Re: [Libguestfs] [PATCH nbdkit 1/3] sh: Implement inline scripts.

On 12/14/18 4:16 PM, Richard W.M. Jones wrote: >This implements something like a readonly 1MB disk reading as zeroes: > >nbdkit sh script=- <<'EOF' > case "$1" in > get_size) echo 1M ;; > pread) dd if=/dev/zero count=$3 iflag=count_bytes ;; > *) exit 2 ;; > esac >EOF > >Use of "-" is analogous to reading passwords from stdin. >--- >@@ -26,6 +30,19 @@ like this: > You may have to add further C<key=value> arguments to the command > line. >+=head2 Inline shell scripts >+ >+It is also possible to write a shell script plugin "inline" using C<-> >+as the name of the script, like this: >+ >+ nbdkit sh script=- <<'EOF' >+ case "$1" in >+ get_size) echo 1M ;; >+ pread) dd if=/dev/zero count=$3 iflag=count_bytes ;; >+ *) exit 2 ;; >+ esac >+ EOF >+ Worth a specific mention that 'script=' is required, since otherwise the '-' looks like an option to nbdkit proper rather than a script parameter?

Probably not worth a mention that a local file named '-' can still be invoked via [script=]./- (there, script is optional because the leading ./ avoids the leading -). >+static char * >+inline_script (void) >+{ >+ const char scriptname[] = "inline-script.sh"; >+ char *filename = NULL; >+ char *cmd = NULL; >+ >+ if (asprintf (&filename, "%s/%s", tmpdir, scriptname) == -1) { >+ nbdkit_error ("asprintf: %m"); >+ goto err; >+ } >+ >+ /* Safe because both the tmpdir and script name are controlled by us >+ * and don't contain characters that need quoting. >+ */ >+ if (asprintf (&cmd, "cat > %s", filename) == -1) { Useful comment :) And I verified it is true. Looks good. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org