snprintf函数用法 .

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转载自这个博客哈http://blog.csdn.net/wealoong/article/details/8667028

snprintf(str, sizeof(str), "0123456789012345678"); //从源串中"0123456789012345678"拷贝sizeof(str)-1,字符到目标串中str中

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：
char test[8];
int ret = snprintf(test,5,"1234567890");
printf("%d|%s/n",ret,test);

运行结果为：
10|1234

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)

#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:(不推荐使用)

#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函数返回值的测试：

#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

解释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

转载自这个博客哈http://blog.csdn.net/wealoong/article/details/8667028

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