Oops! I hit reply and it went to Erik. Sorry! On Tue, 29 Nov 2022 08:21:47 -0600 Eric Blake <ebl...@redhat.com> wrote: > On Sat, Nov 19, 2022 at 09:42:07PM -0500, David Niklas wrote: > > Hello, > > > > I know I could do this with bash, awk, and probably several other > > languages, I wanted to use m4. > > > > I was trying to do a basic "If the file is there then include it," > > directive with m4. > > > > echo 'define(`mkv'\'', `ogg'\'')ifelse(`1'\'', syscmd(`test -f > > f'\'')sysval, `-i'\'' f `-map 1'\'')dnl' | m4 -D f="$i" - > > You are testing whether 'f' exists, rather than whether the filename > contained in macro f exists. You probably want your m4 script to say > something like: > > syscmd(`test -f 'defn(`f'))
Sorry for taking so long to get back to you. The new command is: for i in *.mkv; do echo 'define(`mkv'\'', `ogg'\'')ifelse(`1'\'', syscmd(`test -f '\''defn(`f'\''))sysval, `-i'\'' f `-map 1'\'')dnl' | m4 -D f="$i" -; done I get the following output: sh: 1: test: MY-FILE: unexpected operator ... I'm not really sure what's going on. The filenames do need to be quoted, but if I replace the test command with the echo command I get the expected string output. -f MY-FILE 01.ogg -f MY-FILE 02.ogg ... > plus the extra quoting needed to write ' in shell. > I think I got that, see above. > > > > As a bit of a bonus question, can I somehow tack a period onto the > > front of the mkv macro expansion? That way, instead of matching > > "mkv", it would match ".mkv". > > If you are asking "can m4 treat '.mkv' as a macro name", the answer is > no for m4 1.4 unless it was built with --enable-changeword (which > penalizes speed performance). But if you are asking if you can write > an m4 macro that inspects whether its argument includes the substring > '.mkv' and if so does something, then yes. > I'd like to have a "macro that inspects whether its argument includes the substring '.mkv' and if so does something." Thanks!
