Re: Writing contents of large variable into a file

[John Graham-Cumming]

On Fri, 2005-02-18 at 10:56 +0100, address@hidden wrote:
> Unfortunately I could not figure out how to write the content of JAVA_SRCS 
> into a file without running into the shell limit:
> 
>    make: execvp: /bin/sh.exe: Argument list too long
>    make: *** [compile] Error 127

So imagine that what you want to do is this:

    $(shell echo $(TOO_LONG) > long_file)

But can't because you hit a limit in the shell.   

A slow way to handle this would be 

    $(shell rm -f long_file)$(foreach w,$(TOO_LONG),$(shell echo -n 
    "$w " >> long_file))

But that's very slow because there's a shell invocation per word in
TOO_LONG.  So the right way to do this is to write a function that
breaks the long list of words at a fixed point and writes out lines to
the file iteratively.

Like this (in GNU Make 3.80 and above):

    write-var-to-file=$(strip $(shell rm -f $1)$(eval __a :=)$(foreach 
    w,$($2),$(if $(filter $3,$(words $(__a))),$(shell echo -n "$(strip 
    $(__a)) " >> $1)$(eval __a:=))$(eval __a +=$w))$(shell echo $(__a) 
    >> $1))

write-var-to-file has three arguments: the name of the file to be
written, the name of the variable to write and the number of words to
gather up before writing to the file.

e.g.  $(call write-var-to-file,long_file,TOO_LONG,200)

would write out the contents of TOO_LONG performing a shell echo every
200 words to a file call long_file.

John.
-- 
John Graham-Cumming

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