usr/src/lib/libc/stdio/mktemp.c

/*
 * Copyright (c) 1987 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)mktemp.c    5.4 (Berkeley) %G%";
#endif LIBC_SCCS and not lint

#include <sys/types.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdio.h>
#include <ctype.h>

#define YES     1
#define NO      0

mkstemp(as)
        char    *as;
{
        int     fd;

        return (_gettemp(as, &fd) ? fd : -1);
}

char *
mktemp(as)
        char    *as;
{
        return(_gettemp(as, (int *)NULL) ? as : (char *)NULL);
}

static
_gettemp(as, doopen)
        char    *as;
        register int    *doopen;
{
        extern int      errno;
        register char   *start, *trv;
        struct stat     sbuf;
        u_int   pid;

        pid = getpid();

        /* extra X's get set to 0's */
        for (trv = as; *trv; ++trv);
        while (*--trv == 'X') {
                *trv = (pid % 10) + '0';
                pid /= 10;
        }

        /*
         * check for write permission on target directory; if you have
         * six X's and you can't write the directory, this will run for
         * a *very* long time.
         */
        for (start = ++trv; trv > as && *trv != '/'; --trv);
        if (*trv == '/') {
                *trv = '\0';
                if (stat(as, &sbuf) || !(sbuf.st_mode & S_IFDIR))
                        return(NO);
                *trv = '/';
        }
        else if (stat(".", &sbuf) == -1)
                return(NO);

        for (;;) {
                if (doopen) {
                    if ((*doopen = open(as, O_CREAT|O_EXCL|O_RDWR, 0600)) >= 0)
                        return(YES);
                    if (errno != EEXIST)
                        return(NO);
                }
                else if (stat(as, &sbuf))
                        return(errno == ENOENT ? YES : NO);

                /* tricky little algorithm for backward compatibility */
                for (trv = start;;) {
                        if (!*trv)
                                return(NO);
                        if (*trv == 'z')
                                *trv++ = 'a';
                        else {
                                if (isdigit(*trv))
                                        *trv = 'a';
                                else
                                        ++*trv;
                                break;
                        }
                }
        }
        /*NOTREACHED*/
}