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/*
* NAME
* mkstemp - create a unique temporary file
*
* SYNOPSIS
* int mkstemp(char *template);
*
* DESCRIPTION
* The mkstemp() function generates a unique temporary file name from tem-
* plate. The last six characters of template must be XXXXXX and these
* are replaced with a string that makes the filename unique. The file is
* then created with mode read/write and permissions 0600. Since it will
* be modified, template must not be a string constant, but should be
* declared as a character array. The file is opened with the O_EXCL flag,
* guaranteeing that when mkstemp returns successfully we are the only
* user.
*
* RETURN VALUE
* The mkstemp() function returns the file descriptor fd of the temporary
* file or -1 on error.
*
* ERRORS
* EINVAL The last six characters of template were not XXXXXX. Now tem-
* plate is unchanged.
*
* EEXIST Could not create a unique temporary filename. Now the contents
* of template are undefined.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
int mkstemp(char *template) {
int retfd=-1;
int i, temp_len;
temp_len=strlen(template);
if (temp_len<6) return(-1);
if (strcmp(template+(temp_len-6), "XXXXXX")!=0) return(-1);
srand(getpid()+temp_len);
for (i=0; i<6; i++) {
template[temp_len-i-1]='A'+((rand()+i)%26);
retfd=open(template, O_EXCL|O_CREAT|O_RDWR, 0600);
if (retfd>=0) break;
}
return(retfd);
}
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