Re: (cross post from bug-make) A complete example of quoting an arbitrary value as a word in a shell script

[Poor Yorick]

The code in the original message on this topic didn't quite work:  Its 
uses of
double quotes meant that some characters were interpreted by the shell 
as
special when they shouldn't have been.  Below are three hopefully 
correct
approaches, each one more simple than the preceding one.

This code is demonstrates a user-defined function, "shquote", that 
quotes a value
for substitution into a shell script.  It provides functionality similar 
to
.ONESHELL, but without the disadvantage of changing the behaviour of all
recipes in all rules.  Notably, heredocs can be used, which makes it 
possible
to pass virtually any value from Make into a shell script.

One difference between the direct shell quoting and posix shell quoting 
below
is that the direct shell quoting preserves trailing newlines while the 
posix
shell quoting does not.  There seems to be no way around that 
difference.
Heredocs can be used to work around issues that might arise from the 
loss of
trailing newlines.


<code>
SHELL = bash
#SHELL = dash

define newline


endef

define script0
        echo 'line one \\
        line two '

        cat <<-'eof'
                line three
                line four
        eof
        $$var1
        var2="line five"
        printf '%s\n' "$$var2"
        echo 'last
                line'






endef


ifeq ($(shell printf '%s' $$'\n'),$$\n)
    $(warning posix shell quoting, trailing newlines not preserved)
    # this is more difficult


    # one way to do it is to quote things enough the final printf 
doesn't need to add newlines back
    ## replace each single quote with escaped single quote, and add an 
extra layer of quoting for eval to strip off
    #shquotequote = $(subst ','\\'\\\\\'\\'',$(1))
    ## replace each newline with command-substitution to produce a 
newline enclosed in ingle quotes for eval to strip off
    #shnlquote = \''$(subst $(newline),'$$(printf "'\n'")',$(call 
shquotequote,$(1)))'\'
    ## during evaluation command substitution produces newlines, and a 
layer of quoting is consumed
    #shquote = "$$(eval eval printf "'%s'" "$(call shnlquote,$(1))")"



    ## another slightly more simple way is to let the final printf add 
newlines back

    ## replace each single quote with escaped single quote, and add an 
extra layer
    ## of quoting for eval to strip off
    #shquotequote = $(subst ','\'\\\'\'',$(1))

    ## replace each newline with command-substitution to produce a 
newline
    ## enclosed in ingle quotes for eval to strip off
    #shnlquote = \''$(subst $(newline),'$$(printf "'\n'")',$(call 
shquotequote,$(1)))'\'

    ## during evaluation command substitution produces newlines, and a 
layer of
    ## quoting is consumed
    #shquote = "$$(eval printf "'%sxxx\n'" $(call shnlquote,$(1)))"


    # but even more simple is to forget about trying to encode each 
newline with
    # a $(printf), and just provide a space-separated sequence of quoted 
values,
    # each of which is a single line, and let a single printf add all 
the
    # newlines
    shquotequote = $(subst ','\'',$(1))
    shnlquote = '$(subst $(newline),' ',$(call shquotequote,$(1)))'
    shquote = "$$(printf '%s\n' $(call shnlquote,$(1)))"

else
    $(warning direct shell quoting, trailing newlines preserved)
    # this is easy...

    # Replace each single quote with a quoted single quote,
    # call shnlquoe to deal with newlines
    # Add the first and last single quotes
    shquote = '$(call shnlquote,$(subst ','"'"',$(1)))'

    # replace each newline character with a
    shnlquote = $(subst $(newline),'$$'\n'',$(1))
endif


script0:
        eval $(call shquote,$(script0))
.PHONY: script0

printscript0:
        printf '%s\n' $(call shquote,$(script0))
.PHONY: printscript0
</code>


--
Yorick

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