)

======
2. ruby 2.0.0-p247

in `prepend’: can’t modify frozen String (RuntimeError)

7

Matthew K. wrote in post #1133419:

Arun kant sharma wrote in post #1133323:

It would be
ENV[‘PATH’] = ‘/newpath’ + ENV[‘PATH’]
and it is as easy as it can get. Not aware about any method like +=.

It isn’t a method; a += b' is syntactic sugar fora = a + b’

And you forgot the path separator:

ENV[‘PATH’] = ‘/newpath:’ + ENV[‘PATH’]

Yes, but I just want to know whether there is more elegant way without
writing ENV[‘PATH’] twice.

8

Previn L. wrote in post #1133420:

Yes, but I just want to know whether there is more elegant way without
writing ENV[‘PATH’] twice.

Well, apparently String#prepend has been a part of ruby since at least
1.9.3

$ ruby -ve ‘p “a”.prepend(“b”)’
ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-linux]
“ba”
$

If it’s not defined, you could always do this:

class String; def prepend(o) “#{o}#{self}”; end end

It’s not identical in behaviour, but it’s close enough.

9

Arun kant sharma wrote in post #1133323:

It would be
ENV[‘PATH’] = ‘/newpath’ + ENV[‘PATH’]
and it is as easy as it can get. Not aware about any method like +=.

It isn’t a method; a += b' is syntactic sugar fora = a + b’

And you forgot the path separator:

ENV[‘PATH’] = ‘/newpath:’ + ENV[‘PATH’]

10

Subject: Re: How to add path in the head of original ENV
Date: ven 17 gen 14 05:29:34 +0100

Quoting Previn L. ([email protected]):

Yes, but I just want to know whether there is more elegant way without
writing ENV[‘PATH’] twice.

prepend exists here on 2.2.0dev. But then, if I run

ENV[‘PATH’].prepend(’/path_new:’)

it balks with:

RuntimeError: can’t modify frozen String

:-/

Previn: if I were you I would write ENV[‘PATH’] twice and be over with
it. There are times when one has to be pragmatic.

Carlo

11

Carlo E. Prelz wrote in post #1133425:

Previn: if I were you I would write ENV[‘PATH’] twice and be over with
it. There are times when one has to be pragmatic.

Carlo
Yes, this is not so important, let’s close this case. :slight_smile: