keith@seismo.UUCP (Keith Bostic) (09/18/84)
Just got back from a news vacation -- found a long ago article suggesting
that people use mktemp(3) to produce unique file names -- and a small
program that allowed it to be called from the shell.
This is a dangerous fix on EUNICE machines. The EUNICE shell does not
increment process id's as expected under UNIX. Just as an example:
#include <stdio.h>
main()
{
static char buf[] = "fileXXXXXX";
char *mktemp();
printf("file name: %s\n",mktemp(buf));
}
when run twice in a row will produce the same file name.
Keith
ARPA: keith@seismo
UUCP: seismo!keithchip@t4test.UUCP (Chip Rosenthal) (09/20/84)
--- REFERENCED ARTICLE --------------------------------------------- >From: keith@seismo.UUCP (Keith Bostic) >Date: Mon, 17-Sep-84 15:08:51 PDT > >This is a dangerous fix on EUNICE machines. The EUNICE shell does not >increment process id's as expected under UNIX. -------------------------------------------------------------------- That is true...but `mktemp' works anyway. As suggested, `mktemp' just tries to stick the PID on then end of your template. If that already exists, it inserts an `a' before the PID. If that exists, it tries it with a `b'. The result is that I will personally double your money back guarantee you that you will be able to get at least 27 unique filenames for a given process ID. What `mktemp' does after `z', I'm not sure. Who knows...maybe someday I'll find out the *hard* way. (Hey...we're getting some discussions going in net.eunice. I love it!!) -- Chip Rosenthal, Intel/Santa Clara { idi|intelca|icalqa|kremvax|qubix|ucscc } ! t4test ! { chip|news }
keith@seismo.UUCP (Keith Bostic) (09/24/84)
> --- REFERENCED ARTICLE --------------------------------------------- > > >From: keith@seismo.UUCP (Keith Bostic) > >Date: Mon, 17-Sep-84 15:08:51 PDT > > > >This is a dangerous fix on EUNICE machines. The EUNICE shell does not > >increment process id's as expected under UNIX. > > -------------------------------------------------------------------- > That is true...but `mktemp' works anyway. As suggested, `mktemp' > just tries to stick the PID on then end of your template. If that > already exists, it inserts an `a' before the PID. If that exists, > it tries it with a `b'. The result is that I will personally double > your money back guarantee you that you will be able to get at least > 27 unique filenames for a given process ID. What `mktemp' does after > `z', I'm not sure. Who knows...maybe someday I'll find out the *hard* > way. Okay -- go for it -- put this in your system *instead* of mktemp and all your nasty little problems go away. Because, interestingly enough, mktemp returns "/" after 'z'. Which is probably one of the most brain- damaged pieces of software written since the world began. Anyway -- here is a mktemp that gets around the problem EUNICE has in incrementing the process id, 'cause it will give you more temporary files than a cat will kittens. It's behavior (up to 'z') is identical to the standard versions, and it's just as fast, if not faster. Keith ARPA: keith@seismo UUCP: seismo!keith ............... cut on the dotted line................. #include <ctype.h> char * mktemp(as) register char *as; { register char *start, /* note start of X's */ *trv; /* travel through string */ unsigned pid; pid = getpid(); for(trv = as;*trv;++trv); /* fill in pid */ while(*--trv == 'X') { *trv = (pid % 10) + '0'; pid /= 10; } for(start = ++trv;;) { if (access(as,0)) return(as); for(trv = start;;) { if (!*trv) return((char *)0); if (*trv == 'z') *trv++ = 'a'; else { if (isdigit(*trv)) *trv = 'a'; else ++*trv; break; } } } }