Question

I have a short bash script to get source code’s dependency files.

#!/bin/sh
rule=$(cpp -P -w -undef -nostdinc -C -M file.cc)
rule=${rule##*:}
#echo $rule
echo ${rule//\\}

Unfortunately, it outputs ./findDep.sh: 5: ./findDep.sh: Bad substitution.
But if I uncomment echo $rule, the script will execute without any problem:

lib.h macro.inc fundamental.h lib/fs.h lib/net.h \ lib/net/fetch.h
lib.h macro.inc fundamental.h lib/fs.h lib/net.h  lib/net/fetch.h

Any one know why?

Thanks in advance.

Answer 1

I can’t reproduce your problem here with Bash 4.2.29.

However, did you know that read will join lines with \ newline continuations by default?

read rule < <(cpp -P -w -undef -nostdinc -C -M file.cc)
echo "${rule##*:}"

Or, in a more sh-compatible way (I think),

cpp -P -w -undef -nostdinc -C -M file.cc | {
    read rule
    echo "${rule##*:}"
}