Doug McIlroy <d...@cs.dartmouth.edu> wrote: |I must be missing something in the discussion about random |numbers. Why does groff need them? In the offered example | tmp="$d/eqn2graph$groff_rand" |the "random number" serves only to make a (supposedly) unique |name. But of course, if the number is truly random, it is not |guaranteed to be unique. Why does groff not use the time-honored |$$ to serve the purpose? The only requirement for an absolute |guarantee of uniqueness is that the shell script whose pid $$ |represents lives as long as the temporary file.
POSIX also loomed some notes on temporary files in the shell [1]: Having a function like tmpnam( ) in the ISO C standard is important in many high-level languages. The shell programming language, however, has built-in string manipulation facilities, making it very easy to construct temporary filenames. The names needed obviously depend on the application, but are frequently of a form similar to: $TMPDIR/application_abbreviation$$.suffix In cases where there is likely to be contention for a given suffix, a simple shell for or while loop can be used with the shell noclobber option to create a file without risk of collisions, as long as applications trying to use the same filename name space are cooperating on the use of files after they have been created. [1] <http://pubs.opengroup.org/onlinepubs/9699919799/utilities/pathchk.html> --steffen
