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jakobcreutzfeldt

Member

Registered: 2011-05-12

Posts: 1,041

How portable are shell parameter expansions?

I'm finding that the simplest solution to a problem in a Makefile that I'm writing is to use the ${var#param} parameter expansion. How portable is this? I've tried using both bash and sh and they both work as expected, but I'd like to make sure that this is a standard feature present in all relevant shells.

$ bash -c 'var="Hello";/usr/bin/echo ${var#Hell}'
o
$ sh -c 'var="Hello";/usr/bin/echo ${var#Hell}'
o

Last edited by jakobcreutzfeldt (2013-03-13 15:44:03)

WorMzy

Forum Moderator

From: Scotland

Registered: 2010-06-16

Posts: 11,863

Website

Re: How portable are shell parameter expansions?

fish looks problematic, but zsh and dash are fine:

$ zsh -c 'var="Hello";/usr/bin/echo ${var#Hell}'
o
$ dash -c 'var="Hello";/usr/bin/echo ${var#Hell}'
o
$ fish -c 'var="Hello";/usr/bin/echo ${var#Hell}'
fish: Unknown command “var=Hello”. Did you mean “set var Hello”? For information on assigning values to variables, see the help section on the set command by typing “help set”.
Standard input: var="Hello";/usr/bin/echo ${var#Hell}
                ^
fish: Could not expand string “${var”
Standard input: var="Hello";/usr/bin/echo ${var#Hell}
                                          ^

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jakobcreutzfeldt

Member

Registered: 2011-05-12

Posts: 1,041

Re: How portable are shell parameter expansions?

Ok thanks. It seems that fish isn't Bourne-compatible (given the way it handles vars).