Re: How do I determine the existence (or non-existence) of a file from an AWK script?

[david kerns]

On Mon, Apr 10, 2023 at 1:40 PM Neil R. Ormos <ormos-lists@ormos.org> wrote:

> Alan Mackenzie wrote:
>
> > Hello, gawk.
>
> > This should be something quite simple, but I
> > can't work out how to do it.
>
> > Given a file name in an AWK script, does a file
> > with that name actually exist?  In a shell
> > script, I'd simply do [ -f "$FOO" ].  What do I
> > have to do in AWK?
>
> > The context is a script which checks certain
> > syntactic things in a git commit message.  I
> > want to extend it to check that the noted file
> > names in the commit message don't have typos, or
> > missing directory parts, that kind of thing.
>
> You might use something like:
>
>     fres=!(system("/usr/bin/test -f " foo));
>
> where foo is an awk variable containing the name of the file.
>
> fres will be 1 if the file exists and is a regular file; otherwise 0.  The
> -e test might be appropriate in some cases.
>
> Also, you will want to escape or quote the contents of foo, as required by
> the shell, if foo is not guaranteed to be free of characters special to the
> shell.  On my systems, calls to gawk's system() function run /bin/sh.  I
> don't know if that's universal on all platforms.
>
> or this: (same warnings about filenames containing space applies)

$ gawk '
function stat(file,        cmd, line) {
  cmd = "/bin/file " file
  cmd | getline line
  close(cmd)
  return line
}
BEGIN {
        print stat("/tmep");
        print stat("/tmp");
        print stat("/etc/hosts");
}'
/tmep: cannot open (No such file or directory)
/tmp: sticky directory
/etc/hosts: ASCII text