tmpfile.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/*
 * This file not used on plan9: see ../plan9/tmpfile.c
 */
/*
 * pANS stdio -- tmpfile
 *
 * Bug: contains a critical section.  Two executions by the same
 * user could interleave as follows, both yielding the same file:
 *	access fails
 *			access fails
 *	fopen succeeds
 *			fopen succeeds
 *	unlink succeeds
 *			unlink fails
 * As I read the pANS, this can't reasonably use tmpnam to generate
 * the name, so that code is duplicated.
 */
#include "iolib.h"
FILE *tmpfile(void){
	FILE *f;
	static char name[]="/tmp/tf000000000000";
	char *p;
	while(access(name, 0)==0){
		p=name+7;
		while(*p=='9') *p++='0';
		if(*p=='\0') return NULL;
		++*p;
	}
	f=fopen(name, "wb+");
	unlink(name);
	return f;
}