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

[Neil R. Ormos]

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.