要读取一行11位数字和'\n'放入 string 至少需要13个数组来存储 string 。没有什么理由要那么紧。建议使用2倍的预期最大大小

  char upcbuf [100] [12]; //足够容纳100 *（11个数字和\0）
 ... 
 #define BUF_SIZE（13 * 2）
 char buf [BUF_SIZE]; 
 while（i< 100& fgets（buf，sizeof buf，f）！= NULL）{
 

放弃潜在的拖尾'\n '

  size_t len = strlen（buf）; 
 if（len&& buf [len-1] ==‘\n’）buf [-len] =‘\0’; 
 

检查长度并以某种方式处理。

 如果（len！= 11）退出（EXIT_FAILURE）; 
 

保存/打印数据

  // strncpy（upcbuf [i]，buf，11）; //无法确保
结尾处为空字符strcpy（upcbuf [i]，buf）; 
 i ++; 
 puts（upcbuf [i]）; 
 

比较字符串

  if（strcmp（UPC_Val，upcbuf [i]）== 0）{
 //字符串匹配
} 
 

I have a text file, it has values(I usually call them as upc_values) of

01080006210
69685932764
40000114485
40000114724
07410855329
72908100004
66484101000
04000049163
43701256600
99999909001
07726009493
78732510053
78732510063
78732510073
78732510093
02842010109
02842010132
78732510213
02410011035
73999911110

 char *UPC_val = "99999909001";
 char upcbuf[100][12];
 char buf[12];

 memset(buf,0,sizeof(buf));
 memset(upcbuf,0,sizeof(upcbuf));

When I tried to fgets, I stored that in a 2D buffer.

 while ( fgets(buf, sizeof(buf), f) != NULL ) {
        strncpy(upcbuf[i], buf, 11);
        i++;
 }

I tried to print the data in the buffer.

 puts(upcbuf[0]);

upcbuf[0] has the whole data in a continues stream,

0108000621069685932764400001144854000011472407410855329729081000046648410100004000049163437012566009999990900107726009493787325100537873251006378732510073787325100930284201010902842010132787325102130241001103573999911110

and I want to compare this upc values(11 digit) with another string(11 digit). I used,

 if(strncmp(UPC_Val,upcbuf[i],11) == 0)
 {
      //do stuff here
 }

It didn't work properly, I used strstr() too like,

 if(strstr(upcbuf[0],UPC_val) != NULL)
 {
     //do stuff here
 }

I am totally unaware of what it is doing, am I doing the comparison properly? How to do this, any help please?

Thanks in advance.

To read a line of text of 11 digits and a '\n' into a string needs an array of at least 13 to store the string. There is little reason to be so tight. Suggest 2x expected max size

char upcbuf[100][12];  // large enough for 100 * (11 digits and a \0)
...
#define BUF_SIZE (13*2)
char buf[BUF_SIZE];
while (i < 100 && fgets(buf, sizeof buf, f) != NULL ) {

Lop off the potential tailing '\n'

  size_t len = strlen(buf);
  if (len && buf[len-1] == '\n') buf[--len] = '\0';

Check length and handle that somehow.

  if (len != 11) exit(EXIT_FAILURE);

Save/print the data

    // strncpy(upcbuf[i], buf, 11);  // fails to insure a null character at the end
    strcpy(upcbuf[i], buf);
    i++;
    puts(upcbuf[i]);

To compare strings

    if(strcmp(UPC_Val,upcbuf[i]) == 0) { 
      // strings match
    }