int snprintf(char *restrict buf, size_t n, const char * restrict format, ...);
函數說明:最多從源串中拷貝n－1個字符到目標串中，然后再在后面加一個0。所以如果目標串的大小為n 的話，將不會溢出。
函數返回值:若成功則返回欲寫入的字符串長度，若出錯則返回負值。
Result1(推薦的用法)
#include <stdio.h>
#include <stdlib.h>
int main()
{
char str[10]={0,};
snprintf(str, sizeof(str), "0123456789012345678");
printf("str=%s/n", str);
return 0;
}
root] /root/lindatest
$ ./test
str=012345678
Result2:(不推薦使用)
#include <stdio.h>
#include <stdlib.h>
int main()
{
char str[10]={0, };
snprintf(str, 18, "0123456789012345678");
printf("str=%s/n", str);
return 0;
}
root] /root/lindatest
$ ./test
str=01234567890123456
snprintf函數返回值的測試：
#include <stdio.h>
#include <stdlib.h>
int main()
{
char str1[10] ={0, };
char str2[10] ={0, };
int ret1=0,ret2=0;
ret1=snprintf(str1, sizeof(str1), "%s", "abc");
ret2=snprintf(str2, 4, "%s", "aaabbbccc");
printf("aaabbbccc length=%d/n", strlen("aaabbbccc"));
printf("str1=%s,ret1=%d/n", str1, ret1);
printf("str2=%s,ret2=%d/n", str2, ret2);
return 0;
}
[root] /root/lindatest
$ ./test
aaabbbccc length=9
str1=abc,ret1=3
str2=aaa,ret2=9
解釋SIZE：
#include <stdio.h>
#include <stdlib.h>
int main()
{
char dst1[10] ={0, },dst2[10] ={0, };
char src1[10] ="aaa",src2[15] ="aaabbbcccddd";
int size=sizeof(dst1);
int ret1=0, ret2=0;
ret1=snprintf(dst1, size, "str :%s", src1);
ret2=snprintf(dst2, size, "str :%s", src2);
printf("sizeof(dst1)=%d, src1=%s, /"str :%%s/"=%s%s, dst1=%s, ret1=%d/n", sizeof(dst1), src1, "str :", src1, dst1, ret1);
printf("sizeof(dst2)=%d, src2=%s, /"str :%%s/"=%s%s, dst2=%s, ret2=%d/n", sizeof(dst2), src2, "str :", src2, dst2, ret2);
return 0;
}
root] /root/lindatest
$ ./test
sizeof(dst1)=10, src1=aaa, "str :%s"=str :aaa, dst1=str :aaa, ret1=8
sizeof(dst2)=10, src2=aaabbbcccddd, "str :%s"=str :aaabbbcccddd, dst2=str :aaab, ret2=17
補充一下，snprintf的返回值是欲寫入的字符串長度，而不是實際寫入的字符串度。如：
char test[8];
int ret = snprintf(test,5,"1234567890");
printf("%d|%s/n",ret,test);
運行結果為：
10|1234
本文來自CSDN博客，轉載請標明出處：http://blog.csdn.net/crfoxzl/archive/2008/01/23/2062139.aspx