snprintf函数用法(转)

  1. #include <stdio.h>
  2. int snprintf(char *restrict buf, size_t n, const char * restrict format, ...);
函数说明:最多从源串中拷贝n-1个字符到目标串中,然后再在后面加一个0。所以如果目标串的大小为n 的话,将不会溢出。

函数返回值:若成功则返回欲写入的字符串长度,若出错则返回负值。

Result1(推荐的用法)

  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. int main()
  4. {
  5. char str[10]={0,};
  6. snprintf(str, sizeof(str), "0123456789012345678");
  7. printf("str=%s/n", str);
  8. return 0;
  9. }
  10. root] /root/lindatest
  11. $ ./test
  12. str=012345678

Result2(不推荐的用法):
 

  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. int main()
  4. {
  5. char str[10]={0, };
  6. snprintf(str, 18, "0123456789012345678");
  7. printf("str=%s/n", str);
  8. return 0;
  9. }
  10. root] /root/lindatest
  11. $ ./test
  12. str=01234567890123456

 

snprintf函数返回值的测试:

  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. int main()
  4. {
  5. char str1[10] ={0, };
  6. char str2[10] ={0, };
  7. int ret1=0,ret2=0;
  8. ret1=snprintf(str1, sizeof(str1), "%s", "abc");
  9. ret2=snprintf(str2, 4, "%s", "aaabbbccc");
  10. printf("aaabbbccc length=%d/n", strlen("aaabbbccc"));
  11. printf("str1=%s,ret1=%d/n", str1, ret1);
  12. printf("str2=%s,ret2=%d/n", str2, ret2);
  13. return 0;
  14. }
  15. [root] /root/lindatest
  16. $ ./test
  17. aaabbbccc length=9
  18. str1=abc,ret1=3
  19. str2=aaa,ret2=9


解释SIZE:

  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. int main()
  4. {
  5. char dst1[10] ={0, },dst2[10] ={0, };
  6. char src1[10] ="aaa",src2[15] ="aaabbbcccddd";
  7. int size=sizeof(dst1);
  8. int ret1=0, ret2=0;
  9. ret1=snprintf(dst1, size, "str :%s", src1);
  10. ret2=snprintf(dst2, size, "str :%s", src2);
  11. printf("sizeof(dst1)=%d, src1=%s, /"str :%%s/"=%s%s, dst1=%s, ret1=%d/n", sizeof(dst1), src1, "str :", src1, dst1, ret1);
  12. printf("sizeof(dst2)=%d, src2=%s, /"str :%%s/"=%s%s, dst2=%s, ret2=%d/n", sizeof(dst2), src2, "str :", src2, dst2, ret2);
  13. return 0;
  14. }
  15. root] /root/lindatest
  16. $ ./test
  17. sizeof(dst1)=10, src1=aaa, "str :%s"=str :aaa, dst1=str :aaa, ret1=8
  18. sizeof(dst2)=10, src2=aaabbbcccddd, "str :%s"=str :aaabbbcccddd, dst2=str :aaab, ret2=17
  19. 补充一下,snprintf的返回值是欲写入的字符串长度,而不是实际写入的字符串度。如:
  20. char test[8];
  21. int ret = snprintf(test,5,"1234567890");
  22. printf("%d|%s/n",ret,test);
  23. 运行结果为:
  24. 10|1234






posted @ 2015-06-17 19:23 外禅内定,程序人生 阅读(...) 评论(...) 编辑 收藏