Shell variable with spaces , quoting for single command line option
Autoconf scripts have trouble with a filename or pathname with spaces. For example,
./configure CPPFLAGS="-I\"/path with space\""
results in (config.log):
configure:3012: gcc -I"/path with space" conftest.c >&5
gcc: with: No such file or directory
gcc: space": No such file or directory
The compile command from ./configure is ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5' and I am not able to modify this (I could perhaps, but working around autoconf in this way is not a general solution).
I think it comes down to getting a shell variable that contains spaces to be parsed as a single command line variable rather than split at spaces. The simplest shell example I can come up with is to create a file with spaces and attempt to list is with ls with a shell variable as the argument to ls:
$ touch "a b"
$ file="a b"
$ ls $file
ls: a: No such file or directory
ls: b: No such file or directory
This works, but is illegal since in autoconf I can't modify the shell code:
$ ls "$file"
a b
None of the following attempts at quoting things work:
$ file="\"a \"b"; ls $file
ls: "a: No such file or directory
ls: b": No such file or directory
$ file="a\ b"
$ file="a\\ b"
$ file="`echo \\"a b\\"`"
and so on.
Is this impossible to accomplish in shell scripts? Is there a magical quoting that will expand a shell variable with spaces into a single command line argument?
Answer
You should try to set the $IFS environment variable.
from man bash(1):
IFS - The Internal Field Separator that is used for word splitting after expansion and to split lines into words with the read builtin command. The default value is ''space tab newline''.
For example
IFS=<C-v C-m> # newline
file="a b"
touch $file
ls $file
Don't forget to set $IFS back or strange things will happen.